Assessment of airborne scanning laser altimetry (lidar) in a deltaic wetland environment

Abstract

The objective of the study was to evaluate the airborne scanning light detection and ranging (lidar) technology for hydrological applications in wetlands, deltas, or other similar areas. A comparison of lidar data with in situ survey data revealed a negative elevation bias of 0.21 m, which was corrected by block adjustment. The evaluation demonstrated that the lidar pulses had difficulties penetrating thick willow cover and dense thatch layers beneath the grasses and sedges (graminoids). After block adjustment, the lidar data achieved a root mean squared error (RMSE) of 0.15 and 0.26 m in graminoid and willow vegetation, respectively. The bare ground points produced an RMSE of 0.07 m. To be useful in hydrologic modelling, elevation data need to be interpolated into an even grid, or a digital elevation model (DEM). Four interpolation algorithms were evaluated for accuracy. The input elevations were best honoured when interpolated into a 0.25 m grid using a kriging algorithm and, thereafter, averaged to a 4 m resolution DEM. The RMSE of the DEM was 0.22 m. Despite some problems in dense vegetation, the lidar DEM provided useful topographic detail in a resolution and accuracy that is acceptable for many hydrologic purposes.