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Determine if Positions are Near Land

Source: R/ifcb_is_near_land.R
ifcb_is_near_land.Rd

Determines whether given positions are near land based on a land polygon shape file. The Natural Earth 1:10m land vectors are included as a default shapefile in iRfcb.

Usage

ifcb_is_near_land(
  latitudes,
  longitudes,
  distance = 500,
  shape = NULL,
  source = "ne",
  crs = 4326,
  remove_small_islands = TRUE,
  small_island_threshold = 2e+06,
  plot = FALSE,
  utm_zone = deprecated()
)

Arguments

latitudes

Numeric vector of latitudes for positions.

longitudes

Numeric vector of longitudes for positions. Must be the same length as latitudes.

distance

Buffer distance (in meters) from the coastline to consider "near land." Default is 500 meters.

shape

Optional path to a shapefile (.shp) containing coastline data. If provided, this file will be used instead of the default Natural Earth 1:10m land vectors. A high-resolution shapefile can improve the accuracy of buffer distance calculations. Alternatively, you can retrieve a more detailed European coastline automatically by setting the source argument to "eea".

source

Character string indicating which default coastline source to use when shape = NULL. Options are "ne" (Natural Earth, default) and "eea" (European Environment Agency). Ignored if shape is provided.

crs

Coordinate reference system (CRS) to use for input and output. Default is EPSG code 4326 (WGS84).

remove_small_islands

Logical indicating whether to remove small islands from the coastline. Useful in archipelagos. Default is TRUE.

small_island_threshold

Area threshold in square meters below which islands will be considered small and removed, if remove_small_islands is set to TRUE. Default is 2 square km.

plot

A boolean indicating whether to plot the points, land polygon and buffer. Default is FALSE.

utm_zone

[Deprecated] This argument is deprecated. UTM zones are now determined automatically based on the longitude of the input positions.

Value

If plot = FALSE (default), a logical vector is returned indicating whether each position is near land or not, with NA for positions where coordinates are missing. If plot = TRUE, a ggplot object is returned showing the land polygon, buffer area, and position points colored by their proximity to land.

Details

This function calculates a buffered area around the coastline using a polygon shapefile and determines if each input position intersects with this buffer or the landmass itself. By default, it uses the Natural Earth 1:10m land vector dataset.

The EEA shapefile is downloaded from https://www.eea.europa.eu/data-and-maps/data/eea-coastline-for-analysis-2/gis-data/eea-coastline-polygon when source = "eea".

Examples

# Define coordinates
latitudes <- c(62.500353, 58.964498, 57.638725, 56.575338)
longitudes <- c(17.845993, 20.394418, 18.284523, 16.227174)

# Call the function
near_land <- ifcb_is_near_land(latitudes, longitudes, distance = 300, crs = 4326)

# Print the result
print(near_land)
#> [1]  TRUE FALSE  TRUE FALSE