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Check whether points are located on land

Source: R/check_onland.R
check_onland.Rd

Identifies records whose coordinates fall on land, optionally applying a buffer to allow points near the coast.

Usage

check_onland(
  data,
  land = NULL,
  report = FALSE,
  buffer = 0,
  offline = FALSE,
  plot_leaflet = FALSE,
  only_bad = FALSE
)

Arguments

data

A data frame containing at least sample_longitude_dd and sample_latitude_dd. Both columns must be numeric, within valid ranges (longitude: -180 to 180, latitude: -90 to 90), and use WGS84 coordinates (EPSG:4326).

land

Optional sf object containing land polygons. Used only in offline mode.

report

Logical; if TRUE, returns a tibble listing rows on land and warnings. If FALSE (default), returns a subset of data containing only records on land.

buffer

Numeric; distance in meters inland for which points are still considered valid. Only used in online mode. Default is 0.

offline

Logical; if TRUE, the function uses the local cached shoreline (if available). If FALSE (default), the OBIS web service is queried.

plot_leaflet

Logical; if TRUE, returns a leaflet map showing points colored by whether they are on land (red) or in water (green). Default is FALSE.

only_bad

Logical; if TRUE and plot_leaflet = TRUE, only points on land (red) are plotted. Default is FALSE, meaning all points are plotted.

Value

If report = TRUE, a tibble with columns:

  • field: always NA (placeholder for future extension)

  • level: "warning" for all flagged rows

  • row: row numbers in data flagged as located on land

  • message: description of the issue

If report = FALSE and plot_leaflet = FALSE, returns a subset of data with only the flagged rows. If plot_leaflet = TRUE, returns a leaflet map showing points on land (red) and in water (green), unless only_bad = TRUE, in which case only red points are plotted.

Details

The function supports both offline and online modes:

  • Offline mode (offline = TRUE): uses a local simplified shoreline from a cached geopackage (land.gpkg). If the file does not exist, it is downloaded automatically and cached across R sessions.

  • Online mode (offline = FALSE): uses the OBIS web service to determine distance to the shore.

The function assumes all coordinates are in WGS84 (EPSG:4326). Supplying coordinates in a different CRS will result in incorrect intersection tests.

Optionally, a leaflet map can be plotted. Points on land are displayed as red markers, while points in water are green. If only_bad = TRUE, only the red points (on land) are plotted.

Examples

# \donttest{
# Example data frame with coordinates
example_data <- data.frame(
  sample_latitude_dd = c(59.3, 58.1, 57.5),
  sample_longitude_dd = c(18.6, 17.5, 16.7)
)

# Report points on land with a 100 m buffer
report <- check_onland(example_data, report = TRUE, buffer = 100)
print(report)
#> # A tibble: 1 × 4
#>   field level     row message                        
#>   <lgl> <chr>   <int> <chr>                          
#> 1 NA    warning     1 Coordinates are located on land

# Plot all points colored by land/water
map <- check_onland(example_data, plot_leaflet = TRUE)

# Plot only bad points on land
map_bad <- check_onland(example_data, plot_leaflet = TRUE, only_bad = TRUE)

# Remove points on land by adding a buffer of 2000 m
ok <- check_onland(example_data, report = FALSE, buffer = 2000)
print(nrow(ok))
#> [1] 0
# }