These categories are further divided into subcategories that convey additional information about the cover type. This system of standardization facilitates the comparability of use across the country. Other classification approaches have been developed and used across the country, although many are based on the Anderson system. The smallest area mapped for urban classes, bodies of water, quarries and some agricultural areas is 10 acres. A minimum mapping unit of 40 acres is used for all other categories.
Maps are available in two formats.
The vector polygon format displays land cover information as points, lines, and areas. Software packages have been developed by the USGS's National Mapping Program to compile and execute the program that displays and manipulates LULC data. These programs are available on magnetic tape or floppy disk. A Cartographic Applications Software factsheet is also available on request. These maps are referenced by individual quadrangle, which is generally named for the largest town or city in the multi-county area.