Always equal-area, and always centred on the data rather than on a continent.
Arguments
- x
As for
display_crs().
Value
An sf::crs object.
Details
A Lambert azimuthal equal-area projection centred on the middle of the data. Distortion in an azimuthal projection grows with distance from its centre, so centring it on the thing being measured is what keeps the error small, and it is why this is computed per dataset rather than fixed to a national projection such as Albers North America (EPSG:5070). That one is equal-area too, but its standard parallels are placed for the conterminous United States; the Bay of Fundy is not in the conterminous United States.
This is not necessarily the CRS the map is drawn in – see display_crs()
for why those are separate questions.
Examples
pts <- sf::st_as_sf(data.frame(lon = c(-70, -68), lat = c(42, 44)),
coords = c("lon", "lat"), crs = 4326)
equal_area_crs(pts)
#> Coordinate Reference System:
#> User input: +proj=laea +lat_0=43.0 +lon_0=-69.0 +x_0=0 +y_0=0 +datum=WGS84 +units=m +no_defs
#> wkt:
#> PROJCRS["unknown",
#> BASEGEOGCRS["unknown",
#> DATUM["World Geodetic System 1984",
#> ELLIPSOID["WGS 84",6378137,298.257223563,
#> LENGTHUNIT["metre",1]],
#> ID["EPSG",6326]],
#> PRIMEM["Greenwich",0,
#> ANGLEUNIT["degree",0.0174532925199433],
#> ID["EPSG",8901]]],
#> CONVERSION["unknown",
#> METHOD["Lambert Azimuthal Equal Area",
#> ID["EPSG",9820]],
#> PARAMETER["Latitude of natural origin",43,
#> ANGLEUNIT["degree",0.0174532925199433],
#> ID["EPSG",8801]],
#> PARAMETER["Longitude of natural origin",-69,
#> ANGLEUNIT["degree",0.0174532925199433],
#> ID["EPSG",8802]],
#> PARAMETER["False easting",0,
#> LENGTHUNIT["metre",1],
#> ID["EPSG",8806]],
#> PARAMETER["False northing",0,
#> LENGTHUNIT["metre",1],
#> ID["EPSG",8807]]],
#> CS[Cartesian,2],
#> AXIS["(E)",east,
#> ORDER[1],
#> LENGTHUNIT["metre",1,
#> ID["EPSG",9001]]],
#> AXIS["(N)",north,
#> ORDER[2],
#> LENGTHUNIT["metre",1,
#> ID["EPSG",9001]]]]