一种适合低空机载平台SAR成像运动补偿方法

低空机载平台的运动存在剧烈的扰动和不确定性,使得通过其进行SAR成像的难度增大,本文提出了将快速后向投影(FFBP)算法和RTK系统高精度定位信息结合进行运动补偿,从而可以快速地获得高质量的SAR图像的方法.由于定义测绘区和成像过程中的子图像划分采用不同的坐标系,使得成像时需要对感兴趣区域进行锁定,本文提出成像区域锁定算法,能够进一步提高计算效率.最后将RTK系统的空间位置信息引入FFBP算法时本文分析了两种思路,一种是将航迹拟合为直线,将各个子图像的原点补偿至一条直线上,另一种思路是将子图像的原点补偿至一条曲线上,后者具有更高的补偿精度和适应性,但是同样也带来更高的复杂度,影响计算效率.通过两组实测数据的比较,本文认为在机载平台航线能够拟合为一条直线的情况下,应该采用近似补偿的方法以获得较高的计算效率.

A Motion Compensation Method for Low Altitude Airborne SAR

Terrible disorder and serious uncertainty of the low-altitude airborne system's motion increase the difficulty of SAR (Synthetic Aperture Radar) imaging. This paper presents a motion compensation method that brings the RTK data of high precise position information into FFBP (Fast Factorized Back Projection) algorithm to get a high quality SAR image. The coordinates of the defined target area are different from the sub-image's coordinates, how to aim at the interested area under the polar coordinates is presented in order to increase the computation efficiency. There are two methods to introduce the position information into FFBP to compensate motion error. One method is to approximate the track to a line, and the origins of the sub-images are set on it. Another method set al.l the origins on the trace curve that bring in higher compensation precision and also higher complexity. Finally two practical results are presented to prove the algorithm's availability, and also suggest the approximate compensation method (the former one) for efficiency reason when the asymptote of the aircraft's trace is linear.