基于改进的切比雪夫多项式轨道的SAR影像正射纠正

Orthorectification of SAR Image Based on Improved Chebyshev Polynomials Orbit Model

在利用SAR(合成孔径雷达)严格几何模型(距离-多普勒)进行影像正射纠正时,为消除卫星轨道误差对影像正射纠正精度的影响,提出了一种新的卫星轨道模型——切比雪夫多项式。首先利用切比雪夫多项式对SAR影像元数据中提供的若干卫星轨道状态矢量进行拟合,以获得影像成像期间内卫星轨道状态矢量关于时间的函数关系式;然后利用少量地面控制点修正切比雪夫多项式拟合的参数;最后将修正之后的卫星轨道模型用于SAR严格几何模型的正射纠正,从而提高正射纠正影像的定位精度。结合SAR的几何成像参数、数字高程模型,选择广西桂林某地区的Radarsat-2卫星拍摄的SAR影像进行试验,利用所提出的方法与传统正射纠正方法进行对比,试验结果得出正射纠正精度在40m以内,定位精度优于传统方法。

In order to eliminate the influence of satellite orbit error on the accuracy of image orthorectification when using SAR rigorous geometric model(range-Doppler),a new satellite orbit model based on improved Chebyshev polynomials was proposed.Firstly,several satellite orbit state vectors provided in SAR image metadata were fitted by Chebyshev polynomials,and the function relation of the state vectors were obtained with respect to time during the imaging period.Then,the fitting parameters of the Chebyshev polynomials were modified with sparse ground control points.Finally,the modified satellite orbit model was used in the orthorectification based on the SAR rigorous geometric model,thereby improving the positioning accuracy of the orthorectified image.Combined with SAR geometric imaging parameters and digital elevation model,the SAR images taken by the Radarsat-2 satellite in a certain area of Guilin,Guangxi,were selected for experiment.The proposed method was compared with the traditional orthorectification method.The test results show that the orthorectification accuracy is smaller than 40 meters,and the positioning accuracy is better than the traditional method.