The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part Bl. Beijing 2008
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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