The Gap Analysis Program (GAP) Land Cover Viewer displays data on the vegetation and land use patterns of the continental United States. The GAP Land Cover Data Version 2.2 provides detailed information on the vegetation of the United States using consistent satellite base data and classification systems. This allows data users to make conservation or land use planning decisions for the entire range of a habitat type across administrative boundaries.
GAP Land Cover Data Version 2.2 combines ecological system data from previous GAP projects in the Southwest, Southeast, and Northwest United States with recently updated California data. For Alaska ,and areas of the continental United States, where ecological system-level GAP data has not yet been developed, data from the LANDFIRE project used. This approach allowed GAP mappers to construct a seamless representation of ecological system distributions across the continental United States and Alaska. In Hawaii, data created by the Hawaii GAP project was used. This data set uses a classification system developed by the project for Hawaii and not the ecological system.
The Alaska and Continental U.S. portion of the data set contains 680 Ecological systems and 28 land use, introduced vegetation or disturbed classes. The Hawaii data contains 28 natural vegetation classes and nine land use, introduced vegetation or disturbed classes.
Frequently, this high number of classes provides a level of detail that exceeds a user’s needs. To accommodate these users, we have crosswalked the ecological system level data to the five highest levels of the National Vegetation Classification System( NVC). The vegetation features used to distinguish these classes range from growth form, and climate regimes at the Class level to regional differences in substrate and hydrology at the Macrogroup level (Table 1; http://usnvc.org/data-standard/natural-vegetation-classification/). The NVC levels provide the user with a variety of options allowing the choice of making a map of the Continental U.S. with eleven classes at the NVC Class level to 583 classes at the Ecological system level.