R Package Gdistance: Distances and Routes on Geographical Grids (version 1.1-1)

This vignette describes gdistance, an R package which provides functionality to calculate various distance measures and routes in heterogeneous geographic spaces represented as grids. Distances are fundamental to geospatial analysis (Tobler 1970). The most commonly used geographic distance measure is the great-circle distance, which represents the shortest line between two points, taking into account the curvature of the earth. However, the great-circle distance does not correspond very well to expected travel time/effort between two points. Travel time and the real distance travelled depend on the means of transport, the mode of route-finding, and the characteristics of landscapes and infrastructure. The great-circle distance could be considered as referring to a special case: goal-directed movement with no obstacles, ‘as the crow flies’. Other distance measures are needed when travel is not (or less) goal-directed and landscape characteristics affect movement in a spatially heterogeneous way. Package gdistance was created to calculate distances and determine routes using geographical grids (rasters) to represent landscape heterogeneity. It provides the following distance and route calculations.