Directional roughness profiles from three-dimensional photogrammetric or laser scanner point clouds

Outcrop-scale directional roughness profiles can be extracted from photogrammetric or laser scanner point clouds using a straightforward five step procedure consisting of: 1) calculation of the dip direction and magnitude for use as a geologically significant reference vector; 2) rotation of the coordinate system into alignment with the dip-line and strike-line; 3) interpolation of scattered points onto a grid in a plane defined by the dip-line and strike-line; 4) extraction of linear profiles in desired directions relative to the dip-line; and 5) estimation of quantities such as Patton asperity angles (i) and Barton joint roughness coefficients (JRC) using published empirical relationships. Because rotation of the coordinate system effectively reduces the dimensionality of the problem, rock surface roughness can be conveniently visualized using contour maps, shaded relief images, or three-dimensional surface plots. Profile data extracted from point clouds can also be used as the basis for more advanced methods such as spectral or fractal analysis of rock surface roughness. Extraction of profiles and estimation of i and JRC values is illustrated using data from a large joint surface encountered in a highway rock slope stabilization project along Interstate 90 near Snoqualmie Pass, Washington, USA.