Terrestrial Laser Scanning of Extended Cliff Sections in Dynamic Environments: Parameter Analysis

Substantial erosion of the unstable seacliffs along the economically important coastline of San Diego County, California, threatens existing developments and public safety. Time-series mapping of the seacliffs and beaches provides valuable information about seasonal and rapid-event erosion. With high resolution terrestrial laser scanning (TLS) georeferenced using real-time-kinematic global positioning systems, it is possible to establish reliable comparisons of time-series surveys for quantitative change analysis of seacliff morphology. This paper introduces new field survey methods for georeferencing TLS surveys collected in dynamic environments where conventional control methods cannot be effectively implemented for large-scale mapping. Specifically, the quality control of scan alignment and the identification of optimal surveying parameters of point separation/density, distance from target, setup spacing, and efficiency are discussed for long cliff sections. These TLS surveys, performed several times along an approximately 17-km segment of seacliffs in San Diego County show an average root-mean-square uncertainty of 7.9 cm between adjacent scans approaching the nominal 7.2 cm accuracy of the survey equipment.