Check for longitude/latitude crs — is.lonlat • terra

Test whether a SpatRaster or SpatVector has a longitude/latitude coordinate reference system (CRS), or perhaps has one. That is, when the CRS is unknown ("") but the x coordinates are within -181 and 181 and the y coordinates are within -90.1 and 90.1. For a SpatRaster you can also test if it has a longitude/latitude CRS and it is "global" (covers all longitudes).

A warning is given if the CRS is missing or if it is specified as longitude/latitude but the coordinates do not match that.

Usage

# S4 method for class 'SpatRaster'
is.lonlat(x, perhaps=FALSE, warn=TRUE, global=FALSE)

# S4 method for class 'SpatVector'
is.lonlat(x, perhaps=FALSE, warn=TRUE)

# S4 method for class 'character'
is.lonlat(x, perhaps=FALSE, warn=TRUE)

Arguments

x: SpatRaster or SpatVector
perhaps: logical. If TRUE and the CRS is unknown, the method returns TRUE if the coordinates are plausible for longitude/latitude
warn: logical. If TRUE, a warning is given if the CRS is unknown but assumed to be lon/lat and perhaps=TRUE
global: logical. If TRUE, the method tests if the raster covers all longitudes (from -180 to 180 degrees) such that the extreme columns are in fact adjacent

Value

logical or NA

Examples

r <- rast()
is.lonlat(r)
#> [1] TRUE
is.lonlat(r, global=TRUE)
#> [1] TRUE

crs(r) <- ""
is.lonlat(r)
#> Warning: [is.lonlat] unknown crs
#> [1] NA
is.lonlat(r, perhaps=TRUE, warn=FALSE)
#> [1] TRUE

crs(r) <- "+proj=lcc +lat_1=48 +lat_2=33 +lon_0=-100 +ellps=WGS84"
is.lonlat(r)
#> [1] FALSE