Figure 9. Orthorectified SAR image 
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Figure 6. Feature points in real SAR and constructed TIN 
5. CONCLUSIONS 
We have proposed a method to orthorectify the space-borne 
SAR image in mountain areas based on DEM directly using 
simulated SAR and it is feasible. The relationship between 
DEM and simulated SAR image can be built according to 
simulated SAR using DEM, then lots of feature points can be 
detected correctly by Harris operator. The homologous points 
distributed in real SAR can also be correctly extracted by 
mutual information matching. The constructed triangle irregular 
network which uses the feature points as vertices is an ideal 
solution to register the simulated SAR with real SAR finely. 
Therefore the real space-borne SAR image can be orthorectified 
finely by DEM and simulated SAR.