Collecting and Maintaining our Geographic Data

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Written by Steve Matheis and Katy Rossiter

The Census Bureau collects and maintains geographic data in order to take censuses and surveys and to prepare and present statistical information.  We store all of our geographic data in the Master Address File/Topologically Integrated Geographic Encoding and Referencing (MAF/TIGER) System.   The MAF/TIGER system has become an essential part of our daily operations and keeping it up-to-date and accurate is vital.  So, how do we do it?

Maintaining Boundaries

The Census Bureau manages several geographic programs to maintain accurate and meaningful boundaries.  We maintain legal, administrative, and statistical boundaries for cities, towns, and unincorporated places, school districts, census tracts, block groups and much more.  In addition, we update each boundary as necessary and at various frequencies.  For instance, we update state, county, township, and incorporated place boundaries annually through the Boundary and Annexation Survey (BAS).  However, we only update census tracts and block groups once a decade through the Participant Statistical Areas Program (PSAP).  We also update several boundaries determined by state governments, such as voting districts, state legislative districts, and congressional districts.  We create other boundaries, like urban areas, based on published criteria the public has an opportunity to help define.  For more information about our geographic programs, visit:  http://www.census.gov/geo/www/programs.html.

Maintaining Features and Addresses

Updating our streets, rivers, railroads, and addresses in the MAF/TIGER system happens continually.  The Census Bureau is constantly updating the features and addresses in order to keep up with the demands of our ongoing survey work.  When the Census Bureau first created TIGER, we used maps from the U.S. Geological Survey to draw the roads and other features you see on our maps.  Then we used our field staff and files from the U.S. Post Office to update the MAF/TIGER system.  In the 2000s, we spent a lot of time and effort overhauling all of the streets in TIGER so they would be more spatially accurate.  We collaborated with tribal, state, county, and local governments to complete this massive MAF/TIGER Accuracy Improvement Project (MTAIP).

The image below shows our hard work paid off because our streets now better match what is on the ground.  The improved quality allowed us to use better technology, such as GPS, to ensure that you are counted in the correct location and improve the overall accuracy of our data.

To prepare for the 2010 Census, we canvassed most of the U.S. to ensure our maps and address list were accurate.  We plan to continue partnering with local governments and others to help us maintain MAF/TIGER and to prepare for the 2020 Census.  To learn more about these efforts, please visit http://www.census.gov/geo/www/gss/index.html.

It is critical that the Census Bureau maintains accurate geographic features so that we can collect and provide meaningful data on our nation’s people, places and economy. Precise geographic boundaries not only help us collect more accurate data but also better interpret the statistics that tell us who we are as a nation.  Through our work in the field and working with our partners, we continue to improve the MAF/TIGER system.

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One Response to Collecting and Maintaining our Geographic Data

  1. Patrick Flanagan says:

    Where did you get your state and international boundaries from and do they change regularly? Also, are the lines defining the coast at a particular tide level and are they updated for erosion and other changes?

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