基于铅垂线轨迹法的星载激光高度计定位方法研究

As a way of acquiring high accuracy elevation without space flying limitation, space-borne laser altimeter improves the capability of anti-stealth and 3-dimensional cartography of satellite optical remote sensing imagery. However, space-borne laser altimeter earth observation footprint in the ground is of dozens of meters diameter, and the laser echo signal of which involves whole distance information of the footprint. Therefore, the elevation acquired by laser echo signal can not be accurate positioned..The project follows the trend of foreign and domestic space-borne laser altimeter application development, studies on the space-borne laser altimeter accurate direct ground positioning method. Firstly, space-borne laser altimeter laser echo signal is differential analyzed, the big footprint is subdivided, and ground elevation structural information is extracted. Then, the elevation position is iterative computed by Vertical Line Locus (VLL) method in the stereo images. In order to improve the space-borne laser altimeter direct ground positioning accuracy, laser echo signal wave is reconstructed and matched to DEM to exclude gross errors. At last, the above elevation observation results are selected as ground control points to calculate the space-borne laser altimeter, as to improve direct ground positioning accuracy. The project is of far-reaching theoretical significance and extensive application value to improve the remote sensing technology level and meet multi-source remote sensing earth observation demand in China.

星载激光高度计具有较高测高精度，能突破飞行区域限制实现对地高程测量，可以有效弥补遥感影像反隐身及三维探测等能力的不足。由于星载激光高度计对地观测在照射区域一般为直径几十米的大光斑，而接收到的回波信号包含了整个光斑区域内的信息，无法直接得到回波信号计算的高程值所对应的平面位置。. 本项目紧跟国内外星载激光高度计应用发展趋势，探索提高星载激光高度计直接定位精度的方法。首先对星载激光高度计回波信号微分分析，光斑细分，提取地面高程结构信息，由铅垂线轨迹法根据高程值在立体影像中迭代计算寻找其对应的平面位置，通过波形重建及波形与数字地表模型匹配，剔除粗差，优化星载激光高度计直接对地定位精度。并将优化后的直接观测点作为控制点，对星载激光高度计在轨检校，提高星载激光高度计无控对地定位精度。本项目对于提高我国遥感技术水平，满足多源遥感对地观测需求，具有重要而深远的理论意义和广泛的应用价值。

本项目在低频率星载激光高度计辅助立体测绘体制下，进行了高精度星载激光高度计几何定位关键技术研究，提出低频率星载激光高度计在轨检校方法， 配合仿真实验验证，为型号研制奠定理论和技术基础。首先，基于交叉累积剩余熵进行星载激光测高仪大光斑波形数据与地形匹配研究。根据星载激光测高仪大光斑回波波形信号包含地形结构信息的特性，将激光回波波形数据和数字表面模型投影到统计特征空间，建立数据的统计特征向量，消除数据间维度差异，以交叉累积剩余熵为相似性测度匹配波形数据与地形的统计特征。试验结果表明，本方法能够较好的实现激光回波波形数据与地形的匹配，匹配精度达到一个像素以内。然后，在立体图像定位辅助的情况下做了星载激光高度计光斑内细分定位研究，根据全波形数据内部高程相对精度较高的特点，完成利用铅垂线轨迹法及高程结构信息约束的星载激光测高仪定位方法，高程定位精度达到0.16m,平面定位精度与立体图像一致。最后，在高程结构约束条件下，进行立体遥感图像与星载激光高度计数据联合平差研究，提取星载激光高度计大光斑回波波形信号中的高程结构信息，建立观测条件方程，避免大光斑激光数据平面定位精度低的影响，与立体遥感图像联合空中三角测量平差计算。试验结果表明，本方法能够较好的提高立体遥感图像平差平面定位精度达到一个数量级。本项目研究成果已为项目负责人所在单位多个星载激光载荷的研究论证提供数据支撑。