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Census cartographic boundary files designed for thematic maps, not detailed analysis
Summary
Census staff reiterated that cartographic boundary files are generalized and clipped for performance at small scales (three published scales); they preserve topology for mapping but are not substitutes for TigerLine when performing distance or area analysis.
Kevin Holly explained the purpose and limitations of cartographic boundary files and walked through visual comparisons with TigerLine files.
"Cartographic boundary files are simplified representations of geographic area boundaries that are best used for small scale thematic mapping and web map applications," Holly said. He outlined the three published scales (1:20,000,000; 1:5,000,000; 1:500,000) and showed side‑by‑side comparisons where the cartographic files are clipped to representative coastlines and simplified to reduce coordinate complexity.
Using examples — Michigan (Great Lakes clipping), Florida (ocean and gulf limits), and Mississippi River boundary smoothing in Louisiana/Arkansas/Mississippi — Holly cautioned that cartographic files can visually differ from full‑detail TigerLine files and recommended using TigerLine products when precise boundaries or area/distance calculations are required.
