Skip to contents

Add projected coordinates

Source: R/utility.R
add_xy.Rd

Adds projected coordinates X and Y to a data frame with longitude and latitude, or the reverse: longitude and latitude to a data frame with projected X and Y, e.g. a prediction grid built in kilometres with make_survey_grid(). Spatial models and distance-based grid operations need projected coordinates, in which a distance is the same in all directions.

Usage

add_xy(
  d,
  crs = 3035,
  units = c("km", "m"),
  lon = "lon",
  lat = "lat",
  xy = c("X", "Y"),
  inverse = FALSE
)

Arguments

d

A data frame, or a datras_raw object, in which case the coordinates are added to HH.

crs

Coordinate reference system of X and Y, as accepted by sf::st_crs(). Default 3035, the ETRS89 Lambert azimuthal equal-area projection for Europe.

units

Units of X and Y: "km" (default) or "m".

lon, lat

Names of the longitude and latitude columns (decimal degrees, WGS84).

xy

Names of the projected coordinate columns. Default c("X", "Y"), as in the output of make_survey_grid().

inverse

Logical. If FALSE (default), X and Y are computed from longitude and latitude. If TRUE, longitude and latitude are computed from X and Y.

Value

d with the coordinate columns added.

Details

Rows with missing coordinates get NA. Existing columns of the same names are overwritten.

See also

make_survey_grid(), add_bathymetry()

Examples

if (requireNamespace("sf", quietly = TRUE)) {
  x <- add_xy(dab)
  head(x[["HH"]][, c("lon", "lat", "X", "Y")])

  ## A 10 km grid, with longitude and latitude for each node
  grid <- make_survey_grid(x[["HH"]]$X, x[["HH"]]$Y, resolution = 10)
  grid <- add_xy(grid, inverse = TRUE)
  head(grid)
}
#>      X    Y        lon      lat
#> 1 3510 2980 -1.2151146 49.37472
#> 2 3520 2980 -1.0787174 49.38832
#> 3 3530 2980 -0.9422514 49.40175
#> 4 3540 2980 -0.8057172 49.41501
#> 5 3550 2980 -0.6691157 49.42811
#> 6 3560 2980 -0.5324476 49.44104