Stereonet Data from Terrestrial Laser Scanner Point Clouds

Abstract

In order to assess the stability of a rock slope, it is essential to characterise rock discontinuities at the exposed rock face. Conventionally, a field engineer will use simple instruments (compass and clinometer) to take a limited number of measurements of dip angle (DA) and dip direction (DD) directly on the rock face. This data is then entered into an analysis system and is presented as a stereonet. The accuracy of the analysis is limited by how representative of the whole slope the DA and DD data is. If there are inaccessible areas of the slope it cannot be used in the analysis. Through the generation of a “point cloud”, terrestrial laser scanning (TLS) has the ability to map entire rock faces without contact. This paper presents a strategy for extracting DA and DD data from a point cloud using Cyclone software. The strategy was tested by comparing the stereonet of a slope produced by both conventional (manual) and TLS survey. It was found that the TLS derived data was as accurate as, and more precise than, the manual measurements and provided more information and improved the stereonet analysis compared to that of the conventional survey.