On Sun, Dec 20, 2009 at 12:53 PM, Anthony <o...@inbox.org> wrote: > > 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?). > > Also, some zip codes not only overlap, but overlap on only one side of a street inside an area kind of like two interlocking combs.
<gory example> In another example, when Collegedale, TN (http://osm.org/go/ZQvRbHZs-) incorporated as a city, the USPS assigned ZIP 37315 to all PO Boxes, but left all home mailboxes in ZIP 37363 (unincorporated Ooltewah, TN). To add to the fun, all home mailboxes inside Collegedale city limits must be physically located on the odd numbered side of the street. Incorporated Collegedale, TN (ZIP 37363) and incorporated Chattanooga, TN (ZIP 374xx) have annexed most if not all of unincorporated Ooltewah, TN but the 37363 ZIP code remains. Every time a house is purchased inside Collegedale city limits the new owner has to choose to either register the address as a delivery point with the 37363 post office, or lease a PO box in the 37315 post office. </gory example> To summarize, the USPS ZIP data is constantly in flux and does not necessarily map to any particular geographic or political boundaries. Yes, we could theoretically import ZIP data as polygons, but then someone would have to automate and QC weekly/monthly/annual diffs as the USPS data changed. Chris
_______________________________________________ Talk-us mailing list Talk-us@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-us
