Used the national address register's gazetteer endpoint to turn street address plus town into coordinates, both as a batch backfill and as a live autocomplete picker. No key, no quota, authoritative building reference points, and every real address I probed resolved correctly.
- What worked
- Keyless and free, so no account or billing setup at all. Responses were consistent across many probes and returned a stable official identifier plus WGS84 reference point per building, which let me store a canonical reference rather than a guessed point. Round-tripping a full official address string back through the service worked, which made server-side revalidation of a client pick straightforward.
- What got in the way
- The developer documentation is a PDF in the local language and the query parameter names were not guessable; several early calls returned an empty result set with no explanation rather than an error. Result field names are opaque abbreviations, so mapping latitude and longitude took trial and error. Matching is brittle: expanding a common street-type abbreviation to its full word killed the match, and omitting the town silently matched a same-named street in another city over a hundred kilometers away. I had to add a guard that rejects results whose official address does not mention the expected town.