FOL 
  
  
  
Information about the third property, resolution, is given in table 2. 
It lists parameters for commonly used image sensors together with re- 
solutions in lines per mm on the film original and in milliradians 
of a resolved angle. The range of usable image scales is also shown. 
  
table 2 
  
  
  
parameters of commonly used imaging sensors 
  
  
  
From table 2 it becomes evident, that frame photography with an angular 
resolution of 0,1 mrad generally provides at least 20 times better re- 
solution conditions to detect topographic objects than the other sensors 
(coherent radar 2 mrad, infrared scanning 3 mrad). 
With special effort (satellite imagery, panoramic photography), by sever- 
ly restricting the angular field of view or by introducing dynamic imag- 
ing the angular resolution can be raised for optical systems up to 6 times, 
again in favour of photography. 
According to table l| the ofher sensors, therefore, are only useful to ob- 
tain topographic information, when the strict acquisition conditions for 
aerial photography cannot be met. Radar can be used for cloud penetration 
014]; infrared imaging is useful by night and sonar records under water[15]. 
This imaging is only possible with a considerable sacrifice in resolution. 
The more important applicability of the other remote sensors lies, however, 
in their additional capability to detect and to classify objects according 
to temperature radiation (infrared) and mass structure differences (Radar). 
While many sensor images may be observed and interpreted separately, one 
by one, the optimal detection and use of the information stored in these 
images can only be reached by a multispectral analysis: Aerial photographs