临近空间SAR几何定位

对合成孔径雷达（SAR）图像上的目标进行几何定位主要有两种模型：斜距转地距模型和距离多普勒（RD）模型，其中斜距转地距模型计算简单但忽略地球曲率因素，而RD模型不仅考虑了SAR成像机理还考虑了地球的曲率变化。仿真实验表明：在临近空间情况下，斜距转地距模型得到的结果定位精度低，与之相比，RD模型定位结果有着显著的优势，因此，在临近空间平台下对SAR目标进行定位必须考虑地球曲率因素。文中进一步在临近空间条件下对RD模型的定位精度进行了分析，推导了定位不确定性公式，并基于这些公式得出了仿真结果。

Geolocation for Near Space SAR

There are two main geolocation models for synthetic aperture radar (SAR): slant-to-ground range model and range Doppler (RD) model. The slant-to-ground rang model is easily calculated, but the earth curvature is ignored. And in RD model, not only the imaging principle is considered, but also the earth curvature variation is included. In this paper, the simulation experiment is implemented to show that the slant-to-ground range model has low accuracy of geolocation in the near space condition. Compared with the slant-to-ground range model, RD model has overwhelming superiority in this situation. Thus it is concluded that the earth curvature variation must be considered for near space SAR geolocation. Furthermore, the geolocation accuracy of the RD model is analyzed. The geolocation uncertainty formulas are derived, and the simulation experiment results are obtained based on the derived formulas.