tmaptools (version 1.0)

projection_units: Get or translate units of a projection

Description

Get the units from a projection (CRS) or a shape and determine the multiplier to transpose it in other units.

Usage

projection_units(x = NA, target = "m", orig = NA, to = NA, latitude = 0, show.warnings = TRUE)

Arguments

x

A projection (see get_proj4) or a shape (from class Spatial, Raster), or sf.

target

target unit, one of: "m", "km", "mi", and "ft".

orig

units by the x is defined. Only needed if this information is missing from x and x is projected. Options: "m", "km", "mi", and "ft".

to

multiplier used as follows: orig * to = target. Only needed when orig or target is unknown. For instance, if target is set to "hm" (hectameter), and orig is "m", then to should be 100, meaning 1 hectameter equals 100 meters.

latitude

latitude. Needed if the projection coordinates are in latitude longitude units. In that case the orig will be defined as longitude coordinates at latitude latitude.

show.warnings

should warnings be shown?

Value

list with the following items, orig, target, and to either according the specified argument, or determined determined. The value is NA for items that cannot be determined. The final item is projected, which is determined using is_projected

See Also

approx_distances for distances between two points and approx_areas for areas.

Examples

## Not run: 
# if (require(tmap)) {
#     data(World, land)
#     projection_units(World, target = "miles")
# 
#     projection_units(land)
#     projection_units(land, latitude = 45)
#     projection_units(land, latitude = 89)
# }
# ## End(Not run)