Apollo 11 Lunar Surface
        Journal


Photogrammetric Analysis Of Apollo 11 Imagery:
New camera-station map with improved locations

Copyright 2010 by Vladislav Pustynski and Eric M. Jones.
All rights reserved.
Last revised 16 December 2013.

 Contents

1. Introduction
2. Photogrammetric Revisons to the Camera Station Map
2.1 Panoramas
2.1.1 Pan 1 at the foot of the ladder
2.1.2 Pan 2 on the rim of Double Crater near the tip of the LM shadow
2.1.3 Pan 3 on a crater rim 7 m north of the plus-Y footpad
2.1.4 Pan 4 17 m out from the SEQ Bay
2.1.5 Pan 5 on the southwest rim of Little West Crater
2.2 Comments on Individual Images and Camera Stations
2.3 1978 USGS/Defense Mapping Agency Site Map
3. Boulders Visible in Lunar Reconnaissance Orbiter Camera (LROC) Images, Hasselblad Images, and Descent Film
3.1 Boulders northwest of the LM
3.2 Boulders northeast of the LM
3.3 Boulders between Little West Crater and West Crater
3.4 Boulders near the south rim of West Crater
3.5 Boulders southeast of the LM
3.6 Boulders southwest of the LM
3.7 Boulders recognized in Deconvolved LROC Images
3.8 Boulders visible in the descent film
4. Features of Special Interest
4.1 Passive Seismometer Experiment Package (PSEP)
4.2 Bootprint Penetration Experiment
4.3 LM Insulation
4.4 Buzz and the US Flag
4.5 Craters
5. Comparisons between the Photogrammetric Map and LROC images
6. Accuracy of the 3D Scene
6.1 Error Sources
6.2 Benchmark error estimates
6.3 Accuracy of camera station locations

1. Introduction


During 2009,  one of us (VP)  got interested in precise photogrammetry of Apollo photos; and, through several Russian forums, got an opportunity to collaborate with a person nicknamed "N.A.", who was using photogrammetric software ImageModeler to identify and locate several boulders visible in the direction of West Crater in the Apollo 11 surface photography.  Although, ImageModeler is intended for architectural purposes, but it is useful for photogrammetry of the Apollo images.  It has a few drawbacks.  For example, it sometimes has trouble with photos containing only benchmark points distributed on a relatively planar surface - such as parts of the lunar surface - a problem that can be remedied by the introduction of virtual benchmarks a few meters above the surface. ImageModeler also can become stubborn or even unstable when the number of features in the scene under construction gets large.  Nonetheless, ImageModeler is excellent software for obtaining good quantitative results in a simple way.

Figure 3-15 in the Apollo 11 Preliminary Science Report is a camera-station map compiled by R.M. Batson and K.B. Larson at the USGS soon after the mission.  (A camera station is the location of the camera when a particular photo was taken.)  The map is dated 11 August 1969.  See, also, a re-drafted, color version by ALSJ Contributor Thomas Schwagmeier.  The methods used by Batson and Larson were necessarily simplistic but were chosen to allow rapid compilation of a map adequate for the Preliminary Science Report and for other early studies of the landing site.  They wrote in the Preliminary Science Report:

The surface traverse and sampling activities of the astronauts have been reconstructed from clues provided by the voice transcript, from review and analysis of the lunar television pictures, from analysis of the 16-mm pictures taken with a time-sequence camera mounted in the LM cockpit, and from detailed study of photographs taken with Hasselblad cameras before, during, and after the EVA. The camera stations for Hasselblad survey panoramas taken on the EVA were located by photographic triangulation from mosaics. Horizontal angles between the LM footpads were measured on the photographs as a function of  the known field of view, and the angles were drawn on tracing paper. The paper was then  manipulated over a scale drawing of the LM until the lines intersected the appropriate pads  at the proper place. Once the panorama locations had been determined, azimuths were measured from two or more panoramas to conspicuous features on the surface, and the positions of the features were plotted by triangulation to produce the map of figure 3-15. Individual photographs were located, and their orientations were measured by similar methods, using for control both the LM footpads and other features on the lunar surface that had been located by triangulation from the panoramas.

Because the graphical method by which these data have been obtained is fairly crude, azimuths shown for individual frames may have errors of 3 or more. Positions of most of the camera stations are probably within a 1.5-m circle centered at the point shown. The determinations are sufficiently accurate, however, to provide a useful control net for an overall view of the astronauts' traverse and a starting point  for more rigorous analytical photogrammetric measurements.

A 1978 USGS/Defence Mapping Agency site map, discussed in section 2.3, is probably derived from the "more rigorous analytical photogrammetric measurements" for which time became available in the years after Apollo ended.

2. 2010-11 Photogrammetric Revisions to the Camera-Station Map

Visual study of the 1969 map convinced VP that it is quite schematic and not very precise. An initial photogrammetric analysis with ImageModler produced improved locations and orientations for each image, along with locations for boulders and the US Flag, TV, LRRR, and PSEP.  The initial analysis made use of 116 of the 123 photos Neil and Buzz took during the EVA.  As with the work of Batson and Larson, all locations are calculated relative to structures on the LM.  Of the seven images that were not used, 5904 is an accidental image of one of the spacesuits, and is the only one of the 123 images that can not be placed by any means.  Five of the others are 5876 to 5880, photos documenting the bootprint penetration experiment Buzz did for the soil mechanics experimenters.  As discussed in Section 5.2, the two bootprints Buzz made at this spot have been identified in photos taken later in the EVA and out Buzz's window after the EVA.  This allows placement of the five documentation photos, which are shown with empty arrowheads.  Finally, 5966A is the second of seven images exposed when Neil advanced the film at the MESA, before removing the magazine.  It shows only an underexposed, blurred image of the MESA interior but can be placed with confidence close to the MESA. 5966A is also shown with an empty arrowhead.

Of the 116 images used in the initial photogrammetric analysis, the eight photos Neil took near the southwest rim of Little West, 5954-61, were not accurately placed because the locale is up-Sun of the LM and because only distant benchmarks can be identified in the Pan 5 images.  However, as is discussed more fully in section 2.1.5, these eight stations can be placed with good accuracy using local photogrammetry and specific features seen in both the Hasselblad images and LROC images of the site.  The Pan 5 images are shown with empty arrowheads.


In summary, accurate camera-station locations were determined in the overall photogrammetric for a set of 108 out of the 123 photos Neil and Buzz took during the EVASeven of the 108 are LM inspection photos that were not shown on the 1969 map.  Of the remaining 15 images, 14 could be placed using local photogrammetry and/or other information.  Of the 123 EVA photos, only 5904 could not be placed at all.

Note that the map also includes the rims of Double Crater and eight small small craters.  These rims were defined using photgrammetric determinations of the locations of small rocks on the rims.  These craters are discussed in Section 4.4.


24 January 2012 revision of a11psrf3-15

This 24 January 2012 revision of the Apollo 11 camera-station map is based on photogrammetric analysis done for 116 of the 123 Hasselblad images taken during the EVA.  Six others were placed by alternate means.  Only one photo, 5904, could not be placed.  The arrows show azimuthal pointing of the images, with arrow length indicating vertical tilt.  Each small dot represents a location for a camera station (blue) or a rock (red).  Boulders labeled with Roman letters can be identified in LROC images. For Pans 1, 2, 3, and 4,  all of the camera locations and orientations were calculated in the overall photogrammetric analysis. The Pan 5 stations were determined in a separate analysis discussed in Section 2.1.5.  In each panorama, the central location of the stations is plotted as a violet dot.  A violet circle shows the characteristic distance of the stations from the pan's central point; and the dashed circles indicate mean-square deviations.  Because of the large number of camera stations near the LM ladder, Pan 1 information has been moved to an empty area northeast of the LM.  See, also, an animated comparison  between the original 1969 map and the revision.  The major differences are: (1) the locations of the LRRR and PSEP and associated camera stations, which are farther south of the LM in the new map than in the original; (2) camera station locations near the MESA (Quad IV) on the northwest side of the LM; and (3), the detailed distribution of camera stations within each panorama are now available. (Click on the image for the full map in PDF format.)




Batson and Larson estimated that camera station locations in the original 1969 map were accurate to about 1.5 meters and that azimuths were accurate to 3 degrees.  Comparing the original map with the revision, although we see that there are location differences great than 1.5 m, in many cases it is a good estimation, especially for camera stations not far from the LM. As for the 3-degree azimuth-error estimation, in most cases photogrammetric azimuths differ by less than 3 deg from the 1969 determinations. Azimuthal differences are larger mostly for camera stations  with large location differences between the 1969 and 2010 results.  The accuracy of camera-station locations may be lower for shots where only relatively distant boulders are visible, particularly in the case of Pan 4 photos taken toward the east.  As mentioned above,  the special case of Pan 5 required a separate photogrammetric analysis and is discussed in detail in section 2.1.5.

2.1 Panoramas


Panorama Camera Stations



Camera stations for the five panoramas.  For each pan, the central location of the stations is shown with a violet dot and the characteristic distance from that central point is shown with a violet circle.  Mean-square deviations are indicated by dashed circles.  Azimuth arrows for photos taken by Neil are in blue; those taken by Buzz in green. (Click on the image for a larger version in PDF format.  See, also, an overlay on the Dec 2009 LROC image, M116161085R)





The following table lists the panoramas and the camera stations in each.


Pan No. and Location
No. of frames
Frame Sequence (AS11-40-)
Characteristic distance
from central point (meters)
Mean-square deviation
(meters)
Pan 1, Foot of LM ladder
9
5850-5858
0.60
0.16
Pan 2, 10m west of ladder foot pad,
on the rim of Double Crater
12
5881, 5882, 5882A, 5883-5891
0.82
0.33
Pan 3, 10m north of plus-Y(north) footpad
12
5905-5916
0.89
0.16
Pan 4, 20m southeast of SEQ Bay
12
5930-5941
0.51
0.18
Pan 5, rim of Little West Crater (partial)
8
5954-5961
0.66
0.30


While taking a panorama, the astronaut took one frame and then turned about 30 degrees before taking the next frame.  Except for the special case of Pan 5, all the pans were taken in clockwise order, with the astronaut turning to his right between frames. 

On a relatively level surface, the astronaut is able to turn without moving much off one spot on the ground. If we could see the pattern of footprints made while the pan was taken, it would be a tight pattern.  However, because both Neil and Buzz took their pans with the Hasselblad out in front of the RCU - Neil with the camera on the RCU bracket and Buzz holding his camera out in front - camera stations (identical to the center of the film plane) will be on a circle 0.5 to 1.0 meters in diameter around the footprint pattern.  Among other things, the outward displacement of the film plane from the turn axis will generally produce some stereo separation between sequential frames.  Remapped images generated with panorama-stitching software Hugin give an impression of the direction and amount of the stereo separation and, as well, can indicate cases in which the astronaut moved forward or back between frames.

Pan 5 was taken in a very different manner.  Neil wanted to get a portrait of Little West Crater and was in a hurry.  He took one photo, moved about a meter east and took three more, turning to his left between them, and then moved another meter east and took two more, turning to his left between them.  He then moved west and took two final frames toward the west, turning left between them.  Two pairs of images give excellent stereo.



2.1.1 Pan 1

Apollo 11 Pan 1 with times marked
              when Neil turned between frames

Pan 1 camera-station map, with the location of the MESA-mounted TV camera marked (x).  Times when Neil turned to his right between frames are discussed in the text.  (Click on the image for a larger version.)



Neil took this pan just west of the ladder.  Pan 1 is the only one of the five pans for which we have a TV record.  The Apollo 11 EVA video was digitally restored in 2009, which gives us good detail of Neil's movements.  Colin Mackellar has produced a 2 min 31 second video clip ( 14 Mb ) which starts at about 109:30:49, four seconds before Neil tells Houston, "I'll step out and take some of my first pictures here."  Neil begins by adjusting the f-stop and/or focus on the Hasselblad, then takes up-Sun photo AS11-40-5850.  He makes the first turn to his right 49 seconds after the start of the video clip and then, five seconds later, sidesteps a little farther from the MESA-mounted TV camera.  This sidestep may explain the relatively large WSW displacement between the 5850 and 5851 stations. In a table of camera station locations, the 5850 station is an outlier.  Neil's subsequent turns are at 1:08, 1:22, 1:32, 1:36, 1:50, 1:55, 1:59.  Because this was Neil's first lunar panorama, he may have taken his time while he was taking the first few frames.  The interval between the first turn/step and the next turn is 14 seconds.  The next two intervals are 14 and 10 seconds.  With one exception, subsequent intervals between turns are 4-5 seconds, perhaps indicating that Neil had gained confidence that he could turn between frames without trouble.  The exception is the 14-second interval during which Neil took 5855. As indicated on a decal on the top of flown Magazine S, photographed at the National Air and Space Museum in 2006 by Ulrich Lotzmann, Neil planned to change the f-stop setting from 5.6 to 8 or 11 when taking down-Sun photos. In the video, it appears that, in preparation for taking 5855,  he increases the setting at about 1:39,  takes 5855 at about 1:44, and goes back to 5.6 after 5855 at 1:45.  The unprocessed scans are available on the LPI website.

On the first lunar pan, Neil got  significant overlap only in the sequence 5855-58.  These four images have been combined as a mini-pan.  A side-by-side comparison of the remapped images generated by panorama-stitching program Hugin has been made by horizontally aligning a horizon feature near the center of the overlap region for each pair of images. In each pair, a vertical white line is drawn downward near the center of the overlap region in the lefthand image.  A horizontal white line is then drawn low in the left hand image.  In the righthand image, yellow traces of the white lines are drawn from rock-to-rock, shadow-to-shadow.   An anaglyph made from a pair is displayed between the two images.  For these three pairs of images, the yellow traces of the vertical lines slope down to the left, indicating that, as expected, the camera station for the righthand image is to the right of the camera station corresponding to the lefthand image.   Terrain, particularly relatively large craters, can produce local distortions of the yellow trace of the vertical white line.  In lower part of each righthand image, upward displacement of the yellow traces of the horizontal white line in the lefthand image would indicate that Neil moved back between a pair of frames.  Downward displacement would indicate that he moved forward.
Side-by-side comparisons of 5855 to 58

Side-by-side comparisons of images 5855-58, indicating that, as Neil turned to his right between frames, the center of the film plane also moved to the right.  In these three pairs, Neil got enough overlap to provided unintended stereo. An anaglyph is displayed between each pair.  Note the effect on the vertical yellow line of the crater on the left in 5858.  Comparison of the horizontal white and yellow lines indicate that Neil did not moved noticeably forward or back during this sequence.  (Click on the image for a larger version.)






2.1.2  Pan 2


Apollo 11 Pan 2 Map 8 January 2012

Pan 2 camera station map.  The distribution of stations is elongated roughly along the trend of the raised crater rim, indicating that Buzz was careful where he stood.  The rim of the western component of Double Crater is drawn at the outer edge of the relatively steep inner wall.   (Click on the image for a larger version.)


Buzz took this pan near the southern edge of the LM shadow about 10 meters from the pluz-Z footpad.  During the post-flight Technical Crew Debriefing, he said that he took the pan with the camera handheld. In the next figure, the camera stations are plotted on a detail from the deconvolved version of the  22 December 2009 LROC image, M116161085R.  This part of Double Crater has a raised rim, as can be seen in a mini-pan assembled from three frames from Neil's ladder pan, AS11-40-5852-54.  The footprints he made while taking the pan can be seen in oblique views provided by various frames he took out his window after the EVA.  An example is a detail from A11-37-5488, which is shown along with the camera station map with scaled bootprints added.  The sole of the boot is 33 cm long by 15 cm at its widest, so a 3 x 3 array of bootprints would cover a rectangular area about 1.0 by 0.5 meters on a side.  Other than the elongation of the overall pattern, there are no outliers in the distribution of stations.  Details are listed in the  table of camera station locations.




Pan 2
              Map on M116161085R and M175124932

Superposition of the Pan 2 map on a deconvolved detail of LROC image M116161085R provided by GoneToPlaid and a detail from M175124932LRM116161085R was taken with the Sun low in the east and emphasizes the break in slope at the top of the inner, eastern wall of the crater.  The elongation of the pattern of camera stations along the crater rim suggests that Buzz was careful about where he stood.  (Click on the image for a larger version.)


The 22 December 2009 LROC image was taken with the Sun 8.2 degrees above the eastern horizon and shows the eastern half of the crater filled with shadow.  Pre-EVA (AS11-39-5756) and post-EVA (AS11-37-5501) photos taken out Neil's window show the crater with the Sun 10.9 and 15.1 degrees above the horizon, respectively.  In the pre-EVA photo, some of the inner, eastern wall of the crater is in shadow, whereas the post-EVA photos, taken 8 hours later, show very little shadowing,  These images suggest that the inner slope at the eastern end of the crater is 10 to 15 degrees.
 
There are two sequence of frames showing adequate stereo separation:  5882a-5884 (mini-pan including 5885) and 5888-90 (mini pan).



5882-84 side-by-side comparison
Side-by-side comparison of frames 5882a to 5884, showing the view from northwest to north. Although the camera station map suggests that Buzz took 5883 forward of both the 5882a and 5884 locations, comparison of the horizontal white and yellow lines within each pair do not support that conclusion.  The indicated relative error of the photogrammetrically-determined 5883 location is about 1 meter.  As expected, both vertical yellow lines slope downward to the left.  (Click on the image for a larger version.)



The 5883 station position may contain error of ~0.5 m due to a slightly-wrong focusing distance set at the time of its addition to the IM scene model. IM refuses to accept a correction.


side-by-side 5888-90
Side-by-side comparison of 5888-90 showing the eastern component of Double Crater and part of the western component.  The yellow horizontal line in 5889 is lower than its white counterpart in 5888, indicating that Buzz moved a bit forward between the two frames. Note the significant effect of the craters on the shapes of the vertical yellow lines.  (Click on the image for a larger version.)






2.1.3  Pan 3

Apollo 11 Pan 3 Map 8 January 2012


Pan 3 Camera Station Map.  Buzz took this pan about 8 meters north of the plus-Y footpad, on the rim of an 8-m crater. A labeled detail from the  22 December 2009 LROC image shows the camera station location relative to the crater.  (Click on the image for a larger version.)





As can be seen in a detail from Neil's Pan 4 photo AS11-40-5932, the Pan 3 crater does not have a raised rim, so Buzz did not have to be quite as careful with his footing as he was when taking Pan 2.  As was the case with Pan 1, the stations are well ordered around the mean-distance circle,  The exceptions are AS11-40-5915 and 5916.  Both show parts of the LM, so the station locations are well determined. In 5916 we see the back of Neil's PLSS.  Neil is just to Buzz's left, a bit closer to the LM, and is using the Apollo Close-up Stereo Camera. What may have happened is that, after Buzz took 5915, he realized he would have to go around Neil on the north side and get far enough west to finish the pan.  Neil may have backed in the field-of-view just as Buzz was taking 5916.  Another factor may have been a fist-sized rock on the south edge of the mean-distance circle.  Details from the best photos we have of this rock - AS11-40-5858, taken as part of Pan 1; and 5929 and  5932, taken as part of Pan 4 - suggest that it sits on the southwestern rim of a small, fresh crater.  The rock and fresh crater may have contributed to Buzz's decision to move around them on the north side.  In 5932, note the patch of undisturbed soil east of the rock, which is another indication that Buzz moved from the 5915 station to the 5916 station on the north side of the rock.


Side-by-side comparison of 5907-11


Side-by-side comparions for 5907-11 (mini pan), covering the Pan 3 crater, labeled "α" in the camera station map.  The crater isn't very deep, so it doesn't have as large an effect on the vertical yellow traces as Double Crater did in the Pan 2 comparisons. The photogrammetric map indicates that Buzz moved back between 5908 and 5809, and then forward again before taking 5910.  The side-by-side comparisons do not support that result.  The implied position error is about 0.5 m.  (Click on the image for a larger version.)




2.1.4  Pan 4


Apo;;o 11 Pan
              4 Map 8 January 2012

Pan 4 Camera Station Map.  Neil took this pan about 17 meters from the SEQ Bay on an azimuth about 30 degrees south of east.  (Click on the image for a larger version.)




Neil took this pan after taking a few photos of Buzz offloading the EASEP packages.  Details of this pan show the importance of benchmark distance in determining camera station locations. As can be seen in a comparison, the five camera stations (5930, 31, 32, 40, and 41) for showing parts of the LM and/or boulders near the LM are well ordered along the circumference of the mean-distance circle.  The other 7 camera stations in the pan rely on distant benchmarks and are not well ordered.  As detailed in the table of camera station locations, the mean distance of the 12 stations from the central point is 0.428 meters, with a standard deviation of 0.272 meters.  The five stations on the west side of the pan have a mean distance of 0.310 meters and a standard deviation of 0.054 meters.  The remaining seven stations have a mean distance of 0.461 meters and a standard deviation of 0.305 meters.  Neil demonstrated while taking Pan 1 that he was able to turn in a systematic way without trouble, suggesting that the distribution differences between the two groups of Pan 4 camera stations is due unavoidable photogrammetric uncertainties when only distant boulders are available for use as benchmarks.

Note that the largest displacement of a camera station from its expected position on the violet circle is about 1.0 m, in the case of 5934.

With the exception of the up-Sun images, 5936 and 37, Neil got enough overlap between adjacent frames for assembly of a nearly complete panorama (5.7 Mb).  Side-by-side comparisons of the ten overlapping frames demonstrate that Neil took the pan much as he did Pan 1, turning on about the same spot with little motion forward or back between frames.

Side-by-side comparisons of 5930 to 5934

Side-by-side comparisons of frames 5930 to 34.  In the photogrammetric analysis, the 5933 and 5934 camera stations are not part of a well-ordered sequence comparable to those of Pan 1 and Pan 3.  The side-by-side comparisons demonstrate that Pan 4 was, indeed, taken in a very orderly fashion and, that, as expected, the scatter in the photogrammetrically-determined locations is due to the availability of only distant boulders for doing triangulation.  (Click on the image for a larger version.)





Side-by-side comparisons for 5937 to 41 plus 5930

Side-by-side comparisons for frames 5937 to 41, plus 5930.  This sequence tells the same story: Neil took a well-ordered pan.  Note that Neil actually took 5941 from a spot to the right of 5930.  To make a comparison with 5930 attached to the end of the sequence,  the white lines were drawn in 5930 and the yellow traces on 5941.  Because of Neil's shadow, two vertical lines were used. Note that the vertical displacements of the horizontal lines in 5930 and 5941 indicate that Neil ended the pan a very short distance back from where he started.  (Click on the image for a larger version.)






2.1.5  Pan 5

Pan 5
              result from separate analysis
Neil took Pan 5 about one crater diameter from the rim of a 4.5-m crater just inside the rim of Little West Crater, about 38  meters east of the Pan 4 location. This map shows the station locations determined in the separate analysis done for Pan 5.  See, also, a version superimposed on details from LROC images M116161085R and M175124932LR.   (Click on the image for a larger version.)




The Pan 5 station locations calculated in a full, 116-station photogrammetric analysis had some obvious discrepancies, particularly with regard to their locations relative to the prominent 4.5-meter crater just a few meters north of the spot where Neil took the pan.  These discrepancies were due to (1) technical issues in using IM when the number of benchmarks is large; and (2) the fact that the only benchmarks visible in photos 5954-59 were distant boulders. 

To remove these discrepancies, we performed a three-step process to determine the correct station locations:

(1) We did a dedicated photogrammetric analysis for 5954-5959 using about fifty local rocks as benchmarks.  A labeled detail from the assembled pan and a plan view show a set of fifteen of these rocks. The analysis demonstrated that the relative positions and azimuths of frames 5954 and 5956-59 differed only slightly from those found with the Pan  photos included in the full photogrammetric analysis.  The differences are well within the range of expected errors and are not shown.  The local analysis also showed that, although the azimuth calculated for 5955 was virtually the same as in the full analysis, the station location was virtually identical to that of 5957, instead of being about 2 meters NNE of 5957.  As discussed below, detailed intercomparisons of the 5955-5957 images confirm that the the three were taken about the same spot.

(2) The local photogrammetric analysis is not directly tied back to images of the LM and, therefore, only gives relative locations of the six stations.  However, Neil took Pan 5 near a sharp-rimmed, fresh crater just inside the southwest rim of Little West Crater.  Consequently, we included in the local analysis ten small rocks on or near the rim of the 4.5-m crater.  The photogrammetric locations of these ten small rocks was then fit with a circle.  The pattern - circle and stations - was then scaled so the radius of the circle matched the 4.5-m radius of the small crater and was then shifted to place the circle over the crater rim.

(3) As a final step, stations 5960 and 61 were moved in tandem along a line defined by the 5961 central azimuth until the azimuth from 5960 to the true position of boulder j2 agreed with the value of 15 degrees to the right of the 5960 central azimuth derived from the 5960 image.  The two stations were moved 0.9 meters toward the other Pan 5 stations.


Three-step movement of Pan 5 station
              to proper location


Animation illustrating the three-step process used to place the Pan 5 stations at their proper positions near the 4.5-m crater just inside the southwest rim of Little West Crater.  Note that the red dot near the top left in the figure indicates the actual position of boulder j2, with the sunlit face on the right (east) and the shadow on the left.   (Click on the image for a larger version.




The result can be confirmed by noting that, in LROC images taken with the Sun above 30 degrees elevation, Neil's track out to Little West shows up quite well.  Examples include M109080308R, taken at 23:50:40 UTC on 1 October 2009 with the elevation 87.8;  M122054682R, taken at 03:50:15 on 1 March 2010 with the solar elevation  62.3; M175124932LR taken at 09:34 UTC on 5 November 2011; and  M113799518R, taken at 14:44:11 UTC on 25 November 2009 with the solar elevation 35.8.  Note that, with the Sun above 30 degrees or so, there is relatively little surface-brightness variation.  Increasing contrast to bring out subtle features like astronaut tracks produces images that are "grainy" near the resolution limit which, for three of the images is about 0.5 meters.  M175124932 was taken from 25-km altitude and has a resolution of about 0.25 m. An animation compares the new Pan 5 station locations in M109080308, M113799518, and M175124932.  It is pleasing that the new analysis puts Pan 5 at the end of the Neil's track.


2.1.5.1  Camera Stations 5954-59

As indicated in the map above, Neil began Pan 5 with 5954, taken about 1.5 meters WSW of the ALSCC.  He then moved about a meter southeast and took a set of three frames, starting with 5955 which shows a view aimed a bit more easterly than 5954, and then turned to his left to take 5956, and left again for 5957.  Neil then moved about a meter ENE and took 5958 and 59, turning left between frames.  He finished the sequence by moving to a spot beyond the ALSCC to take 5960, which shows the TV and other benchmarks north of the LM, and 5961, which is aimed at the LM.

In the following, a series of side-by-side comparisons confirm the relative locations of frames 5954 to 5959.  We begin with two pairs - 5956-57 and 5958-59 - with excellent stereo separation.


Side -by-side comparison of 5957 and 56

Side-by-side comparison of AS11-40-5957 (left) and 5956 (right). As shown in the photogrammetric map, 5957 was taken slightly to the left of 5956. This is confirmed by the fact that the yellow trace in 5956 of the vertical white line slopes down to the left.  In addition, there are only very small vertical differences in the  intersections of the horizontal yellow lines with the vertical yellow line  compared with their white counterparts.  This indicates that the two camera stations have no appreciable forward or backward position difference.   (Click on the image for a larger version; and click here for a full version of the anaglyph.)




While the side-by-side comparison of 5957 and 56 confirms the relative locations of the two camera stations, the anaglyph made from the two images shows two major breaks in slope which conceal portions of the crater floor beyond each of them.  These breaks in slope are on the right in 5957 and across most of the image in 5956. 

Details of breaks in slope
Comparison of details showing breaks in slope in 5957 (top) and 5956 (bottom).  The dashed red-lines approximate breaks in slope.  (Click on the image for a larger version.)



The breaks in slope can be identified by three techniques.  First, at some places there is a discernible change in image clarity across the breaks  The images were taken at 74-foot focus, so the surface on the near side of a break in slope will be more out-of-focus than the surface beyond. Second, patterns of rocks and shadow on one side or the other of a break in one of the images can be identified at the same relative location in the other image.  However, a pattern across a break in one frame will have a lateral discontinuity in the other frame.  For example, in 5956 a pattern beyond a break in slope will be displaced to the the right compared to its location in 5957. And third, rocks and shadows that are visible in one frame of a pair may not be visible in the other if the latter was taken behind the first.

One other pair of frames, 5958 and 5959, form an excellent stereopair.  A side-by-side comparison confirms  the relative placement of the camera stations in the photogrammetric map, with 5959 having been taken just to the right of 5958 and with no significant forward/backward displacement.  Click here for a full resolution version of the anaglyph.

The photogrammetric map indicates that 5958/59 were taken to the right and forward of 5957/56.  Image 5956 has no overlap with either 5958 or 59, except right at Neil's feet.  Image 5957 has a useful amount of overlap with both 5958 and 59.



Side-by side of 5957 with both 5958 and 5959



Side-by-side comparisons of 5957 (center) with both 5958 (right) and 5959 (left). The white vertical and horizontal lines in 5957 are traced in yellow on each of the other images.   (Click on the image for a larger version.)



The side-by-side comparisons between 5957 and both 5958 and 5959 show, not surprisingly, nearly identical yellow traces of the vertical line, indicating nearly identical displacement of 5958/59 to the right of 5957.  The fact that the yellow traces of the foreground horizontal line both slope down to the right is another indication that the 5958/59 stations are to the right of 5957.  Both stations are also forward from 5957, as can be seen by the fact that the intersections of the foreground yellow traces with the vertical yellow traces are lower (farther from the horizon) than the corresponding intersection in 5957.  The forward displacement is large enough to preclude good stereo of the foreground.


Rocks and shadows hidden by a break in slope

Comparison of details of 5957 and 5958 showing the 4.5-m crater. The dashed portions of the yellow traces indicate parts of the surface that are visible in 5958 but are hidden in 5957 by the crater rim. This is a clear indication that 5958/59 were taken forward of 5957.  (Click on the image for a larger version.)




The special photogrammetric analysis done for 5954-59 shows that the 5955-57 stations are tightly bunched.  We have seen that 5957 was taken a short distance to the right of 5956, with enough separation to give good stereo.  A comparison between 5955 and 56 (next below) shows that the intersections between the yellow traces in 5955 are slightly above the corresponding intersections in 5956, indicating that 5955 was taken slightly behind 5956.

Side-by-side comparison of 5955 and 5957

Side-by side comparison between 5956 (left) and 5955 (right).
(Click on the image for a larger version.)

In addition, portions of rocks visible in 5956 are hidden in 5955.  A detail showing the break in slope that hides part of the central mound in both images clearly shows that more of the central mound is visible above the break in slope in 5956 than in 5957.  A second detail, covering the break in slope nearest Neil, shows similar differences.  The fact that the yellow trace in 5955 of the vertical white line is very close to vertical indicates that the 5955 station is virtually on the backward extension of the 5956 aiming azimuth.



The photogrammetric map shows 5954 and 5956 where aimed in the same direction, with 5956/7 having been taken about a meter to the right.  It appears that 5956 may have been taken a short distance farther into the scene than 5954.

Side-by-side comparison of 5954 and 5956

Side-by-side comparison of 5954 (left) and 5956 (right). 
(Click on the image for a larger version.)

The fact that the horizontal yellow traces slope down to the right and the vertical yellow traces slopes down to the left confirm that 5956 was taken to the right.  In addition, the yellow intersections are below the white intersections, indicating that 5956 was taken forward (in the northeast direction) of 5954.  See, also, a full resolution version of the anaglyph.



2.1.5.2  Camera Stations 5960-61


Side-by-side comparison 5961-60-59

Side-by-side comparison of 5961, 60, 59.  Stereo information available from the image pairs is strongly influenced by relative displacement of the camera stations along the azimuths defined by the centers of the overlap regions.  The center-line azimuth of the 5961/60 overlap is roughly 15 degree north of west; and the center-line azimuth of the 5960 overlap is roughly 40 degrees north of west. The anaglyphs have been rotated left so that the red and blue images of prominent features line up horizontally.  In each case, a rotation of 45 degrees gives reasonable stereo.  (Click on the image for a larger version.)



Of the final two images, 5961 shows the LM and various benchmarks near it, while  5960 shows the TV camera near the left edge.

As indicated by the slight leftward slope of the vertical yellow trace in 5960 (above), 5961 was taken slightly to the left of 5960.  The upward displacement of the horizontal yellow traces in 5960 indicate that 5961 was taken a short distance farther into the scene than 5960.  The leftward slope of the vertical yellow trace in 5959 indicates that 5960 was taken to the left of 5959.  The leftward displacement of 5960 from 5959 is significantly great than the leftward displacement of 5961 from 5960.  Similarly, the upward displacements of the horizontal yellow traces in 5959 indicates that both 5960 and 5961 were taken much farther into the scene than 5959.


To summarize, comparisons between pairs of Pan 5 images that have some overlap demonstrate that the apparently haphazardous distribution of camera stations is actually a reasonable representation of how Neil took this set of photographs.  Specifically, Neil took 5954 near the ALSCC, then moved a meter east, perhaps to get farther away from the ALSCC.  He took 5955, turned slightly to his left - moving forward a bit in the process, took 5956, and then turned left again to take 5957.  Next, he moved about a meter farther east and took 5958 and 5959, turning slightly to his left between the frames.  Finally, he moved toward the ALSCC,  took 5960, aiming a bit north of the LM, and finished off with a shot of the LM, 5961.




2.2 Comments on images and camera stations

General comments: Figure 3-15 in the Apollo 11 Preliminary Science Report (hereafter, the Preliminary map) is in good general agreement with the new photogrammetric results. Most differences between the two maps are within the ranges of uncertainty estimated by Batson and Larson  Notable exceptions include  (1) tilt angles of many stations shown in the Preliminary map are estimated erroneously; (2) some camera stations are misplaced, such as 5892, 5921, and 5967-70; (3) azimuths are sometimes wrong, as with 5942-44; (4) distances from LM to the PSEP and associated camera stations are underestimated; and (5) individual stations within each panoramas were not determined by Batson and Larson.



5851: This is one of a few photos in Pan 1 and Pan 2 that include in the field-of-view a very old, eroded ~22-meter crater just next to the Double Crater on the southeast. This crater is visible in LROC images - such as a labeled detail from 22 December 2009 - but its presence is difficult to pick out in EVA photos. This crater is between the foreground and the ~6-m  ι crater (seen just in front). Boulders l1 and l2, which are identifiable on LROC images, are near the horizon to the left from the center, boulder a is to the right from the center, the top of boulder s seen just below a to its left. 

5855-56: A sharp, fresh crater is seen on the righthand edge of 5855 and at the center of 5856.   Photogrammetric analysis confirms that this is the crater identified in a details from LROC images M131494509L and M111443315R.  The crater is about 70 meters from the LM.  See, also, a labeled version of a pan Buzz took out his window after the EVA and a similarly-labeled animation made from nine LROC images of the site.

5858-59:  The new locations show that Neil moved about 3.8 meters north from the Pan 1 location before he took 5859.

5859-61: In a map detail, the three camera stations marked with red dots.  These indicate that Neil moved slightly to his left after taking the first of the three frames, then farther left and forward after the second.  A side-by-side comparison of 5860 and 61 shows that there is no significant forward or backward separation between the two.  5859 has significant motion blurring; 5860 is better; but 5861 is the only one of the three what is reasonably sharp.

5862-63:  These two images of Buzz crawling out of the LM hatch were not shown in the Preliminary map.

5863-65:  A tight cluster of stations,  less than 0.5 m from each other.

5866:  The bright boulder visible above the MESA and beyond the inside edge of the north strut can also be seen in 5903, the well-known, full-length portrait of Buzz.

5867-69:  All three photos made from nearly the same place, with only slight azimuth and tilt changes. Made from the rim of the older, eastern component of Double Crater.

5871: During early stages of the photogrammetric analysis, the 5871 station location depended primarily on distant boulders.  During September 2010, a number of very small pieces of rock were added to the benchmark pool so that station locations could be determined for 5865 and other close-up photos.  One of us (VP) realized that some of these small rocks were in the 5871 field-of-view.  Forcing IM to accept these new benchmarks in re-positioning 5871 required painstaking work and about 40 recalibrations.  The net result is that the 5871 camera station shifted about 0.5 meters to its present location.  This exercise provides an order-of-magnitude estimate of the uncertainties in station location dependent solely on distant boulders.

5872-73: The azimuthal difference between these two photos is less than 2 degrees, with Neil moving forward along that line after taking 5872.  West Crater is near the horizon on the lefthand side of 5872 (detail) and can also be seen in 5873. The landscape is so flat that it is difficult to estimate distances.  As can be seen in a labeled detail from the 22 July LROC image, the southern portion of Little West Crater lies in the same direction as the portion of West Crater visible in these two images.  A detail from 5872 may show Little West, as labeled.  The southern portion of Little West blocks our view of the lower parts of various boulders located between the two craters.  See, also, a discussion in section 3.4 of a shadowed wall inside the east rim of an old, heavily-eroded crater immediately southwest of West Crater.

5874-75: Several boulders identifiable on LROC images are present.  The largest is boulder a.

5876-80:  These Boot Penetration Soil Experiment photos are not included individually in the camera station map because determining the locations would be a very tricky photogrammetric task.   However, their positions and azimuths are found approximately from photos where BPSE area is clearly visible: 5884/85, 5905, various post-EVA window photos, and the 16-mm film shot out Buzz's window.
 
5881-91: Panorama 2 made from the rim of the younger and sharper, western component of Double Crater.

5883: The station position may contain an error of ~0.5 m due to a slightly-wrong focusing distance set during modeling. Correction of this error would be tricky. Actual location is to the south of the location on the map, so the actual location is closer to the panorama central point.

5888: In a labeled detail, the old eroded crater mentioned in the comment for 5851 (above)  is in the center just next to the eastern rim of Double Crater. Left portion of t-group of LROC boulders are to the left near the horizon (where the southern portion of the rim of West crater is seen), l1 and l2 are near the horizon to the right.

5892/93: 5892 was wrongly placed in the Preliminary map. It was shot in front of Quad I, not Quad II. In fact, 5892 and 5893 were shot from essentially the same location (calculated horizontal separation ~16 cm) and at similar azimuths (difference ~13.6 deg). It appears that, having positioned the camera to shoot under the LM in 5892, Buzz immediately repositioned himself slightly, tilted his camera up by ~45 deg and took 5893, showing the Ascent Stage. It's interesting that there are no common details in 5892 and 93, so the camera locations were calculated photogrammetrically completely different sets of benchmarks. However, photogrammetry reveals that the locations are nearly coincident. This pair may serve as an indirect demonstration of the accuracy of the model: such close coincidence of two consecutive camera locations cannot be accidental.

5894: Photogrammetric position less than 0.5 m from 5892/93.

5897/98/99: Not present in the Preliminary map.  These three photos of the plaque have nearly identical station locations, virtually over the center of the plus-Z footpad.  5897 and 98 are separated by about 2 cm, while 5899 is about 8 cm from both.  Inclination, azimuthal, and rotational differences are small.  The three inclinations are 30.3, 30.1, and 28.7  degrees below horizontal, respectively. Neil can be seen taking these photos in clip from the 2009 restoration of the video linked at 110:41:07.  Neil took them with the camera handheld far enough forward that it was over the center of the footpad.

5900: Not present in the Preliminary map.  This final plaque photo was taken from a location about 0.8 m northwest of the center of the plus-Z footpad. The camera inclination is only 13 degrees below horizontal.

5901/02: These two photo were taken from virtually the same spot.  Between the frames, Neil turned to his left, not to his right as the Preliminary map shows.  Boulders  b and c are the largest LROC boulders visible in these to images.

5903: Shows both b and c.

5904:  This is the only one of the 123 EVA photos for which a location can't be assigned.  No recognizable features except the suit are visible.

5905/16: Panorama 3, taken from the rim of the ~8-meter crater ι to the north of the LM.

5905: The Preliminary map shows the flag well to the right of center and indicates that the SWC should be in the frame.  The new map and actual photo show the flag centered and the SWC out of the frame.

5907/08: Show the "fresh" crater and boulders in e-group.

5909/10/11:  Show LROC boulders to the north and northeast of the LM.

5910: In the Preliminary map, the estimated azimuth points too far left.  Perhaps the authors of the Preliminary map did not recognize the relative brightness of the Sun-facing inner wall of the α crater.

5912:  Camera tilt ~14 below the horizon.

5915/16:  Buzz moved more than 1.6 m to his right between the frames, probably trying to avoid Neil, who was moving toward him from the right, carry the ALSCC.  Despite Buzz's efforts, Neil's back appears in 5916.

5917/18/19:  The tilts of 5917 and 5919 were overestimate in the Preliminary map.  Buzz appears to have taken these three along a line, stepping to his left about 1 meter between the frames.

5920/21: The Preliminary map shows 5921, which is a view under the LM of the descent engine bell, as having been taken out in front of Quad IV and aimed toward the southeast. The shadows show that it was taken out in front of Quad III, aimed toward the southwest.  It was taken only ~0.3 m north of 5920.  Buzz turned to his left by ~100 deg between the shots.

5922:  Not shown in the Preliminary map.  Azimuth very close to that of 5921.

5923/24:  Not shown in the Preliminary map.

5925/26: The new locations differ from those in the Preliminary map only by centimeters.  The tilt of 5926 was underestimated in the Preliminary map.

5927/28/29:  Contrary to what is shown in the Preliminary map, these three images were shot from the same location, all within ~10 cm of each other.

5930-41:  Panorama 4 was made near the northern rim of the old, eroded crater mentioned in the comments for 5851 and 5888.  This old crater is only evident in the LROC images taken with the Sun at low elevation.  Note that the azimuths of the first (5930) and last (5941) frames differ by only about 6 deg.

5938:  The azimuth crosses the very old, eroded crater mentioned in the comments to 5851 and 5888. Although the crater interior is in the foreground, only the far (southern) rim can be picked out as a slight rise that is brighter than the more distant surface and obscures part of it. As indicated by a line of small, yellow dots in a detail, the rim line passes through the row of reaseau crosses just below the horizon. The rim line hides the lower part of the boulder a.

5942/43/44: In the old map, these camera locations are closer to the LM and direction arrows point more toward the east than in the new map.  The new positions and orientations are much more consistent to the location of the crater Buzz is passing and the locations of the stones beyond it.  The Preliminary map indicates that Neil turned to his right between frames.  He actually turned left.

5945:  Azimuth very close to that of 5942.

5946/47:  Taking from the same location with the same azimuth.  Camera tilted up for the second image.

5948: The PSEP is actually to the left of center on 5948, not to the right as on the old map. Also, the small stones shown around the PSEP and LRRR on the Preliminary map are difficult to identify in the photos.

5949/50: Taken at the same location but with different azimuths and tilt.

5951:  Not surprisingly, the location on the Preliminary map relative to the PSEP is very accurate.  The tilt is overestimated.

5952:  Taken ~3.2 m from the LRRR.

5953:  Taken ~1.3 m from the center of PSEP; ~0.4 m from the western solar panel; camera tilt ~30 degrees below the horizon.

5954-61:  Pan 5 images taken at the end of the track Neil made running out to the southeast rim of Little West Crater.  Extensive discussion in  Section 2.1.5.

5954/55:  The largest boulder in these photos is c, a ~2-meter-tall boulder ~140 meters from the Pan 5 location.  Boulder c is ~315 m from the rim  of  West Crater, from which is was probably ejected.

5958/59: Boulder b, a 2.5-m, elongated rock is near the center of these images.

5965/66: Not shown in the Preliminary map.  While standing at the MESA, Neil advanced the film by seven frames before removing the magazine from the camera an stowing it in the ETB.  These two images show a small vertical slice of the surface in the southeast direction, including ι crater.  The station locations were determined using a selection of small rocks as benchmarks.  Although the locations could be expected to be more uncertain than 5967-70, which show nearly full-frame views in the direction of the SWC shaft, the positions of the two groups of camera stations are separated by only about a meter.

5966A: This is a view into the MESA shadow and is so underexposed that only faint details can be seen.  However, similar details can be seen in the dark areas of 5965 and 5966.  We assume that 5966A was taken at virtually the same location as 5966.

5967/70:  The locations of these last four EVA images differ significantly from the locations indicated in the Preliminary map.  Their actual locations are within 0.8 m of 5965-66A.


2.3  1978 USGS/Defence Mapping Agency Site Map

Perhaps the most striking feature of the 1978 map compared with the 1969 map is the very different distribution of craters.  The craters sketched in the 1969 map were probably derived from the best Lunar Orbiter image, supplemented by photographs taken out the LM windows and on the surface.  Photogrammetric methods are not well suited to mapping crater rims.  Only small, fresh craters with raised, circular rims can be located accurately with trigonometry provided that camera stations are well defined.  Further discussion of craters can be found in Section 4.4.


1969-1978 comparison


Left: The 1978 map includes the locations of the TV, U.S. flag, LRRR, and PSEP along with trails made by the astronauts.  "ALSCC" denotes locations where the Apollo Lunar Surface Close-up Camera can be seen in various Hasselblad images.  Right: An overlay of the 1969 and 1978 maps indicates that, in the 1978 map, the TV and US flag are about 2.5 and 1.3 meters, respectively,  farther west and somewhat north of the 1969 mapped locations.  The SWC at the same location in both maps; and the LRRR and PSEP are 3.8 and 5.9 meters, respectively, farther south in the 1978 map. Differences between the two presentations of the craters is discussed below. (Click on the image for a larger version.)



One notable feature of the 1978 map is inclusion of the trails made by the astronauts.  These trails are clearly based on Figure 3-16 in the Apollo 11 Preliminary Science Report with some modification that probably resulted from the reanalysis.  In January 2009, Journal Contributor Scott Cruickshank recognized that Neil's outbound path to Little West as shown in the 1969 and 1978 maps was wrong.  Using the sizes of astronaut images in the TV record and tracks visible in images 5961, the last frame Neil took at the Pan 5 site, and 5962, which Neil took on the way back to the LM, Cruickshank was able to demonstrate that, rather than having started his run to  Little West from near the PSEP, Neil first went to the get the ALSCC, which he had left perched on a flat-topped rock near the LRRR and then ran directly to the spot where he took Pan and then back directly to the LM along a route close to that shown in both the 1969 and 1978 maps.  The path Cruickshank proposed is very close to the one seen in the 5 November 2011 LROC image, taken from 25-km altitude with a resolution of 0.25 meters.

The 1978 map was necessarily based on the same set of images (Lunar Orbiter, 16-mm descent film, and Hasselblads) as the original map, but does not include camera stations.  The next figure compares the 1978 map with the 2012 camera-station map and a detail from the December 2009 LROC image.  The 2012 map includes a dozen craters small craters with rim locations determined photogrammetrically; and astronaut trails revised by Thomas Schwagmeier, who used the  5 November 2011 LROC image to modify the trails shown in Figure 3-16 in the Apollo 11 Preliminary Science Report.

Compare 1969,
            1978, LROC

(Top) A comparison between the 1978 site map and the 2012 camera-station map shows excellent agreement for the locations of the TV, flag, SWC, LRRR, PSEP, and photogrammetrically defined crater rims.  (Bottom) A comparison between the 2012 map and a detail from the December 2009 LROC image between illustrates the quality of the work that went into the 1974 map. (Click on the image for a larger version.)



3. Boulders Visible in Hasselblad Images, LROC Images, and the Descent Film

Boulders - by definition, pieces of rock bigger than 25 cm - are large enough and scarce enough on the lunar surface that any particular example can often be identified in two or more photos taken from different surface locations. In addition, some examples a meter or more in size can be identified in images taken with the Lunar Reconnaissance Orbiter Camera (LROC), particularly at low solar elevations.  The following illustration shows a portion of a deconvolved version of the LROC image taken at 22:43:38 UTC on 22 December 2009.  The Sun was at an elevation of 8.2 degrees above the eastern horizon at an azimuth of 90.7 degrees.  In the version on the right, locations of some of the boulders used in the photogrammetric analysis are marked with red dots () or yellow dots ().  The letter designations attached to these boulders are related to the order in which they were added to the photogrammetric analysis.  Boulders that appear in a number of Hasselblad images taken from a variety of azimuths with various parts of the LM also visible were necessarily done first.  Boulders visible in the Hasselblad images that could be identified in the initial LROC images taken from altitudes of 100 km or more also received early letter designations.  Later, when fourteen smaller boulders visible in the Hasselblad images could also be identified in LROC images taken from 50 km or less, these received designations in the "gt" series and are shown with yellow dots.


Identified
            boulders
Portion of the deconvolved 22 December 2009 LROC image provided by GoneToPlaid, showing some of the boulders visible in multiple Hasselblad images and in the LROC images, marked with either red dots () or yellow dots ().  (Click on the image for a larger version.)





3.1 Boulders Northwest of the LM

3.1.1  Group e boulders

During a post-flight press conference, Neil said, "(There were) rocks in a boulder field (that we photographed) out Buzz's  window that were 3 and 4 feet in size.  Very likely pieces of lunar bedrock.   And it would have been very interesting to go over and get some samples of  those.  We have the problem of a 5-year-old boy in a candy store.  There are just too many interesting things to do."  This boulder field can be seen in 5516, below, with labels applied to ten rocks that have been located photogrametrically.


Group 'e'
              boulders out Buzz's window


Frame AS11-37-5516, taken out Buzz's window after the EVA, shows a boulder field northwest of the LM.  Note the small, fresh crater along the line-of-sight to e9. (Click on the image for a larger version.)



  The boulders in this group can be identified in the LROC image taken on 22 December 2009, when the Sun was only 8.2 degrees above the eastern horizon.  The boulder field visible out Buzz's window contains far more than ten rocks. In the window photos, many smaller pieces of stones are visible all around; and , in the LROC image, a couple of larger stones with distinct shadows are seen to the north and to the west of the ten labeled boulders. However, Im not able to recognize these stones in any photos taken during the EVA. Window photos, by themselves, do not give useful photogrammetric results because of very small parallaxes provided by any pair of window photos. Some of the larger stones visible in the LROC images but not in the EVA photos may be hidden behind the local terrain.  One example is a rock west of boulder e2. Because small rocks are much more numerous than large ones, few can be identified with confidence and, consequently, are not labelled.



Group-e
            in Dec 09 LROC

This portion of the 22 December 2009 LROC image contains the boulders in Group eIn the bottom panel, actual locations of the boulders are marked with red dots () and yellow dots ().  (Click on the image for a larger version.)




Although some of the Group e boulders, such as e1, are visible from a variety of directions, others are only visible in photos taken out Buzz's window and in frames 5960-61 from pan Neil took on the rim of Little West Crater.  From other locations, they are hidden by a rise to slightly higher ground west of the LM.  Evidence of this rise can be seen in an animation made from two LROC images: one taken with the Sun low in the west; and the other with the Sun low in the east.  In the July 2009 image, the sloping ground west of the LM is facing away from the Sun and is darker than other parts of the image because it is being illuminated at a shallower angle.  In the December 2009 image, the sloping ground is facing the Sun, so it's relatively bright.

 
This slope to slightly higher ground west of the LM blocks the view to many boulders which are otherwise visible only in photos made from the window (with the camera altitude of ~5.3 m above the LM footpads) and in Pan 5 photos taken from the rim of Little West Crater, which has an altitude about the same as the LM windows. Unfortunately, in Pan 5 photos 5960-61 the group e boulders are seen from a far distance, and are near the horizon.  In addition, 5960 is badly blurred. These factors make identifications difficult. In addition, the combination of the two positions - Pan 5 and the Buzz's LM window - provide only a small parallax. Fortunately, from the Pan 2 location on a crater rim just south of the tip of the LM shadow, six members of group e are visible in frames 5883-84.  This gives larger parallaxes.

In the following descriptions, reference is made to a "fresh crater" and and an adjacent depression.  These are labeled in a detail from AS11-37-5512, taken out Buzz's window after the EVA; in a detail from the December 2009 LROC image; and in a labeled frame from the landing film shot out Buzz's window.



e1 distance ~ 92 m from the center of LM; length/height 1.5/1.5 m. This boulder is the largest in the group; its shadow is very prominent even in the lower-resolution  July LROC image.

e2:  distance ~ 92 m from the center of LM; length/height 1.5/1 m. This boulder is not seen on majority of photos, except for window shots and Pan 5. Fortunately its top is also seen from the high point of Pan 2 (5883/5884), this helps to improve parallax and accuracy. This boulder is particularly prominent in the 29 October LROC image, taken when the Sun was east of the zenith at an elevation of 64 degrees.

e3:  distance ~ 80 m from the center of LM; length/height 1.5/1 m. In the Hasselblad images, this boulder is seen only in the window shots and in Pan 5.  In a frame from the Apollo 11 descent film shot out Buzz's window, note the proximity of boulders e1, e2, and e3 to

e4:  the eastern-most boulder in the group, sits on the rim of an 8-m crater. As can be seen in a detail from 5515, e4 is actually a group of at least 3 boulders:  one large boulder, with two smaller ones in the foreground. Distance ~56 m from the center of LM; length/height of the main boulder 1/0.5 m; the lesser boulders are two times smaller. This very prominent group is seen on many shots in the northern direction due to its high position on the rim of the small crater. Despite its prominence, it is barely distinguishable even on high-resolution LROC photos, obviously due to its short shadow cast onto the nearby rim portions.

e5:  a group of at least 2 boulders side-by-side (see a detail from 5883) on the rim of the depression behind the "fresh" crater. Distance ~64 m from the center of LM; length/height of the each boulder 0.5/0.5 m. The upper portions of e5 can be seen in many shots in the northern direction due to their position on the rim of the depression. In LM window shots,  e5 is directly projected onto boulders e6 and e7.  This gives the impression that  e6 and e7 are associated with e5, but they are not.

e6 and e7:  only about 3 - 4 meters apart, at virtually the same distance from the LM, and close to the lines-of-sight from the LM to e3 and e5. Distance ~71 - 72 m from the center of LM; length/height  cannot be accurately estimated since only upper portions are seen from the window and because of the large distance from Pan 5 location. The very top of e6 is seen from the high point of Pan 2 (detail from 5883). Not seen on other shots being obliterated by the rim of the depression and the rim of the fresh crater. e7 is barely seen on some of high-resolution LROC photos. In the LM window shots, as seen in a detail from 5516, e6 and e7 are partially hidden by e5 and seem to be a part of the same grouping. (Actually, before I got low-sun, high-resolution LROC images, these boulders were enigmas for me. I could not identify two boulders on 5960/61 since nothing seemed to correspond to them on other photos. At the same time I saw two unexplained boulders that appeared to be clustered with the two e5 boulders in window photos, one to the left and one to the right of the central group.  Before I had the LROC images, I could not understand e6 and e7 because the two e5 boulders, being very prominent, do not have any nearby boulders in any of the EVA photos that would correspond to e6 and e7.)

e8, distance ~ 93 m from the center of LM; length/height 1/0.5 m. Screened by the rim of the depression and by the rim of the fresh crater, so is seen only in window shots and on Pan 5.

e9, the most distant in the group. Distance ~ 103 m from the center of LM; length/height 1/0.5 m. Screened by the rim of the depression and by the rim of the fresh crater, so is seen only on window shots and on Pan 5.

e10, distance ~ 93 m from the center of LM; length/height 1/0.5 m. This relatively small boulder is situated farther east than most members of group e, so it is not hidden by the slope west of the LM and can be seen in Pans 1, 2, 3, and 5 and from Buzz's window.

3.1.2 Boulder f

This boulder is 31 m from the center of the LM and only 10 m west of the TV camera.  Its size is about 0.5 m. Due to its proximity to LM and its presence in many EVA photos (such as 5883) and from Buzz's window photos (as in 5483), photogrammetry locates it very accurately, with an error well less than its size.  As can be seen in an animation, boulder f is barely visible in the Oct and Dec 2009 LROC images.  However, it seems to be the closest boulder to LM that may be distinguished on LROC images, so I decided to include it in the photogrammetric analysis.  (It is interesting that several such boulders are at the limits of visibility in the original LROC images; but when the originals are resized with interpolation, some such boulders become more visible.  Nonetheless, if you do not know a boulder is there, you're not able to say that it is really a boulder and not a minor relief feature.)


3.1.3  Boulder eq1

This boulder is near fresh crater C1, as discussed in section 4.4.3eq1 is about 565 m from the LM and is visible only from the LMP's LM window.   The large distance and the tiny parallax available from the window shots means that no meaningful photogrammetric distance can be determined.  However, because of its size and azimuth, boulder is easily identified in LROC images. In the window photos, the width of the visible portion is  ~1.5 m.  The LROC images give a width of ~2.5 m.


3.2 Boulders Northeast of the LM


Boulders in this group primarily appear in Pan 2 and Pan 5.  In principle, this combination should give large parallaxes and accurate locations for the boulders.  For two reasons, this did not happen in a full photogrammetric analysis that included the Pan 5 stations.  First, as discussed in section 2.1.5, the Pan 5 stations are not well tied to the LM.  Second, many of the northeast boulders are far enough from the LM that only small parallaxes are available without use of the Pan 5 photos.  The net result was that, rather than improved accuracy of the boulder locations, the full photogrammetric analysis put the Pan 5 stations about 6 meters east of their true locations. (See a discussion in section 3.2.2.)   Of the eleven boulders, the three largest - b, c, and d -  are easily visible in the lower resolution, July 2009 LROC image. Three others of intermediate size -  j, h, and q5 - and the five smallest ones - g, i, j1, j2, and k - can be picked out in LROC images taken after the spacecraft was moved down to 50-km altitude. Some of these are seen only because their shadows fall on ground that is sloping down, away from the Sun.  Boulders i and j sit on ground that slopes down to the west; Pan 5 images, taken with the Sun low in the east, illustrate the effect of a slope on shadow length. Visibility of some of the boulders, such as k, may be enhanced in LROC images because their top surfaces are relatively bright, particularly when the Sun is high in the local sky.  See, also, labeled versions of 5886, 5903, and 5958. Note that q5 is only visible from the Pan 5 location.

NE boulders from Buzz's plus-Z pan


Identified boulders northeast of the LM as seen in Buzz's plus-Z pan (Pan 2). The central part of the pan assembly was made from frame 5885, in which boulder h  is hidden behind the US flag.  Frame 5886 was taken from a slightly different location and shows boulder h.  A small piece of 5886 has been inserted in the figure at the proper location.  (Click on the image for a larger version.)







NE bolder
            from Neil's Little West pan


Identified boulders northeast of the LM as seen in Neil's Little West pan (Pan 5). Boulder e4 is also visible, directly under the green dot ().  (Click on the image for a larger version.)




22 Dec
            2009 LROC, boulders northeast of the LM


This portion of the 22 December 2009 LROC image contains identified boulders northeast of the LM.  In the bottom panel, boulders visible in the raw LROC image are marked with red dots () or yellow dots (). (Click on the image for a larger version.)





Distances in the following descriptions were measured on GoneToPlaid's deconvolved version of the 22 December 2009 LROC image.  Distances are given from the center of the LM and from the central point of Pan 5.

3.2.1  Boulder b

This boulder is seen in many photos showing an area NE of the LM and NW of Little West. The boulder is about 68 m from the LM and 66 meters from Pan 5. It is located just between two small craters. Both craters are discernible on in Pan 5 photo 5958 and from other locations. Boulder  b is one of the largest boulders near the LM.  It is very elongated in the E-W direction being about 2.5 m long on that axis. It is about 0.8 meters tall and, as can be seen in 5866, 5886 and 5903, appears to have a triangular cross-section when viewed from the SW. Its shadow would be much wider if its orientation were North-South, rather than East-West.  It casts a distinct shadow in the July 2009 LROC image; and, in the 1 October 2009 LROC image, shines brightly at local noon.  In the 29 October 2009 LROC image, taken with the Sun east of the zenith at an elevation of 64 degrees, boulder b rivals the LRRR cover in brightness.  Of the boulders north of the LM, only e2 comes close to b in brightness.


3.2.2 Boulder c

Distance ~175 m from the center of LM; ~135 m from Pan 5 location; width/height ~2.0/1.8 m.

For a long time I was unable to identify boulder c in the Pan 5 photos, in part because I was thinking that the boulder that turned out to be c was on or near the rim of Little West. This illusion is due to the fact that the rim on that side of Little West hides a large portion of the surface between the rim and c.  In a detail from 5955 (next figure), a portion of the apparent rim is marked with a string of small white dots.  Below that line of dots, we are seeing material on the Little West rim while, above it, we are seeing the surface well away from the rim.  In particular, along that portion of the apparent rim, we see the tops of four boulder with bottoms apparently hidden by the rim.


Details from 5955 and LROC 22 Dec 2009


Detail from 5955, taken as part of Pan 5, combined with a detail from the 22 December 2009 LROC image.  The latter has been rotated 48 degrees left to put Boulder c directly over the Pan 5 location. What appears to be a portion of the apparent rim of Little West to the right of c is marked with small, white dots.   (Click on the image for a larger version.  See, also, an anaglyph, made from 5954 and 5964, which shows the apparent break in the scene beyond the rim.)





Consequently, the boulder is projected to the photographic plane near the rim, and that led me to underestimate the distance. Without information from Pan 5, photogrammetry of c depends on pairs of photos taken near the LM.  Parallaxes are small; position errors are large.  Photogrammetry using on the photos taken near the LM give a distance of ~160 m, with an error of about 10 %.  However, that approximate position - combined with the long shadow that indicated a large size - led me to identify the boulder on Pan 5 photos and to get a distance with better accuracy

Distances to boulders to the north-east contain relatively large errors: for some boulders nearly 10 %. There is a reason for that. These boulders are visible only in five Pan 5 images and in a few images taken very close to the LM.  Use of only the near-LM images only provides small parallaxes and, therefore, large distance uncertainties.  Pan 5 images provide views from the side but, unfortunately, the Pan 5 photogrammetric locations have errors - mostly systematic - bigger than any other camera stations.  The problem is that many Pan 5 photos contain only small stones and not any point-like benchmarks such as features on the LM, flag, TV camera etc. In addition, the Pan 5 photos  do not show any objects in the close foreground large enough to be seen and identified in photos taken near the LM. That means that photogrammetric camera locations for all Pan 5 images, except for 5960 and 5961, are deduced from distant rocks only. Because there are no point-like benchmarks on these rocks, accuracy of Pan 5 camera locations is relatively low. Indeed, as discussed in section 2.1.5, the photogrammetric analysis puts the Pan 5 stations about 6 meters east and - a bit south - of their true locations or about 10% of their distance from the LM.

The influence of Pan 5 location uncertainty is of the same order as systematic errors in photogrammetric positions of boulders which are identified using Pan 5 photographs. Essentially, all photogrammetric positions are shifted eastwards by several meters from the actual positions. An animation shows (1)  the unshifted photogrammetric positions of this group (green dots), (2) the positions shifted 6 meters to the west (green dots), and (3) a comparison of the shifted positions with the actual boulder locations. The shifted locations are generally much closer to the actual locations. Boulder c has largest remaining error in the distance from the LM: ~6 m or ~4 %, compared with the unshifted error of ~11 m or ~7 %. For b, the error dropped from ~5 m to a value less than the size of the boulder. VP writes: "Correction of the systematic error also helped me to identify boulders j2, gt13 and gt14, since it revealed the correspondence between photogrammetrically located object and the boulders."

Limitations of IM do not permit use of the Gold Camera as an additional scale restriction; but I believe that it may be possible to create an an approximate photogrammetric map from the Pan 5 photos alone,  using the Gold Camera for scale and, thus, determine relative Pan 5 camera station locations more precisely.

3.2.3 Boulder d

Distance 96 m from the center of LM; 116 m from Pan 5 location; width/height ~1.5/0.5 m.

Boulder d appears to be a flat rock - or, perhaps, a close grouping of separate rocks, as seen in 5513, taken from Buzz's window, 5869, taken near the ladder, and 5958 taken from the rim of Little West Crater.  It is marginally discernible in the July 2009 LROC photo but is easily visible in the Dec 2009 image.  In the latter, its shadow is not very long but, because the boulder is wide in the N-S direction, the contrast between its illuminated and shadowed portions is sharp.

3.2.4 Boulder g

Distance 92 m from the center of LM; 108 m from Pan 5 location; width/height ~1.0/0.5 m. Positioning accuracy ~2%.

Small boulder about 10 m far from d. Before the high-resolution, December 2009 LROC image became available, I had not noticed this boulder in the Hasselblad images and had not used it as a photogrammetric benchmark. So I was surprised to see something at this place on the LROC image. I started looking at Hasselblad photos in its direction and very soon saw the only probable candidate in Neil's photos of Buzz's egress, such as 5869, and, later, in Pan 2 and Pan 5. Photogrammetry confirmed my identification. I think this boulder is seen on LROC images only thanks to a long shadow that it casts because it seems to be sitting on a small patch of raised ground.

3.2.5 Boulder h

Distance 80 m from the center of LM; 79 m from Pan 5 location; width/height ~1.5/0.5 m.

Situated not far from b (~15 m).  From the Pan 5 location, it appears elongated like b, but smaller. It looks smaller in the both the October 2009 and December 2009 LROC images, too.

3.2.6 Boulder i

Distance 83 m from the center of LM; 59 m from Pan 5 location; width/height ~0.7/0.5 m.

Small boulder not far from j (~10 m). Visible in the December 2009 LROC image, thanks to a long shadow which, in 5957, seems to be falling on ground sloping down to the west.

3.2.7 Boulder j

Distance 77 m from the center of LM; 48 m from Pan 5 location; width/height ~1.0/1.0 m.

From near-LM locations  the line-of-sight to j is just to the right of boulder c. See, for example, a detail from 5903.  Boulder j is also visible from the Pan 5 location.  It is not visible in the early, low-resolution LROC images, but shows up very well in the December 2009 LROC image, about one half of a crater diameter north of the Little West rim.


3.2.8 Boulder j1


Distance 82 m from the center of LM; 49 m from Pan 5 location; width/height, ~1.0/1.0 m, tooth-like boulder 7 m east of j.  As can be seen in a comparison, in the early-morning, 22 December 2009 LROC image (M116161085RE), j1 is vaguely detectable since its shadow falls on the dark eastern side of the small depression immediately west of the boulder. In mid-morning, 25 November 2009, LROC image (M113799518RE), the depression is fully illuminated so that j1 and its short shadow are more visible against the more uniform background.

3.2.8 Boulder j2

Boulder j2 is only about 24 m from the Pan 5 location, closer than another boulder identified in the LROC images. Distance from the rim of Little West,  ~7 m; distance from the center of the LM, ~44 m. j2 appears to be eroded, with width ~0.9 m, height ~0.5 m. It is adjacent to the western rim of an apparently fresh ~2.5-meter crater. Its shadow is relatively long in the Dec 22 LROC image since it is cast down the outer slope of Little West.  Note that j2, among others, was captured in the landing film shot out Buzz's window.

3.2.10 Boulder k

Distance 86 m from the center of LM; 77 m from Pan 5 location; width/height, ~0.6/0.5 m.  This small boulder near h (~15 m), as can be seen in 5958, taken from the Pan 5 location. Visible in the December 2009 LROC image thanks to its bright top only, I think.

3.2.11 Boulder q5

q5 is at too great a distance from any of the camera station for useful photogrammetry.  Like boulders q1-q4, discussed in section 3.3, there are no other plausible candidates along its azimuth, which permits identification with high confidence.  A detail from the 22 December 2009 LROC image gives a distance of ~350 m from the LM  and ~320 m from the Pan 5 location. Its shadow is about 0.4 times that of the boulder c shadow, suggesting a height of about 0.7 m.  From the Pan 5 location, q5 is about 0.1 degrees tall, giving a linear height of about 0.5 m.  The Pan 5 image gives a width of ~1.2 m, in good agreement with an estimate from the LROC image.


3.3 Boulders between Little West Crater and West Crater

In the higher-resolution LROC images of the site, quite a few large boulders, up to several meters is size, can be spotted between Little West Crater and West Crater.  All of them are probably ejecta from West Crater.  Unfortunately, only a limited number of these are distinctively seen on EVA photos because of  rugosity of the terrain.  Some boulders are hidden by the raised rim of Little West, and others by rugae ('waves' or 'wrinkles') that can be seen in the LROC images taken at low solar elevation.  In the following detail from the 22 December 2009 LROC image, there are a number of broad areas of light and dark ground.  With the sun at an elevation of only 8.2 degrees in the east, the dark areas are sloping down to the west while the light areas are sloping up to the west.  Spots with dark ground on the right and light ground on the east - such as boulders t1 and v3 - are at low points in the terrain; and spots with light ground on the right and dark on the left - such as boulders v1 and v4 - are at high points.  The boulders labeled in the figure - q1 to q4, t1 to t4, and v1 to v5 - can be found in at least some of the Hasselblad images.  Many other boulders between Little West and West craters are hidden from observers near the LM.




Light and dark areas in the region of the qtv boulders


Detail from the 22 December 2009 LROC image.  The Sun is low in the east, so ground sloping up to the west will be lighter than ground sloping down to the west.  Yellow azimuth lines have been drawn for the four q-group boulders. Because of the small parallaxes available from the Hasselblad images, photogrammetric distances to the q boulders is very uncertain.  The azimuths are well determined, which permit identification of the boulders.  (Click on the image for a larger version.)





qtv
            boulders on deconvolved LROC

Group q, t, and v boulders - along with other boulders closer to the LM -
marked on the deconvolved version
of the 22 December 2009 LROC image. (Click on the image for a larger version.)



Is indicated by the naming, the visible boulders are divided into three groups: q1 to q4 are virtually up-Sun from the LM and are well separated from the others in the Hasselblad images;    t1 to t4 are four prominent boulders with larger apparent sizes than the rest because they are physically larger and/or closer; v1 to v5 are less prominent objects. In the figure linked below, an additional group of three w boulders are also labeled. These are discussed in section 3.4

The best overview of the boulders visible in the EVA photos is provided by 5872 (next figure), taken near the US flag;  and 5887/8 (next after 5872) taken at Pan 2 station, which is particularly favorable because of its raised position on the rim of Double Crater. Glimpses of some of the boulder are available from the Pan 1 site (5850), the Pan 3 site (5913), and the Pan 4 site (5936). The line-of-sight from the Pan 3 location passes close to Little West and, consequently, the rim either partially or totally hides some of the named boulder. The Pan 4 location is lower than the Pan 2 location so views of some of the boulders are either partially or totally blocked. In addition, the quality of 5936 is reduced by sun glare.






AS11-40-5872 with boulders t1-4 and v1-6 labeled


Detail from 5872 with labels applied to twelve boulders in the general direction of the south rim of West Crater. Four prominent boulders assigned to the t group; and five less-prominent boulders assigned to the v group.  The heavily-shadowed rim of West Crater runs to the left from beyond boulder t2Two boulders associated with a thin, dark line - the inner, east wall of an old, eroded crater - are labeled w1 and w2  and are discussed in section 3.4. (Click on the image for a larger version.)




Boulders q1, t1-4, and v1-6 in 5887
              and a portion of 5886


Up-Sun image 5887 from Pan 2, with a small piece of 5888 added at the upper right, showing boulders q1 - q4, t1 - t4, and v1-v5  Buzz aimed the camera low to avoid getting direct sunlight in the lens.  (Click on the image for a larger version.)




All the t-group boulders are visible in all the Hasselblad images taken in their direction.  Because of intervening terrain, the lower parts of some of these boulders are hidden.  Regrettably, none of the Pan 5 images were aimed far enough to the southeast to include them.  They are also visible in the first LROC image of the site, despite the relatively low resolution of that 12 July 2009 image.
 

3.3.1  Boulder t1

This is the largest and most distant of the t-group boulders. Distance ~156 m from the center of LM. Position estimation accuracy ~3%. Because lines-of-sight from locations near the LM pass close to Little West, the boulder's base is hidden by the outer parts of the crater rim.  Because Pan 2 was taken from a relative high spot on the rim of Double Crater, more of the boulder is visible in 5887 than in any other Hasselblad image. From the Pan 1 location (5850), t1 is completely hidden by the LM; from the Pan 3 site (5913), only the tip is visible; and, from the Pan 4 site (5936) also only the upper portion is visible in the glare of the Sun. The width of the portion visible in 5887 is about 2 meters, with a measurement on the Dec 2009 LROC image confirming this estimate. The portion visible in 5887 is about 1 m wide.  The height cannot be estimated from EVA photos since the base of the boulder is hidden by the rim of Little West. We see about 1 m of its upper portion on 5887. The t1 shadow length in the Dec 2009 LROC image is ~8 m.  With the Sun at an elevation of 8.2 degrees, the inferred height is 1.2 m.

3.3.2 Boulder t2

This is the smallest of the group and closest to the LM. Distance  ~ 108 m; accuracy ~4 %. Height/width ~1 m. In the October 2009 LROC photo, with the Sun virtually overhead, there is no sign of t2 at its known location, which is at the center of the box drawn on a labeled detail.
 

3.3.3 Boulder t3

The October and December LROC images indicate that t3 is only a bit smaller than t1.  Distance ~124 m, accuracy ~3%. Height ~1.3 m, width ~2.3 m. Distance from t2 ~16 m; from t1 ~34 m. 
 

3.3.4 Boulder t4

t4 is about as tall as t2, but has enough width to be visible even in the October 2009 LROC image. Distance ~120 m, accuracy better than 2 %. Height ~0.9 m, width ~1.3 m. On Pan 1 (5850) only the rightmost (south) side of the boulder is seen, the rest being hidden by a landing gear strut. Distance from t3 ~8 m, from t2 ~18 m, from t1 ~40 m.

 
The boulders in the v group are less prominent in the Hasselblad images than the t-group boulders. Most are farther from the LM, which means that, generally, we are seeing only their tips as faint, black, blurred spots sticking up over the rugae of the terrain. On some photos they are present, on others some of them are hidden entirely by the terrain or by the two largest t-group boulders: t1 and t3. When combined with low parallaxes, these factors make them difficult to distinguish in the photos. Without photogrammetry we hardly would be able to identify most of them. Even with photogrammetric data, I have some doubts about the identifications and/or reality of a couple of these boulders.

Boulder groups t and v in 5936


Boulder groups t and v in AS11-40-5936, taken as part of Pan 4, which Neil took while Buzz was offloading the EASEP packages.  Large parts of the t1 to t4 boulders and one of the w boulders are visible; these are marked with red arrows.  I  put red dots above the tops of boulders that are mostly hidden, and blue dots at the photogrammetrically-determined locations where unseen boulders would be if they were not screened by the terrain or foreground boulders. I haven't included v3 in the inset because of it's separation from the others.  v3 is marked with a blue dot in the full image because it is hidden by a group of bright, foreground boulders; the blue arrow and dot indicates the position of v3 behind this group, not the bright group.  (Click on the image for a larger version.)



3.3.5 Boulder v1

Its upper portion is nicely seen from the the rim of Double Crater rim (5887); a smaller portion is seen on 5872/73. From the Pan 4 site (5936), I'm not sure it can be identified with confidence because of the sun glare; on 5913 (Pan 3) it is hidden by the rim of Little West; from the Pan 1 site ( 5850 ) it is hidden behind the LM. Distance ~184 m, accuracy ~3% Distance from t1 ~30 m. Its size may be estimated roughly only from the December 2009 LROC photo. According to the size of its image and the length of the shadow, v1 seems to be similar to t4, i.e. height/width is ~1 m/ 1.5 m. As seen from orbit, it is near a small (~7 m) crater.
 

3.3.6 Boulder v2

v2 seems to be quite large on December 2009 LROC images, it is also the most distant in the group: ~400 m from the center of LM, compared with 175m for boulder c Accuracy ~5%, which seems more a matter of luck, given the small parallaxes available. v2 is entirely hidden by the rim of Little West from Pan 3 site (5913) while, from Pan 4 site (5936), it is hidden by t2.  The tip of v2 is all that is visible from near the US flag (5872/73), from the Pan 2 site on the rim of Double Crater (5887), and from the Pan 1 site (5850). The size may be roughly estimated from the December 2009 LROC photo. v2 actually seems to be a tight cluster of at least two boulders, which may be parts of a single boulder that broke apart when it landed. The southern component is the largest; the length of its shadow suggests a height of 1.5 m or more. The northern component is about half its height. The width of each component is ~2 m or more.  The group, as a whole, spans ~4-5 m.
 

3.3.7 Boulder v3

Closest to the LM of the v-group. Distance ~120 m, accuracy better than 2%. In the December 2009 LROC image, the boulder appears to be  smaller than t4; so it may be about 0.5 m high & ~1 m wide. From the LM, it is nearly completely hidden by a terrain ruga. Only its very tip is discernible in 5872/73, 5850 (Pan 1) and 5887/8 (Pan 2).
 

3.3.8 Boulder v4

Distance ~140 m, positioning accuracy better than 2%. v4 is a small boulder on the rim of a tiny (3 m) crater. Became discernible only in LROC images taken from 50 km or lower. Only a small part of v4 is seen behind t3 in 5872/73.  In 5913 (Pan 3), it is completely hidden by t3 (distance to t3 is ~18 m). Size of 1 m/1.5 m (height/width), comparable to t4, v1, and v3. Distance from t1 ~20 m, from t3 ~18 m, from t4 ~21 m.

3.3.9 Boulder v5

Distance ~195 m, positioning accuracy ~3%. Seen in 5872, 5887/88 (Pan 2) and also, very vaguely, in 5913 (Pan 3). Size of 1 m/ 1.5 m (height/width) comparable to t4, v1, v3, and v4. Distance from v1 ~31 m, from t1 ~45 m.
 
 

3.3.10 Boulder q1

Little West Crater and the Q boulders in 5865


Detail from AS11-40-5865 showing boulder q1 beyond the southern part of the Little West rim. This is the only Hasselblad image taken near the LM that shows all of Little West, including some of the interior. (Click on the image for a larger version.)





q1 is a boulder for which a useful photogrammetric location cannot be calculated from the Hasselblad images but an identification in the December 2009 LROC image is almost certain.  q1 is visible only in 5887 (Pan 2 on the rim of Double Crater) and 5865 (above; taken left of the ladder during Buzz's egress).  These camera stations are high enough for us to "look over" the rim of Little West.  In a detail from 5936 (Pan 4), a yellow dot shows where q1 would be seen if our view wasn't blocked by Little West.  Unfortunately, perpendicular to the line-of-sight to q1, the 5865 and 5887 are only separated by about 2 meters, which is no more than half the width of the boulder likely to be q1. Consequently, a photogrammetrically-determined distance will be very uncertain.  However, a line along the azimuth of q1  passes very close to the boulder labelled q1 on a detail from the December 2009 LROC map. A pair of boulders ~40 m WNW from this boulder are not likely candidates since they are very probably hidden by Little West; additionally, if not blocked by terrain, the pair of boulder would appear as a pair from the direction of the LM. Although we can see numerous boulder closer to the LM along the line-of-sight in the LROC image, they are much smaller than my candidate for q1. So I think my identification is likely to be correct. In this case, the smaller boulders in front of it are hidden by the terrain.
 
If the identification is correct, q1's range derived from the LROC image is ~260 m. The triangular shape of the shadow is consistent with the apparent conical shape seen in 5865 and 5887.   Assuming a distance of 260 meters, the portion of the boulder visible 5887 is ~3.6 m wide and ~2.2 m high.  Size estimation by the LROC image gives width ~3.5m. The visible shadow length is ~14 m.  Assuming that the shadow is resolved and is falling on level ground, its length corresponds to a boulder height of ~2 m.


3.3.11 Boulder q2

q2 is about 230 meters from the center of the LM and is seen only in 5865 (above) and 5887.  In the LROC images, it is the only candidate at this azimuth. In 5887, it is adjacent to the bright lens flare; and, in 5865, only the tip is visible above the rim of Little West. In the LROC image, another, slightly smaller, boulder is seen only 4 meters north from q2, but it is probably invisible in 5887 behind the sun flare and in 5865 this smaller boulder is obviously hidden behind the Little West rim. In the LROC image, the width of q2 is about 0.5 m while the shadow length suggests a similar height.

3.3.12 Boulder q3

q3 is about 385 meters from the center of the LM and is seen indistinctly in 5865 (above) and 5887. The size estimated from the December 2009 LROC image is about 1 m.  There is a second candidate on the same azimuth, at about the same distance from the LM as q1; but this candidate appears is be in a low spot, with light-colored ground immediately west and dark ground immediately east.  The second candidate also has a short shadow, indicating that it is not very tall and/or that the shadow is falling on ground rising to the west.

3.3.13 Boulder q4

q4 is about 410 meters from the center of the LM and, therefore, is the farthest boulder identified in both EVA and LROC images. Being at such a distance, it lies near the base of the outer slope of the West Crater rim, about 30 m horizontally from the rim crest. q4 is distinct and well defined in 5865 (above) and 5887, although we may not be seeing the top of the boulder against dark outer slope of West Crater.. Both the Hasselblad and LROC images show the boulder is about 4 meters wide. It is difficult to estimate the height from the LROC images since the shadow is cast down slope.  In the Hasselblad images, the visible part of the boulder is about 40 percent of its width, indicating a height of at least 1.6 meters

3.4 Boulders near the south rim of West Crater

 
Detail from 5872 showing t2, t3, t4, v4, v5, and
          w1 and w2


Detail from AS11-40-5872 showing w1 and w2From the 5872 camera station, the azimuths of boulders t3, v4, v5, and t4 bracket those of the two w boulders.





The photogrammetric distances to the three w boulders are in the range of 430 to 550 meters, but  have large uncertainties because of the small range of parallaxes available.  As noted previously, they seem to be associated with a thin, dark band, which turns out to be the inner, east wall of an old, eroded crater.


Old Eroded Crater southwest of West Crater

Composite LROC image showing the old, eroded crater.

The left portion of  composite image above is a detail from the 12 Jul 2009 LROC image taken with the Sun low in the west.  The right portion was taken on 22 December 2009 with the Sun low in the east.  The December image was scaled to the July image, using separate scaling factors in the vertical and horizontal directions to permit an accurate overlay.  In the December image, ground sloping down to the west is relatively dark; in the July image, ground sloping down to the east is relatively dark.  The composite image shows the inner walls of the eroded crater better than either image would on its own.



From camera stations near the LM, lines-of-sight to the w boulders pass close to the t boulders.  Frames used in the following analysis are:  5873, one of Neil's photo of Buzz deploying the SWC, taken northwest of the LM; 5888, a frame from Pan 2, taken by Buzz on the rim of Double Crater just south of the LM shadow; and 5913, a frame from Pan 3, taken by Buzz about 10 meters north of the LM.  Because the t boulders are unambiguously identified in the LROC images, we are able to use relative azimuths to identify two of the w boulders.



detail from 120124 camera station
                map



Detail from the 24 January 2012 camera station map.  The three images used to identify boulders w1 and w2 - 5873, 5888, 5913 - are shown with red arrow shafts.


Although the combination of stations 5873 and 5913 provides only small parallax, each of them can be combined with 5888 to provide  adequate parallax for identification.

To make identification as confident as possible, we begin with a new 2x overlay of the camera station map on a composite made from   GTP's deconvolved version of M150368601RE, taken on January 22, 2011 at 20:48:53 UTC, with a portion of  GTP's deconvovled version of M119693197LE, taken on February 1, 2010 at 19:52:11 UTC.  As can be seen in a animation discussed below, the flat areas around West are well matched in the two LROC images, but the inner portion of West shows differences. This is undoubtedly the result of vertical profile within the crater; the two photos were made from different orbital locations, so the vertical profile projects differently onto the image plane. This proves the well-known fact that orbital images are not the same thing as map projections, photogrammetric rectification is required to remove projection distortions and to produce a true map.

Identification of two of the w boulder was done by the following method: For each of the two boulders in each of the three EVA photos, we calculated an angular distance from one of t-boulders. A corresponding line-of-sight was then drawn on the LROC composite, beginning at the camera station and passing the selected t boulder at the measured angular distance.  Lines for w1 are shown in red; w2 in yellow.


Azimuth ines relative to t-boulders

Lines-of-sight starting at camera stations 5873, 5888 and 5913 to w1 (red lines) and w2 (yellow lines) and passing selected t boulders at angular distances determined from the Hasselblad images. (Click on the image for a larger version.)

If this construction were absolutely precise, each system of lines would intersect at single point and we would see a prominent boulder at the intersection. However, due to uncertainties in the 3D-scene, in its matching to LROC images and to uncorrected distortions of LROC images, neither system of lines intersects at the single point.  In each case, the lines from stations 5888 and 5913 interest south of the rim of West Crater near prominent boulders, while the lines from 5888 and 5873 intersect farther west in boulder-free areas.  Notice, too, that in each case the lines from 5873 and 5913 are virtually parallel to each other and are only separated by about 5 meters.  This distance is only 1-to-2 times the expected size of the boulders, so any candidate boulder should be close to all three of the lines.  In each case, there is a sizeable boulder near the 5888/5913 interestion and between the 5873 and 5913 lines.

Identification of W1 and W2

Boulders w1 and w2 are the only prominent boulders south of West Crater and along the lines-of-sight positioned relative to the t boulders.


An animation shows (1) the area south of West Crater in M150368601RE; (2) the same area in M119693197LE; (3) lines-of-sight and boulder identification in M119693197LE; (4) lines-of-sight and boulder identifications in M150368601RE; (5) boulder identification in M150368601RE; and (6) boulder identification in M119693197LE.

w1 is about 530 m from the center of the LM, as measure in the LROC images. Based on that distance, its apparent width measured in the Hasselblad images corresponds to a physical width of ~2.5 m.  Its width estimated in the LROC photos is 3 m or slightly more. These values do not contradict each other since we obviously see only the upper portion in EVA photos. The height visible in EVA photos is ~2 m, but lower portions of the boulder may be hidden by intervening terrain.

w2 is about 600 m from the LM, the largest distance of any boulder identified in the Apollo 11 Hasselblad images. At that distance, the EVA photos give a width of ~2 m.  The LROC photos give ~2.5 m, thus they are in agreement.

3.5  Boulders southeast of the LM


SE Boulders in Pan 4

Identified boulder southeast of the LM as seen in Pan 4.  There are views of some or all of these boulders in Pan 1, Pan 2, and Pan 3.   Note that boulder y1 is visible only from the CDR window. (Click on the image for a larger version.)





Southest boulders plotted on 09 Dec 2009 LROC

Southeast boulders in the deconvolved 22 December 2009 LROC image. Identified boulders are marked in the right panel.  (Click on the image for a larger version.)




3.5.1 Boulders a and s

Compare boulders in 5875 and 5548
Comparison between flag photo AS11-40-5875 (left) and CDR window photo AS11-37-5548 (right), with boulders a and s on the left in both images.  In 5875, only the tip of s is visible, with the rest of boulder hidden by the rim of a shallow depression discussed below. Note that boulder z, marked here in yellow,  is not in the AS11-37-5548 field-of-view. (Click on the image for a larger version.)




Boulder a  was the first boulder I identified in the low-resolution LROC photos available in the second half of 2009.  It is one of the largest boulders close to the LM. Distance from the center of the LM ~110 m; positioning accuracy better than 2 %; length at least 2.5 m; height ~0.8 m. Boulder s is in much the same direction, but is only ~76 m from the center of the LM.  Location accuracy better than 2 %.  It was not visible in the early, low-resolution LROC images, but is clearly visible in the subsequent 0.5-m-resolution LROC images. Boulder s is ~0.9 m wide, ~0.5 m high.

It is interesting that, thanks to their relatively large sizes, these boulders provide information on the rugosity of the terrain south of the LM. A detail from LROC image M117338434R, taken at 13:46:07 UTC on 5 January 2010 with the Sun only 6.4 degrees above the western horizon, shows that both a and s are located in a large, shallow depression south of the PSEP.  This depression is not obvious in any of the EVA or window photos and only shows up in LROC images taken at low solar elevation. One interpretation of the pattern of light (sloped terrain facing the Sun) and dark (sloped terrain facing away from the Sun) in the area suggests a diameter of ~100 m.

Four
              views of boulders a and s from near the LM

Four views of boulders a and s from near the LM.  The images are shown in the order of the west-to-east locations of the camera stations. Pan 2 (upper left) was taken farthest west; Pan 1 (upper right) from near the MESA and west of the Minus-Y strut; Neil's window is east of the minus-Y strut; and Pan 4 is the farthest east of the four locations. In that order, the position of a labeled crater beyond boulder a appears to move from right to left relative to the boulder.  Because boulder s is closer to the LM than boulder a, it appears to move left to right relative to a.  (Click on the image for a larger version.)




As can be seen in AS11-37-5548 (above, lower left), Neil's window is about 5 meters above the surface, giving us an unobstructed view of the floor of the depression and of the shadows cast by both boulders.  The rim of Double Crater is about a meter higher than the ground around the LM and, as seen in AS11-40-5851 (upper right), gives us a full view of boulder s and it's shadow.  Boulder is closer to the LM than boulder a and, from the Pan 2 location, the base of the boulder and the boulder's shadow are hidden by the near rim of the depression.  The Pan 1 location near the MESA is lower than the rim of Double Crater and, in AS11-40-5851 (upper right), while the base and shadow of boulder a are visible, only the tip of boulder s is visible above the rim of the depression.  Finally, although the Pan 4 location where AS11-40-5938 was taken (lower right)  is closer to the depression rim than any of the other three locations, it is low enough that only about the upper half of boulder a is visible, while boulder s in completely hidden by the rim, as indicated by the small red dot showing the location of the tip of the boulder given by the IM program.

3.5.2 Boulders r1, r2, r3

boulders r1-3

View of r1, r2, and r3  in Pan 2.

This is a grouping of three medium-sized boulders.  Distances 31.1 to 34.5 m.  Position accuracies 2%.  r1 is the smallest of the three and cannot be seen in the LROC images.  r2 and r3 are ~0.7-0.8 m long and ~0.4 m high.  r3 sits on on the rim of a crater about 4.5 m in diameter.  The whole group is on the east rim of a very shallow, eroded crater about 25 m in diameter.  This old crater is immediately east of Double Crater and can be seen in low-Sun images taken on the first and second passes of the spacecraft over the landing site on 12 July 2009.  The PSEP and LRRR are just outside the western rim of this depression.  Pan 2 photo AS11-40-5888 gives a slightly elevated view.  Because these boulders are on the east rim of the depression, with the Sun low in the east, their shadows fall on the inner, eastern wall of the depression and are longer than they would be on level ground.  This is the reason why such small boulder are visible in at least some LROC images.

3.5.3 Boulder p
Pan 4 views of SE boulders p and n

View of p and n in AS11-40-5937 (Pan 4).

This is a tight cluster of three medium-sized rocks which, in the LROC images show up as a single spot.  Position accuracy  ~2%. Distance from the LM center about 55m and about 36m from the Pan 4 site.  The size of the groups is ~ 2 m; the size of the largest boulders ~1 m; heights ~0.5 m.

3.5.4 Boulder n

Distance from the LM center ~65 m; from the Pan 4 site  ~46 m.  Location accuracy better than 2%.  Situated about 10 m from group p. The LROC image shows that n  is between two small crater  In 5937 (above), this boulder appears to be sitting on of a 1.5-m wide, 0.5-m tall hummock of soil.

3.5.5 Boulder o
Distance ~62m from the center of the LM; ~44 m from the Pan 4 site; ~10 m from n and p. Size: width ~0.8 m, height ~0.4 m. LROC images show that it is situated on the rim of a 5-m crater that is invisible from near the LM. Positioning accuracy better than 2%.

3.5.6 Boulders l1 and l2

Boiulders o, li, and l2 in Pan 4

View of boulders o, l1, and l2 from the Pan 4 site.

Two boulders about ~167 m from the LM center; ~4.5 meters from each other. As can be seen in a labeled detail from the deconvolved version of the Dec 2009 LROC image,   l1 is on the southeast rim of a crater about 7 m across; l2 is on the south rim of an adjacent crater of about the same size. Distance estimation accuracy ~5%. l1 is about 1.1m wide and 0.8 m high.  It is larger than its companion and is a very prominent boulder seen from many places. During the EVA, it was casting a long shadow into the l2 crater. l2 is only ~0.4 m tall,  but seems to be elongated in the east-west direction, so its size is difficult to estimate.  The views from near the LM suggest the length of at least ~0.7 m.

3.5.7 Boulder m

Distance from the LM center ~232 m.  Distance accuracy ~4%. It is barely visible in the LROC images.  Appears in Pans 1, 2, 3, and 4 but without much detail. Length at least 1.3 m (but may be larger due to projection issues); height ~0.4 m.  See a detail from Pan 1.

3.5.7 Boulder u

Approximately 140 m  south of the center of the LM; positioning accuracy better than 2%. Barely discernible on LROC photos, similar to "m". Length ~0.8 m, height ~0.4 m.  See a detail from Pan 4.


3.5.8 Boulders y1 and y2

These two boulders are about 150 and 146 m from the center of the LM, respectively, and about 7 m from each other.  Position accuracy ~1-2%. Widths ~0.5 m, heights ~0.3-0.4 m.   See a detail from AS11-37-5449, taken out the CDR window before the EVA.

3.5.9 Boulder x

One of the most distant boulders identifiable in the Hasselblad images.  Distance ~221 m from the center of the LM, nearly exactly south.  Position accuracy ~3%. Seen clearly on LRO images. Width ~1.1 m; height ~0.4 m.  See a detail from pan 4.


3.6 Boulders southwest of the LM


Group Z in
              Pan 1

Boulders southwest of the LM identified in Pan 1.  Boulder zd is hidden by terrain in this view, but can be seen in a southern detail from Pan 2. Boulders ze and zf also appear in a western detail from Pan 2.    (Click on the image for a larger version.)





Group Z in M116161085R (deconvolved)

Group Z boulders identified on a version of LROC image M116161085R deconvolved by GoneToPlaid.  The red dots show the actual locations of the boulder; the green dots the photogrammetrically-determined locations.  Note that five of the boulders in this group (zb1, zb2, zb3, zc, zg, and zh) are just outside the rim of a 140-m crater at the southwest corner of this detail.  The nearest part of the rim is ~310 m to the south-west of the LM. The bottom of this crater is not visible from the elevation provided by the CDR's window, but the near rim is seen projected onto the inner wall on the far side of the crater.  An animation made from AS11-40-5847, taken out Neil's window after the landing, highlights the near rim with a row of red dots. (Click on the image for a larger version.)






3.6.1 Boulder
z

Distance from the center of the LM, 49m; width, ~0.8 m; height, ~0.3 m. Seems to be an eroded boulder of a peculiar shape or a cluster of boulders.  It is visible from numerous camera stations.

3.6.2 Boulder za

Distance from the center of the LM, ~227 m; width and height, ~0.5 m. From several different directions, za appears to have a pyramidal shape; but, due to a relatively large distance from the camera stations, its image is blurred and its true shape is uncertain. An animation made from 5847 shows a 2-3 m crater near the boulder.

3.6.3 Boulder zg

Distance from the LM, ~290 m;  width/height, ~0.5 m. Visible due to its high position near the eastern rim of the 140-m crater. A ~25 meter crater is just north of  zg. This small crater outside the north-eastern rim of the 140-m crater is highlighted in an animation made from AS11-40-5847.

3.6.4 Boulder zh

Distance from the LM, ~345 m;  width/height, ~0.6 m. The farthest from the LM of the Z group and ~20 m south of zg.  Like zg, it is seen mostly thanks to its elevated position.  It is also the most distant of any of the boulders identified in both the Hasselblad and LROC images.

3.6.5 Boulders zb1, zb2, zb3

A group of boulder near a small, ~7-meter, slightly elliptical crater ~263 m from the center of the LM. zb1 and zb3 are situated on the rim, zb3 is discernible only a version of LROC image M116161085R deconvolved by ALSJ Contributor GoneToPlaid (GTP).  See an animation  made from the GTP deconvolution.

zb1 is a heap-like boulder or rather a cluster of boulders ~270 m from the center of the LM on the rim of the 7-m crater. Length ~2.5 m, height ~0.5 m. The object is elongated in the east-west direction in such an extent that its length is discernible also in LROC images.

zb2 is a triangular boulder with the length/height of ~0.5/0.5 m.  It is situated ~4 m west of zb1. Distance ~274 m from the center of the LM.

zb3 is a small (~0.3 m) boulder on the rim of the 7-m crater, ~2 m from zb1. Vaguely discernible only on the GTP deconvolution.  It's visibility is due elongation of its shadow on ground sloping down to the west from the crater rim, as shown in an animation.

3.6.6 Boulder zc

Views of boulder zc from the CDR's
                window and Pan 2

Views of boulder zc in details from AS11-40-5847 (left) and AS11-40-5891.



Distance from the LM, ~300 m; width, at least 1 m; height, at least ~0.5m.

The animated detail from CDR window shot AS11-40-5847 shows the near rim of the 140-m crater cutting across the boulder, which is to the left and above the black, vertical smudge in the animation.  In frame 5891 from Pan 2, the boulder is on the horizon.  The two images suggest that zc is at a relatively high elevation and that it is inside the rim of the 140-m crater.


3.6.7 Boulder zd

~249 m from the center of the LM; length, ~0.7 m; height ~0.25 m. Due to low height, this boulder is hidden by the terrain in Pan 1, Pan 4, and from other low points. Visible from the CDR window and in Pan 2.  zd is about 5 m northeast of the rim of a  ~15-m crater, as indicated in an animation made from AS11-40-5847.


3.6.8 Boulder ze

~174 m west southwest from the center of the LM;  width and height, ~0.5 m. Visible only from the windows and from Pan 2 elevated position on the rim of Double Crater, hidden by the terrain from lower positions.

There is a much more prominent boulder of a similar size in the same direction but at half the distance from the LM (~89 m).  It is labeled in green in an animation made from AS11-39-5786, a pre-EVA shot from Buzz's window.  The photogrammetric location of this boulder is accurately known and is associated with a  ~2.5 m, light colored, fresh crater, as highlighted in both the 5786 animation and in an animation made from the deconvolved version of LROC image M116161085R.  The pattern of light an dark in the LROC image of this crater is unusual and probably results from the presence of the boulder.  However, the boulder cannot be identified in the LROC image with any certainty.


3.6.9 Boulder zf

~72 m from the center of the LM; width, ~0.6 m; height, ~0.3 m).  Visible from many points. Appears to be on an elevated spot, producing a relatively long shadow on LRO photos.


3.7 Boulders recognized in deconvolved LROC images (gt Group)

3.7.1 Boulders within 30 meters of the LM

3.7.1.1 Boulder gt2

Portraits of gt2 from the Pan 1, 3, and 4
                    sites

Views of gt2 starting with the most up-Sun view (Pan 3)  counter-clockwise to the most cross-Sun (Pan 4).  (Click on the image for a larger version.)



This is a double boulder situated 25.5 m from the center of the LM in the north-east direction.  gt2 consists of two boulders of similar size, each with a maximum dimension of about 0.5 m.  The similar profiles of the two pieces in 5911 suggest they are halves of a single boulder that split in two when it landed, presumably having been ejected from West Crater.  gt2 is visible from the Pan 1 (5858), Pan 3 (5911), and Pan 4 (5932) sites. It also appears in a frame from the landing film; and in a detail from GTP's deconvolution of the December 2009 LROC image, M116161085RE.

3.7.1.2 Boulder gt7

Detail from 5927 of gt7

Boulder gt7 in a detail from 5927, one of Neil's pictures of Buzz offloading the seismometer package from the SEQ Bay.


This is the closest boulder to the LM that can be identified in the LROC images.  It is located only about 5.5 m from the center of the LM, on a radial line midway between the  -Y (south) and -Z (east) struts.. Size about 0.7 m. Best seen in 5927 to 29, which were all taken from virtually the same spot.  See, also, a detail from the deconvolution of the December 2009 LROC image.

3.7.1.3 Boulder gt8

detail from 5932 of gt8

gDetail from AS11-40-5932 showing boulder gt8.  The image is part of Pan 4 and was taken from only 5.5 meters away.


Double boulder about 14 m from the center of the LM.  It appears to have been a single boulder that broke in two when it landed.   The best images of gt8 are two frames from Pan 4, 5931 and 5932, taken from only 5.5 m away.  With gt8 in the overlap region for the two frames, we get a good stereo view (red-blue anaglyph by Yuri Krasilnikov). We have two views from the Pan 3 site, 5913 and 5914.  Because gt8 is not  well focused in either frame (distance about 23 meters), the stereo view they produce is not of high quality.

In the map from the Preliminary Science Report this object is depicted as a conglomerate of three boulders. The 3rd component is seen in 5932 (above) as a smaller, elongated rock lying behind (to the north) of the righthand (east) component of the main pair. Although the 5913/14 images are not a high quality, there doesn't appear to be an obvious source site where the third component would have been before it broke off.  The rocks in the pair are similar in size, but the eastern component seems to be slightly larger, about 0.4 m high and wide. The gap between the two components is about 10-15 cm wide. In a detail from the December 2009 LROC image we see that gt8 is on the western rim of a ~4 m wide, shallow depression. The bottom of that  depression appears to be at the lower-right corner of 5932, where the ground is more heavily shadowed.  In the 5931-32 analgyph, we see a break is slope beyond the third component.



3.7.1.4 Boulders  gt9 and gt10



detail from 5944 showing
                  gt9 and gt10

Detail from AS11-40-5944.  Buzz is carrying the EASEP packages to the deployment site.  He has just passed to the right of gt9.


These two boulders lie in a rocky area to the south of the LM and are two of the largest in the immediate area. Both appear to have soil build-up at the edges, particularly gt9, which has a skirt of soil - called a fillet - on the side facing the camera. gt9 is ~14 m from the LM center  and ~10 m from the -Y (south) footpad. gt10 is ~16 m from the LM center  and ~12 m from the -Y pad. The two boulders are ~1.5 m apart. gt9 is about 0.7 m wide and 0.3 m high. gt10 is slightly larger, about 1 m wide and 0.4 m high. These two boulders appear in 5940, 5949, and others.  They are also labeled in a detail from the December 2009 LROC image.


3.7.1.5 Boulder gt11

detail from
                    5953 with gt11 just north of PSEP

Detail from AS11-40-5953 showing boulder gt11 just north of the Passive Seismometer Experiment Package (PSEP). (Click on the image for a view that shows more of the PSEP


gt11 is a split rock less than 2 m to the north of the PSEP, about ~25.5 m from the center of the LM to the south. Both components are of similar size, ~0.3 - 0.4 m wide and high. The length of the group is about 0.8 m, the slit between the components (which almost certainly once formed a single boulder that later broke apart , probably on landing at their current location) is about 10 cm. The pair is observable from many places including Neil's window, but the closest view is 5953 made near the PSEP.  Other views include 5940, 5944, and 5949gt11 is labeled in a detail from the December 2009 LROC image.


3.7.2 Boulders northeast of the LM and more than 30 meters away

3.7.2.1  Boulder gt3 

Situated ~76 m from the center of the LM; ~16 m to the east from boulder b. Seen from many places, including the Pan 5 location on the rim of Little West. See a labeled detail from AS11-40-5957 and a detail from 5959.  Length about 0.6 m, height about 0.5 m. Although it is tall enough to cast a shadow that is long enough to be resolved in LROC images taken from 50 km, it is situated near the east rim of a small crater ~2-3 m in diameter.  In a detail from the 12 December 2009 LROC image, with the Sun low in the east,  the shadow cast by gt3 falls on the shadowed interior of the crater.  However, a detail from the 5 November 2011 LROC image taken from 25 km altitude with a resolution of 0.25 m/pixel - gt3 is well resolved.

3.7.2.2  Boulder gt4

Situated ~93 m  north-east of the center of the LM, 81 m from the Pan 5 center, and 11 m to the east of boulder k.  Best seen from the Pan 5 site, as in a labeled detail from AS11-40-5957. Possibly present in images taken near the LM.  Only marginally resolved  in the deconvolved December 2009 LROC image, but clearly resolvable in the 25-km LRO image. Length is about 1 m, height is difficult to estimate since the lower part is obliterated by the terrain, probably it is about 0.5 m or less.

3.7.2.3  Boulder gt5

About ~88 from the center of the LM, ~70 m from the Pan V site, 9 m from the boulder i. Best seen from Pan V, as in a labeled detail from AS11-40-5957; vaguely from near the LM.  Like gt4, is only marginally resolved in the deconvolved December 2009 LROC image, but is clearly seen in the 25-km LRO image. Length about 1 m, height less than 0.5 m.

3.7.2.4  Boulder gt6

About ~73 from the center of the LM, ~43 m from the Pan V site. Lies only about 6 meters north of the rim of Little West. Best view from Pan V site, as in a labeled detail from AS11-40-5957. Marginally resolved in the deconvolved December 2009 LROC image, but is resolved sufficiently
clearly in the 25-km LRO image. Its difficult to estimate its size, probably the length is ~1 m or less, height is probably less than 0.5 m.

3.7.2.5  Boulder gt13

This obeject is on the rim of a small hollow ~1 m size in diameter.  About 52 m from the center of the LM. Seen from many places, but the
best view is from the Pan V site (~39 m), in a detail from 5959. It may be a long boulder, cluster of boulders, or even a soil mound  Lies between the rim of
Little West (~14 m from the rim) and a ~13-m prominent crater lying 18 m to the north-west from Little West. Tentatively resolved in the deconvolved December 2009 LROC image and not much better in the 25-km LRO image. Length ~1 m, height about 0.3-0.4 m.

3.7.2.5  Boulder gt14

 ~100 m from the center of the LM; ~78 m from the Pan V site; ~14
m from gt4; 12 m from gt5. Best seen from the Pan V site in a detail from 5957, vaguely seen
from near the LM. Marginally visible in both the deconvolved December 2009 LROC image and the 25-km LRO image. Length about ~1 m;
height about 0.5 m, although the lower part my be hidden by intervening terrain.


3.7.3 Other boulders more than 30 meters from the LM


3.7.3.1  Boulder gt1

gt1 is the only gt boulder northwest of the LM. It lies on the rim of the depression behind the "fresh" crater, ~69 m from the center of the
LM. It is about 1 m long, but its height is probably less than 0.4 m over the rim, so it does not cast long shadow and is poorly visible at 0.5 m resolution. It is best seen in photos from the Buzz's window.  It is labeled in a detail from AS11-37-5516 and in a detail from the December 2009 LROC image.

3.7.3.2 Boulder gt15

gt15 is southwest of the LM.  The best view is from the LM windows, as in AS11-39-5742. The boulder is about 0.6 m wide with a similar height,.  It is 92 m from the LM center, on the rim of a ~3-m crater. The crater wall facing the LM is relatively bright, suggesting that the crater is fresh. An animation made from the deconvolved version of the 12 December LROC image shows what appears to be a raised rim, at least on the east side.  Brightness along the rim varies considerably from place to place, making the boulder somewhat difficult to pick out.

3.7.3.3 Boulder gt12

gt12 is south of the LM, at a distance of 130 m on the rim of a 15-m crater. The best view is from Neil's window in AS11-37-5548, which also shows gt11.  Although it is half the size of gt15, with width and height of ~0.3 m. The pattern of brightness around the crater rim is relatively uniform, giving gt12 good visibility in a detail from the deconvolved LROC image.







3.8  Boulders (and craters) in the descent film


After Neil got his first good look at the lunar surface at pitchover, he realized the were headed into a boulder field that surrounds West Crater.  In order to fly past the boulders, he took manual control and tipped the LM more upright than planned at that time in the descent.  This slowed the descent and moved the landing target westward.  After a short time, he then tilted the LM back a bit to slow their forward velocity and then began the final approach to the landing.  The Data Acquisition Camera that filmed the descent was mounted in the cabin above Buzz's window and provided only a limited view of the lunar surface.  Resolution of boulders and craters in the field-of-view depended on distance from the LM and, in the case of objects west of the eventual landing site, good views were only obtained during  the brief time Neil tilted the LM back to slow their forward velocity. 



Boulders C and J

Neil has the LM tilted more upright than planned to slow their descent. Boulders c and j are the only boulders visible in this frame that are also visible in the EVA Hasselblad images. (Click on the image for a larger version.)








frame from the descent fil showing the three
                largest "e" boulders


With the LM tilted back a bit to slow its forward velocity, we get our best view of the area north and west of the eventual landing site.  Although the LM is still east of Little West Crater, the three largest of the e-group of boulders are resolved.  We also get a reasonable view of the fresh crater - and the depression beyond it -  discussed in Section 4. The next image shows the foreground boulders from closer range. (Click on the image for a larger version.)






Boulders north of Little West


After Neil tilts the LM more upright to begin the final descent, we get an excellent view of nine boulders north and northwest of Little West that have been identified in the EVA Hasselblad images. (Click on the image for a larger version.)





DAC
                view of the area between Little West and Pan 3 Crater


Now closer to the landing site, we get good views of eleven small craters and six small boulders which can be identified in a detail from AS11-40-5934, a frame from Pan 4, and in a detail from Pan 5. (Click on the image for a larger version.)






Rocks in the
              vicinity of the Pan 3 Crater


On the final approach, the descent engine is sweeping fine dust from the surface.  Eagle will land just off screen to the left of the Pan 3 Crater.  Excepting only x3, the rocks and craters beyond the Pan3 Crater can also be seen in a detail from a panorama Buzz took out his window after the EVA, and in a detail from Pan 3.




4. Features of Special Interest

4.1  Passive Seismometer Experiment Package (PSEP)

Buzz with deployed Seismometer

Detail from AS11-40-5948 showing Buzz with the deployed PSEP
(Click on the image for a high-resolution scan of the full photo.)


PSEP
                  dimensions meausre by Allan Needell

Dimensions of a qualification unit.  Courtesy Allan Needell, National Air and Space Museum.
(Click on the image for a larger version.)


A comparison has been made between photogrammetrically-determined dimensions of the deployed PSEP and dimensions measured on a qualification unit in the collection of the Smithsonian Institution's National Air and Space Museum. The available photos are those Neil took from just south of the PSEP after Buzz deployed it and those Neil took out his window after the EVA.

The measurements provided by Allan Needell are given to the nearest quarter inch (0.006 m).

Feature
Lunar
Dimension (m)
NASM
Dimension (m)
Solar panel length
1.866
(average of four edges;
both tops and bottoms
1.860
Solar panel width
0.328
(average of four ends)
0.330
Top edge separation
1.463
(average of near and far corners:
1.466 and 1.460 m, respectively)
1.524
Bottom edge separation
1.793
(average of near and far corners)
1.750
Solar panel tilt from vertical
30 degrees
20 degrees

Clearly, the derived lengths and widths of the lunar solar panels agree with the qualification unit measurements to within the 0.006 meter precision of the measurements.  Good agreement is expected because each image showing the PSEP shows both panels.  Determinations of lengths and widths, therefore, begin with high-accuracy differential measurements on each image but depend most critically on the accuracy of the distance of each camera station from the PSEP.  Because the four end points on each of the solar panels are well defined and because many of the PSEP images also show the LM and benchmarks near it, the relative locations of the stations are well defined.  In addition, post-EVA photos taken out Neil's window,  help accurately establish the relative distance of the PSEP and associated camera stations.  Consequently, the largest uncertainty in the photogrammetrically-determined lengths and widths of the solar panels is the overall scale of the IM generated scene.  The excellent agreement between the photogrammetic dimensions and the measurements made of the qualification unit give confidence that the overall distance scale is good to better than one percent.

The derived separations on the lunar unit are significantly larger than the qualification unit measurements and far larger than the photogrammetric uncertainty implied by the comparisons of length and width. Needell notes that some components of the unit, as received from Bendix, are not original.  It is not known how much refurbishment was done on the unit before delivery to the Smithsonian; but it would not be surprising that such things as the solar panel deployment linkage was not in original condition.  That would easily explain the 5 cm differences in top-edge and bottom-edge separations and, consequently, the difference in panel tilt.



4.2 Boot Print Soil Mechanics Experiment (BPSE)

Pre- and
                      post-EVA images of the BPSE area

Pre-EVA (left) and post-EVA (right) images of the BPSE location with a number of
small rocks labeled.   Rocks 65, 435, 436, and 437 were used to get photogrammetric
locations for the two bootprint Buzz made and photographed for the soil mechanics
experimenters.  The rocks labeled with letters appear to be undisturbed in the
post-EVA image. (Click on the image for a larger version.)


Starting at about 110:25:09, about 1 hour 29 minutes into the EVA, Buzz  performed the Boot Penetration Soil Experiment (BPSE), listed as "Pene-Photo Footprint" on Buzz's sewn-on cuff checklist.  After selecting a patch of undisturbed lunar soil, he took a "before" photo (AS11-40-5876), stepped forward to make a bootprint, and then stepped back to photograph the result (AS11-40-5877-78).  He then made a second boot print (AS11-40-5879-80) forward of the first.  Unexpectedly, these two bootprints have survived, despite all the activity near the LM during the remainder of the EVA, and have been located photogrammetrically using small, nearby rocks visible in the bootprint photos, in pre-EVA window photos, in Pan 2 photos, in frames from the 16-mm movie shot out Buzz's window during the EVA, and in post-EVA photos.

Five small rocks (65, 435, 436, 437, and 438) associated with the bootprints are labeled in a detail from pre-EVA window photo AS11-39-5771; in a detail from Pan 1 frame 5855; and in a detail from the photogrammetric map. Two of these (435 and 436) are visible in a labeled version of first-bootprint photo 5877.  A labeled detail from a DAC frame taken about 110:27:02 shows rocks 435 and 437 near the second bootprint.  A labeled detail from AS11-40-5885, a frame from Pan 2, shows both bootprints and rocks 65 and 435.  Finally, a labeled detail from post-EVA window shot AS11-37-5484 shows the same scene from a different perspective.

4.3 LM Insulation

LM
                    insulation pieces 22 Sep 2010 Solar El 88 Az 195


Six pieces of LM insulation in an LROC image taken with the Sun about 9 degrees west of the zenith.  Piece 2 is about 120 meters from the LM.  Deconvolved LROC image by GoneToPlaid.  (Click on the image for a larger version.)



The ascent films shot out the LMP's window on each of the missions show pieces of LM insulation and even whole thermal blankets flying away from the LM at speed.  For example, an Apollo 15 thermal blanket, probably from the MESA, comes into view in the ascent film about 1.9 seconds after first spacecraft motion, hits the surface at about 6.83 seconds 11 meters north of the ALSEP Central Station and 110 m from the LM, rises again, and eventually comes to rest about 180 m from the LM.  At least on smaller piece of insulation left the LM at lower speed and, necessarily, came to rest closer to the LM.

Necessarily, none of these piece appear in any of the Hassleblad images used in the photogrammetric analysis of the site, they are visible in at least some of the LROC images used in the present discussion.  One of us (VP) has identified six, bright, point-like objects that each appear in multiple LROC images and don't have rock-like characteristics such as shadows.  The following table lists the pieces identified in each of six LROC image. It is useful to remember that the insulation was installed in a wrinkled condition, so that piece torn off the descent stage by the ascent exhaust are likely to be far from planar in shape. In some cases, the location of a piece is in shadow and, therefore, does not reflect sunlight toward the LRO spacecraft.  In others, although the location is in full sunlight, there is no bright object present, suggesting that the piece of insulation is oriented such that there is no significant reflection of sunlight toward the spacecraft.  And, finally, there are cases in which the location of the glint appears to be in slightly different locations from one LROC image to another, suggesting that the piece of insulation is large enough that one surface produces a glint at a particular Sun angle while another surface on the same piece produces a glint at another Sun angle.

LROC image
linked to
labeled version
Date
Time (UTC)
LRO Altitude (km)
Pixel width (m)
height (m)
Solar El/Az
1
2
3
4
5
6
M109080308R
01 Oct 2009
23:50:41
49.96
0.53
0.54
87.8 / 195.3
Yes
Yes No
Yes Yes Yes
M119693197L
01 Feb 2010
19:52:11
40.74
0.92
0.88
34.9 / 270.3
No
Yes
No
Displaced
Yes
No
M122054682R
01 Mar 2010
03:50:15
41.52
0.43
0.55
62.3 / 271.3
Yes Yes faint
Yes Yes Displaced
M131494509L
18 Jun 2010
10:00:42
39.75
0.4
0.55
10.8 / 89.7
Yes
Yes
In Shadow
Yes
In Shadow
In Shadow?
M150361817R
22 Jan 2011
18:55:49
38.73
0.4
0.55
27.4 / 270.5
No
Yes
Yes
Yes
No
No
M139755141R
22 Sep 2010
00:37:53
45.86
0.46
0.55

81.1 / 255.4
Yes
Yes
Yes
Yes
Yes
Yes




4.4 Buzz and the US Flag

Detail from AS11-40-5875

Detail from AS11-40-5875 showing Buzz looking over at Neil.
Click on the image for a high-resolution version.)



4.4.1 Flag Dimensions

Anne Platoff's article about the Apollo 11 flag gives two different sizes for the flag: 3 x 5 ft (91 x 152 cm) and 28 x 54 inches (71 x 137 cm).  Standard proportion for a US flag of width (W) are length = 1.9 W, stripe width = W/13, and star field (union) area width = 7W/13.  A hem was sewn into the top of the flag for insertion of the crossbar that would support the flag.  During deployment, Neil and Buzz were unable to fully extend the crossbar.

Comparison of dpeloyed
                    flag and preflight photo


Comparison between the deployed flag in details from AS11-40-5875 (left and right) and a pre-flight photo (S69-38748, center)  of the flag and staff.  Photogrammetry done with EVA frames AS11-40-5886, 5875, and 5905 give distances in cm from the top of the staff to the bottom of the uppermost knurled section (110 cm), the top of the next knurled section (122 cm), the bottom of that section (151 cm) and the centers of the two, thin knurled bands (205 and 212 cm) just above the ground surface.  The width of the flag from the top of the horizontal rod to the bottom of the flag at the point where is it attached to the staff is 83 cm. The average width of four stripes near the bottom of the flag is and five and the top were also determined. (Click on the image for a larger version.)



The following table compares the locations of well-defined features on the flag staff determined photogrammetrically for the deployed flag with measurements made on the pre-flight photo, S69-38748.  Because we do not have a means of determining actual lengths in the pre-flight image, the comparison is done in terms of distances from the top of the staff scaled to the distance from the top of the staff to the bottom of the second long knurled section.  The relative distances agree quite well and indicate that they are accurate to about  2 cm.


Deployed flag from photogrammetry
Preflight image S69-38748
Location
Distance from top (cm)
Relative distance from top
Relative Distance from top
Top
0
0.0
0.0
Bottom of 1st knurl from top
110
0.519
0.515
Top of 2nd knurl
122
0.575
0.566
Bottom of 2nd knurl
151
0.712
0.712
Upper Thin knurl
205
0.967
0.967
Lower Thin knurl
212
1.000
1.000
lunar surface
217
1.024

staff bottom
(235)

1.109

The following dimensional information can be derived from the photogrammetry and the comparisons
  1. The total length of the assembled staff is 235 about 2 cm)
  2. Neil and Buzz were able to get the staff about 18 cm (7 inches) into the ground.  This is similar to the distance Buzz was able to hammer in the core tubes.
  3. Width of the flag from the top of the pole to the point where its corner is bound to the pole: 83 cm.  This implies a stripe width of 83/13 = 6.38. The average width of the four stripes near the bottom is 6.68 0.17; for the five near the top, 6.34 0.54; and for all nine, 6.49   0.43.  The 83 cm width implies a flag length of 1.9 x 83 = 158 cm.
  4. During the deployment, Neil and Buzz told Houston they were unable to extend the rod to its full length. The photogrammetrically-determined length is 118 cm (from the end to the middle of the pole), which is 40 cm shorter than the inferred flag length.



4.4.2 Flag location and attitude
  1. Distance to the LM center: 10.7 m ( 0.2 m maximum, but more likely better than 0.1 m).
  2. Distance to the +Y pad center: 7.8 m.
  3. Distance to the TV camera tripod center: 14.3 m.
  4. Distance to camera stations inside the LM at the right (LMP) window, also
    the approximate distance to DAC: 10.9 m (calculated from 5483 camera
    coordinates).
  5. Flag pointing azimuth: Relative to the axis with its origin at the center of the +Z footpad and passing through the center of the -Z footpad, the horizontal rod that supports the flag points 37.3 degrees to the right.  Neil landed with the LM rotated 13.3 degrees counterclockwise from east-west, so the flag is pointing 24 degrees south of east.
  6. Flag pole east-west tilt:  Using four EVA photos - 5884, 5905, 5920, and 5925 - hotogrammetry gives us the positions of the top and bottom of the flag pole and of the tip of the flag shadow.  Trigonometry then gives the angle at the top of the pole between the pole and the line to the tip of the shadow as 73.2 degrees.  If the pole were perfectly vertical, the angle would be 90 minus the solar elevation.  At the times the four photos were taken, the solar elevations were 14.661, 14.763, 14.797, and 14.822, respectively.  The average is 14.76 so that, in the case of a perfectly vertical pole, the angle at the top of the pole would be 75.24.  The difference between that value and the photogrammetrically-determined value of 73.2 indicates that the pole was titled about 2 degrees to the west.  During a post-flight press conference Neil said "We had some difficulty, at first, getting the pole of the flag to remain in the surface. In penetrating the surface, we found that most objects would go down about 5, maybe 6, inches and then it would meet with a gradual resistance. At the same time, there was not much of a support force on either side, so we had to lean the flag back slightly in order for it to maintain this position." With the flag pointing in an easterly direction, they would have tilted it in a westerly direction to get the center-of-mass closer  to being over the bottom of the pole.  The photogrammetrically-determined tilt is certainly in the right direction.  Any north-south tilt would be small.

4.4.3 Buzz's location in AS11-40-5874 and 75


Detail from 5875 showing rock or clump just
                      behind Buzz's boots

Detail from 5875 showing a small soil clump or rock behind Buzz's boots.  Neil is about 6.2 meters from Buzz and about 7.5 m from the flag. (Click on the image for a larger version.)

The soil clump also appears in 5885 and 5905. Photogrammetry using the three images gives a location for the clump and, from that, Buzz's location.

Map showing Buzz's
                    location in 5874 and 5874

Map showing Buzz's location when 5874 and 5875 were taken.


4.4.3 Buzz's location in AS11-40-5903

Labelled detail for AS11-40-5903

Labelled version of AS11-40-5903, showing Buzz coming out of a shallow crater toward Neil.  Behind Buzz's right foot is part of a full boot print he made on the crater floor;  the back of the heel print is marked in red.  Because Buzz is walking, rather than running or hopping, as he comes up the inner slope of the crater, his weight is pressing his toes into the relatively soft soil of the slope.  The toe of his left boot - marked in red - is making a deep imprint next to a small, distinctive rock.  A full-resolution detail shows that Buzz is moving his right boot forward from the print he made of the floor of the crater, pushing some soil ahead with his toe.  As his right leg comes forward, the left toe will sink deeper into the slope. (Click on the image for a larger version.)




Lablled detain from 5915 showing the small
                    rock and bootprints identified in 5903

Labelled detail from AS11-40-5915 showing the rock and boot-print features identified in 5903.


Labelled detail from 5915 showing Bootprint
                    features marked in 5903

Labelled detail from AS11-40-5915  showing the boot prints Buzz made coming out of the small crater.  The heel of the full right (R) bootprint at the bottom of the crater is marked in red.  When Buzz stepped forward with his left leg onto the rising slope, the toe of his left boot (L) penetrated the soft surface and compacted the marked area.  The approximate forward edge of that print is marked in red.  As seen in 5903, as Buzz moved his right leg forward, he pushed some soil forward (to the right in this image). The disturbed soil is marked.  There is also some disturbed soil downslope of his next left bootprint, which may be a combination of soil pushed forward as he moved his boot and soil displaced backward as his toe penetrated the surface.





Map segment showing locations of the 5903
                    bootprints

Locations of the rock and left-and-right bootprints determined photogrammetically from a number of EVA photos.


Comparison of
                      features in 5903 and 5914


In 2013, Ulli Lotzmann did an independent comparison of 5903 and 5914 and identified the imprint of the toe of Buzz's right boot made when, shortly after 5903 was taken, he moved his left foot forward.
(Click on the image for a larger version.)

4.5 Craters




Location and sizes
                    of well-defined craters near the LM
Double Crater plus nine small craters with rims that are well-defined in the Hasselblad images.  (Click on the image for a larger version.)



4.5.1 Craters near the LM Located Photogrammetrically

The map includes nine small craters near the LM, chosen primarily because their rims are well defined in the Hasselblad images.  These craters are labeled with Greek letters.  Each crater is assumed to be circular.  For each crater, 3 to 4 stones as close to the rim as possible were picked as benchmarks. In the case of crater ε, two small rocks and the southern end of the LRRR tool were used. The benchmark locations were calculated and plotted on the map as small red dots.  A circle was then drawn manually to fit the benchmarks.  There are, or course,  many other small crater visible in the Hasselblad and LROC images.



4.5.2 Double Crater

Detail from the
                    photomap


Detail of the photomap showing the benchmarks used to define the complex rim of Double Crater.  Fourteen small rocks were used to define the rim of the western (younger) component; nine for the eastern (older) component; and six for the small, irregular southern component.


This pair of overlapping craters - together with an older, overlapped feature on the south side - are visible out Neil's window, just south of the LM shadow.  The complex rim structure is defined by 29 benchmarks which were then used to define smooth, osculating curves.  The two figures that follow show the locators used to define the western component.


IM display of benchmarks
                  in 5786


Screen grab of IM display of benchmarks in AS11-39-5786.  Some of these were used to define the western component of Double Crater and are labeled in the next figure.  Note that, in the IM display, benchmarks are labelled as 'locators'.  (Click on the image for a larger version.)




Western
                  component of Double Crater


Benchmarks visible in AS11-39-5786 (previous figure) that were used to define much of the rim of the western component of Double Crater.  Placement of the rim is necessarily subjective.


The complex rim of Double Crater is not well defined.  The rim of the eastern component, in particular, has been worn down and, even the rim of the fresher, western component in well enough worn that the rim is best defined as a finite region between the break in slope at the top of the inner wall and, farther out, the break in slope at the top of the outer wall.  This region might be termed the rim zone.  In the Hasselblad images, the stones used to define the rim in the previous illustration - such as 366 and 368 - are clearly at the outer edge of the rim zone.  An alternate analysis using shadowing of the inner crater wall  puts the inner edge of the rim zone about 1m closer to the center of the crater.



4.5.3 Large Craters Northwest of the LM


Detail from
                    AS11-37-5513, taken out Buzz's window

Detail from AS11-37-5513 showing the view to the northwest over the plus-X thruster outside Buzz's window. Two previously identified boulders, e4 and e10, are labeled in the foreground. Four craters ranging in size from 18 to 60 m are labeled in the distance, along with boulder newly identified boulder eq1, near crater C1.


Detail
                      from M116161085R

Northwest craters C1, C2, C3, C4 and boulder eq1 in an LROC detail from GoneToPlaid's rectified version of M116161085R. Crater C5 is discussed in a following section.  Note, also, that eq1 is just outside the south rim of C1. (Click on the image for a larger version.)




C1:   This crater is the more northerly, more distant, and fresher of two overlapping craters.  The older, more southerly companion is not visible from Buzz's window.  The center of the fresh crater is about 670 m from the LM, has a raised rim, and a diameter of ~60 m.  The older companion has a diameter of ~90 m.  The raised rim of C1 is prominent in an unrectified detail from M132678405RE.  Finally, there is a relatively-fresh, 40-m crater with a raised rim  that is tangent to the rim of the older companion to C1.  This fresh crater is ~40 m south of C1; and ~30 m west of eq1.  It doesn't appear to be visible from Buzz's window.

C2:  An ~18-meter crater ~525 m north-west from the LM; and ~50 m to the south-east from the older companion to C1.  A smaller crater about 9 m across notches the southern rim of C2.

C3: ~35 m diameter and ~430 m from the LM.

C4: ~40 m diameter and ~370 m from the LM. It lies in a very shallow depression and it remains in shadow in M132678405RE.

4.5.4 Crater Rims on the Western Horizon

Detail showing
                  two hills on the western horizon

Detail from Buzz's post-EVA window pan showing two hills on the western horizon. The horizontal yellow line approximates the level horizon.  Bounding azimuths for each of the hills are indicated with short, vertical lines and the numerical values are given in red at the bottom.  Note that there is elevated ground between the two hills, perhaps indicating that they are high points on the rim of a large crater.  (Click on the image for a larger version.)


Lebeled
                  version of Lunar Orbiter Inage 5076-h3

Lunar Orbiter image 5076-h3 with the yellow lines showing the bounding azimuths from the LM of the two hills.  (Click on the image for a larger version.)


There are two candidate craters.  The obvious one is the crater complex named before the flight as the Cat's Paw.  With the Sun relatively low in the east, we see rising ground in the azimuth bounds on the outer slopes of the southeast and northeast portions of the near component of the Cat's Paw rim closest to the LM.  As can be seen in the flown copy of LAM-2, those patches of rising ground are about 6 km from the LM.  The near component has a diameter of about 2 km. A second candidate is a crater labeled C5 in the Lunar Orbiter image and in a detail from M116161085.  C5 has a diameter of ~200m and the near rim is ~200m from the LM.

In the view from the LM, the hills on the western horizon are about 0.6 degrees high.  At 200m distance, that corresponds to a height of about 2 meters.  At 6 km, the linear height would be 60 meters.  For a fresh crater, the rim height (h) is related to the crater diameter as

h = 0.036 D1.014

when both are given in kilometers (Lunar Sourcebook, Table 4.1, p66).  When fresh, crater C5 had D = 0.2 km and h = 7 meters; and the near component of the Cat's Paw had D = 2 km and h = 70 meters.  While these numbers are only approximate, they seem to argue against the possibility that the hills on the western horizon at Tranquility are portions of the Cat's Paw rim.  If the near component of the Cat's Paw was still fresh, the rim would be visible from Tranquility at would rise about 0.7 degrees above the horizon.  However, it would extend across 19 degrees of the horizon at more or less uniform height.  The Lunar Orbiter images shows that, while the rim is elevated, it has been subject to considerable impact erosion.  Compare its appearance with the small fresh crater south of the Cat's Paw, near the bottom of the image above, or with West Crater.  In the case of C5, the rim is heavily eroded but would only need to have retained 2 meters of an original height of 7 meters.

Detail
                    from M132678405R


Detail from GoneToPlaid's deconvolution of M132678405R, showing the east rim of crater C5 when the Sun was only 2 degrees above the western horizon.   Although the LM is sunlit, the ground between the C5 eastern rim and the LM is in shadow, excepting only the eastern rims of fresh craters.  See, also, an animation comparing this sunset view with the morning view from M116161085.

Shadowing of the ground between the eastern rim of C5 and the LM indicates that the surface is sloping down to the east.  See the full version of the deconvolution for context.  It seems likely that the northern hill is associated with the C5 rim between azimuth lines 3 and 4.  The case for the southern hill is less clear.

Finally, we have the following exchange between Neil and Buzz at LM pitchover, about ten seconds into the ascent.

124:22:15 Aldrin: Very smooth.  Balance couple, Off.  (Pause)  (To Houston)  Very quiet ride.  (To Neil)  There's that one crater down there.  (Pause)

124:22:26 Armstrong (onboard): (Garbled) See if you can see the, er, Cat's Paw. (Pause)

This exchange can be interpreted to mean that, at 124:22:15, after getting the DAC started about 6 seconds after ignition, Buzz had a view into the crater associated with the hills while, at 124:22:26, Neil realizes that he won't have the Cat's Paw on his side of the LM and suggests that Buzz look for it.  If this interpretation is correct, "that one crater" is C5.  Indeed, C5 nearly fills the frame in the first part of the ascent video.  Of course, the DAC is pointing down at a steep angle, so it is possible that Buzz is referring to another crater.  The near component of the Cat's Paw does come into view in the DAC film (bottom two DAC frames) starting at about 52 second.


Comparioson of Lunar Orbiter images with A11
                  Ascent Film

Comparison between Lunar Orbiter image 5076-h3 and a selection of frames from the Apollo 11 ascent film between 52 seconds after the start of the film clip and 1 min 11 sec.  The frames are not evenly spaced in time, but were chosen to include small features that can be identified in both the Orbiter images and in the ascent frames.  (Click on the image for a larger version)


4.5.5 Craters Southwest of the LM

C6-11
                  in a detail from M116161085R

Craters C6 to C11 labeled in a detail from M116161085.
(Click on the image for a larger version.)


detail from
                      post-EVA photo AS11-37-5500

Detail from post-EVA photo AS11-37-5500 taken out Neil's window.
(Click on the image for a larger version.)


As discussed in Section 3.6, boulders zb1, zb2, zc, and zc are just outside the rim of 140-m crater C7. The nearest part of the rim is about 310 meters southwest of the LM.  The near part of the rim is seen against a background provided by the southwestern, inner wall of the crater, as can be seen in an animation made from post-landing photo AS11-37-5847.

C6 is a fresh, blocky rimmed crater ~300 m from the LM, with a diameter of about 45 m.  Perhaps because C6 is on the outer slopes of both C7 and a larger crater to the west,  the near rim of C6 is lower than the far rim, which gives us a good view of the numerous blocks on the southwest inner wall.

C8 is a ~22 m crater that appears to be on a broad level area on the northeast rim of C7.
from the LM. We can see a bit of the shadowed inner wall on the far side of C8.


detail from AS11-37-5550 showing C9-11

Detail from AS11-37-5550 showing craters C9, C10, and C11.  Boulder x, in the middle distance, is ~221 m from the center of the LM, with width ~1.1 m and height ~0.4 m.
(Click on the image for a larger version.)


C9 is a fresh, sharp-rimmed crater on the outer, northeast flank of the large crater immediately south of C7. Diameter about 17 m and distant from the LM ~440 m.  In the LROC detail, we see a similar-sized crater, sharp rimmed crater west of C9.
C9 overlaps this crater, indicating that C9 is younger.  In a 2x-detail from 5550, the only possible sign of this crater are boulders on the local ridge line but, because the slope north of both craters is littered with rocks, it seems more likely that the rocks are ejecta from West Crater and that the crater overlapped by C9 is hidden by local terrain.

C10 is ~405 m from the LM, with a diameter of ~26 m.  It is a fresh, sharp-rimmed crater and overlaps a slightly smaller crater on the west. Visibility in a 2x-detail from 5550 is marginal, Portions of the rim are illuminated in sunset image M132678405R.

C11 is a large eroded crater with its near rim ~435 m from the LM and its diameter ~75m.  We have a view of the inner, southern wall along most of its east-west extent.  In a 2x-detail, the inner, southern wall is noticeably brighter than material closer to the LM.

4.5.6 Craters Northeast of the LM visible in Pan 5

Detail from M116161085R showing craters C12-16

Detail from M116161085R showing craters C12-16.
(Click on the image for a larger version.)


Detail from
                    AS11-40-5956 showing C12-17

Detail from AS11-40-5956.  This view to the NNE shows craters C12 to C17 from Neil's elevated position at the Pan 5 location on the southwest rim of Little West Crater. (Click on the image for a larger version that includes context.)


C12 is a 10-m crater ~300 m from the LM.  It is just inside the rim of a very eroded, ~170-m crater.  The near rim of the eroded crater is ~170 m from the LM. Most of the eroded crater is hidden by the rim of Little West.

C13 is a 9-m crater, ~320 m from the LM.  In the LROC image, it appears  to be farther from the center of the eroded crater and nearer the rim crest.

C14 is an 11-m crater, ~340 m from the LM. It is just outside the eroded crater.

C15 is a 12-m crater, ~450 m from the LM.

C16 is a 16-m crater, ~740 m from the LM.

C17 is a heavily-eroded, ~80 m crater ~580 m from the LM. From
the Pan V location, the northern rim appears to be higher than the southern rim, but this is probably a result of the generally rising ground in that direction. The LROC image shows a number of younger crater within C17.  The largest has a raised rim and a diameter of ~25 m.  It is just inside the northwest rim of C17.


4.5.7 Craters Near the LM Viewed from the Windows



All of these craters have been identified in comparisons between photos taken out the LM windows and GoneToPlaid's deconvolution of LROC image M116161085R.  Parallaxes available in the window photography are too small to allow meaningful photogrammetry.


A version of ConeToPlaid's deconvolution of M116161085R with labels for craters C18 - C70  and selected boulders is linked here.  Details from the LROC image and from the window photos are linked in the following table.

Crater
Diameter (m)
Distance (m) Window Notes
Window Photography
LROC Details
C18
6 (each)
65
LMP
tangent pair
C18-C20
C18-C24
C19 6 x 3
35
LMP
overlapping pair
C20 9 + 3.5
58
LMP crater with a small one overlapping western rim; e4 boulders on southwest rim.
C21 5
26
LMP θ crater in the photogrammetric map
C21-C22
C22 5
55
LMP
"Fresh crater" in previous sectons
C23 4
47
LMP

C23
C24 7.5 + 5.5
38
LMP
Overlapping craters; larger component on the southwest
C24
C25 22
155
CDR

C25-C27
C25-C26
C26 23
105
CDR small rim craters visible in CDR photo 5743
C27 3
28
CDR just outside southern rim of the western component of Double Crater
C27
C27-C36
C28 16
115
CDR

C28-C30

C29 8 x 18
80
CDR cluster with two pairs of overlapping craters.  The craters in each pair are oriented NNW-SSE.  Each crater is 5-6 meters in diameter.
C30 3
53
CDR
C31 8 x 12
50
CDR two overlapping craters, northern component ~9 m, southern component ~5 m and younger
C31-C41
C32 6
50
CDR
C33 3
45
CDR
C34 5
45
CDR
C35 6
115
CDR
C36 16
115
CDR boulder gt12 is on the southeastern rim
C37 5
195
CDR
C37-C44
C38 14
195
CDR In the window photos, C36 appears to be very close to C38.  The craters are actually 80 meters apart, with the ground between hidden by terrain rugae that manifests itself in the window  photos by a clearly-visible separation line with C35 and C36 north of the line and C37 and C38 south of it. The same ruga hides a raised-rim, 13-m crater ~155 m from
the LM center, about midway between C35 and C37 and about its own diameter west of the line connecting them.  In the LROC image, there is a prominent boulder on the southern rim of the hidden crater.
C39 9
190
CDR From CDR window, boulder y2 appears to be close to the eastern rim.  In fact, C39 is more than 40 m
beyond y2. The area between y2 and C39 is hidden by the rugae.
C40 7
195
CDR Its eastern rim is slightly elevated.
C41 9
215
CDR A 4-m crater is just south and slightly east of C41, with about a 2 m separation between the rims. The small crater is also visible from the CDR window. Several craters are
hidden - or partially hidden - behind the rugae in an area with C40-C41 on the south and boulders y1- u on the north.
C42 6
210
CDR Sits near the bottom of a low area between dark ground the rises to the east and lighter ground that rises to the west.  It is also in the southern rim of an old, 20-m crater.


C42-C49





C43 4 x 9
205
CDR Two overlapping craters on the eastern rim of the old, 20-m crater.  Each of the craters has a diameter of 4-5 m.
C44 15 x 8
230
CDR Elongated feature that could be the result of (1) two or three separate impacts, possibly arriving nearly simultaneously from a single impact source or (2) a nearly tangential impact.  (Impacts at all but the slowest speeds produce nearly circular craters unless the impact angle is very small.)
C45 7
105
CDR 2 meters west of boulder a.
C45-C49
C46 3
55
CDR on the rim of the same depression as C31 and C32.
C47 4
50
CDR on the rim of the same depression as C31 and C32, partly hidden by spacecraft structure.
C48 2
27
CDR less than 2 meters east of the PSE
C49 5
125
CDR


4.5.8 Craters in Pan 4

Craters visiblew in Pan 4
Craters visible in Pan 4, southeast (top) and northeast (bottom).
(Click on the image for a larger version)


Crater
Diameter (m)
Distance from LM center (m)
Notes
LROC detail
C50
3
75
~6 m to the north of C34, seen also from CDR window
C50-51
C51 6
32
Crater ι in the photogrammetric map; small, fresh crater on its western rim also seen in LROC image
C52 7
260
Seen also from CDR window
C52
C53 8
155
~20 north-east of boulder l1, 14 m from l2.
C53-55
C54 9
165
Has a second component (~5 m in diameter) on the southwest side.  ~14 m east of C53.
C55 5
180
6 meters east of C54
C56 5 55
C18 is just beyond it to the north
C56-64
C57 7
50
It has an ~5 m component adjacent to the western rim.  The southern rim is very steep, casting a deep black shadow into the crater.  The shadow is quite noticeable in EVA photos, such as 5885/86 where it is just below the flag.
C58 7
80
~9 m south of boulder d, ~7 m south-west of g.
C59 5 x 6
55
slightly elongated N-S, 6 m southwest of boulder g.
C60 ~6-7
25
slightly elongated, quite shallow
C61 7
25
halfway between LM and Little West
C62 13
50
18 m northwest of Little West, seen in many EVA photos and the descent film
C63 8
70
"shallow depression" is a better description than "crater", just northeast of boulder b.
C64 4
50
on the northwest outer wall of Little West


4.5.9 Craters in Pan 2


Labeled section of Pan 2, images 5888-9

Craters visible in the southeastern part of Pan 2, including frames AS11-40-5888-9.
(Click on the image for a larger version.)


Crater
Diameter (m)
Distance from LM (m)
Notes
LROC detail
C65
10
90
13m north of boulder a
C65-67
C66 5
100
2-3m east of C65
C67 5
105
10m east of C66
C68 11
145
14m north of C54
C68
C69 5
35
Boulders r1-r3 are near the rim
C69-70
C70 2
12 southeast of the LM center
Best seen in the foreground in 5942-44. There are astronaut bootprints on the west rim.  These are visible in the Hasselblad images but not in any of the LROC images



5. Comparisons between the Photogrammetric Map and the LROC images


Journal Contributor GoneToPlaid has provided a set of deconvolved LROC images at resolutions of 0.25 and 0.50 m/pixel.  In this section we compare the photogrammetric map with the 0.5 m/pixel versions (which cover four times the area of the 0.25 m/pixel versions) of the 25 November 2009 LROC image (M113799518RE) and the 22 December 2009 image (M113799518RE).  The two LROC images don't overlay precisely on each other, so we have stretched the November image by 2.093 percent (878/860) vertically and 2.620 percent (235/229) horizontally so that the northernmost, southernmost, easternmost, and westernmost boulders overlay, with maximum position differences of 1-2 meters.  The two images were then cropped to a single size and enlarge by a factor of two to accommodate comparisons with the photogrammetric map.  We note that in a comparison with the scale in the photogrammetric map, the 2x enlarged LROC images have 83 pixels in 20 meters or 0.241 m/pixel rather than 0.25.

As we discuss more fully in sections 2.1.5 and 3.2.2, photogrammetric locations of boulders northeast of the LM depend on the small parallaxes available from stations near the LM.  These boulders are also visible in Pan 5 frames taken on the rim of Little West Crater but, because the Pan 5 stations are dependent  primarily on the northeast boulders, IM produced locations (the green dots) for the northeast boulders and the Pan 5 stations that are systematically too far east by about 6 meters.

Map vs M116161085RE boulders shown as dots, no
                  names

Comparison in the central region of the map of boulder locations from the
photogrammetric analysis with a
deconvolved version of the 22 December
2009 LROC image M116161085RE
provided by GoneToPlaid.  Boulders
visible in the LROC image before
deconvolution are marked with red
dots (
). Boulders visible only in the deconvolved image are marked
with yellow dots (
). The photogrammetric locations are marked with
green dots (
).  (Click on the image for the entire map region.)

6. Accuracy of the 3D Scene

6.1. Error sources


In principle, point-like benchmarks visible in the various photographs would permit accurate placement of the camera stations. If the scene is calibrated accurately, each benchmark corresponds to a single point in the actual 3D space. However, for the reasons discussed below, there are few point-like benchmarks available in the scene. As a result, calculated camera station locations and azimuths have errors, and benchmark locations seen in multiple photographs may be inconsistent from one photograph to another.

1) Blurring. Objects chosen as benchmarks may be situated at quite different distances from the camera.  In some images they may be out of focus.  Blurring may also occur if the object is in sun glare or if the camera moved during the exposure. Blurring of objects chosen as calibration benchmarks makes it difficult to place calibration benchmarks correctly, they may be inadvertently shifted from the right place in blurred photographs.

2) Lack of point-like benchmarks. Only a limited number of point-like objects are available in lunar photographs, with most of them being points on artifacts (sharp angles, tips of antennas, etc.). However, construction of a scene with IM requires calibration benchmarks dispersed more or less uniformly over the plane of each photograph, so natural benchmarks (mostly rocks) were used in large numbers. Since most of rocks are not sharp, it is very difficult or nearly impossible to find a specific point on a rock that may be identified precisely in different photographs. Rocks look very different in photographs taken from different locations; and a portion of a rock visible from one location may be hidden from other locations. The same problem often arises with artifacts as well. Consequently, most benchmarks can not be positioned with high accuracy. For many rocks used as benchmarks, the uncertainty can be comparable to the size of the rock in question.

3) Focal lengths are known only approximately. Focal length of the  Biogon f/5.6-60 mm lens used for EVA photography is 61.1 mm. When astronauts focused to closer objects, focal length of the lens became larger (fixed values are 63.50~mm, 61.93~mm and 61.27~mm, they correspond to fixed focusing distances of 5.3, 15 and 74 ft applied in lunar cameras, but intermediate values are also possible). The actual focal length for each photograph depends on the actual focusing distance, which is not known exactly. Focusing distance may be estimated from distance to objects in sharp focus and from blurring of objects that are out of focus, but this estimation is subject to error.

4) Lens distortions. Lens distortions are not of a great importance, since distortions of the Biogon lens are very small.

5) Inexact reference distance basis. Since computed coordinates of the two benchmarks used to determine the reference distance basis contain uncertainties, the basis itself also contains an uncertainty. This uncertainty influences systematically all coordinates and distances expressed in linear units.

The first four factors introduce unbiased errors into the 3D model of the scene created during the calibration of the cameras. The fifth factor introduces an unknown systematic error. As a result, calculated positions of benchmarks and cameras contain uncertainties.

6.2  Benchmark error estimates

Unfortunately, it is virtually impossible to account for each source of uncertainty separately to estimate the overall error of the scene, but we may get reasonable estimations.

1) The uncertainty of the distance reference basis. There are two diagonals between junctions of the primary struts. The mean distance averaged over both diagonals was taken for the reference basis. The difference between the measured lengths was found to be ~1.25 cm. It is comparable to the uncertainty of length measurements (see section 3, below) which was found to be ~2 cm. Dividing 2 cm by the length of the reference basis, we obtained the relative uncertainty of the reference basis, it is ~0.34%. This is a systematic error that it is present in all measured ranges and sizes. For instance, a distance of 10 m may be measured with an accuracy not better than ~3.4 cm.

2) Local vertical. The pole of the SWC experiment is close to vertical and we used its direction as z-axis. To estimate its deviation from the true vertical, we measured the angle at its tip between the pole and the solar rays forming the shadow of the tip. An average value of 72.9 deg was obtained (this angle is measured with error since the solar elevation angle slightly changed during EVA). If the pole had actually been vertical, the measured value would have been 90  - 14.7 = 75.3 deg, 14.7 deg being the mean solar elevation angle during EVA. The difference between 75.3 and 72.9 gives an estimate of a 2.4 degrees western tilt of the pole. Since the positioning accuracy of the ends of the SWC pole is several centimeters, the uncertainty of this angle may be of several degrees. Combining a measured northern inclination of 2 deg of the SWC pole with respect to the LM and 0.5 deg southern tilt of the LM (from the navigation system's alignment data), we obtained the northern tilt of the SWC pole of 2.5 deg. So the total tilt is approximately 4 deg. The coordinate uncertainty in the horizontal plane caused by this tilt is (1 - cos 4) * 100 % = 0.24 %. In the vertical direction, the maximum uncertainty in elevations is sin 4 * 100% = 7%. This error is large enough that the z coordinate cannot be used for elevations. The error caused by this uncertainty is systematic, i.e. it is present in all coordinates. It influences mostly measurements of absolute distances from the origin is relatively unimportant at distance small enough that other errors dominate.  For example, at a distance of 100 m, the horizontal error is roughly 25 cm, which is less than the size of most rocks of interest.

3) Comparison of measured and known lengths. We measured lengths of several objects at distances up to ~30 m from the center of the LM, and compared them to known values. In the following table measured values are given together with their known values (Actual), absolute differences (Δ), and relative errors. In some cases, such as the dimensions of the two PSEP solar panels, we give the largest difference and the mean difference. In the table such measurements are given in separate rows and labeled with "max. differ." and "mean, n" where n is the number of measurements. All values are in meters.  It is important to remember that determination of a length requires the location of the end points, with both usually visible in any one image.  The result is that the lengths are actually differential measurements and, consequently, systematic errors may be unintentionally eliminated.  Accuracy estimations derived in this way give the order of magnitude only.

Table: Comparison of photogrammetrically measured and actual lengths


 Measured (m)
 Actual (m)
 |Δ| (m)
 Rel. Error
 PSEP sol. pan. length (max. differ.)
 PSEP sol. pan. length (mean, 4)
 PSEP sol. pan. width (max. differ.)
 PSEP sol. pan. width (mean, 4)
 1.874
 1.867
 0.323
 0.328
 1.861
 1.861
 0.330
 0.330
 0.013
 0.006
 0.007
 0.002
  0.7%
  0.3%
 -2.1%
 -0.6%
 LRRR array width (max. differ.)
 LRRR array width (mean, 4)
 0.439
 0.445
 0.45
 0.45
 0.011
 0.005
 -2.4%
 -1.1%
 SWC pole length
 SWC foil length (max. differ)
 SWC foil length (mean, 2)
 SWC foil width (max. differ)
SWC foil width (mean, 2)
 1.481
 1.325
 1.325
 0.286
 0.295
 1.5
 1.30
 1.30
 0.30
 0.30
 0.019
 0.025
 0.025
 0.014
 0.005
 -1.3%
  1.9%
  1.9%
 -4.8%
 -1.6%




Some values in the table may contain additional uncertainties. For instance, the height of the SWC pole over the ground level may be smaller than the value in the table.

The following conclusions may be made from the table. Relative errors are smaller for long objects and are larger for shorter objects. That is the expected result, since the role of positioning errors (which do not depend on measured sizes) predominates. Absolute errors are within 2.5~cm for all objects, but they may be reduced to less than 1 cm if averaging over a number of measurements is performed. Two factors should be kept in mind. First, each size measurement includes two points, so uncertainties of coordinates of each point may average. Second, size values are differentials, so systematic errors proper to each point may vanish at size measurements. The average absolute error in the table is ~1.5 cm, and we tripled this value (getting ~5 cm) to get a conservative estimation of positioning errors of individual points. A value of 2~cm may be used as estimation of uncertainty of sizes.

To conclude, the following figures may be adopted as reasonable estimations. The accuracy of single-point coordinate measurements should be within ~ 5 cm in the 30-meter proximity from the LM, and we should also account for a ~ 0.34% systematic error due to uncertainty of the distance reference basis and ~0.24 error due to uncertainty of the local vertical. For size measurements the uncertainty of 2~cm may be adopted, and ~0.34% systematic error due to uncertainty of the distance reference basis should also be taken into account.

It should be pointed out that at larger distances from the LM the photographic coverage of specific areas decreases, parallaxes also become smaller, so the positioning accuracy drops and the role of systematic errors increases. So at distances ~100 m positioning errors may reach several per cent. This fact is confirmed by identification of far boulders visible in LROC photographs. Differences between calculated positions and photographic locations of boulders may reach in some cases 7% (being mostly within 4% limit) at the range of 100 - 350 m.


6.3  Accuracy of camera station locations

It is not simple to estimate the accuracy of camera station locations. There are no camera stations coordinates which are known beforehand, so it is not possible to compare calculated coordinates to known values.

Panorama stations may be used for such check, since each panorama consists of a number of camera stations that should be situated close to each other forming a predictable pattern. We see that the Pans 1, 2, 3 stations are in sequential arrays that are roughly circular.  However, the Pan 4 distribution is more irregular, with individual cameras stations shifted as much as 1m from their expected locations.  Finally, the Pan 5 camera locations contained a systematic error of about 6 meters, that has been corrected using LROC data (see  Section 2.1 for a detailed discussion). The distributions of camera stations within the individual panoramas demonstrate that positioning errors are no more than  ~1 m, and most have much smaller errors.  The stations with relatively large errors are all related to photographs taken up-Sun or in directions where nearby benchmarks are scarce.

Most other camera station locations should have errors much less than 1 m. This is demonstrated by pairs and triples of photographs made from the same location. An examination of the maps shows that calculated camera locations nearly coincide in the tetrad 5967-5970, in triplets 5867-69, 5897-99 and 5927-29, in doublets 5874/75, 5892/93, 5901/02, 5946/47, 5949/50, 5963/64; in all these cases azimuths of successive photographs were similar, so the astronaut remained at one place making these shots. In the pair 5920/21, the astronaut turned changing the camera azimuth ~100 deg, so the camera should have shifted. As it is expected, a distance of ~30 cm between these camera stations is present. It it interesting that the photographs contain nearly no common features in the pair 5892/93 due to a large tilt difference. However, calculated locations of the these two camera stations differ only by ~10 cm.

These observations let us conclude that camera positioning accuracy may reach ~0.1 m or even better if sufficient details of the LM or other artifacts are within the image. Nevertheless, accuracy may fall to ~1 m for cameras where mostly distant rocks were used as benchmarks.

Accuracy of azimuths and tilts cannot be found directly as well. The triplets and pairs mentioned above demonstrate that relative camera rotations by fractions of degree may be revealed (as in the case of 5874/75), but the figure of absolute errors remains questionable. Nevertheless, there is no reason to think that these errors are large, so a conservative estimate of 2 deg may be adopted in the first approximation.






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