Using close range terrestrial digital photogrammetry for 3-D rock slope modeling and discontinuity mapping in the United States

Close range terrestrial digital photogrammetry has evolved into a useful remote characterization tool for rock slope practitioners, particularly in situations where manual discontinuity measurement may be impractical or dangerous. The primary products are high-resolution 3-D photographic surface models that have several advantages over terrestrial laser scanner point clouds, including cost, equipment portability and the ability to include discontinuities that appear as linear traces rather than flat planar surfaces. Models can be made with currently available off-the-shelf digital cameras while commercially available software provides virtual mapping capabilities that allow practitioners to identify, map, and quickly calculate the orientation of modeled discontinuities using the same experience-based logical process used by traditional fieldworkers. Comparison of manually measured and model-derived discontinuity orientations shows good agreement both between individual discontinuities and entire sets of discontinuities. Application of the technique is illustrated using five recent mining and civil engineering projects in the United States.