高分辨率SAR辐射定标中两种角反射器响应测量方法的应用对比研究

Comparative Study on the Applicability of Two Corner Reflector based Radiometric Calibration Methods for High Resolution Airborne SAR Image

利用角反射器进行SAR图像辐射定标是一种简单、实用、精度较高的绝对定标方法。其关键技术包括角反射器响应测量、天线方向图拟合和定标常数确定。针对机载分米级高分SAR影像定标问题,在同一场景中布设了30和10cm两组三面角反射器,依据雷达中心入射角估计值、均方根误差和变异系数等指标,分析了已有的两种角反射器响应测量方法,即峰值法和积分法的适用性,并提出了一种新的天线方向图拟合方法。最后给出了两种方法对高分辨率SAR辐射定标的适用性结论。

Radiometric calibration of Synthetic Aperture Radar （SAR） using corner reflectors is a simple, practical and high precision external calibration approach. The key technologies in the calibration process includes a power estimation of the reflector impulse response,antenna pattern fitting and the determination of absolute calibration factor. In order to compare and analyze the applicability of the two common estima- tion methods of reflector impulse response,i, e. , peak method and integral method, on airborne high-resolu- tion SAR images,two radiometric calibration experiments based on two groups of trihedral corner reflec- tors （C30 and C10） in different sizes are conducted. In view of the unstable platform of airborne SAR,a new method of antenna fitting is proposed in this paper. Six criterions including the estimation value of me- dium incidence angle, RMSE, MEAN, STDEV, coefficient of variation （C. V） and precision of calibration are used to evaluate the applicability of the two methods. Experimental results show that the precision of peak method and integral method is similar when used the C30 corner reflector group,and the peak method performs is better than integral method when used the C10 group. The high resolution SAR image has a strong ability to represent the details of ground objects so that it difficult to select homogeneous back- ground to estimate impulse response in the integral method, so a relatively large size reflectors with a large background should be used. When the imaging system is focused well, the peak method is suggested, other- wise, the integral method should be used.