Map projections

Sets the coordinate system to a geographic projection. Longitude and latitude are projected before being mapped to the panel, so map layers and point layers stay aligned.

Usage

orb_coord_map(projection = "equirectangular", centre = c(0, 0), max_lat = 84)

Arguments

projection

Projection name (see Details).

centre

Length-2 numeric vector, c(longitude, latitude), giving the centre of an orthographic view.

max_lat

Latitude at which the Mercator projection is clipped.

Value

An object of class orb_coord, to be added to a plot.

Details

Available projections:

equirectangular

Longitude and latitude used directly; simple and fast, but distorts area away from the equator.

mercator

Conformal cylindrical projection; preserves angles, greatly exaggerates high latitudes. Latitudes are clipped at \(\pm\)max_lat.

robinson

A compromise projection widely used for world maps.

mollweide

Equal-area pseudo-cylindrical projection.

equalearth

The Equal Earth projection of Savric, Patterson and Jenny (2019): equal-area, like Mollweide, but with continents shaped much closer to the familiar Robinson outline. A good modern default for thematic world maps, because areas are not distorted.

orthographic

A view of the globe from infinite distance, centred on centre; the hemisphere facing away from the viewer is hidden.

References

Snyder, J. P. (1987) "Map Projections: A Working Manual." US Geological Survey Professional Paper 1395. doi:10.3133/pp1395

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

Examples

orb_worldmap() + orb_coord_map("robinson")
#> <orb_spec>
#>   data:   26953 rows x 4 columns
#>   mapping:  
#>   layers:  map 

orb_worldmap() + orb_coord_map("equalearth")
#> <orb_spec>
#>   data:   26953 rows x 4 columns
#>   mapping:  
#>   layers:  map 

orb_worldmap() + orb_coord_map("orthographic", centre = c(20, 15))
#> <orb_spec>
#>   data:   26953 rows x 4 columns
#>   mapping:  
#>   layers:  map