在全球测绘的背景下，为实现无地面控制点的卫星摄影测量，提出了利用公开 D EM辅助国产卫星影像进行无控定位的方法。为充分利用公开 D EM在大范围内具有一致稳定的高精度特性，将其作为基准与从影像中提取的待定位 D EM进行表面匹配，匹配时采用引入截尾最小二乘估计的最小高差(LZD)法，并根据对应点高差的分布自适应探测及剔除 DEM之间的差异；匹配确定的变换参数用于对直接定位结果进行物方改正。设计了多组针对天绘一号和资源三号国产卫星影像的对比试验，结果表明本方法切实可行，能充分利用基准 D EM的优势，具有较好的稳健性；定位精度很大程度上取决于但不限于基准 D EM的精度，基本不受其分辨率的影响；当待定位 D EM分辨率较高时，单景影像利用 S R TM ；D EM即可得到能较好满足1∶5万比例尺地形图测制要求的无控定位精度。本方法还为卫星影像定位精度的检核提供了一种新的有效手段。%With the purpose of revolving the problem of photogrammetry without ground control points (GCPs)(referred to non-controlled positioning),a public DEM-assisted positioning method for Chinese satellite imagery without GCPs was proposed in the context of global mapping.To give full play to the characteristics of global ly consistent,stable and high precision of publ ic DEM,these data were regarded as reference data and matched with the DEM extracted from satellite imagery.Least Z-difference (LZD) method using least trimmed square (LTS)estimator was applied to match,and deformation between DEM is automatically detected and eliminated by analysis of the distribution of Z-difference.The correction parameters in object space which determined by DEM matching were applied to correct the direct positioning results.Multi-groups of comparative experiments for Mapping Satellite-1 and ZY-3 Satellite imagery were designed.Experimental results show that the proposed method is practical and feasible and has good robustness to gross error and deformation between surfaces,which can make ful l use of the advantages of the reference DEM.The positioning accuracy greatly depends on but not limited to the accuracy of public DEMand hardly affected by its resolution.Assisted by SRTMDEM,single imagery can realize high positioning accuracy without GCPs,which can meet the mapping standard of 1∶50,000 scale. This method also provides a new and effective means for positioning accuracy inspection of satellite i magery.
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