leastcostpath (version 1.8.7)

create_barrier_cs: Create Barrier Cost Surface

Description

Creates a cost surface that incorporates barriers that inhibit movement in the landscape.

Usage

create_barrier_cs(raster, barrier, neighbours = 16, field = 0, background = 1)

Value

TransitionLayer (gdistance package) numerically expressing the barriers to movement in the landscape. The resultant TransitionLayer can be incorporated with other TransitionLayer through Raster calculations

Arguments

raster

RasterLayer (raster package). The Resolution, Extent, and Spatial Reference System of the provided RasterLayer is used when creating the resultant Barrier Cost Surface

barrier

Spatial* (sp package) or RasterLayer (raster package). Area within the landscape that movement is inhibited. See details for more

neighbours

numeric value. Number of directions used in the Least Cost Path calculation. See Huber and Church (1985) for methodological considerations when choosing number of neighbours. Expected numeric values are 4, 8, 16, 32, 48 or a matrix object. Default is numeric value 16

field

numeric value or character 'mask'. Value assigned to cells that coincide with the barrier Spatial* or RasterLayer object. Default is numeric value 0. If RasterLayer object supplied in barrier and field is 'mask' then RasterLayer values are assigned to the barrier

background

numeric value. Value assigned to cells that do not coincide with the Spatial* or RasterLayer object. Default is numeric value 1

Author

Joseph Lewis

Details

The resultant Barrier Cost Surface is produced by assessing which areas of the raster coincide with the Spatial* or RasterLayer object as specified in the barrier argument. The areas of the raster that coincide with the barrier are given a conductance value of 0 (default value, with all other areas given a Conductance value of 1 (default value). The conductance value of 0 ensures that movement is inhibited within these areas. Examples of use include rivers, altitudes, and taboo areas. If a RasterLayer object is supplied in the barrier argument then all cells with a value NOT NA will be used as the barrier.

Examples

r <- raster::raster(system.file('external/maungawhau.grd', package = 'gdistance'))

pt = cbind(2667670, 6479000)
pt = sp::SpatialPoints(pt)
polygon <- rgeos::gBuffer(spgeom = pt, width = 200)
raster::crs(pt) <- raster::crs(r)
raster::crs(polygon) <- raster::crs(r)

barrier_pt <- create_barrier_cs(raster = r, barrier = pt)
barrier_polygon <- create_barrier_cs(raster = r, barrier = polygon)

r2 <- r
ext <- raster::extent(2667500, 2667900, 6478800, 6479500)
cells <- unlist(raster::cellFromPolygon(object = r, p = as(ext, 'SpatialPolygons')))
r2[-cells] <- NA

barrier_ras <- create_barrier_cs(raster = r, barrier = r2)