CAPTURING, VISUALIZING, AND ANALYZING GEOLOGICAL OUTCROPS WITH 3D LASER RANGEFINDERS AND TERRESTRIAL LASER SCANNERS AND DIGITAL CAMERAS

摘要

The utilization of GIS and GPS in mapping is still not yet common in geosciences. Methods and technology developed in GIS type mapping applications such as remote sensing are used in geologic mapping but for detailed mapping of exposures on steep slopes and cliffs it is necessary to map digitally and obliquely at relatively close range (often less than a kilometer) using portable and handheld equipment. UTD has used laser rangefinders integrated with digital photography and photogrammetric methods since 1996 integrated with high accuracy GPS. Here we emphasize using portable handheld reflectorless lasers, to map geologic features such as contacts and terrain. The laser "gun" approach has distinct advantages and a new ArcGIS extension 3D Laser Tool (3DLT) demonstrates that using ArcMap, under ArcGIS, using Visual Basic for application language and ArcObjects components in ArcMap providing a simple yet sophisticated platform for mapping, visualizing and analyzing outcrops. It integrates data from a laser rangefinder operating in a continuously rangefinding mode georeferenced with RTK GPS derived coordinates and assigning attributes from an extensive geologic dictionary. The data is visualized in the field in 3D in real time for outcrops at ranges only limited by the type of rangefinder being used, exceeding 800 meters. 3DLT allows conversion and visualization of point features to lines or polygons immediately and some utilization of digital photographic processing. An example of 3DLT data capture and analysis is demonstrated in various locations. 3DLT was used to map stratigraphy and structure and the results were digitally compared to existing vectorized conventional mapping. For comparison a 3D photorealistic model of some examples was built with a terrestrial laser scanner using a unique UTD approach to integrating laser scanning and digital photography.