The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Voi XXXVII. Part Bl. Beijing 2008 
experiment was done to compare the results of the existing 
method and its correction. 
TERRAIN REPRESENTATIVE DISTORTION 
The SCOP approach mentioned that the quality, the level of 
detail and the demand of a complete model of the 3D world of 
DTMs still required to be improved. It gives the suggestion that 
the existing DEM cannot meet the needs of the representation 
of the real terrain. 
As part 1 mentioned, for the inherent grid structure and other 
reasons, grid-based DEM cannot describe the real terrain 
surface accurately, so terrain representative distortion occurs. 
Representing both external characteristics and internal causes, 
terrain distortion of the existing DEM is especially obvious in 
complex landform. However, it should be distinguished from 
DEM’s error and DEM’s uncertainty. DEM’s error is the 
difference between the observed value and the true value of the 
terrain surface and DEM’s uncertainty is the degree of the 
difference. Because of the existing of the terrain distortion, grid 
DEM cannot meet the applied demand of the high quality 
project. 
The terrain representative distortion in grid DEM was analyzed 
in detail and classified into four types, which are spatial 
position distortion, spatial relationship distortion, spatial 
structure distortion and terrain morphology distortion. All those 
distortions were owing to three reasons: 
• Inherent grid structure of DEM; 
• Terrain features lose in collection; 
• Incomplete technique to create DEM. 
Some representative terrain distortion is showed in the 
following pictures (from Figure 1 to Figure 5): 
WÊÊ 
Figure 3. Loss of cliff lines in DEM 
Figure 1. Elevation matching warp of DEM 
Enlarged grid mesh 
Figure 2. Sketch map of the peak point distortion 
Figure 4. Loss of terrace in DEM 
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