terra: cellSize – R documentation

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cellSize

Area covered by each raster cell

Description

Compute the area covered by individual raster cells. Computing the surface area of raster cells is particularly relevant for longitude/latitude rasters.

Note that for both angular (longitude/latitude) and for planar (projected) coordinate reference systems raster cells sizes are generally not constant, unless you are using an equal-area crs.

For planar CRSs, the area is therefore not computed based on the linear units of the coordinate reference system, but on the *actual* area, correcting for distortion. If you do not want that, you can instead use init(x, prod(res(x)))

Usage

## S4 method for signature 'SpatRaster'
cellSize(x, mask=TRUE, unit="m", transform=TRUE, filename="", ...)

Arguments

`x`	SpatRaster
`mask`	logical. If `TRUE`, cells that are `NA` in `x` are also `NA` in the output
`unit`	character. One of "m", "km", or "ha"
`transform`	logical. If `TRUE`, planar CRS data are transformed to lon/lat for accuracy
`filename`	character. Output filename
`...`	additional arguments for writing files as in `writeRaster`

Value

numeric (area)

Examples

# SpatRaster 
r <- rast(nrow=18, ncol=36)
v <- 1:ncell(r)
v[200:400] <- NA
values(r) <- v

# size of each raster cell
a <- cellSize(r)

# illustration of distortion
r <- rast(ncol=90, nrow=45, ymin=-80, ymax=80)
m <- project(r, "+proj=merc")

bad <- init(m, prod(res(m)) / 1000000, names="naive")
good <- cellSize(m, unit="km", names="corrected")
plot(c(good, bad), nc=1, mar=c(2,2,1,6))

terra

Spatial Data Analysis

v1.2-10

GPL (>= 3)

Authors

Robert J. Hijmans [cre, aut] (<https://orcid.org/0000-0001-5872-2872>), Roger Bivand [ctb] (<https://orcid.org/0000-0003-2392-6140>), Karl Forner [ctb], Jeroen Ooms [ctb] (<https://orcid.org/0000-0002-4035-0289>), Edzer Pebesma [ctb] (<https://orcid.org/0000-0001-8049-7069>)

Initial release

2021-05-12