A Simple Method for Measuring Discontinuity Orientations from Terrestrial LIDAR Data

Abstract

The measurement of discontinuity (joint) orientations is critical in assessing the stability of discontinuous rock slopes. The discontinuity orientations are used as input to all discontinuous modeling programs and methods, including kinematic screening methods and limited equilibrium sliding methods. ### Manual Discontinuity Measurements Traditionally, discontinuity orientations are measured manually using a compass (Figure 1). The drawbacks of this method include the fact that these measurements are slow, are tedious, often subject the user to physical danger (from rock falls and/or the need to scale slopes for measurements at heights), and may be inaccurate due to sampling biases when measurements are restricted to accessible areas only. Figure 1. Manual measurements of joints are slow, tedious, expose the user to danger, and are often limited to locations that are easily accessible. ### LiDAR Measurements Terrestrial LiDAR (light detection and ranging) scanners (Figure 2) can return detailed three-dimensional (3-D) maps or point clouds of rock slopes. These include highly accurate maps of planar features such as joints and other discontinuities. Joint orientations can be measured on these point clouds in various ways. LiDAR scanners are increasingly being used for the purpose of measuring discontinuity orientations (Bulut and Tudes, 1996; Feng, 2001; Post, 2001; Donovan et al., 2005; Strouth and Eberhard, 2006; Haneberg, 2008; Olariu et al., 2008; Lato et al., 2009; Sturzeinegger and Stead, 2009; Gigli and Casagli, 2011; and Otoo et al., 2011). Figure 2. Leica ScanStation II in Saudi Arabia. #### Systematic LiDAR Orientation Measurements One way to automatically generate orientations from LiDAR scans is to use advanced algorithms to create solid models (polygonal models) where each polygon represents a planar face. The typical LiDAR measurements work well in general when using scans from vegetation-free continuous rock cuts or slopes where the exposure is entirely composed of discontinuity surfaces. Where vegetation is present, or blast- or …