cabgbbmat {AIGIS} | R Documentation |
A 22195 by 4 matrix containing bounding box data for the US Census block group polygons contained in ‘cabggpc’. Note this is for the polygons, and not the actual block groups (see Details).
data(cabgbbmat)
See description above.
This object used by other functions to provide a fast filter for determining which block groups need to be considered as potentially overlapping with a target polygon. For example, if the the low edge of the bounding box is higher than the high edge of the bounding box for a target polygon, it is impossible for them to overlap. Similarly for the other three sides.
As mentioned elsewhere, the mapping of GIS records provided by the census is not 1 to 1 with the number of block groups. This file is specific to the polygons provided, not the block groups.
The polygons from which these bounding boxes were extracted are found here: http://www.census.gov/geo/www/cob/
data(cabgbbmat)