Beginning Google Maps Applications

This is just a quick post to warn everyone that Google’s geocoder has a strict rate-limiting “feature”. You can do up to 50,000 lookups per day as we reported earlier, but that number can only be achieved if you request one geocode every 1.75 seconds consistently throughout the day. Exceeding this threshold for more than a few points in a row causes the geocoder to start throwing 403 forbidden errors which take up to 48 hours to clear (and may never depending on how badly you abuse the system).

Therefore when batch geocoding you need to account for this and build scripts that throttle themselves.

If the number of points you’re geocoding per day is less than 5,000 you might be better to use Yahoo’s service and consult Google’s geocoder for a second opinion when you get an ambiguous (or multiple) answer. I’m sure that will be against Yahoo’s terms of service soon, but for now it might work.