14 posts tagged with "Resolver / WOF"

Type Vienna, Austria into our geocoder and, until this week, it answered with a confident set of coordinates: 39.32, −81.54. That's Vienna, West Virginia — population about ten thousand, a few miles up the Ohio River from Parkersburg. The capital of Austria is 7,500 kilometers and one ocean away, and the geocoder had no doubt whatsoever.

You can point a Nominatim client at Mailwoman now. Same endpoints — /search, /reverse, /status — same JSON shape, so your existing code doesn't change. The difference is what's behind it: no PostgreSQL, no osm2pgsql import that takes hours and tens of gigabytes, no server you can't ship inside an app. A geocoder that answers Nominatim's questions from a SQLite file.

We had just watched our geocoder beat Nominatim across the United States by fifteen points, and we were feeling good about ourselves. So we pointed the same benchmark at Europe expecting a victory lap. Europe handed us a double-digit loss instead.

That sat badly. Not because losing is shameful — Nominatim is the bar, it carries the whole planet on community-contributed data, and clearing it anywhere is the goal. It sat badly because we didn't understand it. We knew our parser wasn't ten points worse in Europe than in America. So what was the gap actually made of?

This is the answer, the two fixes, and — because we'd be kidding you otherwise — the parts the fixes didn't reach. For the European leg we added a third system to grade against: Pelias, by way of geocode.earth, the hosted Elasticsearch stack a lot of people reach for. It turns out to be the real bar, and we'll be honest about where it still beats us.

Open the demo, type an address in Kabul, and watch nothing happen. Not a wrong pin a few streets off. Not a city-center fallback. Nothing — the gazetteer has never heard of the place. Try Hong Kong. Try Tirana, or Chişinău, or anywhere in the Democratic Republic of the Congo. Same silence. We had been calling this gazetteer "world coverage" for weeks, and it covered 97 of the world's ~195 countries. The other ninety-odd were simply not in the file.

The whole geocoder runs in your browser. You type an address, you get a rooftop coordinate, and no server ever sees your query — the gazetteer it resolves against is a SQLite database sitting on a CDN, and the page reads it with HTTP range requests, a few kilobytes at a time. It's a lovely trick. We were proud of it. Then we counted the requests it took to find a single city, and the number was 243.

So the questions for the day: why does looking up one name cost 243 round trips? What goes wrong when you search a database you can only read a slice at a time? And how do you get a global gazetteer — every country, region, county, and city we resolve against — down to about a dozen reads without putting a server back in the loop?

Overnight I taught the geocoder Canada. Or I thought I did. I pulled 843,000 Canadian postcodes, computed a centroid for every one, spot-checked the result — M5H 2N2, downtown Toronto, 43.652, −79.382, dead on — and validated the database every way I could read it: every postcode present, every coordinate right, nothing else disturbed. Green, top to bottom. This morning, before flipping it live, I asked the demo to find a Toronto address. It dropped the pin in Ohio.

So, the questions for the morning. How does a database that passes every check still land the answer 600 kilometres wrong? What does it actually mean to "validate" a thing? And why is Toronto in Ohio?

We turned the demo into a real geocoder — type an address, get a rooftop coordinate, all in your browser, no server. The last touch was the one that makes a search box feel alive: autocomplete, so the city finishes itself while you type. We already had the autocomplete. We'd shipped it as a command-line tool days earlier, watched it rank San Francisco above San Diego, and called it done. So we dropped the same function into the box, typed New Yor, and it suggested Denver.

The questions that opened up: why does a function that nails San choke on New Yor? What's the difference between completing a word and completing the word a person is in the middle of typing? And how does an autocomplete that knows ten thousand cities fail to finish one of them?

Our resolver scored 93.7% on the metric we'd been quoting for months. On the same addresses, its median answer was 326 kilometers from the truth.

Both numbers are correct. That's the awkward part.

There is a particular kind of engineering misery where you fix a bug three times and it never gets better, because the bug is in your ruler. This is that story.

Our neural parser handles German two ways. Native order — Hauptstraße 5, 10115 Berlin — is the layout real German feeds and real German people use. International order — 5 Hauptstraße, Berlin, 10115 — is the Americanized layout our evaluation set happens to ship. For months, international-order German "collapsed": locality accuracy sat around 44% while native cleared 80%. We had a story for it. The postcode anchor — a side-channel that feeds the model a country hint derived from the postcode — sits at the trailing postcode, which in international order lands on the far side of the locality from where it's needed. Plausible. So we retrained.

Ask a geocoder for "Berlin" and it has to make a choice. There's the one in Germany, obviously. There's also Berlin, New Hampshire (population nine thousand and change), Berlin, Wisconsin, Berlin, Connecticut, and a dozen more scattered across the United States like the name was on sale. The parser hands you the word Berlin tagged as a locality; something downstream has to decide which dot on the map that is. How would you even know if it picked right?

For a long time our answer was a scorecard that checked the name. Did the resolved place's name equal the expected name? Tick. Move on. It is a completely reasonable thing to measure, and it was lying to us for months.