Terrestrial laser scanning in geology: data acquisition, processing and accuracy considerations

Terrestrial laser scanning, or lidar, is a recent innovation in spatial information data acquisition, which allows geological outcrops to be digitally captured with unprecedented resolution and accuracy. With point precisions and spacing of the order of a few centimetres, an enhanced quantitative element can now be added to geological fieldwork and analysis, opening up new lines of investigation at a variety of scales in all areas of field-based geology. Integration with metric imagery allows 3D photorealistic models to be created for interpretation, visualization and education. However, gaining meaningful results from lidar scans requires more than simply acquiring raw point data. Surveys require planning and, typically, a large amount of post-processing time. The contribution of this paper is to provide a more detailed insight into the technology, data collection and utilization techniques than is currently available. The paper focuses on the workflow for using lidar data, from the choice of field area and survey planning, to acquiring and processing data and, finally, extracting geologically useful data. Because manufacturer specifications for point precision are often optimistic when applied to real-world outcrops, the error sources associated with lidar data, and the implications of them propagating through the processing chain, are also discussed.