On 11/29/2012 9:12 PM, Steven Johnson wrote:
Secondly, about Census data... The Census Bureau publishes ZIP Code
Tabulation Areas (ZCTAs, as polygons) but they are an approximation of
US Postal Service data and used for downstream analytical purposes.
But as far as USPS is concerned, the ZIP code is a point data feature
that only exists to deliver the mail. The USPS does not maintain ZIP
codes as polygons.
For points coming from parcel centroids, Property Appraisers store
mailing addresses, and they need to get that right in order to deliver
the tax bills. When the owner mailing address and site address match, I
would bet there is a high degree of accuracy for the city and zipcode
values in the site address fields (where they are populated).
Where the site address zipcode was not available, and mailing street
address matched site address, I have used mailing address zipcodes to
map zipcode boundaries and obtained what appeared to be good results.
Brian
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