viewshed: Compute a viewshed

In terra: Spatial Data Analysis

Compute a viewshed

Description

Use elevation data to compute the locations that can be seen, or how much higher they would have to be to be seen, from a certain position. The raster data coordinate reference system must planar (not lon/lat), with the elevation values in the same unit as the distance unit of the coordinate reference system.

Usage

## S4 method for signature 'SpatRaster'
viewshed(x, loc, observer=1.80, target=0, curvcoef=6/7, output="yes/no", filename="", ...) 

Arguments

x	SpatRaster, single layer with elevation values. Values should have the same unit as the map units
loc	location (x and y coordinates) or a cell number
observer	numeric. The height above the elevation data of the observer
target	numeric. The height above the elevation data of the targets
curvcoef	numeric. Coefficient to consider the effect of the curvature of the earth and refraction of the atmosphere. The elevation values are corrected with: elevation = elevation - curvcoeff * (distance)^2 / (earth_diameter). This means that with the default value of 0.85714, you lose sight of about 1 meter of elevation for each 385 m of planar distance
output	character. Can be "yes/no" to get a binary (logical) output showing what areas are visible; "land" to get the height above the current elevation that would be visible; or "sea" the elevation above sea level that would be visible
filename	character. Output filename
...	Options for writing files as in writeRaster

References

The algorithm used is by Wang et al.: https://www.asprs.org/wp-content/uploads/pers/2000journal/january/2000_jan_87-90.pdf.

See Also

terrain

Examples

if (gdal() >= 3.1) {
	f <- system.file("ex/elev.tif", package="terra")
	r <- rast(f)
	x <- project(r, "EPSG:2169")
	p <- cbind(70300, 96982)
	v <- viewshed(x, p, 0, 0, 0.85714)
}

terra documentation built on Oct. 14, 2024, 5:07 p.m.