843,000 postcodes and no Canada
· 5 min read
Overnight I taught the geocoder Canada. Or I thought I did. I pulled 843,000 Canadian postal codes, 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?