激光测高数据辅助卫星成像几何模型精化处理

资源三号02星搭载了中国首个对地观测试验性激光测高载荷。借鉴目前较成熟的卫星影像区域网平差理论的基础上,结合近年来激光测高数据精度的大幅提升以及资源三号02星激光测高数据的特点,首次提出了激光测高数据辅助卫星立体影像进行成像几何模型精化处理的通用理论。首先,利用传统的区域网平差算法对所处理影像进行高精度连接点匹配处理,并对其进行无约束的自由网平差处理,获得高精度相对精度及不亚于原始成像几何模型的绝对精度;其次,根据激光测高数据3维坐标和精化后参考影像成像几何模型获取激光数据参考影像坐标;而后将参考影像坐标通过几何模型映射获取目标影像上待匹配影像坐标,通过连接点匹配算法,对待匹配目标影像坐标进行精化获取高精度像方同名点;最后,以同名点作为高程控制进行区域网平差计算,对影像成像几何模型进一步处理,获取高精度补偿参数。通过湖北、青海两测区的试验,以激光测高数据辅助卫星影像几何模型精化精度可分别达到1.97 m、3.23 m,结果表明本文提出的方法可有效提高卫星立体数据测图精度。

Laser altimetry data-aided satellite geometry model refined processing

ZiYuan3-02 (ZY3-02), which was launched on May 30, 2016, is the second satellite in the ZiYuan3 series and is mainly used for developing China''s civil space infrastructure. A laser altimeter, a core payload in ZY3-02, is China''s first earth observation laser altimeter experimental instrument. Evaluation accuracy is a crucial factor in stereoscopic mapping and is occasionally even more difficult to improve than a planar. In the conventional block adjustment combined with the increasing accuracy of laser altimeter data and the characteristics of laser altimetry data in the ZY3-02 satellite, in this study, we proposed a geometric imaging model refinement general theory of satellite stereo images aided with the laser altimeter data.
First, high-precision tie point matching in the conventional block and free network adjustments without constraints were conducted to obtain a high-precision relative accuracy and absolute precision, which was not worse than that in the original imaging geometric model; second, in accordance with the 3D coordinates of the laser altimetry data and refined imaging geometric model of reference data, the reference image point coordinates could be acquired. These coordinates were used to map the target image point coordinates using the geometric model, and high-precision homonymous image points could be determined in the target images after a refinement process through the tie point matching algorithm; finally, the block adjustment with the homonymous points as elevation controls was performed to further process the imaging geometry model and compute high-precision compensation parameters.
The experiments in Hubei and Qinghai showed that the elevation accuracy of the satellite geometry model refined by altimeter data can reach 1.97 and 3.23 m, correspondingly. The comparison experiments in Hubei and Xinjiang area presented with an obvious phenomenon wherein the system error became large given the weakening of the control strength.
The abovementioned experiments demonstrate that the proposed method could effectively improve the accuracy of satellite stereo mapping. The application of the laser altimetry data was subject to the topographic relief. The laser altimetry data would become increasingly effective in a flat area but require a certain pre-process in mountainous areas before use. In practical applications, the laser data should be distributed evenly at no more than one track in the space interval.