Simplified COG Admin Express (metropole + DROM + Saint-Martin/Saint-Barthelémy)

The [IGN Admin Express COG] database (https://geoservices.ign.fr/adminexpress) of administrative limits is compatible with the [COG] (https://www.insee.fr/en/information/8377162), but since 2021 its finer resolution and therefore its size (300 MB for the single common layer) makes its handling sometimes cumbersome and can be irrelevant when you want to do small-scale mapping throughout France. *adminexpress\_cog\_simpl\_000\_20xx.gpkg* therefore has the following properties: * geopackage format * COG 2024 or 2025 compatible; * WGS84 coordinate system (EPSG:4326); * only the common layers, departments, regions, capitals, EPCI; * Simplification of geometry (slightly more detailed than the old IGN GeoFLA base) while retaining topology. Pass of 606 MB (shp) -> 57 MB (gpkg). Simplification Visvalingam (preserved 2% / weight 0.7); * is based on the scope of the agricultural census (metropolis + DROM and addition of Saint-Barthélemy and Saint-Martin from the BDTOPO; they have the codes "977" and "978" and the virtual region code "01\_SBSM"). However, the region layer is not amended with the geometry of these two communities; * creation of layers derived from the "internal limits" (suffixed "\_int", without the coasts or borders) for more aesthetic cartographic work in certain cases (e.g. with raster funds); * addition of Cartesian (in the local projection) and geodetic surfaces of the original data; it is not advisable to use area calculations on simplified entities; * corrected capitals: completed (+6 "[dead communes](https://en.wikipedia.org/wiki/Villages_fran%C3%A7ais_d%C3%A9truits_durant_la_Premi%C3%A8re_Guerre_mondiale)" without inhabitants but with agriculture) and relocated to their commune (there are outsourced capitals) to have a point location more precise than a centroid when possible; simplification can lead a capital to be outside its municipality, it is then replaced by the centroid; in all these cases the name _chl is not prefixed by "Mairie"; * debunking of the Gironde estuary (comparable to the CARTO version) for a more usual cartographic rendering. Why not use directly "ADMIN-EXPRESS-COG-**CARTO** edition 20xx whole France"? * The old CARTO versions (before 2022) made some islands disappear: in Brittany and the Golden Islands, including entire municipalities (e.g. Brehat; However, this no longer seems to be the case). * Low level of simplification does not really reduce file size. * It lacks the chiefs-places and Saint-Barthélemy + Saint-Martin. NB: there is now also a [small-scale version](https://geoservices.ign.fr/adminexpress#telechargementCogCartoPE) of Admin Express but it is not directly whole France, removes notable islands and is not in WGS84. The file can be read directly with the GDAL drivers; *e.g.* in R: ''R'' library(sf) # version 2025: st_layers("/vsicurl/https://static.data.gouv.fr/resources/admin-express-cog-simplifiee-metropole-drom-saint-martin-saint-barthelemy/20250422-065405/adminexpress-cog-simplify-000-2025.gpkg") # Driver: GPKG # Available layers: # layer_name geometry _type features fields crs_name # 1 commune Multi Polygon 34877 12 WGS 84 # 2 Department 103 4 WGS 84 # 3 region 19 3 WGS 84 # 4 capital Point 34877 7 WGS 84 # 5 epci Multi Polygon 1266 4 WGS 84 # 6 commune_int 102173 0 WGS 84 # 7 Department _int 238 0 WGS 84 # 8 region _int 23 0 WGS 84 # 9 epci_int 3526 0 WGS 84 regions <- read_sf("/vsicurl/https://static.data.gouv.fr/resources/admin-express-cog-simplifiee-metropole-drom-saint-martin-saint-barthelemy/20250422-065405/adminexpress-cog-simplify-000-2025.gpkg", layer = "region", options = "IMMUTABLE=YES") “““”