高分七号卫星(GF-7)是全球首颗同步搭载了光学立体相机和激光测高仪的对地观测卫星,可以同时获取亚米分辨率的两线阵光学立体影像和稀疏地面激光高程点,并期望通过激光高程点来提升立体影像的高程精度,以保障GF-7卫星能够服务于全球范围1:1万比例尺立体测图。本文根据卫星相机和激光测高仪工作过程中的误差传播机理,分析了利用激光高程点提升立体影像高程精度的基本原理。设计了一种GF-7立体影像与激光高程点复合测绘处理方法,包括构建了激光高程点在立体影像上自动精确量测方法、激光高程点与立体影像联合区域网平差模型等。最终实现立体影像高程精度有效提升。选取了中国河北省北部区域共计70景GF-7立体影像和463个激光高程点开展复合测绘处理试验,结果表明,立体影像在平地、丘陵、山地、高山地和全区域的高程中误差分别由原来的3.0m、4.68m、2.86m、2.48m和3.19m,降低至0.35m、0.66m、0.74m、0.91m和0.68m；平面中误差分别是4.99m、3.52m、4.42m、5.99m和4.82m。影像平面和高程精度均已满足中国1:1万比例尺立体测图的精度要求。目前采用本文所述方法构建的GF-7立体影像与激光高程点复合测绘处理系统已在GF-7卫星牵头主用户单位实现业务化应用,对未来全球范围1:1万比例尺地理信息资源建设具有重要意义。

The GF-7 satellite is the world"s first earth observation satellite synchronously equipped with an optical stereo camera and an operational laser altimeter, which can simultaneously obtain sub-meter resolution dual linear-array stereo images and sparse ground laser altimetry points (LAPs). And it was expected that the LAPs can be used for improving the elevation accuracy of stereo images, so as to ensure that the GF-7 satellite can be applied to the global 1:10,000-scale stereo mapping. Based on the error propagation principle of the working processes of satellite cameras and laser altimeter, the basic principles of improving the elevation accuracy of stereo images by utilizing LAPs was firstly analysed in this study. Then, an integrated processing method of GF-7 satellite stereo images and LAPs was designed, including the construction of precise measurement method of LAPs on stereo images, and the combined block adjustment model of LAPs and stereo images. Finally, the elevation accuracy of the stereo images are effectively improved. A total of 70 stereo images and 463 LAPs of GF-7 satellite in the northern region of Hebei province, China, were selected to carry out integrated processing experiments,and the results show that the vertical root mean square error (RMSE) of stereo images in the flat, hilly, mountainous, high-mountainous and entire region was reduced from the original 3.0m, 4.68m, 2.86m, 2.48m and 3.19m to 0.35m, 0.66m, 0.74m, 0.91m and 0.68m, respectively, and the horizontal RMSE of stereo images were 4.99m, 3.52m, 4.42m, 5.99m and 4.82m, respectively. It can be seen from these results that the horizontal and vertical accuracy of GF-7 stereo images had satisfied the accuracy requirements of China"s 1:10,000-scale mapping in China. At present, the integrated processing software system of GF-7 satellite stereo images and LAPs constructed by the method described in this paper had achieved business application, which had the great significance for the future construction of global 1:10000-scale geographical information resources.