Calculate Distance to Coastline — splnr_get

This function calculates the shortest distance from the centroid of each Planning Unit in an sf object to the nearest coastline. It can use either a default coastline from the rnaturalearth package or a custom-provided coastline sf object.

Usage

splnr_get_distCoast(dat_sf, custom_coast = NULL, res = "medium")

Arguments

dat_sf: [sf]
An sf object containing polygon or point features representing the Planning Units. Must have a valid CRS.
custom_coast: [sf]
An optional sf object representing a custom coastline. If NULL (the default), the coastline is downloaded from rnaturalearth.
res: [character(1)]
The resolution of the rnaturalearth coastline to use. Options are "small", "medium" (default), or "large". This parameter is ignored if custom_coast is provided.

Value

An sf object identical to dat_sf but with an added column coastDistance_km representing the distance to the nearest coastline in kilometers.

Details

The function adds a new column named coastDistance_km to the input sf object, containing the calculated distances in kilometers. The CRS of the input data is preserved. It is crucial to ensure the input sf object has a suitable projected CRS for accurate distance calculations.

Examples

if (FALSE) { # \dontrun{
# Example 1: Calculate distance to coast for a simple grid
bbox <- sf::st_bbox(c(xmin = 0, ymin = 0, xmax = 3, ymax = 3))
grid <- sf::st_as_sf(sf::st_make_grid(bbox, n = c(3, 3)))
grid_with_dist <- splnr_get_distCoast(grid)
plot(grid_with_dist["coastDistance_km"])

# Example 2: Using a specific resolution for the coastline
# Note: Requires the 'dat_sf' object to be created first, e.g., using
# splnr_get_planning_units()
if (exists("dat_sf")) {
  dat_sf_dist <- splnr_get_distCoast(dat_sf, res = "large")
  summary(dat_sf_dist$coastDistance_km)
}

# Example 3: Using a custom coastline
# First, create a custom coastline (e.g., from a country polygon)
landmass <- rnaturalearth::ne_countries(
  scale = "medium",
  returnclass = "sf"
)

if (exists("dat_sf") && exists("landmass")) {
   # Transform landmass to the same CRS as the planning units
  landmass_proj <- sf::st_transform(landmass, sf::st_crs(dat_sf))
  dat_sf_custom_coast <- splnr_get_distCoast(dat_sf, custom_coast = landmass_proj)
  summary(dat_sf_custom_coast$coastDistance_km)
}
} # }