Interaction of Laser Pulses with the Water Surface - Theoretical Aspects and Experimental Results
Exact water level heights are required in laser bathymetry as the basis for measuring correct water depths, in hydraulic modelling as reference data for calibrating flood maps, for discharge estimation in hydrology, for topographic map production, and in many other fields. Measuring water surface heights with lasers is feasible but the interaction of the laser beam with the air-water-interface is complex. In this contribution, first, the various parameters influencing the backscatter from the water surface (laser wavelength, incidence angles, beam divergence and footprint size, surface albedo, specular reflection, etc.) are discussed in theory based on the LiDAR equation. In the second part, results from various real-world, flight experiments with topographic and bathymetric laser sensors mounted on manned and unmanned aerial platforms (airplane, octocopter UAV) are presented, demonstrating the effect of the individual parameters (incidence angle, range, laser wavelength) in practice.