To achieve a geometrically accurate representation of the water bottom, airborne LiDAR bathymetry (ALB) requires the correction of the raw 3D point coordinates due to refraction at the air–water interface, different signal velocity in air and water, and further propagation induced effects. The processing of bathymetric LiDAR data is based on a geometric model of the laser bathymetry pulse propagation describing the complex interactions of laser radiation with the water medium and the water bottom. The model comprises the geometric description of laser ray, water surface, refraction, scattering in the water column, and diffuse bottom reflection. Conventional geometric modeling approaches introduce certain simplifications concerning the water surface, the laser ray, and the bottom reflection. Usually, the local curvature of the water surface and the beam divergence are neglected and the travel path of the outgoing and the returned pulse is assumed to be identical. The deviations between the applied geometric model and the actual laser beam path cause a coordinate offset at the water bottom, which affects the accuracy potential of the measuring method. The paper presents enhanced approaches to geometric modeling which are based on a more accurate representation of water surface geometry and laser ray geometry and take into account the diffuse reflection at the water bottom. The refined geometric modeling results in an improved coordinate accuracy at the water bottom. The impact of the geometric modeling methods on the accuracy of the water bottom points is analyzed in a controlled manner using a laser bathymetry simulator. The findings will contribute to increase the accuracy potential of modern ALB systems.

为了实现水底的几何精确表示，机载LiDAR水深测量（ALB）需要校正原始3D点坐标，这是由于空气-水界面处的折射，空气和水中的信号速度不同以及进一步的传播引起的影响。测深LiDAR数据的处理基于激光测深脉冲传播的几何模型，该模型描述了激光辐射与水介质和水底的复杂相互作用。该模型包括激光，水面，折射，水柱中的散射以及底部扩散反射的几何描述。传统的几何建模方法引入了有关水面，激光射线和底部反射的某些简化方法。通常，忽略了水面的局部曲率和束发散，并且假定出射和返回脉冲的行进路径相同。所应用的几何模型与实际激光束路径之间的偏差会导致水底的坐标偏移，从而影响测量方法的准确性。本文提出了一种改进的几何建模方法，该方法基于对水表面几何形状和激光射线几何形状的更精确表示，并考虑了水底处的漫反射。完善的几何模型可改善水底坐标精度。使用激光测深仪模拟器以受控方式分析了几何建模方法对水底点精度的影响。