Cartographic Boundary File Description

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The cartographic boundary files are simplified representations of selected geographic areas from the Census Bureau’s MAF/TIGER geographic database.   These boundary files are specifically designed for small scale thematic mapping. 

When possible generalization is performed with intent to maintain the hierarchical relationships among geographies and to maintain the alignment of geographies within a file set for a given year.

To improve the appearance of shapes, areas are represented with fewer vertices than detailed TIGER/Line equivalents.  Some small holes or discontiguous parts of areas are not included in generalized files.

Generalized boundary files are clipped to a simplified version of the U.S. outline.  As a result, some off-shore areas may be excluded from the generalized files.  This simplified U.S. outline is available for download for reference.

Advantages

• Simplified shapes improve the appearance of geographic areas when displayed at small scales.
• These boundary files take up less disk space than their ungeneralized equivalents.
• Cartographic boundary files take less time to render on screen.

Limitations

• These files should not be used for:
  • geographic analysis including area or perimeter calculation.
  • geocoding addresses.
  • determining precise geographic area relationships.
• Some geographic areas are excluded from these files.
• Geographic areas may not align with the same areas from another year.

File Naming Convention

The 2010 cartographic boundary files are named gz_2010_ss_lll_vv_rr.zip where:

• ss = state fips code or 'us' for a national level file
• lll = summary level code
• vv = 2-digit version code
• rr = resolution level
  • 500k = 1:500,000
  • 5m = 1:5,000,000
  • 20m = 1:20,000,000

For a complete list of 2010 summary level codes for the cartographic boundary files, please see our Summary Level Codes Page.

For the naming convention of cartographic boundary files created prior to 2010, please see our naming convention page for previous versions.

Scale

Files are available at target map scales of:

• 1:500,000
• 1:5,000,000
• 1:20,000,000

Geographic areas are not available at all target scales.

Need More Detailed Files?

If the Cartographic Boundary files are not detailed enough to meet your needs, try one of our other types of TIGER Mapping Files.

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