Update on the Master Address File/TIGER Accuracy Improvement Project

By Joe Francica

At the National States Geographic Information Council Annual Conference in Austin recently, Robert LaMacchia, Chief of the Geography Division of the U.S.Census Bureau, provided an update on the Master Address File/Topologically Integrated Geographic Encoding and Referencing (TIGER) Accuracy Improvement Project (MAF/TIGER® AIP).The Census Bureau is trying to improve accuracy of TIGER's digital street centerline to approximately 96%.The spatial accuracy of the centerline is intended to be not more than 7.6 meters.Harris Corporation has the contract to complete the eight-year project with independent checks by the Census Bureau using points collected by Harris.Harris brings in vector files from sub-contractors, utilizing the commercial GIS sector as well as vectors extracted from imagery and sometimes driving the streets.Harris then brings in a vector file, realigns TIGER, and returns the data to the Census Bureau for quality assurance.

In addition, the Census Bureau is trying to reduce the use of paper maps by supplying their field staff with handheld computers.

Present Status

Over 2000 counties of data acquired from field staff.Over 1500 have been evaluated; one-third has failed.Failures are due to not meeting the 7.6 meter accuracy requirement.

The production schedule includes the completion of:

  • 250 counties in FY2003
  • 600 in FY2004
  • 610 in FY2005
  • 700 in FY2006
  • 680 in FY2007
  • 383 in FY2008
Lessons Learned from Evaluating Data Supplied from Local Governments
The Census Bureau's requirements differ from locally provided GIS files. Street Centerline approach differs from cadastre-level geography.Local data files may not follow the Census Bureau's definition of topology (i.e. layers may not align perfectly; overshoots/undershoots as layer are attempted to be integrated).The algorithm for coming up with 96% accuracy is the difference from the centerline that is observed.

TIGER 2004 First Edition

The 2004 TIGER/line files (first edition) is now expected in October. The Census Bureau will release updates every 6 months now.Census Bureau will provide additional record types in "local editions" that will include address ranges and street names to counties to show how streets were aligned. According to the Census Bureau:

The Census Bureau has added a new record type to the 2004 First Edition TIGER/Line files.Record Type M provides spatial metadata for each feature in a TIGER/Line file, identifying the source for the spatial coordinates.A description and explanation of the fields in Record Type M is available.We also have added two new fields (UACU and URCU) to Record Type A containing the corrections to the Census 2000 Urbanized Areas and Urban Clusters announced by the Census Bureau in August 2002.Click Here for the 2004 TIGER/Line file Record Layout.
Maintenance
As part of the 2010 census there will be a complete address canvass that will capture new street features using a GPS equipped hand held computer. The 2010 Census is a $12 Billion project, a $5 Billion increase over the 2000 census.

Published Saturday, October 9th, 2004

Written by Joe Francica



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