Analysis and correction of ocean wave pattern induced systematic coordinate errors in airborne LiDAR bathymetry
Analysis and correction of ocean wave pattern induced systematic coordinate errors in airborne LiDAR bathymetry
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DOI：
10.1016/j.isprsjprs.2017.04.008
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发表时间：
2017-06
影响因子：
12.7
通讯作者：
P. Westfeld;H. Maas;Katja Richter;R. Weiß
中科院分区：
文献类型：
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作者：
P. Westfeld;H. Maas;Katja Richter;R. Weiß
本文研究了海洋波型对激光雷达三维水下点坐标测量精度的影响。对有限直径激光脉冲通过空气/水界面的折射进行了严格的微分模化。对典型的波型和传感器配置进行了仿真，系统分析了它们对水体底部三维坐标的影响。结果表明，波浪对水下地形三维点云坐标的平面坐标和深度坐标都有很大的影响，尤其是对现代小空间激光雷达系统而言。平面效应可能达到几个分米甚至几米，深度坐标误差也达到几个分米，即使在水平水体底部的情况下也是如此。模拟结果表明，在某些波型条件下，对于大足迹系统(将激光波束在水面上扩散到直径几米)，波浪效应平均的简化假设(如大多数激光测深数据处理工具所做的那样)甚至不能满足。波束发散较小的现代系统对波浪引起的折射条件的变化更加敏感，并将经历显著的与波型有关的坐标误差。如果波型可以通过激光测深水面反射或其他观测来模拟，则本文的结果为更严格的坐标校正奠定了基础。此外，还将表明，除了局部波面相关的准随机部分外，诱导坐标误差还包含非零偏差，这允许建立与波型相关的改正项，以便通过消除系统的波型相关效应来提高激光测深的精度。
This contribution investigates the effects of ocean wave patterns on 3D underwater point coordinate accuracy for LiDAR bathymetry. The refraction of the finite diameter laser pulse passing the air/water interface is modeled differentially in a strict manner. Typical wave patterns and sensor configurations are simulated, and their impact on the 3D coordinates at the bottom of the water body are systematically analyzed. It can be shown that waves have a significant effect on both the planimetry and depth coordinates of underwater topography 3D point cloud coordinates, especially for modern small footprint LiDAR systems. Planimetric effects may reach several decimeters or even meters, and depth coordinate errors also reach several decimeters, even in the case of a horizontal water body bottom. The simulations show that the simplified assumption, that wave effects average out (as is made in most LiDAR bathymetry data processing tools) is not even fulfilled for large footprint systems (spreading the laser beam to a diameter of several meters at the water surface) under certain wave pattern conditions. Modern systems with smaller beam divergence are much more sensitive to wave-induced variations of the refraction conditions and will experience significant wave pattern dependent coordinate errors.The results presented here form a basis for a more strict coordinate correction, if the wave pattern can be modeled from the LiDAR bathymetry water surface reflections or from other observations. Moreover, it will be shown that the induced coordinate errors contain a non-zero bias in addition to a local wave surface dependent quasi-random part, which allows for the formulation of wave pattern dependent correction terms in order to increase the accuracy of LiDAR bathymetry by removing systematic wave pattern dependent effects.