International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B3. Istanbul 2004 
  
      
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Fig. 10 DSM from aerial photographs 
3.1.4 Evaluation result 
We compared the height at each point where the horizontal 
coordinates of two DSMs are the same. The average of vertical 
differences (absolute values) of 1 million points is 13.6m. The 
standard deviation of that is 26.5m. The maximum of that is 
164.1m. Fig. 11 shows the distribution of differences. 
  
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Fig. 11 the comparison between two DSMs 
About 20 thousand points (2% of whole points) have the 
difference of more than 100m. 
We checked the height of some wrong points by stereo-scoping. 
The height values from aerial photographs and QuickBird 
imagery at each point are almost the same and these values are 
near the values of DSM from aerial photographs. Then it is 
probable that the DSM from QuickBird is not good. 
3.2 Test field 2 (Central Tokyo) 
We used another stereo pair of QuickBird. The images are also 
panchromatic basic imagery with radiometric correction and 
sensor characteristic correction. The observation date of images 
is May 5, 2003. The off-nadir angle of the forward view is 29.8 
degree and that of the backward view is 30.7 degree. For the 
evaluation, we use DSM from the aerial laser scanner as 
reference data. 
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3.2.1 Orientation 
The method of orientation was the same as that of the test field 
|. In this case, the horizontal coordinates of GCPs are obtained 
from Numerical Map 2500 published by GSI. Accuracy of the 
Numerical Map is declared as 1.75m in horizontal. The vertical 
coordinates of GCPs are from 1:25000 topographic map of GSI, 
and the accuracy is 3.3m. The coastal line is also used to 
determine sea level (0m). The horizontal and vertical residuals 
for 12 GCPs were less than 0.5 pixels. 
3.2.2 DSM generation 
We generated DSM from QuickBird stereo imagery (Fig. 12) 
by using the same digital photogrammetry software as above. 
DSM of the same area from the aerial laser scanner is shown in 
Fig. 13. The area is 2km*1.5km and located in the middle of 
the QuickBird stereo pair scenes. The elevation range of this 
area is about 180m. The grid interval of both DSMs is 5m. 
Therefore, the number of points is 120 thousand. 
  
Fig. 13 DSM from aerial laser scanner 
3.2.3 Evaluation result 
We compared the height at each point where the horizontal 
coordinates of two DSMs are the same. The average of vertical 
differences (absolute values) of 120 thousand points is 10.1m, 
the standard deviation of that is 18.0m, the maximum of that is 
167.6m. Fig. 14 shows the distribution of differences. 
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