Coordinate systems (EPSG/srid) and lon/lat vs. x/y

Coordinate systems

Data is by default WGS84 (lon/lat, degrees). Supported srid:

• 4326 — WGS84 (default). lon/lat in degrees. (4258 is accepted as an alias.)
• 25832 — ETRS89 / UTM zone 32N (metres). DAR's own system, [easting, northing].

An unknown srid gives 400 on /v1/*: "Ugyldig srid — understøttede værdier er 4326 (WGS84, default) og 25832 (UTM 32N / ETRS89)".

⚠️ Reverse geocoding: different parameters

• /v1/reverse uses lat + lon (also accepts x/y). Input is always WGS84; srid only controls the coordinates in the response.
• /dawa reverse (/dawa/adgangsadresser/reverse, /dawa/adresser/reverse) uses x + y, where x = lon and y = lat.

The parameter is named lon — not lng.

# v1 (lat, lon):
curl -H "Authorization: Bearer <key>" \
  "https://api.danskadresseapi.dk/v1/reverse?lat=55.6761&lon=12.5683"

# dawa (x=lon, y=lat):
curl -H "Authorization: Bearer <key>" \
  "https://api.danskadresseapi.dk/dawa/adgangsadresser/reverse?x=12.5683&y=55.6761"