svf: Sky view factor from DEM RasterLayer

In horizon: Horizon Search Algorithm

Description

Computes the sky view factor (fraction of sky not obstructed by terrain within a hemisphere), within a maximum search distance, for each pixel in a digital elevation model raster object.

Usage

svf(x, nAngles = 16, maxDist = 1000, ll = TRUE,
    filename = "", blockSize = NULL, verbose = TRUE)

Arguments

x	RasterLayer object
nAngles	integer. Discrete number of angles used to calculate sky view factor.
maxDist	integer. Maximum search distance in meters.
ll	logical. If TRUE, coordinates should be in degrees; else planar.
filename	character. Output raster filename. Optional.
blockSize	integer>0. Number of raster rows processed simultaneously. Default is the number of rows in the input raster divided by 10.
verbose	logical. If TRUE, progress messages are displayed.

Details

The sky view factor is estimated by calculating and averaging the horizon elevation angle and sky view factor for a discrete number of azimuth angles. Increasing this discreet number of angles 'nAngles' will provide a better estimate of the actual sky view factor, at the expense of longer processing time.

The 'maxDist' parameter determines the maximum search radius for determining the horizon angle. Increasing the value of 'maxDist' will provide a better estimate of the actual sky view factor, at the expense of longer processing time.

The 'blockSize' parameter may be reduced to avoid memory errors when processing large input RasterLayer objects.

Value

RasterLayer object. Values between 0 and 1.

See Also

horizonSearch

Examples

r <- getData('alt', country='ALB')

s <- svf(r, nAngles=8, maxDist=500, ll=TRUE)

horizon documentation built on May 2, 2019, 11:37 a.m.