LASER-BASED 3D GEOLOGIC MAPPING, FROM FEATURE TRACING TO PHOTOREALISTIC OUTCROPS: AN OVERVIEW WITH CASE HISTORIES

It is feasible for the geologist to efficiently, accurately and digitally capture 3D geology at close range because of the global coordinates from the Global Positioning System (GPS), reflectorless laser rangefinding technology (RLR) and a unique way to combine this information with imagery, at a wide range in cost and sophistication depending on the objective. The RLR can trace geologic features, such as contacts and faults in 3D using GIS based software integrated with GPS. Examples of such mapping are subtle regional structures in Wyoming (relatively small amplitude folding, less than 100m, and long wavelengths, several kilometers) and detailed sedimentology in the Ferron sandstone in Utah (for reservoir characterization which included GPS positioned ground penetrating radar, wells and stratigraphic sections). At high cost and complexity is the use of fast laser scanners (ground LIDAR) capturing the outcrop at high resolution and accuracy, some even recording the visible spectrum at the laser points. More advanced than this is the integration of the detail of scanning and the pixel information of close-range imagery capturing the entire outcropping digitally and photorealistically, e.g. a true 3D virtual outcrop. The color information is mapped (not rubber sheeted) onto the high resolution terrain. With such outcrops, one can “navigate” or observe from various locations, perspectives and distances the outcrop, e.g. take a virtual field trip. The identification of specific features and their digitization in three-dimensions can be done in the office as shown with photorealistic outcrops around the world. Issues about data sharing, such as standardizing formats, archiving and requirements for its utilization, need to be addressed.