Scale, Generalization, and Limitations of the Cartographic Boundary Files

Scale and Generalization

The cartographic boundary files are primarily designed for small scale, thematic mapping applications at a target scale range of 1:500,000 to 1:5,000,000.

The cartographic boundary files are a generalized extract from the U.S. Census Bureau's TIGER database. Line simplification/smoothing was performed with a tolerance of 0.005 decimal degrees and a coordinate reduction using the Douglas-Peucker method with a tolerance of 0.0003 decimal degrees. Very small polygons were eliminated when the combination of geographic codes existed elsewhere. The geography was clipped back to the shoreline of the United States, in contrast to TIGER/Line® which shows the full extent of geography out to the 3-mile limit.

These generalized cartographic boundary files are originally produced to support the spatial geographic infrastructure for certain mapping functions within the Census Bureau's American Fact Finder and in support of the LandView Geographic Data Viewer. The generalized files have a much smaller file size than the original file extraction from the Census Bureau's TIGER database, resulting in faster download and processing times.

Limitations

Because of coordinate thinning:

1. Cartographic boundary files should not be used for geocoding;
2. Some offshore, redundant, zero population and housing land areas may be absent from the files;
3. Cartographic Boundary files are not necessarily vertically integrated with previous boundary file sets.

For more information, click here

Source: U.S. Census Bureau, Geography Division, Cartographic Operations Branch