Annotation_map does not work with coord_sf

[markpayneatwork]

When usingcoord_sf() to change the projection of a map, the background layer produced by annotation_map() is not getting reprojected.

First, a plot without changing projection, using the annotation_map layer to give more context to North Carolina

library(ggplot2)
library(sf)
nc <- sf::st_read(system.file("shape/nc.shp", package = "sf"), quiet = TRUE)

ggplot() +
  annotation_map(map_data("state"),fill="antiquewhite",colour="darkgrey")+
  geom_sf(data = nc)

However, changing the projection looses the annotation layer, but reprojects the geometry layer

ggplot() +
  annotation_map(map_data("state"),fill="antiquewhite",colour="darkgrey")+
  geom_sf(data = nc)+
  coord_sf(crs = st_crs(3347))

It looks to me like the annotation_layer is not being reprojected.

[clauswilke]

This happens because annotation_map() is old code that predates geom_sf(). Only sf layers are reprojected. While it would be nice to reproject other layers, there are numerous technical hurdles that make me think it's not going to happen anytime soon.

At this point, the best way forward is probably to amend the documentation accordingly.

[thomasp85]

@clauswilke has this been fixed by #3659?

[clauswilke]

Yes, correct, just need to set the appropriate default crs. This particular case is actually included in the examples, so I think we're good as is.

library(ggplot2)
library(sf)
#> Linking to GEOS 3.8.1, GDAL 3.2.1, PROJ 7.2.1
nc <- sf::st_read(system.file("shape/nc.shp", package = "sf"), quiet = TRUE)

ggplot() +
  annotation_map(map_data("state"),fill="antiquewhite",colour="darkgrey")+
  geom_sf(data = nc) +
  coord_sf(crs = st_crs(3347), default_crs = st_crs(4326))

^{Created on 2022-05-18 by the reprex package (v2.0.0)}