<div dir="ltr">ZIP code / government addressing data expert here :)<div><br></div><div>* ZCTA = ZIP Code Tabulation Area. ZCTAs are established by the <b>US Census Bureau not the US Postal Service.</b> ZCTAs have been established to tabulate population statistics around an area people may identify as a city, because there isn't an incorporated legal city there (for instance).</div>
<div>* ZIP Code = Zoning Improvement Plan Code. ZIP Codes are established by the US Post Office to <b>route mail</b>, <i style="font-weight:bold">ZIP Codes do not have a direct spatial component, like a polygon boundary, per se.</i></div>
<div><br></div><div>Therefore you can't technically map US ZIP Codes with a polygon. Any maps you see where ZIP Codes are mapped, those boundaries are <i>derived </i>from addresses. Technically a USPS ZIP Code map would be a point cloud of address points. If you stand on a vacant parcel with no address it also technically does not have a ZIP Code until the USPS says it does. There are many oddities in ZIP Codes, like holes and enclaves.</div>
<div><br></div><div>In the USA, ZIP Codes are established based on imaginary boundaries surrounding post office locations. They are set up to route mail efficiently.</div><div><br></div><div>* End expertise, begin opinion *</div>
<div><br></div><div>Since there are areas in the USA where there are no incorporated cities (that is, ones with a government / mayor), people often identify the place they live based on whatever the city field is on their mail.</div>
<div><br></div><div>For OSM, I believe we should only be mapping postal codes by attributing them to addresses. CDP and ZCTA boundaries could arguably be included, as some kind of admin level.</div><div><br></div><div>Elliott</div>
<div>Baltimore Co. GIS.</div><div><br></div><div><br></div></div><div class="gmail_extra"><br><br><div class="gmail_quote">On Thu, Jun 26, 2014 at 3:33 PM, Richard Welty <span dir="ltr"><<a href="mailto:rwelty@averillpark.net" target="_blank">rwelty@averillpark.net</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div class="">On 6/26/14 3:20 PM, John F. Eldredge wrote:<br>
> Postal code usually means Zip code, or its non-USA equivalent, not city.<br>
</div>this is one of those fussy points in US geocoding.<br>
<br>
the zip code can be mapped to the postal "city", which is what is<br>
in everyone's addresses, and is what i think most us residents<br>
initially expect when typing an address into a search box.<br>
<br>
the underlying point being that there isn't one true geocoder,<br>
it depends entirely on what you're trying to accomplish. something<br>
driven by postal codes/addresses can be correct for many<br>
applications, while being wrong for others.<br>
<br>
to my mind the fact that we keep going in circles about this<br>
is evidence that we're thinking about the problem the wrong way.<br>
<div class="HOEnZb"><div class="h5"><br>
richard<br>
<br>
--<br>
<a href="mailto:rwelty@averillpark.net">rwelty@averillpark.net</a><br>
Averill Park Networking - GIS & IT Consulting<br>
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<br></blockquote></div><br><br clear="all"><div><br></div>-- <br><div dir="ltr">Elliott Plack</div><div dir="ltr"><a href="http://about.me/elliottp" target="_blank">http://about.me/elliottp</a></div>
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