The USPS treats ZIP codes as an extension of address data and as such, they should be treated as point data, since they are an attribute of the address associated with a building or a property parcel. The problem with creating polygons out of these points is that the ZIP codes don't cleave neatly along natural geographic boundaries (e.g. roads, hydrographic features, etc.). This doesn't prevent map publishers from aggregating them into polygons, however published maps of ZIP polygons should be considered rough approximations, rather than officially recognized ZIP code polygons.<br>
<br>I think it's best to keep the ZIP as part of the address tags rather than try to shoehorn ZIPs into polygons which would be inaccurate and subject to frequent change.<br><br>SEJ<br>----<br>"Wretches, utter wretches, keep your hands from beans." -Empedocles<br>
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<br><br><div class="gmail_quote">On Sun, Dec 20, 2009 at 16:00, Anthony <span dir="ltr"><<a href="mailto:osm@inbox.org">osm@inbox.org</a>></span> wrote:<br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<div class="im">On Sun, Dec 20, 2009 at 3:34 PM, Frederik Ramm <span dir="ltr"><<a href="mailto:frederik@remote.org" target="_blank">frederik@remote.org</a>></span> wrote:<br></div><div class="gmail_quote"><div class="im">
<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
Still, the post codes are *commonly* used as a shortcut geo reference; it is a very popular way of doing e.g. a store finder on a web site - enter your post code and we'll show you the nearest store. Because of this, there is high demand for post codes to be available in OSM and I am certain that we will eventually either map or import them.</blockquote>
</div><div><br>I have responded to that, though. A single point in the approximate center of the general area where a zip code is used is fine. I don't think OSM is really the best place to store those (slightly less than) 99999 points, because it so easily stands alone and isn't something that lends itself to public editing (you just import a database every so often, it's not really something individual OSMers can survey). But I'll get over that - if you really get a kick out of importing 99,999 or so zip code centroids, fine. In fact, I can probably find a CSV file where the centroids have already been calculated for this. It's quite a common application. (You'll basically be converting someone's table of zip codes to lat/lon pairs into OSM nodes, so geocoders can then take those OSM nodes and convert them back to a table of zip codes to lat/lon pairs. But, whatever, have a ball.)<br>
<br>If you want to do more than that, as Katie said, "It would be appropriate to attach zip code as attributes to addresses." <br></div></div>
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