Kevin:
Now that the Census has released SF3, does the LIST
know of way to download
(at once) all of the Block Group SF3 data for a county, or do I have to
download each Tract individually and merge them?
The structure of SF 3 is one header file plus 76 (!) data files, none with
more that 250 fields, to handle the 16,520 fields in the 405 tables for
Census Tracts and above. There are "only" 5558 fields in 281 tables for
Block Groups.
Each file has all summary levels mixed together, so you have to search each
file that has the tables you want to look for the block groups or other
areas you want.
TransCAD and Maptitude users have it a lot easier. TransCAD users get the
SF 3 Data CD for their state free as part of their maintenance agreement,
plus the State Data CD with Block Group and other boundaries for their
state. Maptitude users (or TransCAD users that want other states) can buy
these CDs for $195 each. Nationwide Census Tracts, ZCTAs, counties, MSAs,
etc. come with both TransCAD and Maptitude.
The SF3 Data CDs have all 77 files merged, then split into each summary
level: Block Groups, Census Tracts, etc. With the Table Chooser for SF 3,
an add-in to TransCAD and Maptitude, you can easily pick the geography and
tables that you want, and output a geographic file (with the tables
attached) or just a tabular file.
SF 3 Data CDs are being released as the Census Bureau releases the states.
12 states are out, and seven more are due tomorrow. For more information,
please visit (
http://www.caliper.com/DataCDs/SF3DataCD.htm).
Peter
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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(a)caliper.com
Newton MA 02461-9926 Web site:
http://www.caliper.com