How to use the Census Redistricting Summary File in Access - ctpp-news

18 Feb 2011

Since I have seen a lot questions about this I thought I would post my
personal notes. If your state hasn't come out yet I strongly suggest
downloading a different state and practicing. Once you get the method down,
it will be easy to repeat. 

These instructions are for Access 2003 but I think they are similar for
Access 2007.

You will need the following documents. Download them to your computer and
keep them close at all times.

0FILE_STRUCTURE.pdf  found at
http://www2.census.gov/census_2010/01-Redistricting_File--PL_94-171/0FILE_ST
RUCTURE.pdf

0GEOID_Construction_for_Matching.pdf  found at
http://www2.census.gov/census_2010/01-Redistricting_File--PL_94-171/0GEOID_C
onstruction_for_Matching.pdf 

pl94-171_tech_doc.pdf found at
http://www.census.gov/prod/cen2010/doc/pl94-171.pdf

1. Go to
http://www2.census.gov/census_2010/01-Redistricting_File--PL_94-171/ and
download the access document that matches your MS Access version, either
PL2010_Access.accdb or PL2010_Access2003.mdb.

2. In the same directory, go to the folder your state is in and download
everything in the folder. 

3. Unzip the files.

4. Open the PDF called 0FILE_STRUCTURE.pdf. Read the first page, it has
useful information. The go to the section marked "For Access Users" on page
2. FOLLOW THESE INSTRUCTIONS EXACTLY.

5. After the tables are imported into Access, you should have the two data
tables and the geography table automatically joined by the LOGRECNO field.
...
 From here, you can use queries to extract tables on a
single geography and on the topics of your choice. Start a new query in design view.
I recommend
starting all queries by adding the entire geography table until you get a
feel for which fields you don't need. 

6. SUMLEV is the field that will let you extract a particular geography,
such as tracts or counties. You can find a full listing of SUMLEVs under
Chapter 4 of pl94-171_tech_doc.pdf. So if you want a table that has all the
census tracts in your state, type "140" under the Criteria field of the
SUMLEV column in your query design.

7. The other two tables list your data fields. The table names are given in
the back of 0FILE_STRUCTURE.pdf.

8. Export the query to the format of your choice - Excel, dbf, txt, ect.
Note that only the newest Excel program will handle more than 65,000
columns.

9. If you are using the data in GIS, you will need to construct a GEOID
field to match the one in the shapefile. The file
0GEOID_Construction_for_Matching.pdf provides formulas for doing this.
Concatenate the fields found in the geography half of your exported table
into a GEOID field.

10. Analyze! Analyze! Analyze!

TIP: Compare the number of records in your shapefile with the numbers of
records in your exported table to make sure the table was extracted
correctly.

Hopefully these steps make things less confusing, not more. Good luck!

Mara

Mara Kaminowitz
GIS Analyst
.........................................................................
Baltimore Metropolitan Council
Offices at McHenry Row
1500 Whetstone Way
Suite 300
Baltimore, MD  21230
410-732-0500 ext. 1030
 <mailto:mkaminowitz@baltometro.org> mkaminowitz(a)baltometro.org
 <http://www.baltometro.org/> www.baltometro.org

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