14 posts tagged with "Geocoding"

Here are two addresses. Tell me if they're the same place.

123 Main Street, Suite 400, Springfield IL 62704
123 Main St #400, Springfield, Illinois

Easy — yes. Now these two:

Jyllandsgade 15, 9000 Aalborg
Jyllandsgade 75, 9000 Aalborg

Also easy — no. They're 650 metres apart.

Now imagine a string-similarity matcher looking at those same four lines. The first pair, the same place, scores low: different punctuation, "Street" vs "St", a reordered unit. The second pair, different places, scores 0.96 — one character apart. The tool you'd reach for gets both backwards. This isn't a tuning problem you can threshold your way out of. It's the wrong coordinate system.

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 neural address parser passes 20.7% of our test suite. The rule-based parser it's meant to replace passes 93.7%. By that scoreboard, we should delete the neural model and go home.

We shipped the neural model instead. Here's why both numbers are true — and why the one that matters says the opposite.

Who's On First is the best open gazetteer we have. It's also one of the strangest datasets you'll encounter as a developer. This post is about what makes it hard to use, what makes it worth the effort, and the tooling we built inside Mailwoman to tame it.

If you've ever tried to answer "what city is this address in?" programmatically, using open data without paying a geocoding API, you've probably already run into WOF. And you probably had some questions.