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Group Quarters Assistance - The Census Geocoder

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The Census Bureau published a Federal Register Notice on the Final 2020 Census Residence Criteria and Residence Situations on February 8, 2018. In the Notice, the Census Bureau stated we will continue the practice of counting prisoners at the correctional facility, to ensure that the concept of usual residence is interpreted and applied consistent with the intent of the Census Act of 1790. The Notice also stated the Census Bureau recognizes that some states have decided, or may decide in the future, to ‘move’ their group quarters (GQ) population (e.g. student, military, and prisoner population) to an alternate address for the purpose of redistricting. To assist those states with their goals of reallocating GQ population for legislative redistricting, the Census Bureau is offering the use of a geocoding service based on 2020 Census geographic data.

The Census Geocoder

The Census Geocoder is a geocoding service the Census Bureau provides to assist governments and data users with locating census geography associated with address information. The geocoding service is an address look-up tool that converts an address to an approximate coordinate (latitude/longitude) and returns information about the address range that includes the address and the census geography the address is within. The Census Geocoder features the address ranges used in the TIGER/Line Shapefiles, derived from the Master Address File (MAF), and is available as a web interface and as an API (Representational State Transfer – REST – web-based service). 

Using the Census Geocoder for Redistricting

The Census Geocoder was updated to include 2020 Census geographic data in January 2021. Official state redistricting liaisons and technical staff can use the Census Geocoder to locate the census geography associated with the addresses for which they need to reallocate group quarters population to support redistricting. 

The geocoding service provides states the ability to:

  • Identify and verify the locations of their GQs to assign geographic identifiers to their GQ address list.
  • Use the GQ address list, the user-defined unique identifiers and the returned geographic identifiers to create their own tabulation adjustment tables.
  • Link user supplied race, ethnicity, and age data associated with each record and the tabulation adjustment table through the user defined unique identifier. 

Batch Geocoding (10,000 Address Records – more or less)

State redistricting officials may submit a file with up to 10,000 address records to the external Census Geocoder at one time. State officials, and only state officials, have the additional option to submit a pre-formatted list of 10,000 to 50,000 addresses to the Census Bureau for geocoding via the secure email file transfer system (SWIM). States with more than 50,000 addresses to geocode should pre-format and split the list of addresses into multiple files, so that each file has less than 50,000 total addresses, and submit each applicable file via SWIM to the Census Bureau. The Census Bureau will submit the file(s) to the geocoding service on behalf of the state and securely return the output to the state submitter. Both methods of submitting addresses for geocoding require the files to be in the specified format.

File Submission through SWIM

SWIM, the Secure Web Incoming Module, is a tool state officials can use to submit lists of more than 10,000 addresses to the Census Bureau for geocoding assistance. To access SWIM, state officials should click on the following URL: https://respond.census.gov/swim

If you already have a SWIM account, you should enter your Email address and Password and click the Login button to enter the tool. If you do not yet have a SWIM account, click the Register Account button to start the registration process. 

For previously released guidance on how to use SWIM, please refer to Section 9. File Submission through SWIM in the Voting District Project GUPS User’s Guide for step-by-step instructions on how to submit files through SWIM. When at step 9.x please choose the CD/SLD radio button in place of the BBSP/VTD radio button. 

How to Format your Address List for Batch Geocoding

Addresses should be formatted in a single line with comma delimiters. Each address should consist of:

  • Unique ID,
  • House Number and Street Name,
  • City,
  • State,
  • ZIP Code 

City and State, or ZIP Code may be left blank, but there must be the appropriate number of commas to represent the blank data. 

The following examples are formatted correctly:

  • 1,1600 Pennsylvania Ave NW,Washington,DC,
  • 2,1600 Pennsylvania Ave NW,,,20502  

The following examples are formatted incorrectly, and will not return a geocode result (no match):

  • 3, 1600 Pennsylvania Ave NW, Washington, DC
  • 4, 1600 Pennsylvania Ave NW, 20502 

Please Note: The batch geocoder can process up to 10,000 address records at a time. Files close to the 10,000 maximum threshold may take a few minutes to process. 

Batch Geocoding Results

The Census Geocoder takes the addresses and determines the approximate location offset from the street centerline. The service then returns an interpolated longitude/latitude coordinate, along with the address range the Census Bureau has on that stretch of road. 

The Census Geocoder will return one of the following results for each address:

  • Match/Exact
  • Match/Non-Exact
  • Tie
  • No Match 

If a Tie is encountered, there are multiple possible results for that address. The address can be input for single address geocoding to view the multiple results. 

Using the web interface “Final Locations Using…” option, the results include the estimated longitude/latitude coordinate, TIGER identifier of the street, and full address range on the road segment. 

Using the web interface “Find Geographies Using…” option, results are returned for the State, County, Census Tract, and Block the address is located within. In addition, attributes of these pieces of geography, such as an urban/rural indicator are included. 

Contact Information

For questions about redistricting and submitting files with more than 10,000 addresses to geocode, please contact the Census Redistricting & Voting Rights Data Office at 301-763-4039 or rdo@census.gov. 

For questions specifically about the geocoder, please contact the Geocoding Services team at geo.geocoding.services@census.gov. 

Page Last Revised - October 8, 2021
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