The Research And Implementation Of Small-Scale Relief Shading

Terrain is one of the most basic elements of geographic information,shaded relief is the most commonly used and intuitive type for representing the terrain. Relief shading depends on three basic principles,principle of geometrical optics,principle of halftone and principle of aerial perspective. With the development of technology,shaded relief derived automatically from computer has been taken the place of traditional manual shading,which calculating the grey value of one point through illumination model. It is faster and less expensive,but the manual shading is still superior to the automatic shading in three-dimensional relief impression.Nowadays, there are many improvement scheme have been developed for automatic relief shading,for example,adjustment of light direction or exaggerating the elevation.When generating the small scale shaded relief, correcting the DEM’s data is necessary.The shaded relief generated from DEM’s data is usually disturbed by topographic details that impair the portrayal of the main relief features,especially in small scale sheded relief.the traditional methods such as re-sampling, Wavelet Transforms or isotropic filter,have some shotages.This paper proposes a novel method for small-scale relief shading, which could remove the disturbing topographic details. Firstly, the DEM data were filtered unitarily; Then the terrain features are exaggerated or deepened based on curvature; At last relief shading from the processed DEM data. Experiments have shown the validity of this method, which has effectively removed broken terrain details while retaining the terrain features, thus generating a superb over-all portrayal.