The test between two methods which located directly using the single image , one located without gcp or dem , the other located without dem . results of the test implied that the location accuracy acquired from the method which located objects directly using the ers image achieved the demand of the 1 : 250000 topographic map 对单片无控制无dem和有dem支持的直接定位方法进行了试验，实验结果表明基于ers的sar图像直接定位精度可满足1 : 25万地形图的精度要求。
At first , this article introduces the digital imaging principle of the sar image , deduces the mathematic expression of the range - doppler model . on the base of analysis the r - d model function in image location , we ascertained the direct location based of the sar assistant data and verified the algorithm 本文首先介绍了sar数字成像原理，详细推导了距离?多普勒( r - d )模型的数学表达式，在分析了r - d模型在图像定位中作用的基础上，系统给出了基于sar辅助数据直接定位的原理与方法，并对算法进行了验证。
