Modelling 3D topography by comparing Airborne LiDAR data with unmanned aerial system (UAS) photogrammetry under multiple imaging conditions

Abstract

This study presents the effect of image data sources on the topographic modeling of part of the National Trust site located at Weston-Super-Mare, Bristol, United Kingdom, covering an approximate area of 1.82 hectares. The accuracy of the DEM generated from 1m resolution and 2m resolution LiDAR data together with the accuracy of the DEM generated from the UAV images acquired at different altitudes, are analyzed using the 1 m LiDAR DEM as reference for the accuracy assessment. Using the NSSDA methodology, the DEMs' horizontal and vertical accuracy generated from each of the four sources was computed. Simultaneously, the paired sample t-test was conducted to ascertain the existence of a statistically significant difference between the means of the X, Y, and Z coordinates of the checkpoints. The result obtained shows that with an RMSE of -0.0101499 and horizontal accuracy of -0.175674686m, the planimetric coordinates extracted from 2 m LiDAR DEM were more accurate than the planimetric coordinates extracted from the UAV based DEMs. In contrast, the UAV based DEMs proved to be more accurate than the 2m LiDAR DEM in terms of altimetric coordinates. However, the DEM generated from UAV images acquired at 50 m altitude gave the most accurate result when compared with the vertical accuracy obtained from the DEM generated from UAV images acquired at 30 m and 70 m flight heights. These findings are also consistent with the result of the statistical analysis at a 95% confidence interval.