Good points, Orlando. All completely true. 

The concept of ZIP codes as a boundary is completely foreign to the USPS (and in their view probably missing the point.) ZIP codes are used to route mail to the right post office and then to deliver to the right location (house, building, etc.) There are plenty of ZIP codes (+10,000) that have no geographic representation as they might represent a P.O. Box, an individual building, or even a specific business in a building. Locations are assigned a ZIP code (which could change.) It is a nice side effect that you can draw a boundary around locations with the same postal code and get a contiguous area - hence ZCTAs. 

The question, as always, is how will the data be used and what level of accuracy will be good enough. 

On Wed, Mar 16, 2016 at 2:38 PM, Rodriguez , Orlando <[log in to unmask]> wrote:

Several years ago I was looking for ZIP Code polygons and learned the following:

 

* Census ZIP Code polygons are inaccurate.  Check the Census Bureau documentation.

* The USPS does not maintain up to date ZIP Code boundaries.

* In rural areas, neighboring post offices often decide among themselves where the boundary is and don’t tell anyone about changes.

 

The best solution at the time was to buy a ZIP Code boundary file from a reputable vendor.

 

Orlando

 

PS. Check the source of the ESRI data.  Just because it’s free doesn’t make it accurate.

 

 

 

From: Northeast Arc Users Group [mailto:[log in to unmask]] On Behalf Of Olivares, Miriam
Sent: Wednesday, March 16, 2016 1:19 PM
To: [log in to unmask]
Subject: Re: Postal Zip Code Layer

 

Daniel,

 

Do you have access to Esri Data and Maps as part of your license (if your organization holds one)? I believe there are point and polygon zipcode data available

http://www.esri.com/data/data-maps

 

Miriam

 

-----

Miriam Olivares, GISP

GIS Librarian

Center for Science and Social Science Information

Yale University

 

219 Prospect Street | New Haven, CT 06511

Voicemail 203.436.5891 | [log in to unmask] 

GIS LibGuide | Get an appointment!

 

Let's work together to transform your project through the geospatial lens

 

Hi gang...

 

I have been tasked with finding a zip code layer specifically for the state of RI (yes we have more than one zip code) but I'll expand the range if thats whats available.  Where might I ?look to find just such a thing???  Does the postal service have such data available?

 

 

Daniel Bradley

GIS Coordinator

Warwick Fire Department

Lieutenant Engine Co 3

Station 3 - Oakland Beach

 

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