The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part B4. Beijing 2008 
line generated. Nine groups of data are obtained. As Table 6 
displays, the differences among these nine data groups are very 
small. The maximum error of the epipolar line is about 1 pixel, 
which can meet the need of the image matching. Comparing 
these data, it can be found that the increment of the time 
elevation changes has little influence on the accuracy within the 
same elevation range. However, the range of elevation should 
be selected in a rational range. After the analysis, the authors 
come to the conclusion that the elevation range and the time 
elevation changes in the generation have little influence on the 
accuracy of the epipolar line. 
Times Elevation 
Changed 
Interval of Elevation 
(m) 
Range of Elevation 
(m) 
Min 
(pixel) 
Max 
(pixel) 
RMSE 
(pixel) 
1000 
-200-800 
0.009 
0.999 
0.513 
1 
2000 
-500-1500 
0.005 
0.975 
0.513 
3000 
-1000-2000 
0.006 
0.963 
0.512 
300 
-200-1000 
0.010 
1.015 
0514 
4 
500 
-500-1500 
0.009 
1.027 
0.515 
1000 
-1000-3000 
0.022 
1.292 
0.558 
300 
-400-1400 
0.009 
1.026 
0.515 
6 
500 
-500-2500 
0.004 
1.091 
0.521 
1000 
-1000-5000 
0.027 
1.475 
0.614 
Table 6. Accuracy of the approximate epipolar lines 
In the actual generation of epipolar line, the true elevation range 
of the area the scenes covered can be used to generate the 
approximate epipolar line. Select a point p (6259.4, 4727.9) on 
the left scene, project p to the right scene respectively with the 
maximum elevation 1500 meters and the minimum elevation - 
200 meters, two points are obtained on the right scene, fit these 
two points to be the approximate epipolar line of the point p as 
Figure 4 shows. 
Coctumn number 
Figure 4. Approximate epipolar line of point p 
4.4 Experiment EH 
Epipolar pairs are generated in this experiment. Start from the 
right epipolar line generated in experiment II, choose seven 
points evenly distributed on the right epipolar line, and generate 
the epipolar line of these points on the left scene, seven epipolar 
lines are obtained on left scene. Figure 5(a) shows the seven 
points selected on the right epipolar, and the blue dot is the 
conjugate point of p. Figures 5(b) and 5(c) display the epipolar 
lines generated. As Figure 5(b) shows seven epipolar lines 
generated on left scene coincide with each other. 
(a) Distribution of selected points on the right epipolar line 
(b) a piece of left scene (c) a piece of right scene 
Figure 5. Approximate epipolar line pairs of point p 
The accuracy of these epipolar lines is assessed. As Figure 6 
displays line 7 has the maximum error, which is 1 pixel; and 
line 4 has the minimum error, which is not more than 0.01 
pixels. When the point selected on right epipolar line and p’ are 
located closer, an epipolar line with higher precision can be 
obtained, and visa versa. 
To highlight the difference among these epipolar lines, zoom in 
the scene within a minor range as Figure 7 shows. These lines 
are parallel to each other. The epipolar lines which locate closer 
are generated from the points locate closer. The second line and 
the third line are almost identical. For the same row coordinate, 
the maximum difference in column coordinate is 1.7 pixels and 
for the same column coordinate the maximum difference in row