EarthWorks Geospatial Catalog

U.S. Census 2000 Data: Block Groups

This polygon layer represents Census Block Groups, which are aggregations of Census Blocks, the finest resolution of geographic boundary data developed by the U.S. Census Bureau for the 2000 Decennial Census (see the CENSUS2000BLOCKS_POLY layer). Each Block Group is assigned a census block group number in the Census' Topologically Integrated Geographic Encoding and Referencing System (TIGER) files which is used to reference tabular data published by the Census Bureau. MassGIS has extracted and reprocessed data from the original TIGER files for use with its other data. Processing included import of the original data with the ArcInfo TIGERTOOL command, projection to the Massachusetts State Plane (NAD83 Meters) Coordinate system, and modification of the attribute table. Blocks were dissolved on the BG_ID field to produce the Block Group geography. MassGIS makes two versions available: - CENSUS2000BLOCKGROUPS_POLY (offshore, zero-population polygons were removed to present the appearance a coastline for display purposes); - CENSUS2000BLOCKGROUPS_POLY_ORIG (all polygons from original data are preserved). MassGIS also makes available several database tables, extracted from the Census SF3 tables, with demographic data that may be joined to the Block Group geography on the LOGRECNO item.
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