Airborne LiDAR bathymetry allows an efficient and area-wide measurement of the water bottom topography in shallow waters. However, the maximum water depth range of this method is mainly limited by water turbidity, resulting in a reduced coverage of the water bottom topography in deeper waters. Water turbidity causes attenuation effects and hampers the reliable detection of water bottom echoes in the digitized full-waveform signal, and consequently, greater water depths are not analyzable by using standard processing methods. To increase the analyzable water depth, an extended full-waveform processing method was developed with the goal of enhancing the reliable extraction and detection of bottom points in deeper waters. This volumetric nonlinear ortho full-waveform stacking approach is based on the combined analysis of information from closely adjacent measurements under the assumption that the water depth is locally steady. Such an approach has the advantage that the influence of sensor noise and erratic non-bottom object echoes is significantly reduced so that weak water bottom echoes are better detectable. The results of the combined analysis were finally applied for water bottom echo detection in individual measurements, thus avoiding smoothing effects. For evaluation purposes, the detected water bottom points were compared with points derived from the standard processing method and with echo sounder measurements. The results of a pilot study in a river with high turbidity showed that the application of the extended full-waveform processing indicate an increase of the analyzable water depth from approximately 1.65 m to approximately 2.20 m, leading to an approximately 210 % increase in the number of detected water bottom points (related to the number of standard processing) and an improved coverage of the water bottom by newly processed points.
|Seiten (von - bis)
|ISPRS Journal of Photogrammetry and Remote Sensing
|Veröffentlicht - 2023
- LiDAR, Bathymetry, Full-waveform processing, Full-waveform stacking, Voxelization, ortho full-waveform