GME

Geospatial Modelling Environment

r.deldir (Delaunay Triangulation / Dirichlet Tesselation)

Computes the Delaunay (Voronoi) triangulation and Dirichlet tessalation of a set of points using the 'deldir' library in R

Description

This tool uses the 'deldir' library in R to compute the Delaunay triangulation and Dirichlet tessellation of a set of points. Given an input point data source, the user can produce one or both of the two outputs (they are both calculated simultaneously so there is no significant processing cost to producing both) as line layers.

Dirichlet tessellation requires a rectangular boundary that defines the limits of the calculation. By default the deldir library will set this to be plus/minus 10% of the range of x and y point coordinates, but this can be specified explicitly with the 'extent' option.

This tool automatically filters any stacked (identically placed) points before running the computation in R.

For citations and a full description of the deldir library, open R and type: library(deldir), then ?deldir. If the deldir library has not been installed on your system, you must first type: install.pacakges("deldir").

Syntax

r.deldir(in, dir, del, [extent], [where]);

inthe input point data source
dirthe output line data source for the Dirichlet (Voronoi) tessellation (optional if 'del' is specified)
delthe output line data source for the Delaunay triangulation (optional if 'dir' is specified)
[extent]the reference layer to clip to (a vector or raster layer), or the coordinates of the rectangle to clip to (min x, max x, min y, max y)
[where]the selection statement that will be applied to the feature data source to identify a subset of features to process (see full Help documentation for further details)

Example

r.deldir(in="C:\data\firestations.shp", dir="C:\data\dirtess.shp");

r.deldir(in="C:\data\firestations.shp", del="C:\data\deltriang.shp");

r.deldir(in="C:\data\samples.shp", dir="C:\data\dirtess.shp", del="C:\data\deltriang.shp", extent=c(346000,450600,4956300,5204300));

r.deldir(in="C:\data\trees.shp", dir="C:\data\dirtess.shp", del="C:\data\deltriang.shp", extent="C:\data\studyarea.shp");


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