The accuracy of scene matching navigation system can be improved greatly when synthetic aperture radar （SAR） is used. However

geometric distortions of SAR real-time image

which are caused by terrain undulation and atmosphere turbulence etc

decrease the matching performance. By analyzing the causations of geometric distortion

a two-dimension separable correction method is presented

which corrects the distortion in azimuth direction by phase compensation along with the imaging processing

and leaves the distortion in range direction to the image post processing. In the end

an experiment was conducted based on three SAR real-time images of different terrains. Each of the images is simulated by digital elevation model （DEM） and orthography

and then corrected by three different methods. Based on the experimental results

some rules of the correction method selection are acquired.