Sar Ortho Image Generation In Sophisticated Area

As an active sensor, SAR can provide an important platform for solving mappingtask of the cloudy and foggy regions of complex terrain. But because SAR system isslant range imaging, which has large geometric distortion and radiation distortioncaused by undulating terrain, particularly prominent in high mountain areas. Thisseriously hampered the information extraction from SAR image and its integrationapplication with other geoinformation. Therefore, to give full paly to the potentialapplication of SAR image, it has important theoretical significance and practical valuefor researches on the method of SAR image orthorectification.This article is based on "China West 1:50000 topographic map blank area mappingproject". And in response to the issues such inherent features of SAR image and thedifficulty in obtaining ground control points in complex terrain, this paper put forwarda set of technical flow and production processes of DOM for SAR image under sparsecontrol conditions. Main researches of this paper are as follows:(1) On the basis of the analysis of the principle of SAR image direct geolocationwithout ground control support, this paper represents a detailed derivation of anumerical method based on least squares;(2) After analyzing and compareing the direct optimization model parameterrectification method and indirect optimization model parameter rectification method,this paper improves the original rectification method, and brings forward aorthorectification method of high-precision SAR image based on R-D model undersparse control conditions. At the same time, in response to the large amount of SARimage data and the slow speed resulted from processing point by point, this paper alsoproposes a grid-based rapid fast-processing algorithm, thus the efficiency of SAR imagerectification can be effectively improved.(3) Radiation error caused by the terrain through ground scattering area cannot beignored, the smaller the angle, the greater the error, especially at high altitudes.Therefore, this article derives in detail the whole process of calculating scatteringnormalized area, so as to effectively realize the terrain radiation error correction ofSAR images.(4) As for SAR image there is a serious phenomenon of shadow and layover, SAR orthorectification of a single data source can not be adjusted to meet the featureannotation, DOM producing, and other requirements. To compensate for thisshortcoming, this paper presents a multi-looking direction SAR image fusion methodbased on slope aspect and grade, thus achieving the favorable compensation for thegrayscale of information gap area caused by shadow and layover, eventually formingcomplete SAR orthoimage meeting the requirements. This method is mainly related to:shadow and layover of SAR images detecting and extraction algorithm, multi-lookingdirections SAR image fusion based on decision tree rule.In addition, by use of visual C++ development platform, corresponding softwaremodules have been founded on the basis of the independent developed software"ImageInfo-SAR workstation", thus providing technical and software support for thesuccessful completion of the West mapping mission.