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Title
Mapping without the sun
Author
Zhang, Jixian

276
Figure 3: RADARSAT scenes
SPOT image Radarsat image
Figure 4: SPOT and RADARSAT scenes
Figure 5: Zoom out of SPOT and RADARSAT scenes
Figure 6: Stereo IKONOS scenes
Figure 7: Zoom out of IKONOS scenes
For these five pairs of images, the vertical parallaxes of the
conjugate epipolar lines are not more than 1 pixel by the means
of manual visual interpretation. As is shown from Fig(l) to
Fig(5),these images are across-track stereo pairs on which the
conjugate epipolar lines are approximately horizontal, and as is
shown from Fig(6) to Fig(7),IKONOS images are along-track
stereo pairs on which the conjugate epipolar lines are
subvertical. Therefore, it is necessary to emphasize that the
IKONOS imagery should be resampled in accordance with
“sample” when generating epipolar images, and the images’
width and height are interchanged compared with the original
images. Finally, the paper generates the conjugate epipolar
imagery by the means of experiment II.
3,4 Accuracy assessment
This section is performed to evaluate the accuracy of the
generated epipolar imagery.
The first step is to extract a pair of conjugate epipolar lines
generated by experiment II, and choose 10 points which are
uniform distribution on the left epipolar line. The second step is
to project the 10 points to the right image using the RPC Model.
If the line-pairs generated are rigorous conjugate lines, the
points on these two lines should be one-to-one correspondences.
That is to say, a point is on the left epipolar line and its
conjugate point should be on the right epipolar line. According
to this theory, the authors compute the distance from the right
image points obtained by projection to the corresponding right
epipolar line. The distance is presented as the accuracy
standard. Results of the five group images are presented and
compared in Table (2).
Image
Maximum
Error
Minimum
Error
RMSE
SPOT-HGR
0.468
0.037
0.253
RADARSAT
10.008
0.009
4.028
SPOT—
RADARSAT
4.235
0.297
2.715
IKONOS
0.042
0.0001
0.022
Table2 Accuracy of epipolar images (pixels)
Image
X
Y
SPOT-HGR
-0.0005
0.031
RADARSAT
0.104
0.027
SPOT—RADARSAT
0.0155
0.037
IKONOS
-0.014
-0.190
Table 3 Orientation accuracy of stereo-images (pixels)