The Census Bureau began to develop a digital geographic database of 144 metropolitan areas in the 1960s. This earlier database enabled computer-based geocoding and map-based routing in those areas. By 1990, the early efforts had evolved into TIGER: a seamless digital geographic database that covered the whole of the United States and its territories.
TIGER/Line Shapefiles are digital map data products extracted from the MAF/TIGER database. They are freely available from the Census Bureau and are suitable for use by individuals, businesses, and other agencies that don’t have direct access to MAF/TIGER.
6.2.1 Geographies Represented in TIGER and Shapefile Extracts
The MAF/TIGER database is selective. Only those geographic entities needed to fulfill the Census Bureau’s operational mission are included. Entities that don't help the Census Bureau conduct its operations by mail or help field workers navigate a neighborhood are omitted. Terrain elevation data, for instance, are not included in MAF/TIGER. A comprehensive list of the "feature classes” and “superclasses” included in MAF/TIGER and Shapefiles can be found in Appendix F-1 of the 2009 TIGER/Line Shapefiles Technical Documentation. Some examples are given in Table 6.1 below. Examples of superclasses include:
- potential living quarters (e.g., sites of shelters, retirement homes, prisons, dormitories);
- road/path features (e.g., primary roads, secondary roads, local neighborhood roads);
- hydrographic features (e.g., stream/river, lake/pond, ocean/sea);
- miscellaneous linear features (e.g., pipeline, powerline, fence line);
- tabulation areas (e.g., county or equivalent, tract, block group, block).
|MTFCC||Feature Class||Superclass||Point||Linear||Areal||Feature Class Description|
|K2459||Runway/Taxiway||Transportation Terminal||Y||Y||Y||A fairly level and usually paved expanse used by airplanes for taking off and landing at an airport|
|K2460||Helicopter Landing Pad||Transportation Terminal||Y||N||Y||A fairly level and usually paved expanse used by helicopters for taking off and landing.|
|K2540||University or College||Other Workplace||Y||N||Y||A building or group of buildings used as an institution for post-secondary study, teaching, and learning.(including seminary)|
|K2543||School or Academy||Other Workplace||Y||N||Y||A building or group of buildings used as an institution for preschool, elementary, or secondary study, teaching, and learning. (including elementary school and high school)|
Excerpt above from TIGER/Line Technical Documentation. Credit: Census Bureau 2009.
Note also that neither the MAF/TIGER database nor TIGER/Line Shapefiles include the population data collected through questionnaires and by census takers. MAF/TIGER merely provides the geographic framework within which address-referenced census data are tabulated.