[Talk-us] [Imports] Zipcode Import

[Katie Filbert]

I posted some comments on the blog post about zip codes:

For splitting up OSM data, I suggest splitting data up by counties or other
geographic units (e.g. census tracts).

Zip code boundaries are problematic and should not be imported. In reality,
zip codes are merely attributes assigned to addresses and street segments,
and not geographic areas.

People have attempted to create zip code boundaries, though there is no
standard way of creating them. The Census Bureau's zip code boundaries
differ from other sources (e.g. county GIS departments). Also, zip code
"boundaries" change all the time, as new addresses/buildings are added for
mail delivery.

The only official zip code "boundaries" would come from the USPS, however
the USPS does not publish them and has them for internal use only. Changes
in zip code assignments and boundaries are done by a GIS person at the
regional postal facilities (e.g. in Dulles, VA) who adjusts them in ArcView
(or MapInfo), without keeping a history of the changes.

For more about issues with zip code polygons, see:
http://www.biomedcentral.com/content/pdf/1476-072x-5-58.pdf

If we end up deciding to import zip codes, it should be done only after much
discussion and with a lot of care. They should be assigned to address
points, and not as boundaries.

About the data posted to archive.org:

For the Census zip code boundaries, there are the 5-Digit ZIP Code
Tabulation Area (2002), linked from
http://www2.census.gov/cgi-bin/shapefiles2009/state-files?state=34.

There other versions of Census zip code boundaries, aside from that one.
>From the archive.org link and data link there, I can't tell which it is.


And, according to the Census TIGER technical documentation:

"Data users should not use ZCTAs to identify the official USPS ZIP Code for
mail delivery. The U.S. Postal Service (USPS) makes periodic changes to ZIP
Codes to support more efficient mail delivery. As a result, the original
Census 2000 and 2002 ZCTAs may no longer match current ZIP Codes."

http://www.census.gov/geo/www/tiger/tgrshp2009/TGRSHP09.pdf

Regards,

Katie
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