Applications of Terrestrial LIDAR in Engineering Geology and Geologic Hazards

Terrestrial or ground-based LIDAR is a new technology that has many applications in the fields of geologic hazards, engineering geology, structural geology and tectonics. LIDAR (Light Detection and Ranging), also referred to as “3D laser scanning”, employs a laser and a rotating mirror(s) to rapidly scan and image volumes and surficial areas such as rock slopes and outcrops, buildings, bridges and other natural and man-made objects. Ground-based or terrestrial LIDAR refers to tripod-based measurements, as opposed to airborne LIDAR measurements made form airplanes or helicopters.

The output from ground-based LIDAR is a point cloud consisting of millions of laser distance measurements representing the three-dimensional scanned scene. The point clouds are then processed to extract geotechnical information. High-resolution digital images are also taken of the scanned scene, and these images can be “draped” onto the point cloud using texture-mapping techniques to provide a 3D color DTM of the scanned scene. Additional geological and geotechnical information can be extracted from the DTM that would be difficult to observe in the point cloud.

Through field case studies and software development, the usefulness of ground-based LIDAR has been demonstrated in a number of geoengineering applications, including geologic hazard identification and monitoring, rock mass characterization, fault characterization, rockfall and displacement monitoring, and other detailed 3D measurements. Also, detailed three-dimensional output from ground-based LIDAR is being used as input into 3D disontinuum models to predict time-dependent slope and tunnel degradation and failure when subjected to mechanical, thermal, hydrologic and seismic loading.