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This datalayer was produced from the post-census release of 1990 TIGER/Line files for the fourteen counties of Massachusetts. This datalayer includes the boundaries of all census blocks and can therefore be used in conjunction with Census Bureau data summarized at the census block level--the finest available resolution of census data.
The layer is named CENSUS1990BLOCKS_POLY.
Using ArcInfo Workstation, the Census Block data (in coverage format) were created by extracting from county TIGER files all linework, line attributes, and polygon attributes. The coverages were enhanced by dropping redundant data items, appending several demographic data items from the STF-1, STF-3a, and PL94-171 census data matrices, and creating an Arc/INFO ADD file for address-matching. Each polygon in the original county TIGER file was assigned a MassGIS town-ID code, ensuring that all of the original polygons appear within the Town TIGER Geography datalayer.
In some cases, polygons within the TIGER line network were not assigned unique census block numbers by the Census Bureau. That is, more than one polygon was assigned a single census block number, and is thereby related to the same record in the matrices of demographic data published by the Census Bureau. In order to overcome the problem of redundantly assigning data values from the matrices to the TIGER Geography coverages' polygon attribute tables on the basis of these nonunique census block numbers, MassGIS apportioned numeric values among the polygons on the basis of their relative area. This is arguably incorrect, since it assumes demographic heterogeneity among all polygons assigned the same census block number. However, in all cases observed by MassGIS, such polygons were contiguous and relatively small, so the impact of this error is expected to be minimal.
The layer's polygon attribute table includes the following items:
Item Name Description BLK TABULATION BLOCK NUMBER BLKGROUP CENSUS BLOCK GROUP. REDEFINED FROM CTBNA CD101 CONGRESSIONAL DISTRICTS (US HOUSE OF REPS) - 101ST CONGRESS. VALID THROUGH 102ND CONGRESS CD103 CONGRESSIONAL DISTRICTS (US HOUSE OF REPS) - 103RD CONGRESS. CURRENT CONGRESSIONAL DISTRICTS CENID CENSUS FILE IDENTIFICATION CODE CENPOLID CENSUS POLYGON ID. CONCATENATED FROM TIGER ITEMS CENID & POLYID COUNTY FIPS COUNTY CODE CTB CENSUS TRACT/BNA CODE (CHARACTER). REDEFINED ITEM CTBNA CENSUS TRACT/BNA CODE FMCD FIPS 55 CODE (MCD/CCD) FPL FIPS 55 CODE (PLACE). TIGER ITEM 'FPLCDE' HU100 HOUSING UNITS. FROM CENSUS FILE PL94171 ID-720 CONCATENATED ID FOR SUMMARY LEVEL 720. RELATE TO CENSUS SUMMARY TAPE FILES & PL-94171 FILES ID-750 CONCATENATED ID FOR SUMMARY LEVEL 750. RELATE TO CENSUS SUMMARY TAPE FILES & PL-94171 FILES POLYID POLYGON IDENTIFICATION CODE (TEMPORARY) POP100 POPULATION. FROM CENSUS FILE PL94171 SAC10 ACTUAL/PSEUDO VOTING DISTRICT CODE. USED TO VERIFY VTD VALUE STATE FIPS STATE CODE TILE-NAME MassGIS TOWN ID TRACT-BLOCK CONCATENATED TRACT AND BLOCK CODES VTD VOTING DISTRICT CODE USED IN REDISTRICTING
Other Census Metadata
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Last Updated 9/28/2007
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