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| GeoCommunity Mailing List |
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| Mailing List Archives |
| Subject: | Re: [gislist] ZIP Code Boundaries |
| Date: |
10/16/2003 02:25:01 PM |
| From: |
Peter H. Van Demark |
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Travis:
>I am trying to align ZIP Code boundaries in North Carolina to actual
>streets, rivers, etc. Do ZIP Codes follow the same rationale as Census
>tracts? I know that the boundaries change frequently, but I cannot find a
>free source that shows the accurate physical locations. HELP!
ZIP Codes are not areas: they are groups of addresses. Sometimes addresses
with the same ZIP Code can be contained by actual streets, rivers, etc. but
they don't have to be. Any situation you can think of can happen, even
crossing state boundaries, fingering down a street but not including side
streets on the same block, and alternating along the same side of the
street (where people can pick their ZIP Code). They absolutely do not
follow the same rationale as Census tracts!
You have two basic choices:
- Use ZCTA boundaries, designed by the Census Bureau to approximate the
delivery areas at the time of the census (April 2000, with Census data), by
grouping Census blocks based on the predominant ZIP Code for the households
in a block, then doing lots of adjusting, or
- License the ZIP Code boundaries (directly or indirectly) from a
geographic data provider such as Geographic Data Technology (without 2000
Census data), which are more up to date and try to handle the vagarities of
ZIP Code geography.
Maptitude Geographic Information System for Windows includes nationwide
ZCTA boundaries that have about 400 variables from the 2000 Census, in four
profiles from SF 1 and SF 3. For more information, see
(http://www.caliper.com/ovudata.htm).
Caliper Corporation also has quarterly updates of ZIP Code boundaries from
Geographic Data Technology as an additional Data CD for use with Maptitude.
For more information, see (http://www.caliper.com/DataCDs/LatestZIPCodes.htm).
Peter
----------------------------------------------------------------
Peter Van Demark
Director of GIS Products and Training Phone: 617-527-4700
Caliper Corporation Fax: 617-527-5113
1172 Beacon Street E-mail: peter@caliper.com
Newton MA 02461-9926 Web site: http://www.caliper.com
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