The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part B4. Beijing 2008
included in the area covered by the stereo-pair, and the
elevation range of this area is about -200 to 1500 meters.
Scene
Left
Right
Focal length (m)
10
10
Date of capture
2003-02-22
2003-02-22
Time of capture
00:27 GMT
00:27 GMT
Rows and columns
12122 X13148
12122 X13148
Resolution (m)
1
1
Table 1. Specifications of the dataset
(a) left scene (b) right scene
Figure 2. Overview of IKONOS scenes
4.2 Experiment I
This experiment is performed to assess the accuracy of forward
and inverse RPCs. The forward RPCs are provided by the
imagery agent and the inverse RPCs are calculated by the
authors. For the purpose of verification, 62 pairs independent
check points are measured on stereo-pair by operator. The
measurement accuracy of these points is 1/2 to 1/4 pixels.
0 2000 4000 6000 8000 10000 12000
Figure 3. Distribution of check points on left scene
The experiment is carried out as follows, project the
checkpoints on the left scene to ground use inverse RFM, and
then the object space points are back-projected into the left
scene to obtain scene points. Select the different value between
the truth coordinates and the scene coordinates obtained by
projection as accuracy standard. Tables 2 and 3 display the
minimum error, maximum error and root mean square error
(RMSE) of the forward and inverse RPCs. Tables 2 and 3 show
the accuracy of forward and inverse RPCs for the same scene is
better than 0.1 pixels, and there is no difference between the left
and the right scene.
Max
Min
RMSE
Column
0.081
-0.001
0.034
Row
-0.037
0.000
0.014
Table 2.
Accuracy of the forward and inverse RPCs
of the left scene (pixels)
Max
Min
RMSE
Column
0.090
0.006
0.040
Row
0.057
0.000
0.019
Table 3. Accuracy of the forward and inverse RPCs
of the right scene (pixels)
The accuracy is also assessed in another way. Start from the
points on the left scene, project them to the right scene. Select
the different value between the truth scene coordinates and the
projected scene coordinates as the accuracy standard. Then do
the opposite to assess the accuracy of the forward and inverse
RPCs from the right scene to the left scene. As Tables 4 and 5
display, RMSE for the forward and inverse RPCs from the left
to the right scene or from the right to the left scene is more than
1 pixel in row, which is not as well as the accuracy for the same
scene.
Max
Min
RMSE
Column
1.306
-0.063
0.606
Row
-2.480
-0.261
1.818
Table 4.
Accuracy of the forward and inverse RPCs
from left scene to right scene (pixels)
Max
Min
RMSE
Column
-1.272
0.0138
0.585
Row
2.543
0.266
1.816
Table 5. Accuracy of the forward and inverse RPCs
from right scene to left scene (pixels)
4.3 Experiment II
Experiment II is performed to validate the method proposed
and assess the accuracy of the approximate epipolar line
generated. The distance from the conjugate point on the right
scene to the epipolar line generated is presented as the accuracy
standard.
The proposed method is performed with the change of elevation,
so how to select the range of elevation and how many times
elevation should be changed in the generation should be
discussed at first. The experiment is carried out as follows. Use
the conjugate points manual measured in experiment I, generate
the right epipolar line of these points on left scene with
different ranges of elevation and different times of elevation
changed respectively.
With different elevation range respectively changes elevation
for 1, 4, 6 times. Table 6 displays the minimum error, maximum
error and root mean square error of the approximate epipolar