topic Re: Is there a way to get County using latitude and longitude? in SAS Programming

Is there a way to get County using latitude and longitude?

KathyWiz — Fri, 17 Jan 2014 16:49:55 GMT

I have files which contain data for addresses that have been geocoded. They contain latitude and longitude. Is there a way (a function or procedure) within SAS that will return the U.S. county from these coordinates?

Re: Is there a way to get County using latitude and longitude?

Fugue — Fri, 17 Jan 2014 18:32:57 GMT

Have you taken a look at the SASHELP.ZIPCODE dataset?

Re: Is there a way to get County using latitude and longitude?

ballardw — Fri, 17 Jan 2014 19:33:01 GMT

If you can get the lat and long projected (Proc Gproject) to match the USCounty map dataset provided by SAS then Proc Ginside should work.

Re: Is there a way to get County using latitude and longitude?

Fugue — Fri, 17 Jan 2014 19:56:29 GMT

Ballard's suggestion may be preferable, but to elaborate further on my comment . . . .one could use GEODIST function to determine the closest location in the ZIPCODE dataset. This would be somewhat hit-and-miss, since the closest location may, in fact, be in a different county. Ideally, Ballard's approach makes better sense since your lat and long can only fall into unique counties (unless it happens to be exactly on a county boundary).

Re: Is there a way to get County using latitude and longitude?

art297 — Fri, 17 Jan 2014 20:08:11 GMT

Just FWIW, if you enter a coordinate pair as a search string at www.mapquest.com, part of the output will contain the zipcode, city and state and, given that info, you can get the county name from sashelp.zipcode.

The following paper provides example code for automating such a lookup process:

http://support.sas.com/resources/papers/proceedings12/091-2012.pdf

To use it, you would have to get an API key from Mapquest, but that is free and easily done from their web site.

Re: Is there a way to get County using latitude and longitude?

Reeza — Fri, 17 Jan 2014 20:10:11 GMT

There's a proc for that!

SAS/GRAPH(R) 9.2: Reference, Second Edition

Ballardw suggest is probably the easiest and the example in the documentation is for example that problem.

If the projections don't match you can also find the proper version for US county data online in many places and bring that into SAS.

Re: Is there a way to get County using latitude and longitude?

KathyWiz — Wed, 22 Jan 2014 15:14:58 GMT

Thanks for the link and suggestions. I haven't worked with geographic data before, so it is very helpful to be pointed in the right direction.

This questions was actually something I was asked by another programmer, so I'll forward the comments to her so she can try this out.

Re: Is there a way to get County using latitude and longitude?

Doc_Duke — Thu, 23 Jan 2014 15:08:10 GMT

One caution with Arthur's approach. At least in NC, ZIP codes and City boundaries cross county lines.

Reeza's approach will have more precision.

Doc Muhlbaier

Duke

Re: Is there a way to get County using latitude and longitude?

art297 — Thu, 23 Jan 2014 15:54:15 GMT

Doc: Before mentioned it, I wasn't even aware of proc ginside and it is definitely the easiest to implement. However, since both methods start with coordinates thus should be attempting to match with polygons, I wouldn't jump to the conclusion that one would necessarily be more accurate than the other. Can you provide a couple of examples that we could compare?

Re: Is there a way to get County using latitude and longitude?

Reeza — Thu, 23 Jan 2014 15:59:47 GMT

Its not my suggestion, its

But I will test it with Canadian data...out of curiousity. I have ArcGIS that can be the source of "truth"

Re: Is there a way to get County using latitude and longitude?

data_null__ — Thu, 23 Jan 2014 16:06:10 GMT

You seem to forget the OP has long and lat for each address. No need to involve ZIP code that I can see.