The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part Bl. Beijing 2008 
23 
As one can observe, the maximal estimated distortion per 
component (x or y) is 3.83[micron] or 0.32[pixel], The result of 
the bundle adjustment of this calibration block using refined 
image coordinates and with standard deviation of 2 microns is 
given in Table 3. RMS Z values have virtually not changed 
after collocation fit, which is usually the case since the 
collocation trend simply subtracted the systematic part leaving 
random error virtually in the same least-squares state. 
Sigma=2.5[um] 
RMS x = 2.4, RMS y = 2.2 
X[m] 
Y[m] 
Z[m] 
RMS of 8 control points 
0.017 
0.027 
0.021 
RMS of 6 check points 
0.018 
0.029 
0.036 
MAX of 8 control points 
0.032 
0.042 
0.037 
MAX of 6 check points 
0.026 
0.048 
0.052 
RMS GPS 
0.033 
0.040 
0.025 
GPS Block Shift 
-0.029 
-0.032 
0.219 
Table 3. DMC50 calibration block adjustment statistics 
5.1.2 Post-Correction Analysis of a Test Block 
The main goal of the DMC VIR correction grid is to reduce 
DTM block bending in Z. Generally, it cannot improve much 
RMS of the check points in a block with dominant local 
deformations. Therefore, the only reliable estimate of the 
improvement in DTM shape achieved after grid correction is to 
monitor a mean trend difference between some reference DTM 
shape and the test block shape, before and after correction. This 
particular block constitutes a situation when one cannot trust 
very sparse check point statistics and must rely on the mean 
trend estimate. 
In lieu of a separate test block, a sub-block of the DMC50 
project with 4 strips, 38 images, and 60% / 30% overlaps is 
selected. Automatic aerial triangulation is run on this selected 
sub-block. The reference mean DTM shape is computed from 
38 images with calibration conditions (i.e., using tight GPS and 
loose image constraints). The uncorrected sub-block is 
triangulated using 8 control points only (no GPS/IMU) and tight 
image constraints (Std Dev = (2[umj). The mean DTM shape 
deformation is computed by subtracting the DTM mean surface 
of the uncorrected test block from that of the reference block 
(see Figure 6). A similar procedure is repeated with the 
corrected sub-block: a test block of 38 images has been 
reprocessed in the DMC PPS with a correction grid applied and 
re-triangulated following the same procedure applied to the 
block of uncorrected photos. The attenuation of DTM bending 
in this case is 3.36 times (see Figure 7). 
Figure 6. Block DTM bending in Z 
(uncorrected block - reference block) max=0.226[m] 
6.16 6 165 6 17 6 175 6 18 6.185 6.19 
x tO 5 
I 25 
H ° 15 
■' ”0.1 
■ 0 05 
■ -0 
■ ■ -0 05 
¡H -0 1 
Figure 7. Block DTM bending in Z 
(uncorrected block - reference block) max=0.067[m] 
5.1.3 Analysis of Collocation Grid versus Self-Calibration 
Grid 
Self-calibration bundle adjustments were also performed on the 
DMC50 block using different bundle adjustment programs 
(PATB with 44-parameter polynomials (Gruen, 1978)), BLUH 
with one and four sets of APS (Jacobsen, 2007 ), and BINGO 
with one and four-sets of APs (Kruck, 2006). Significant APs 
from these self-calibrating bundle adjustments were used to 
generate the correction grids. The mean trend differences 
between DTMs computed with collocation and self-calibration 
adjustments, using different bundle adjustment programs, as 
well as the collocation and self-calibration grids are given in 
Figures 8 to 12. 
x 10° 
x 10 S 
_ 0.05 
PI 
m 0 03 
10.02 
■ -0.01 
■ -0 
• - -0 01 
¡gH -o 02 
H -0.03 
-0.04 
-0.05 
Figure 8. Mean DTM trend difference, max=0.04[m] 
ISAT vs. PATB