Trisurf multi-scale rugosity, slope and aspect

Calculate multi-scale measures of rugosity slope and aspect for Delaunay triangulated surface meshes

This code implements the method outlined in the paper:

Friedman A, Pizarro O, Williams SB, Johnson-Roberson M, "Multi-scale measures of rugosity, slope and aspect from benthic stereo image reconstructions", PLoS ONE, 2012 (accepted, in press as at 10/2012).

Terrain complexity is strongly correlated to biodiversity in marine environments. Even when terrain is represented as digital bathymetry, it is necessary to abstract these digital terrain models into simpler representations in order to perform analytical work. Ecologists typically use indices, such as rugosity, slope and aspect to describe habitat structure. Rugosity is a measurement that provides a notion of terrain complexity. It is a ratio between the actual length (or area) along the undulating terrain and the straight-line distance (or planar projected area). Values of 1 typically indicate flat terrain and the higher the complexity of the terrain, the higher the rugosity value. Fine-scale rugosity is traditionally measured in-situ by divers along a single, linear profile using chain-tape methods or profile gauges. This code calculates multi-scale measures of rugosity, slope and aspect from fine-scale bathymetric reconstructions. It can be used for multi-beam bathymetry or, as in the case of the presented paper, on fine-scale bathymetry created from geo-referenced stereo imagery.

We propose and implement a new method for calculating rugosity in a Delaunay triangulated surface mesh by projecting areas onto the plane of best fit using Principal Component Analysis (PCA). Slope and aspect can be calculated with very little extra effort, and fitting a plane serves to decouple rugosity from slope.

Performing rugosity calculations over a digital terrain reconstruction is more flexible, robust and easily repeatable compared to diver-based assessments. See the paper for more info.