ve 
($S&PCHH 
  
  
  
  
  
% i n MW. E á 
3 
BSPin3DBH 
  
  
  
  
  
Figure 2: Vertical hill shading. Generated by gradient filter. 
e Combined shadings, i.a., help to reduce the comparatively high cartographic load of the shading tones in the plains 
through a mere oblique shading. Three approaches have been tested which yielded in results which are equivalent 
to manually generated combined hill shadings: 
- A "multiplicative method" based on a mathematical-theoretical approach: For the analog hill shading two princi- 
ples of construction can be distinguished: 
- The shading is the darker, the steeper the slope is. This is the case for a slope aspect image which corre- 
sponds to a vertical shading. 
- The hill shading is the darker, the closer the slope aspect is to the illumination direction. Thus the intensity of 
the shading tone is a function of the slope aspect. 
628 International Archives of Photogrammetry and Remote Sensing. Vol. XXXII, Part 7, Budapest, 1998