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4 EXPERIMENTAL RESULTS
4.1 Experiment Using CE-1 CCD Images
Considering that Sinus Iridum is the pre-selected landing site of
Chang’E-3 lunar rover mission, in our experiment, we choose 3
orbits (No.0561, No.0562 and No.0563) of CE-1 CCD images
located at Sinus Iridum. Figure 3 shows the partial images
(1,000 rows, after grayscale stretching) from three view angles
in No.0562 orbit.
(a) Forward-looking (b) Nadir-looking (c) Backward-looking
Figure 3. Partial forward-, nadir-, and backward-looking CCD
images taken by CE-1 from No.0562 orbit (120m resolution)
In this experiment, we use 1,000 rows of the forward-, nadir-,
backward-looking CCD images of these three orbits. Conjugate
points of stereo images are obtained through feature point ex-
traction by SIFT operator (Lowe, 1999) and feature point
matching by cross-correlation. Statistics of back-projection re-
siduals of more than 15,000 matched feature points for each im-
age is shown in Table 2. The attitude angle bias shown in Table
3 for each image of these three orbits are added to the EOPs,
then ground points are back-projected to image space again and
back-projection residuals are recalculated in Table 4.
N -0.0035 0.0022 -0.0004
B 0.0202 0.039 0.0056
Table 3. Correction values of attitude angle bias for CE-1 CCD
images
Orbit Column direction Row direction
No: Image Mean RMS Mean RMS
(pixel) (pixel) (pixel) (pixel)
F 0.00 0.12 0.00 0.00
0561 N -0.00 0.20 0.00 0.00
B 0.00 0.19 0.00 0.00
F -0.00 0.13 0.00 0.00
0562 N -0.00 0.21 0.00 0.00
B -0.00 0.16 0.00 0.00
F 0.00 0.16 0.00 0.00
0563 N 0.00 0.26 0.00 0.00
B 0.00 0.18 0.00 0.00
Orbit Column direction Row direction
No. Image Mean RMS Mean RMS
(pixel) (pixel) (pixel) (pixel)
F -1.07 0.12 0.00 0.00
0561 N -0.05 0.20 0.00 0.00
B 1.13 0.18 0.00 0.00
F -1.51 0.13 0.00 0.00
0562 N 0.06 0.21 0.00 0.00
B 1.45 0.16 0.00 0.00
F -1.40 0.16 0.00 0.00
0563 N 0.02 0.26 0.00 0.00
B 1.38 0.19 0.00 0.00
Table 2. Back-projection residuals for CE-1 CCD images before
correction (F, N and B are forward-, nadir- and backward- look-
ing for short, the same below)
Orbit
No. Image $ (degree) O (degree) K (degree)
F -0.0099 -0.0324 0.0137
0561 N -0.0062 0.0001 -0.0008
B 0.0163 0.0320 0.0057
F -0.0532 -0.0311 0.0332
0562 N -0.0254 0.0119 0.0046
B 0.0149 0.0432 0.0090
0563 F -0.0162 -0.0416 0.0183
Table 4. Back-projection residuals for CE-1 CCD images after
attitude angle bias correction
Figure 4 shows us that the residuals distributed in column di-
rection before and after adjustment (correction of attitude angle
bias) for forward-, nadir-, backward-looking images of No.0562
orbit.
t
min aiii
LÀ
=
3
>
= 05
E
=
$
ow
4 fore A
S il ili ai iii n u LI
309 500 600
column number
(a) Residuals of forward-looking image
after e at
QR adjustment
-~ M
a " M
column residuals
19 200 300 400 500 600
cobain number
(b) Residuals of nadir-looking image
‘ ii uu. 7
colum zesiduass
n M UL W m lin ir” N
EA. m s
(c) Residuals of backward-looking image
Figure 4. The residuals distributions in column direction before
and after adjustment (take No.0562 orbit for example)
It can be easily observed that after attitude angle bias correction,
mean back-projection residuals of CE-1 CCD images are re-
duced to better than 1/100 pixel. After this refinement, DEM
and DOM generated are automatically generated using CE-1
images and are shown in Figure 5.
293
