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