Test11 K-R (JRW)

Aim and Objectives

Purpose of test: Do determine the effect of sun zenith on the quality of the final solution produced by SPC.

Methodology

Data

• Topography was generated by EP that had 20deg sloped boulders and regular simple craters.
• We chose to analyze a boulder near the center of the region created by EP.
• Image suite (below) of 2cm/px images.

Bigmaps

The following bigmaps were tiled/iterated and evaluated:

Starting topography defined from: START1 created at 20cm from REGION.MAP

Iteration Parameters

Reset albedo/slopes: NO

Calculate Central Vector: YES

Differential Stereo: YES

Shadows: YES

Tile seed

0.00010,49
g
i
a
y
.5
n
x
.025
0
a
b
n
XXXXXX
n
2
b
n
XXXXXX
u
1
v
2
e
a
0,60,.25,.25,0,3
1
0
3
n
0
y
1
0
1
n
0
y
0
c
.5
0
0
40
1
0
3
n
0
y
1
0
1
n
0
y
e
o
.5
0
a
u
1
0
0
40
2
8
2
.01
1
4
1, 2.5, 3  
6
y
y
0
.025
30
0
u
1
v
1
1
0
1
n
0
y
u
1
0
0
40
1
0
2
n
0
y
1
0
1
n
0
y
e
o
.5
u
1
0
0
40
2
8
2
.01
1
4
1, 2.5, 3  
6
y
y
0
.025
30
0
u
1
v
1
1
0
1
n
0
y
u
1
o
RECENT
y
1
o
RECENT
n
3
y
1, 3, 5 w
i
RECENT
n
n
v
1
u
1
#v
#4
o
RECENT
n
1
q
END                               

Iterate Seed

# This script performs two maplet iterations in parallel mode. 
# It reinitializes slope and albedo.
# It recomputes maplet overlaps.
# It recomputes limb fits.
# It recomputes central maplet vector.
# Topography determination from slopes is conditioned by:
#   Initial topography, 
#   Overlapping topography, 
#   Shadowing, 
#   Differential stereo, 
#   Limb heghts. 
# Dataless area slopes are set from the shape model.
#
# The script hides most of the screen output.  In order to obtain the 
# full display replace H* by #H*.
#
# Modified 2011_12_31.  Header and comments added.
# Modified 2014_02_26.  Hide screen output added.
#
H*
x
.025
#
# Initialize slope and albedo.
#
#a
#y
#y
#
# Begin first iteration.
#
0
40
1
0
1
n
0
y
u
0
40
#
# Begin topo determination.
#
2
8                fill no data with shape slope
2                condition with existing topo
.01
7                condition with shadows
.025
1                condition with overlapping maps
4                condition with limbs
1, 2.5, 3  
6                condition with differential stereo
y
0                begin integration
.025
15
0
u
1
0
2
n
0
y
1
0
1
n
0
y
u
#
# Begin second iteration.
#
0
40
1
0
1
n
0
y
u
0
40
#
# Begin topo determination.
#
2
8
2
.01
7
.025
1
4
1, 2.5, 3  
6
y
0
.025
15
0
u
1
0
2
n
0
y
H*
1
0
1
n
0
y
H*
u
#
# Begin overlaps and limb fits.
#
o
RECENT
y
1
o
RECENT
n
3
y
1, 3, 5 
#
# Central vector determination.
#
v
RECENT              
q
END

Results

Discussion

In all cases we were able to achieve an RMS less than the image resolution. A single sun angle performed worse than the rest by about a factor of 2. It isn't surprising that one sun angle did the poorest, but it is surprising that one sun angle did well. In fact, after 100 iterations it did as well as one of the other tests. Nonetheless, using a single sun angle during operations is not recommended. In many of the scenarios there appears to be a wobble to the RMS as you iterate. This is also surprising, but since the RMS is so low it would be more of a science project to understand why; it is not mission critical to learn why there is a wobble. Likewise, the RMS improves for awhile in all cases, then starts getting worse. And the number of iterations it takes before the RMS starts to increase is not predictable. Surprisingly, having more sun angles doesn't help the solutions very much. For example, Q has the most sun angles, and therefore took the longest time to iterate, but actually performed worse than some of the other cases. It appears that 2 or 3 sun angles is sufficient to obtain a good solution.

The value at the end of RESIDUALS.TXT doesn't seem to reflect the RMS very well. RESIDUALS is always greater than the RMS, and while L always has the worst RESIDUAL, the RMS is better than some of the others.

Looking at the transits of the different solutions, it appears that iterating after 20 times doesn't change the shape of the peak, it mostly just moves it around in space.

Conclusions and Recommendations

Two or three sun angles appears sufficient to obtain a good solution. Our test shows that +/-30degrees gives a better solution than +/-45degrees, but they are fairly similar. Adding a 0degree sun angle doesn't appear to improve things. Adding in 60degree angles actually makes the solution a bit worse in some cases.

Tables and Figures