gion has been 
material sub- 
ues of coordi- 
al system de- 
parellel to z 
the section. 
t is visible; 
r least value 
ible. As the 
'e the invisi- 
be appropri- 
are not ex- 
considering 
1er storage, 
ck software 
is somewhat 
1. The flow 
  
ing trans- 
  
  
Professors 
' for their 
  
Explanations for Plates 
Plate 1-3. 
Plate 4. 
Examples of Three-D display of aero-photoes of some regions in North China. 
Example of Three-D display of Landsat image of the Colorado canyon. 
27