himach (version 0.3.2)

st_window: Version of st_transform with view window to avoid dateline

Description

st_window does a st_transform but first cuts the data to an appropriate view window and so avoids problems with objects wrapping around the back of the globe

Usage

st_window(m, crs = himach::crs_Atlantic, longit_margin = 0.1)

Value

sf dataframe, same as the parameter m

Arguments

m

A map dataframe, ie of class sf and data.frame, or an sfc_MULTIPOLYGON

crs

Destination coordinate reference system, as in st_tranform

longit_margin

Amount trimmed off the 'far side' of the projection in degrees.

Details

st_wrap_dateline _should_ handle the break in a map projections but uses `GDAL` for this. Given persistent issues in installing GDAL, st_window achieves the same using s2 instead.

It works for any 'simple' projection, in the sense of one that has a dateline that is a single line of longitude: ie the proj4string contains either "longitude_of_center", so the dateline is that +180; or not, in which case it assumes the "longitude_of_center" is 0.

Examples

world <- sf::st_as_sf(rnaturalearthdata::coastline110)
w_pacific <- st_window(world, crs_Pacific)
ggplot2::ggplot(w_pacific) + ggplot2::geom_sf()

# bad - not run - dateline problem example
# ggplot2::ggplot(st_transform(world, crs_Pacific)) +
#   ggplot2::geom_sf()