EVTs are mapped using decision tree models, field data, Landsat imagery, elevation, and biophysical gradient data. Decision tree models are developed separately for each of the three lifeforms -tree, shrub, and herbaceous and are then used to generate lifeform specific EVT layers.
Attribute tables for LF grid data, served in CSV (comma separated values) file format, are available on the Data Distribution Site and landfire.gov. Generally, these attribute tables provide information pertaining to the grid class value along with class descriptions or labels for these values. Attribute tables, such as the Existing Vegetation Type, provide additional attribute fields that can provide crosswalk links to other classification themes. Color mapping fields are also provided within the attribute tables, providing a standardized, consistent LF color mapping schema for these data layers. The attribute files are in comma separated value (csv) format that can be easily converted to other formats to meet user needs.
The attribute tables are provided as a convenience as calculations with grid data will automatically drop attributes. For example, if a grid is clipped, the rowid, value, and count are the only attributes retained. Attribute fields can be reattached to the grid using a join attribute function having the "value" attribute as the link.
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