对地观测星载激光测高系统高程误差分析

Elevation error analysis of spaceborne laser altimeter for earth observation

星载激光测高系统通过接收卫星平台激光器发出的激光脉冲经地表反射的微弱回波,计算卫星与地表的距离;结合卫星轨道和姿态数据,生成激光脚点精确地理位置和高程结果。其高程误差主要受器件、环境和目标参数影响,目前还没有完整描述对地观测星载激光测高系统平面和高程误差的数学模型。简化并完善了针对固体地表的激光测距误差模型,建立了完整的激光脚点平面和高程误差模型。利用高程精度和空间分辨率更高的机载Lidar数据评估了星载激光测高系统GLAS实测数据的高程偏差,评估结果符合所建误差模型。在较平坦的冰盖表面,GLAS系统高程精度可以达到设计值约15 cm。研究内容对测高系统高程误差评估和系统参数设计具有参考意义。

In space-borne laser altimeter system, the range between satellite and target was calculated by the weak received signal which was transmitted from laser device and reflected by earth surface, and the accurate location and elevation of laser footprint was acquired by combining satellite precise orbit with attitude data. The elevation error was mainly affected by the device noise, the environment and the target parameters, and there is no complete analyzing model of location and elevation error for spaceborne laser altimetry system. The error model of laser ranging for solid surface was simplified and improved.Meanwhile, the location and elevation error analysis model of laser footprint was established in this paper.Utilizing airborne lidar data with better spatial resolution and elevation accuracy, the elevation deviation of GLAS data were evaluated, and the result was consistent with the error model. It is proved that on the flat surface of ice sheets the elevation accuracy of GLAS system can meet its design value of approximate 15 cm. This research is instructive for elevation error assessment and system parameters designing of laser altimeter system.