Date: Wed, 16 Aug 2000 18:13:04 -0600
Reply-To: Jack Hamilton <JackHamilton@FIRSTHEALTH.COM>
Sender: "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From: Jack Hamilton <JackHamilton@FIRSTHEALTH.COM>
Subject: Re: convert census tract to zip or vice versa?
Content-Type: text/plain; charset=us-ascii
SAS doesn't (well, SAS/GIS might, I don't know, but base SAS doesn't).
There are commercial sources for this information, and there are at
least three algorithms for determining ZIP centroids:
1) Geographic center, maybe not a good idea if the ZIP's population
isn't evenly distributed. It might be in the middle of a lake.
2) Sampled center, the lat/lon of an actual populated place in the
ZIP code. If you ask for the lat/lon 5 times using this method,
you might get 5 different answers, but they will all correspond
to real addresses, and heavily populated locations will be
returned more frequently.
3) Population weighted center, the lat/lon weighted by population.
This is probably what you want for calculating distances, but
again the location might be in the middle of a lake.
ZIP codes can be fairly large. I don't know exactly how large
they can get, but it wouldn't surprise me to find a ZIP code that
covers a thousand square miles (in a sparsely populated area).
Does anyone know what the largest ZIP code is?
Development Manager, Technical Group
METRICS Department, First Health
West Sacramento, California USA
>>> "Burley, Mason" <burleym@WSIPP.WA.GOV> 08/16/2000 4:42 PM >>>
You may create an allocation factor (using population, land area, or
housing units) between two overlapping geographic divisions based on
1990 census data using the following web site:
Since this generates factors based on 1990 data, you may miss some newly
created zip codes.
Now a question for the list: I have obtained the formulas to calculate
distances between two places using latitude and longitude. Now I need
to find a file with zip codes and corresponding latitude/longitudes. Do
I have to purchase this data, or does SAS have a facility for this?
Washington State Institute for Public Policy
From: Drew Spencer [mailto:DrewSpen@IMAGIN.NET]
Sent: Wednesday, August 16, 2000 4:02 PM
Subject: convert census tract to zip or vice versa?
Anyone know how I can convert census tract to zip or vice versa?
I am using SAS.
Kent Andrew (Drew) Spencer
Sent via Deja.com http://www.deja.com/
Before you buy.