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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