In the 1995 and later TIGER/Line® files, NAD83 is the coordinate datum used for the 48 contiguous states, the District of Columbia, Alaska, Puerto Rico, and the Virgin Islands of the United States. Regional datums are used for Hawaii and the Pacific Island Areas. NAD27 was the coordinate datum used for the 1994 and earlier versions of the TIGER/Line files except in Hawaii and the Pacific Island Areas where regional datums were used. Because the datum used was not relevant to the Census Bureau's purposes for creating maps, the documentation did not record the specific datum of our source material for Hawaii and the Pacific Island Areas. The Census Bureau plans to move the TIGER® data base for Hawaii and the Pacific Island Areas to a more current datum for post Census 2000 TIGER/Line releases.
The TIGER/Line data are not in a mapping projection even though most of the features were scanned directly from source maps (usually USGS 1:100,000-scale topographic quads) that were in a projection.
For the lower 48 states, most information in TIGER outside the urban centers was derived from the USGS 1:100,000-scale digital line graphs, which were vectorized from the digital scanning of the original artwork. The original art work was in Universal Transverse Mercator (UTM) projection. After the map sheets were scanned, the coordinates were transformed from UTM into projectionless geographic coordinates of latitude and longitude.
For most urban centers, the information in TIGER was derived from the GBF/DIME files produced for the 1980 census. The coordinates in the GBF/DIME files were based on the Census Bureau's Metropolitan Map Series (MMS) map sheets, originally developed for the 1970 census, and subsequently updated by local planning agencies as well as the Census Bureau. The MMS map sheets developed after the 1970 census were based on USGS 7.5 minute topographic quadrangles, enlarged to 1:19,200 and rescribed.
There were a variety of other sources used in creating the Census TIGER data base. The features from those sources also were stored as latitude and longitude coordinates. Subsequent updates to the Census TIGER® data base also came from a variety of sources, including paper maps annotated in the field and subsequently digitized without rigorous adherence to a projection or coordinate system.
The information in TIGER for Puerto Rico originally was derived by digitizing the USGS 1:20,000 topographic quadrangles. The information for Hawaii was based on the GBF/DIME files and available USGS maps for the state. The information for Alaska and the Island Areas originally was developed by digitizing USGS 1:24,000 and 1:63,360 topographic quadrangles and other available sources, including some developed for use in World War II.
The Census Bureau's TIGER/Line metadata provided below is Federal Geographic Data Committee (FGDC) compliant.