cellSize | R Documentation |
Compute the area covered by individual raster cells.
Computing the surface area of raster cells is especially relevant for longitude/latitude rasters.
But 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 coordinate reference system.
For planar CRSs, the area is therefore not computed based on the linear units of the coordinate reference system, but on the *actual* area by transforming cells to longitude/latitude. If you do not want that correction, you can use transform=FALSE
or init(x, prod(res(x)))
## S4 method for signature 'SpatRaster'
cellSize(x, mask=FALSE, lyrs=FALSE, unit="m", transform=TRUE, rcx=100, filename="", ...)
x |
SpatRaster |
mask |
logical. If |
lyrs |
logical. If |
unit |
character. One of "m", "km", or "ha" |
transform |
logical. If |
rcx |
positive integer. The maximum number of rows and columns to be used to compute area of planar data if |
filename |
character. Output filename |
... |
additional arguments for writing files as in |
SpatRaster
expanse
# SpatRaster
r <- rast(nrows=18, ncols=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(ncols=90, nrows=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))
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