3D Structural Modeling Using Remote Sensing and Ground-Based LIDAR

Abstract

High-resolution remote sensing data and 3D modeling techniques offer new tools for structural analysis that improve on the efficiency, accuracy and precision of geologic mapping, and provide insight into the structure of an area that is difficult to obtain otherwise. I combine conventional remote sensing data and geologic mapping with laser survey data into a complete 3D model that constrains the surface and subsurface geometry of a part of the Catalan Coastal Range at the edge of the Ebro Basin, Spain. For lower relief areas two approaches are used to interpret orthophotos: I interpret on orthophotos in map view and then visualize the interpretation in 3D by draping the interpretation and photos over digital elevation models, secondly I interpret directly on the draped orthophotos. I find the latter approach to be much more accurate in interpreting the surface geology. In areas that are impossible to map in a conventional sense with any precision, such as vertical cliff faces 100' s of meters high, I employ 20 cm resolution ground-based LID AR. These data are of such high fidelity that surfaces generated from the scans allow delineation of individual beds that can be interpreted directly on the surface in 3D, similar to interpreting draped orthophotos as discussed above. To extend the surface interpretation into the subsurface I use a technique exploiting the local 3D information of surface contacts with cross section construction to ultimately build a self-consistent 3D model. For surface contacts that have demonstrable relief change, a shallow subsurface 3D model is created. These provide local structural control for cross-section construction. The cross sections are then used as a framework for building of a 3D model. I found that making use of surface data in a 3D environment such as that described above provides additional understanding of the structure of an area than cannot be obtained by conventional mapping alone.