Project longitude and latitude onto a countryatlas map

The transform the polygon backend uses when sf cannot be loaded: a spherical Equal Earth (Savric, Patterson & Jenny 2019) on the authalic sphere, written out in base R so the default map is equal-area on any installation. Use it to place your own points, labels or paths on such a map, which is drawn in metres rather than degrees. Where sf loads, maps are drawn with ggplot2::coord_sf() instead and take layers in longitude and latitude directly, so there is nothing to convert.

Usage

project_lonlat(lon, lat, projection = "equal_earth", recenter = NULL)

Arguments

lon, lat: Numeric vectors of longitude and latitude, in degrees.
projection: "equal_earth" (default), computed here. Any other projection the package knows (see projection_info()) is computed by PROJ through sf, which must then be loadable.
recenter: Optional central meridian, as in world_map().

Value

A tibble of x and y, in metres, one row per point; NA where a coordinate is missing.

References

Savric, B., Patterson, T. & Jenny, B. (2019). The Equal Earth map projection. International Journal of Geographical Information Science 33(3), 454-465. doi:10.1080/13658816.2018.1504949

Examples

project_lonlat(c(2.35, -74.0), c(48.85, 40.7))   # Paris, New York
#> # A tibble: 2 × 2
#>           x        y
#>       <dbl>    <dbl>
#> 1   187424. 5882067.
#> 2 -6255450. 5012972.