Skip to contents

Retrieve OCS GE data from the IGN Géoplateforme

Source: R/data_ocsge.R
get_ocsge_data_ign.Rd

This function retrieves OCS GE (Land Cover) data for a specific Region of Interest (ROI) from the download service of the IGN Géoplateforme (https://data.geopf.fr/telechargement/resource/OCSGE), which needs no API key.

IGN delivers the OCS GE as one compressed GeoPackage per department and vintage (15 to 270 MB each). The departments intersecting the ROI are downloaded in full, extracted and kept in cache_dir, so that later calls on the same departments read the local file only.

Usage

get_ocsge_data_ign(
  roi,
  year = NULL,
  cache_dir = tools::R_user_dir("spacemodR", "cache"),
  quiet = FALSE
)

Arguments

roi

An sf (or sfc) object defining the Region Of Interest. It can be in any projection.

year

Integer. Vintage (millésime) to retrieve. Default NULL takes the latest vintage of each department. Vintages differ between departments; the error raised for a missing one lists those available.

cache_dir

Character. Directory where the extracted GeoPackages are kept. Defaults to the user cache directory of the package. Each department takes several hundred MB once extracted; delete the files to free the space.

quiet

Logical. If FALSE (default), reports the datasets used and the download progress.

Value

An sf object containing the OCS GE polygons intersected by the ROI, with the columns of the IGN delivery (notably code_cs, code_us and millesime), in the projection of the delivery: Lambert-93 (EPSG:2154) in mainland France and Corsica, the local UTM projection in overseas departments.

Details

The function performs the following steps:

  1. Finds the departments intersecting the roi with get_departements_for_roi.

  2. Lists the OCS GE deliveries of these departments (version 2, GeoPackage) and selects the vintage.

  3. Downloads the archives missing from cache_dir, checks their MD5 sum and extracts the OCCUPATION_SOL layer.

  4. Reads the features in the bounding box of the roi and clips them to its exact shape.

Corrective patches published separately by IGN (PATCHCORRECTIF) and the layers of differences between two vintages are not used.

Note

This function requires a working internet connection and a way to extract 7z archives: either the archive package, or the 7z command line tool (7-Zip, p7zip).

See also

get_ocsge, get_ocsge_data_fgb

Examples

if (FALSE) { # \dontrun{
  data(roi_metaleurop)

  # latest vintage
  ocsge_data <- get_ocsge_data_ign(roi_metaleurop)

  # a given vintage
  ocsge_2021 <- get_ocsge_data_ign(roi_metaleurop, year = 2021)

  habitat_vole <- join_ocsge_species(ocsge_2021, "Microtus_arvalis")
} # }