The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part Bl. Beijing 2008 
1115 
Fig. 7: Shaded terrain models (12.5m grid spacing) of 2 
sub-areas in Beijing test-field, where the upper one shows the 
mountain area and the lower one shows the area around the city 
of Beijing. 
4. Conclusion 
In this paper we have reported about an advanced matching 
approach for automatic DSM/DTM generation from 
high-resolution satellite images. It can provide dense, precise 
and reliable results. The method uses a coarse-to-fine 
hierarchical solution with an effective combination of several 
image matching algorithms and automatic quality control. We 
have developed a matching strategy combining local point 
matching of feature and grid points, robust edge matching and a 
relaxation based global relational matching. The DSMs/DTMs 
are generated by a combination of matching results of feature 
points, grid points and edges. 
The proposed approach has been applied to SPOT-5 HRS/HRG 
images over a testfield in Zone of headstream of Three rivers, 
Tibet Plateau, China with variable terrain géomorphologie type. 
The accuracy tests were based on the comparison between as 
many as 160 accurate GPS check points, more than 1400 
manually measured check points and the automatically extracted 
DEMs. The RMS errors for the whole area are 2-7 m, while for 
flat/hilly areas the accuracy is about 2-3 m or even better. The 
proposed approach has been also applied to 23 IRS-P5 stereo 
pairs over Beijing area, the resulting 12.5 m DEM reproduced 
quite well not only the general features of the terrain relief but 
also small geomorphological and other features visible in the 
IRS-P5 images. The DEM shows many topographic details and 
features like small valleys in the mountains, detailed patterns 
related to streets and buildings in suburban and urban areas, 
linear features related to highways and main road networks, 
sparse trees, small clusters of houses and forest areas. From 
these experiments, it’s shown that with the proposed automatic 
DEM generation approach, by using SPOT-5 HRS/HRG and 
IRS-P5 imagery, satisfactory 1:50000 DEMs can be completed 
with a better accuracy than those requirements from Chinese 
Surveying and Mapping regulations. 
A major problem of our automatic DSM generation approach is 
the automated detection of small blunders, which still may exist 
in the results and need carefully manually editing. This 
constitutes a relevant topic for further research and refinement of 
our approach. We also have to collect good enough reference 
DSM/DTM for extensive accuracy test and analysis of our 
approach. 
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