Grid_strain and grid_strain3: Software packages for strain field computation in 2D and 3D environments

Two Matlab (TM) software packages for strain field computation, starting from displacements of experimental points (EPs), are here presented. In particular, grid_strain estimates the strain on the nodes of a regular planar grid, whereas grid_strain3 operates on the points of a digital terrain model (DTM). In both cases, the computations are performed in a modified least-square approach, emphasizing the effects of nearest points. This approach allows users to operate at different scales of analysis by introducing a scale factor to reduce or also exclude points too far from grid nodes. The input data are displacements (or velocities) that can be provided by several techniques (e.g. GPS, total topographical station, terrestrial laser scanner). The analysis can be applied to both regional- and local-scale phenomena, to study tectonic crustal deformations (strain approximate to 10(-8)-10(-6)) or rapid landslide collapses (10(-4)-10(2)), and to characterize the kinematics of the studied system. Errors on strains and geometric significance of the results are also provided. (c) 2008 Elsevier Ltd. All rights reserved.