Photogrammetric Analysis Of Apollo 11 Imagery:
New site map with improved locations of camera stations, deployed
equipment,
and boulders
Copyright © 2010 by Vladislav Pustynski
All rights reserved.
Last revised13 April 2010.
1. Introduction
During 2009, I 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 surface
photography. Actually,
ImageModeler is intended for architectural purposes, but it is suited
very well for photogrammetry of the Apollo images. It has a few
drawbacks. For example, it dislikes "flat" photos, where the
benchmark points are distributed over a relatively flat surface..
Nonetheless, ImageModeler is excellent software for obtaining very good
quantitative results in a simple way.
Figure 3-15
in the Apollo
11 Preliminary Science Report is a map
compiled by R.M. Batson and K.B. Larson at the USGS soon after the
mission. 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 simplicistic but were chosen to allow rapid
compliation of a map adequate for the Preliminary Science Report and
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
may be derived from the "more rigorous analytical photogrammetric
measurements" possible in the years after the last of the Apollo lunar
landings in 1972. That map will be analysed at a later date.
2. 2010 Photogrammetric Revisions to the Site Map
Visual study of the 1969 map
convinced me that it’s quite schematic and not
very precise. Photogrammetry enabled me to improve the location (camera
station) and orientation for each image, along with locations for
boulders, and the US Flag, TV, LRRR, and PSEP. As with the work
of Batson and Larson, all locations are calculated relative to
structures on the LM. As of 10 April, I
had calculated improved locations of 44 camera stations, representative
of the 121 photos Neil and Buzz took
during the
EVA. Three addition stations corresponding to three images taken
out Buzz's window were also used in the photogrammetric analysis, but
are not shown in the site map.
This
10
April 2010 revision of the 1969 Apollo 11 site map is based on 47
photogrammetrically-calculated camera stations. Three are
associated with photographs were taken out the LMP's window after the
EVA and are not shown. Each
small red
dot
represents a location for a camera station, boulder, or piece of
deployed equipment. For each of the
panoramas, from one to four camera locations and orientations
were
calculated; camera stations in particular panorama which were not
calculated retained their
original orientation but were plotted at the new location of the
representative members of the pan. (Click on
the image for a larger version.) See, also, an animated
comparison between the original
map and the revision. The
major
difference
is that the locations of the LRRR and PSEP and associated
camera stations are farther south of the LM in the new map than in the
original.
Batson and Larson estimated that
camera station locations shown in the original 1969 map were accurate
to about 1.5 meters. Comparing the original map with the
revision, we see that there are differences great than 1.5 m. However,
in many cases it is really good estimation, especially for camera
stations not far from the LM. As for 3 deg azimuth error estimation,
in most cases photogrammetric azimuths differ less than 3 deg from
initial azimuths. Difference is larger mostly for cameras locations of
which differ significantly from the initial estimations.
2.1 Panoramas
The following table lists the panoramas
and the representative frames
used to get new pan locations
Pan
No.
and
Location
|
No.
of
frames
|
Frame
Sequence (AS11-40-)
|
Frames
Calculated
|
Pan 1, Foot of LM ladder
|
9
|
5850-5858
|
5850
|
Pan 2, 10m west of ladder
foot
pad
|
12
|
5881,
5882, 5882A, 5883-5891
|
5886, 5887
|
Pan 3, 10m north of
plus-Y(north) footpad
|
12
|
5905-5916
|
5905, 5907, 5916
|
Pan 4, 20m southeast of SEQ
Bay
|
12
|
5930-5941
|
5930, 5931, 5932, 5936
|
Pan 5, rim of Little West
Crater
|
8
|
5954-5961
|
5960, 5961
|
While taking a panorama, the astronaut took one frame and then turned
about 30 degrees before taking the next frame. Four of the five
pans
were taken in clockwise order, with the astronaut turning to his
right between frames; only Neil's Little West pan - with
the exception of a turn to his right after the first frame - was
taken as in counter-clockwise order.
On the rougher
terrain visited by the later crews, the astronauts sometimes had
difficulty staying on one spot while taking a pan. Finding a flat
place was not
any issue at the Apollo 11 site. In three of the panoramas,
we have calculated positions to two, three, or four images.
Except
for one displacement of about 1 meters from the others in Pan 3, the
the spread of camera stations within each pan is 0.5 meters or less.
2.2 Comments on images and camera
stations
5850/59: The new locations show that Neil moved about 3.9
meters north from the Pan 1 location before he took 5859.
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
detail
from the 8 August 2009 LROC image. 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 the three 2009 LROC images of the site.
5859/60/61: As can be seen in a
simplified
map
detail. Neil moved slightly to
his left after taking the first of the three frames, then farther left
and forward after the second.
5861: Original map indicates the LM leg should not be in the
frame. New map and acual photo show the leg in the frame.
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.
5872/73: Original map shows the SWC right of frame center on 5872 and
left of center on 5873. New map and actual photos show SWC left
of center in both images.
5872/73: 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 12 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 is
hiding the
lower parts of various boulders located between the two crater.
Work
to identify these cases is in progress and may allow delineation of
the Little West rim.
See,
also, a discussion (below) of a shadowed wall inside the east rim of an
old, heavily eroded crater that is visible immediately south of West
Crater.
5874/75: The original map shows both the flag amd a rock near the
photographer well to the left of the center. New map and actual photos
show the flag nearly centered and the rock right of center.
5874/75: These frames include a boulder identifiable in LROC images.
5903: Shows two boulders visible in the LROC images.
5905: Original map shows the flag well the the right of center and
indicates that the SWC should be in the frame. The new map and
actual
photo show the fag centered and the SWC out of the frame.
5927/28/29: These three images were shot from the same location.
5948/50: The PSE is actually to the left of center on 5948, not to the
right as on the old map. Also, on the original map, the small stones
shown around the PSE and LRRR are difficult to identify in the
photos; later I may try to find more precise positions for
several stones in this group.
3. Boulders
Boulders - by definition, pieces of rock bigger than 25 cm - are large
enough and scarce enough on the lunar surface that a 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 at the top a portion of the first of three
2009 LROC images. It was taken at 05:06:36 UTC on 12 July.
The Sun was at an elevation of 8.2 degrees and an azimuth of
270.2. Resolution in the raw file is 1.14 m/pixel. The
spacecraft was well to the west of the landing site, so the image has
been stretched bu 19(?) % to correct for foreshortening. The
image is repeated at the bottom of the figure with fourteen boulders
that have been identified in the Hasselblad images marked with green
dots (●).
Portion
of
the
12
July
2009
LROC
image
with
boulders
visible in multiple
Hasselblad images marked with green
dots (●).
(Click on the image for a larger
version.)
3.1 Boulder "a"
This boulder is situated nearly due south of the LM
at the distance of about 110 meters from its center (see map). I
calculated its size based on its angular size in 5875 and the distance
from the photographer. It is about 2.5 m long and about 0.8 m
high. Its location is accurate to about 3 %, i.e. comparable with
the size of the boulder.
Boulder "a" labeled in 5875 (left),
a view to
the south and slightly west past the ladder strut,
and in 5548 (right), a view
to the south out Neil's window.
(Click on the image for a larger
version.)
3.2 Boulder "b"
This boulder is seen on many photos showing an
area NE of the LM and NW of Little West. The boulder is about 70 m from
the LM on the rim of a very shallow crater visible in the LROC images
and in Hasselblad images taken from the Pan V location on the rim of
Little West Crater. The boulder is elongated in the E-W direction and
is about 2 m long on that axis. It is about 0.8 meters tall and
appears to have a triangular cross-section on the SW. It casts a
distinct shadow in the
first (12 July) LROC image and, in the third (1 October) LROC image,
it shines brightly. It's
photogrammetrically-determined distance from
the camera stations is accurate to about 3 % or 2 meters.
Boulders "b" and "c" in 5886 and
5903. Both give a view to the northeast.
In both, the line-of-sight to boulder "c" passes near the plus-Y
(north) footpad.
Boulder "b" is about 70 meters from the LM and "c" about 180 m.
(Click on the image for a larger view.)
(Left)
Boulders
"b"
and
"c"
in
5886,
a view to the northeast taken from within
the LM shadow.
Note the triangular shadow on the end of "b", which may be indicative
of the
cross section perpendicular to the elongated, east-west axis.
(Right) Boulders "b" and "d" in 5958, a view to the north from the Pan
V location on the rim
of Little West Crater. This image shows the east-west elongation
of boulder "b".
(Click on the image for a larger version.)
Boulder "c"
The best view to this boulder is at the upper right in 5886 (above
left). According to the LRO images, the distance is ~180 m, so the
boulder was almost certainly ejected from West Crater. Photogrammetry
gives a distance of ~160 m for a ~15 % error, which is not surprising
given the small parallax available from the 5886/5903 pairing. In
the LROC images, there are no other likely candidates at distances of
150 to 200 m, so the identification seems strong. A boulder
closer to the LM and to the right of "c" in the insets above is two
times closer and not distinguishible on LRO images. The portion of
boulder c visible in 5886 is
1.5 m; the larger lower part of the boulder may be hidden by terraiin
along the line of sight.
Boulder "d" as seen in 5513, taken out
Buzz's window, and 5869, one of a sequence
Neil took of Buzz's egress.
(Click on the image for a larger
version.)
Boulder "d"
This is a very flat rock - or, perhaps, a close grouping of separate
rocks. It is marginally discernible in the first LRO photo.
It is ~95 m from the LM. It's width is about 1 m; and the height may be
0.5 m. Positioned with an accuracy of ~1 %.
Boulders "e1, "e2, "e3"
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." There is a field of stones to the northwest of LM, window
pans provide a great view (see 5516_bould.jpg for instance). One of the
boulders, e1, is clearly
visible in the LRO images. It can also be seen in several EVA
photos. It is ~ 90 m from the LM, is about 2 - 2.5 m in
size. The photogrammetric distance is accurate to 1%. Two
other boulders, e2 and e3, lie is slight depression and can
only be seen in photos taken out Buzz's window and from the rim of
Little West Crater. Because the reulting parallaxes are small, the
photogrammetric ranges of ~95 and 80 meters for e2 and e3, respectively, differ from those
derived from plausible locations identified in the July 2009 LROC image
by 14 and 10%, respectively. Both boulders are similar in size to
e1.
This
portion of the July 2009 LROC image contains boulders "a", "b", "d",
"e1", "e2", and "e3".
Both copies of the LROC have been
stretched horizontally by 19% to correct for foreshortening.
In the labeled version, actual
locations of the boulders are marked with green
dots (●)
and the photogrametrially-determined
locations with red dots (●).
Boulders between Little West Crater and West Crater
In the up-Sun view toward West Crater that is captured in 5872/73 and
some other photos made in the direction of West crater, a number of
large boulders stand out because, loking toward the Sun, we are seeing
only their deeply-shadowed, down-Sun sides. All of them are
probably ejecta from West Crater. In a detail from 5873 (below) I have
divided these boulders into three groups: t1 to t4 are four
boulders closer to the camera than the rest; v1 to v3 are farther away and less
pronounced objects; and w1 to w3 are blurry objects that appear to
be associated with what turns out to be the shadowed, inner wall inside
the east rim of an old, heavily eroded crater.
Detail from 5873 with labels applied
to ten boulders in the general direction
of the south rim of West Crater. Four boulders assigned to the "t" group
are relatively close to Little West Crater; three boulders
assigned to the
"v" group are at intermediate distances; and three boulders assigned to
the
"w" group are indistinct and seem to be associated with a dark band
that extends to the right from the south rim of West Crater
(Click on the image for a larger version.)
In the LRO images, t1 - t4 have been identified with
boulders at ranges of 130, 135, 120 and 165 meters, respectively.
Photogrammetry gives ranges that are systematically lower by 5 - 9 %,
but this is certainly due to low parallax. The visible dimensions
(width/height) of the boulders are about 1.5/1.2 m (t1), 2.5/1.2 m (t2), 0.5/1.0 m (t3), and 2.3/1.2 m (t4). However, the stones may be
larger actually, since we observe only their upper portions visible
above the relief. It is interesting to mention that the relief
certainly goes up towards West crater, so that these boulders may stand
about 5 meters above the level of the LM pads.
The boulders v1-v3 are situated at the range of 325, 215 and 200 meters
respectivly, although photogrammetry gives an error from -8% to +7 %.
The size cannot be estimated since we see only the tips of these
stones. The fartherst one should be quite large, according to LRO
photos.
The calcualted distances to boulders w1,
w2, and w3 have large uncertainties because
of the small range of parallaxes available, but all are more than about
400 meters from the LM. As noted in the figure caption above,
they seem to be associated with a dark band, very likely a shadowed
surface sloping down to the west, most likely the inner east wall of a
crater or an outer west wall. In the next figure, lines-of-sight
to boulders t1, t2, and t3 are shown because they bracket
the lines-of-sight to w1, w2, and w3.
This
12 July 2009 LROC image was taken when the Sun was at an azimuth of
270.2
and an elevation of 8.2 degrees. The center of the old, eroded crater
mentioned in
the text above is southwest of West Crater, with the southwest rim of
West Crater
more or less overlaying the northeast rim of the old crater. A young
crater about the
same size at Little West was puched into the floor of the old crater
southeast of its center.
AS11-40-5872 and 73 were taken on 21
July 1969 at about 03:35 UTC when the Sun was at an azimuth of 88.8 and
an elevation
of 14.4 degrees. Because the solar elevation is similar to that
in the July LROC image and the two azimuths are nearly opposite, the
dark slope associated with boulders w1,
w2, and w3 in 5872-3 is expected to be
relatively
bright in the LROC image. In the figure above, a bright area
which
seems to correspond to the west-facing, inner wall of the old crater is
outlined.
