ABSTRACT

ABSTRACT: COLTOP-3D software performs structural analysis of a topography using a digital elevation model (DEM). A color is defined based on slope aspect and slope angle in order to obtain a unique color code for each spatial orientation. Thus continuous planar structures appear as a unique color. Several tools are included to create stereonet(s), to draw traces of discontinuities, or to compute automatically density stereonet. A new version has recently been developed to represent true 3D surfaces from point clouds. Examples are shown to demonstrate the efficiency of the method. High resolution DEMs acquired with Lidar techniques greatly improve topographic analyses. 1 INTRODUCTION Digital elevation models (DEMs) are used in many hazard assessment methods, including landslides and rock instabilities. Slope angles are used for stability estimation, e.g. infinite slope stability models (Dietrich et al. 2001). Kinematic tests are used to estimate the likelihood of failure in rock slopes, such as slide, wedge and toppling failures (Jaboyedoff et al. 2004, Gokceoglu et al. 2000, Günther 2000). DEMs are also used for modeling rockfall trajectories. Many GIS tools permit a mathematical analysis of topography using slope, slope aspect, second derivative, curvature, flow paths, etc. (Burrough & McDonnell 1998). But very few are dedicated to the analysis of the relief structure. An attempt of merging slope angle and slope aspect in one document was made by Brewer & Marlow (1993) to represent topography using colors dependent on both slope angle and slope aspect, but the results were not used for structural analysis. Using the dip and strike direction of each cell, a DEM can be theoretically represented with a map having a unique color for each spatial orientation, allowing a very simple slope analysis.

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