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The integrated system consists of five parts: SAR simulation imaging system; environment virtual system; 
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image processing and information retrieval; characteristic of ground objects simulation; SAR interactive 
simulation system. Figure 1 shows the framework of Computer 3D Virtual SAR System. 
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4 TECHNIQUE APPROACHES FOR IMPLEMENTING VIRTUAL SAR SYSTEM 
In general, technique approaches for implementing virtual SAR system include two methods. The first is based 
on database of ground object. The other adopts to simulate coherent video signal method. 
4.1 The Method Based on Database of Ground Object 
This technique is based upon the ground real situation map or remote sensing materials or the existed radar 
image according to the imaging mechanism of radar image to produce different 
frequency wavelength polarimetric ways radar images which are applied to various occasion. 
The selected physical model used in radar image simulation is point scattering model. The selected mathematics 
models are the radar imaging equation, the radar equation and the gray equation respectively. These functions will 
be looked up in some references. Figure 2 shows the flow chart of radar image simulation. 
The data sources for SAR simulation image include radar system parameter database of geography information 
and database of ground scattering characteristic. The chtabase of geography information includes DEM and 
database of land use. The database of ground scattering characteristic includes diversified ground objects 
scattering characteristic s at different time and different radar parameters, that is, S ors’. 
When radar imaging, the ground is divided into 
grid cells according to the size of resolution cell. 
  
  
Radar system I mage Display 
  
  
  
  
araneter 
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
Each cell of image pixel is corresponding to each à 
ground cell. Based on the imaging mechanism of Radar i mage 
radar image and scattering characteristic of ground Detabose 9 ground P|simlation system 
objects, we make use of the radar equation and the EEE hy i 
Sy equation to calculate the gray value of ground Duxabas of ground oblect 
object of each cell according to point scattering scattering characteristic 
  
  
  
model, and then form radar image. For gaining a 
better radar image, we should consider the 
geometry characteristics of radar image, for examples, foreshortening and layover and etc (Shu,1997). 
This method to simulate SAR image is sample and easy because it omits the calculation of scattered field of 
Fi aure 2: The Flow Chart of Radar Inmae Si miation 
  
International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part B1. Amsterdam 2000. 125