On Sun, Dec 20, 2009 at 12:45 PM, Jeremy Adams <mile...@king-nerd.com>wrote:
> On Sun, Dec 20, 2009 at 12:41 PM, Anthony <o...@inbox.org> wrote: > >> On Sun, Dec 20, 2009 at 12:29 PM, Jeremy Adams <mile...@king-nerd.com>wrote: >> >>> One can easily figure out what town someone is from based on their ZIP >>> Code. Is this not the case everywhere? >>> >> >> Certainly not. There are lots of zip codes which represent multiple >> towns, and lots of towns which represent multiple zip codes. >> >> You can usually find out an approximate geographical location from a zip >> code (at least if it isn't an APO/FPO zip code). But if that's all you >> want, you're best off just representing zip codes as single points in the >> approximate geographical center of all post boxes which receive mail to that >> zip code. Going in the other direction, from lat/lon to zip code (assuming >> your lat/lon is the location of a building and/or post box), requires a much >> more specialized database which isn't currently available as public domain. >> > > But the code still represents a geographic area? > No, the code doesn't represent a geographic area. You can force it into a geographic area, by defining the area in some particular way (e.g. a multipolygon of all buildings which receive mail addressed to that zip code). Of course, given that definition, some zip codes will overlap (probably not much area-wise if you use only 5 digit zip codes), and lots of areas will have no zip code (what's the zip code for a particular point on the highway of I-95?).
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