Tiger

TIGER (Topologically Integrated Geographic Encoding and Referencing) is a spatial database maintained by the U.S. Census Bureau that includes the geographic coordinates and attributes of roads; railroads; miscellaneous transportation features (pipelines, power lines, etc.); hydrographic features; address ranges; landmarks; and legal, statistical, and administrative entity boundaries for the entire United States as well as Puerto Rico, American Samoa, Guam, Northern Mariana Islands, and the U.S. Virgin Islands. The TIGER system comprises the spatial database and all of the software, specifications, and data capture materials and processes used to create and maintain the database, which is used to produce various products, including maps, address references, and geographic files.

TIGER was developed by the Census Bureau prior to the 1990 Census of Population and Housing, due to inconsistencies in previous censuses between maps, geographic codes, and addresses. While TIGER was originally intended solely for census operations, it quickly became an ongoing updated geospatial data source for public use for all sectors of the United States.

The data in TIGER originated from two main sources: scanned 1:100,000 scale U.S. Geological Survey (USGS) topographic maps for most of the land area and the U.S. Census Bureau's Geographic Base File/Dual Independent Map Encoding (GBF/DIME) files for more urban areas. The two sources were [Page 478]combined into a single digital map database in time for use in the 1990 census. The content of TIGER has been continuously updated ever since.

Originally, TIGER was designed to be used over a 20-year period to assist with the 1990 and 2000 decennial censuses. The 2010 census will utilize a modernized version of the TIGER system. There were three primary factors in the need for a TIGER modernization effort. The first is that the advent and expansion of global positioning system (GPS) technology had made it possible to accurately collect the coordinate position of a housing unit, which is the primary unit for census taking. This, in turn, brought about a need to improve the position of roads, boundaries, and other TIGER features in the database to ensure the correct relationship of the housing unit to census geography in reporting the results of censuses and surveys.

A second factor was the need to replace the “homegrown” TIGER system and software applications, which were developed entirely in-house by Census Bureau staff. Commercial off-the-shelf (COTS) software and related database technology reduced the risk associated with dependencies upon the knowledge of a few individuals who developed the original system and allowed for extendable functionality.

A shift in the role of the federal government concerning spatial data was the third factor for TIGER modernization. Early efforts at capturing and disseminating spatial data, including TIGER, used a top-down approach in which the federal government disseminated spatial data to lower levels of government and to the private sector and academia. The availability of spatial data, especially with access to TIGER data, coupled with the upsurge in availability and use of GIS technology resulted in a shift whereby lower levels of government and other traditional users of spatial data became the custodians of the most current and oftentimes best available resource of spatial data for their areas. As a result, there was a need for the Census Bureau to develop capabilities to incorporate these data sets into a national framework, but, given its unique data structure and in-house software environment, the original TIGER system had no way to effectively interact with and exchange data with these partners.

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