Airborne Scanning
Gottfried Mandlburger et al.: A Decade of Progress in Topo-Bathymetric Laser Scanning Exemplified by the Pielach River Dataset 20.12.2023
Topo-bathymetric laser scanning featuring high spatial resolution and a seamless transition within the littoral zone from land to water evolved considerably in the last decade due to progress in both sensor technology and processing methods. Unlike early systems that focused solely on maximizing depth of penetration, topo-bathymetric scanners enable detailed description of coastal and inland waters at a level of detail that opens up applications in hydromorphology, hydraulic engineering, ecohydraulics, and hydrobiology. Since 2013, a near-natural river section of the pre-alpine Pielach River has been repeatedly surveyed with bathymetric LiDAR sensors from manned and unmanned aerial platforms. The captured time series not only constitutes a valuable data basis for analyzing morphometric change in response to recurring flood peaks, but also allows to trace the progress in sensor, platform and data processing technology.
In this contribution it is demonstrated that over the last ten years, the depth performance could be increased by approximately 60 %, starting from 1 Secchi depths to more than 2 Secchi depths with sub-m spatial resolution. Furthermore, the paper focus on current approaches for improving the geometric sensor calibration, which allow integrated processing of GNSS-, IMU and LiDAR observations for concurrent calculation of both flight trajectories and 3D point clouds with an absolute accuracy better than 5 cm. This is specifically important for repeat surveys and monitoring of fluvial processes. While this contribution confirms substantial progress in the field, further topics like precise modeling of dynamic water surfaces, full waveform processing in complex target situations including littoral vegetation and submerged deadwood, and detection and modeling of underwater vegetation are identified as future research areas.
The evolution of the sensors employed is reflected in the parameters of the survey flights and the resulting 3D point clouds. RIEGL’s first airborne laser bathymetry instrument, the RIEGL VQ-820-G was used from helicopters and fixed-wing aircraft at the beginning of the Pielach River campaign in 2013. This LiDAR instrument was followed by the RIEGL VQ-880-G and later by the RIEGL VQ-880-G II , which are hybrid ALB systems featuring one green and one IR LiDAR channel, camera(s), and an Inertial Measurement Unit (IMU) mechanically tightly integrated to form a unit that is comparatively easy to mobilize. From 2018, a comparatively small, single-channel ALB system with integrated camera, IMU and data memory, the RIEGL VQ-840-G, was used.
The full article is published on the ISPRS platform, and can be found here.
