激光测高数据辅助卫星成像几何模型精化处理

Refined processing of laser altimeter data-aided satellite geometry model

资源三号02星(ZY-3 02)作为资源三号系列的第2颗卫星,于2016年5月30号成功发射,其主要服务于中国空间基础建设等重大工程,星上搭载了中国首个对地观测试验性激光测高载荷。高程精度作为立体测图的重要指标,达到其精度要求的困难程度远大于平面。在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ZY-3 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;然后,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。

ZY-3 02, which was launched on May 30, 2016, is the second satellite in the Zi Yuan3 series and mainly used for developing the civil space infrastructure in China. The laser altimeter, which is a core payload in ZY3-02, is the first laser altimeter experiment instrument of China for earth observation. The evaluation of the accuracy of this instrument is a crucial factor for stereoscopic mapping and occasionally even more difficult to improve than the planar. The basic conventional block adjustment was combined with the increasing accuracy of laser altimeter data and the characteristics of the laser altimeter data in the ZY3-02 satellite. The geometric imaging model of refinement general theory of satellite stereo images aided with the laser altimeter data was proposed in this study. First, high-precision tie-point matching in the conventional block and free network adjustments without constraints was utilized to obtain high-precision relative accuracy and absolute precision, which was not worse than that in original imaging geometric model. Second, the reference image point coordinates, which were used to map the target image point coordinates with the geometric model, could be acquired on the basis of the 3 D coordinates of laser altimeter data and refined imaging geometric model of the reference data. Third, high-precision homonymous image points could be determined in the target images after the refinement process through the tie-point matching algorithm.Finally, the block adjustment with the homonymous point as the elevation control was performed to further process the imaging geometry model and compute the high-precision compensation parameters. The experiments in Hubei and Qinghai indicated that the elevation accuracy of the satellite geometry model refined using the laser altimeter data could reach 1.97 and 3.23 m. The comparative experiments in Hubei and Xinjiang areas presented that the system error became larger given the weakening of the control strength. The experiments discussed above demonstrated that the proposed method could effectively improve the accuracy of satellite stereo mapping. The application of laser altimeter data was subject to topographic relief. It could be more effective in the flat area but requires several necessary preprocesses in the mountain area before utilization. In practical applications, the laser data should be distributed evenly and no more than one track in the space interval.