2010 Census Generalized Cartographic Boundary Files
I’ve had a few interesting projects that have kept me busy at the end of this year. I’ll do a post or two after New Years, once I’m back in the office and can take some screen shots to illustrate.
In the meantime I have one tidbit I can mention – the Census Bureau has released the 2010 version of the Generalized Cartographic Boundary Files. These files are generalized versions of the TIGER files, with smoothed and simplified boundaries and areas of coastal water removed. They haven’t posted them on the same page as the 2000 and 1990 boundaries; they’ve mentioned they’re creating a new interface to host all of them, which is currently a work in process at http://www.census.gov/geo/www/cob/.
However, you can get access to all the 2010 boundaries via the FTP site – you just need to know what you’re looking at. All the files are named with codes to identify the geographic coverage, summary level, and resolution / scale. There’s a README file on the FTP page that tells you how to identify each.
But in brief – The file names look like this: gz_2010_ss_lll_vv_rr.zip, where:
- ss is the state INCITS / FIPS code which you can look up here – ‘us’ is a national level file.
- lll is the summary level or unit of geography – the README file has a table with each code. The most common ones: 040 for state, 050 for county, 060 for county subdivisions, 140 for census tracts, 160 for places, 310 for metropolitan and micropolitan statistical areas, 860 for ZCTAs. (No PUMAs- 2010 PUMA boundaries haven’t been drawn yet, and 2000 PUMA boundaries are still being used in the latest ACS).
- vv is a version number for the file.
- rr is resolution – most of the files are 500k = 1:500,000, which is the least generalized and best for mapping state-level to regional areas. For national level files you also have the option of 5m = 1:5,000,000 and 20m = 1:20,000,000, which are more generalized and better for national mapping.
The Census Bureau has been doing a lot of tweaking to their website lately. The legacy version of the American Factfinder is set to disappear for good on Jan 20, 2012.