Plot world coastline on a projected map

tissot_map() draws the bundled world coastline, projected if a projection is current. The projection is determined in this order:

An explicit target argument
The projection recorded by the most recent call to plot.indicatrix_list(), image.tissot_raster(), or tissot_raster()

Usage

tissot_map(..., target = NULL, add = TRUE)

tissot_abline(x, y = NULL, ..., source = "EPSG:4326", target = NULL)

...: graphical parameters passed to graphics::lines() (if adding) or graphics::plot() (if creating new)
target: target CRS. If NULL, uses the last plot projection (from plot.indicatrix_list()) or draws in lon/lat.
add: logical; add to existing plot (default TRUE) or create new
x: longitude values (or any xy-ish input; see tissot())
y: latitude values (ignored if x is a matrix)
source: source CRS for the coordinates (default "EPSG:4326")

tissot_map() invisibly returns the (projected) world coastline matrix

tissot_abline() is called for its side effect

tissot_abline() draws vertical and horizontal reference lines at a given longitude/latitude in projected coordinates.

r <- tissot(cbind(seq(-150, 150, by = 30), 0), "+proj=robin")
ii <- indicatrix(r)
plot(ii, scale = 6e5, add = FALSE)
tissot_map()