合成孔径侧视雷达影象平面加密精度

On the Planimetric Accuracy Obtained from Synthetic Aperture Side-looking Radar Imagery

  • 摘要: 本文是通过三条合成孔径侧视雷达航带影象的几何处理,检验它的平面加密精度,分析其今后测制中小比例尺地图的前景。几何处理分两步进行:(1)由雷达影象改化成地面坐标。这个过程包括影象的测距方向,航向,地面高差和地球弯曲等项改正。(2)由地面坐标变换到大地坐标。根据158个检查点计算坐标均方根误差(以影象比例尺表示)为mx=0.09mm,my=0.08mm,ms=0.12mm。以上的精度完全满足测制1:5万地图加密点精度要求,同时也适合于测制边远地区1:2.5万地图精度。根据实际计算结果表明,由地面变换到大地坐标,最佳精度并不一定是Derenyi,Leberl推导的高次多项式,而是不含有y2项的二次多项式,因此可以认为二次多项式为该雷达系统成象变形规律。理论的分析与计算结果说明,侧视雷达影象的改化,特需考虑投影差的改正,它能显着地提高平面精度,而侧视雷达航带影象的分段处理也有利于提高平面精度。

     

    Abstract: In this paper the experimental planimetric accuracy through performing geometric processing of three strips of Synthetic Aperture Side-looking Radar(SAR) imagery is reported,and the prospects for mapping medium and small scale maps are analyzed.The proposed method of solution has been procceeded in two stages,In the first stage,coordinates of the imagery of SAR are reduced to ground coordinates,they include the corrections of slant-to-ground rang reduction,along-track coordinates,relief displacements and earth curvature.Then,the reduced coordinates are transformed to geodetic coordinates with the help of a well distributed control points.The RMS errors in position at imagery scale computed from 158 check points are mx=0.09mm my=0.08mm ms=0.12mm The accuracy meets with the requirements of maps at a scale of 1:50000,also with ones of 1:25000 for remote areas.The results obtained herein are also tested by the author by using Derenyi and Leberl's high power polynomials.But the best one occures when the polynomials are limited to the second power without y2 term.Hence the second power polynomial is taken to represent the law of radar systematic distortion.From the exprimental results and the theoretical analysis it is shown that the removal of the adverse effect of relief displacement can increase the accuracy remarkably.This is specially important for radar imagery.It is recommended that dividing the strip imagery into sections is a way to improve its accuracy.

     

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