Viewshed simulation and optimization for digital terrain modelling with terrestrial laser scanning

Abstract

The main objective of this study is the development of a simulation and optimization method for wide-area terrain mapping with terrestrial laser scanning (TLS). The problem can be stated as follows: given a prior digital surface model (DSM) of a region of interest (e.g. from airborne lidar or structure-from-motion photogrammetry), determine the minimum number of scan locations required to seamlessly scan the terrain in the region for a given scanner range and angular field-of-view (FOV). An optimization method for measurement setup is developed using multiple viewshed analysis and simulated annealing (SA) constrained by the system performance characteristics and survey specifications. The method is evaluated at a sediment and erosion control facility with hilly terrain by comparing random scan locations versus optimized three to six scan locations. Statistical results illustrate that average visibility for random sampling increases gradually with scan locations. However, random sampling clearly underperforms in terms of scan visibility relative to five or six optimized scan locations with an average visibility of 100%. Similar patterns in optimized scan locations demonstrate that certain terrain morphometry at the study site is an essential factor for TLS survey design. Finally, an optimized solution is compared to a brute-force manual solution for determining four scan locations for conducting surveys at the study site. Results show the effectiveness of the optimization method for selecting combinations of scan locations that enable more efficient TLS survey coverage over a wider terrain area compared to manual selection. Furthermore, results demonstrate the adaptability of the method to take into consideration different scan parameters and survey conditions, such as pre-determined scan locations that may be required (e.g. a survey control monument).