Caching Google Maps Geocoder Results
After my post Geocoding UK Postcodes with Google Maps API I’ve had a few people contact me about caching geocoding results back to a server, for subsequent pages.
It’s a good question - Google’s geocoder permits you to make 50,000 queries a day, which sounds like a lot. However, that is only 35 a minute, which if you sustain for more than a few minutes, kicks in the limit (apparently…). So you might be interested in caching your results.
If you aren’t fussed about UK geocoding, you can access the regular Google geocoder using HTTP, as documented in the Google Maps Documentation.
However, if you want to temporarily cache results collected by the client (as per my UK geocoding example linked to above), you need to send them back over an AJAX connection, and that is what this article discusses. Although aimed at using the UK geocoding technique, a lot of this tutorial will be applicable to results via the normal Google Javascript geocoder.
So this short tutorial is going to do is show you how once a postcode has been translated into longitude and latitude, the result can be sent back to your server to be temporarily stored in a database. Then we are going to look at how we can query our own database before we query Google’s, for each result.
Note: I’m told it used to be in Google’s Terms that you couldn’t store geocoding results, but it doesn’t appear to be that way now. However, we are only going to store them temporarily, so we don’t have to hit Google’s server repeatedly for the same query.
If you are eager just to see how this all will work, you can go straight to the demo page.
So, lets get going…
