Inspired by the police.uk crime maps, where they cleverly cluster data together depending on how far zoomed in you are, this MySQL snippet goes a long way to explaining the logic behind such an operation.
This snippet groups sites to a perfect grid while the police.uk algorithm has some sort of trickery that moves their points about somewhat, looking at their blogs and documentation I would conclude that they have a predefined set of points, each with a catchment area of postcodes. It looks like a whole lot of scraping and manual labour went into their database and quite frankly I don't have the time nor inclination do attempt such a task.
