REPLACEMENT SENSOR MODEL (RSM) PERFORMANCE ... - asprs

A more challenging extraction test case was established as follows. In one of the QuickBird image sets there
are 56 images in 7 strips of 8 images each. The overlap of two of the strips is at the reasonably favorable
convergence angle of 30 degrees. Along the overlap many tie points have been measured. The extraction test below
is a 10-point simultaneous extraction that uses 4 adjacent images on the strip. The results of this test are
summarized in Table 7 and Table 8.
Table 7. Absolute geopositioning statistics for simultaneous extraction of 10 points from four QuickBird images
Statistic Original RSM Original RSM Horiz. Pos. Vert. Pos.
CE (m) CE (m) LE (m) LE (m) diff. (m) diff. (m)
RMS 24.711 24.715 53.956 53.962 0.037 0.118
Max 35.695 35.696 76.020 75.965 0.065 0.269
Table 8. Relative geopositioning statistics for simultaneous extraction of 10 points from four QuickBird images
Statistic Original RSM Original RSM Horiz. Rel. Vert. Rel.
CErel (m) CErel (m) LErel (m) LErel (m) Pos. diff. (m) Pos. diff. (m)
RMS 31.002 31.001 67.648 67.639 0.053 0.166
Max 50.384 50.365 108.224 108.126 0.115 0.380
The results in Table 7 and Table 8 show that even in a more complex multi-image target extraction the RSM
performance is a very good approximation to that of the original sensor model. The error estimates (absolute and
relative CE and LE) are virtually indistinguishable, with differences between the two less than 0.1 percent. In terms
of the computed absolute point positions, the largest difference was 0.065 m in horizontal position for one of the
points, which was much less than one percent of CE. Similarly, the largest difference in relative positions was 0.38
m which was much less than one percent of the relative LE.
The excellent agreement in QuickBird target extraction results for RSM as compared with the original rigorous
sensor model are typical of what has been seen for other sensors in other studies. We next consider the WorldView
sensor, and additional scenarios that showcase additional capabilities of RSM.
GEOPOSITIONING PERFORMANCE STUDIES WITH WORLDVIEW
The test procedure of Figure 2 is just the first of four tests of increasing complexity that were performed with
two overlapping WorldView images. The second of these, termed the "triangulate/replace/extract" test is shown in
Figure 3. The procedure is for the sensor models to be triangulated with ground control and tie points before being
used for extraction and RSM generation. The adjusted sensor models and the full a posteriori joint error covariance
(a 12x12 matrix) of the adjustable parameters for the two images are provided to both the MIG tool for the rigorous
sensor model target extraction and the RSM Generator. The RSM support data contain the full joint error
covariance of the RSM adjustable parameters, and this is used in the MIG for the RSM sensor model target
extraction.
Original
support
data
Triangulate
Extract
Generate RSM
Extract
ASPRS 2008 Annual Conference
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Compare:
absolute and
relative point
positions,
absolute and
relative error
estimates
Figure 3. "Triangulate/Replace/Extract" RSM geopositioning performance test procedure.