The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part B4. Beijing 2008 
models for the first reflective or visible surface, while Digital 
Elevation Models (DEMs) are usually referred to the bare earth, 
i.e. without trees, buildings or other features on the actual 
surface. They are classical and common products from (digital) 
photogrammetric systems. In modem map production, 
DSMs/DEMs have become unavoidable information for scene 
analysis and understanding, for change detection, for GIS 
database updating and, for cartographic 3D feature extraction 
and reconstruction. 
DEMs are usually generated by automatically matching dense 
pattern feature from two or more images in modem digital 
photogrammetric systems. In the past years, due to the high 
spatial resolution of recent airbome/spacebome sensors in the 
visible and infrared spectrum, a large number of researchers 
around the world have investigated the extraction of elevation 
and/or the production of DSMs/DTMs. A wide variety of 
approaches have been developed, and automatic DSM/DTM 
generation packages are in the meanwhile commercially 
available on several digital photogrammetric workstations 
(Zhangli, 2005). An automatic DEM/DSM generation package 
of Imagelnfo® developed by Chinese Academy of Surveying 
and Mapping is made use of in practice production in the 
Surveying and Mapping of the West Regions in China. The 
package provides multiple primitive multi-image (MPM) 
matching function and has the ability to provide dense, precise, 
and reliable results. Generally speaking, DEMs/DSMs are 
extracted by SPOT-5 HRS stereo images. However, it is 
necessary that applying both SPOT-5 HRG and SPOT-5 HRS 
images to extract DEMs/DSMs of complexity terrains. The 
figure 3 is a shaded relief map of DSMs generated from SPOT- 
5 HRS and HRG images. After generated, DEMs/DSMs are 
overlapped on stereo models and are manually edited the 
mismatching areas by operators. The workloads of edit are very 
low because there are few mismatching in DEMs/DSMs 
generated by the above extraction package. 
traditional algorithm. The comparisons are made as the 
following steps: two DEMs are generated from a manual 
measured contour map by the new algorithm and a traditional 
algorithm, respectively. Then two new contour maps are 
extracted from the two new generated DEMs. Finally the effect 
and the difference are compared by overlap new generated 
contour maps and the original contour map, respectively. 
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