The data is available for distribution as one statewide file or tiled into 56 separate files by USGS 1:100,000 quadrangle. The format for distribution is either ARC/INFO export format or ArcView shapefile.
This dataset was produced with an intended application at the state or ecoregion level - geographic areas from several hundred thousand to millions of hectares in size. The data provide a course-filter approach to analyses, meaning that not every occurrence of animal habitat is mapped; only large, generalized distributions are mapped, based on the USGS 1:100,000 mapping scale in both detail and precision. Therefore, this dataset can be used appropriately for coarse-scale (> 1:100,000) applications, or to provide context for finer-level maps or applications.
Appropriate uses include: 1. statewide biodiversity planning; 2. regional and large area resource planning; 3. coarse-filter evaluation of potential impacts or benefits of major projects/initiatives on biodiversity - such as utility or transportation corridors, wilderness proposals, open space or recreation proposals; 4. environmental impact assessment for large projects such as military activities; 5. education at all levels for both students and citizens. Inappropriate uses of this data include: 1. Generating specific measurements from the data finer than the nearest thousand hectares; 2. Establishing exact boundaries for regulation or acquisition; 3. Establishing definite presence or absence of any element; 4. Determining abundance, health, or condition of any element; 5. Establishing a measure of accuracy of any other data by comparison with this dataset; 6. Combining this data with any other data finer than 1:100,000-scale for analysis; 7. Use of this data to map small areas (less than thousands of hectares) typically requiring mapping resolution at 1:24,000-scale and using aerial photographs or ground surveys; 8. Altering the data in anyway and redistributing it as a GAP product.
To attain a better estimate of accuracy, a formal statistical evaluation utilizing aerial videography validation techniques is in progress, and is due to be completed in 1998. The aerial videography may also provide training data for future updates of the land cover map.
All polygons include attributes for primary land cover and the percent of the polygon occupied by that cover, codes for the source of information from which the polygon was digitized, and codes identifying the digitizer. Other attributes may not be complete for all polygons, either because attributes did not apply to that particular polygon (primary crown cover does not apply to non-forested types), or attributes could not be filled for lack of information/restrictions of the minimum mapping unit.
Approximately 88% of polygons have a secondary cover attribute and percent secondary cover attribute; 15% polygons have a percentage crown attribute; 21 have an other land cover attribute; 11% have a wetlands attribute and 2% have a disturbance attribute.
ArcView shapefile format: Additional files in Dbase format are available with additional attributes and descriptions for codes:
covname.dbf: Full names of primary/secondary/other cover type codes
crown.dbf: Amount of crown closure (canopy) for primary forest types
wetlands.dbf: Description of wetland (or deep water type) occuring in
polygons, based on National Wetlands Inventory classification
scene.dbf: Codes and names of TM scenes used to attribute the polygons
and delineate the polygon boundary. Also includes the path,
row, date, and source of the images, as well as the person(s)
responsible for processing, digitizing and labeling from the
scene.
checker.dbf: Codes and names of persons involved in checking the polygon.
Includes the person's agency and date that they checked the
polygon.
disturanc.dbf: description of 10 type of disturbance recorded
source.dbf: citation of source used to attribute the land cover types
ARC/INFO export file format:
When the file is imported, eight additional INFO files are also imported:
LANDCOV.NAME (same as covname.dbf above) LANDCOV.WETLANDS LANDCOV.SCENE LANDCOV.CHECKER LANDCOV.CHECKED LANDCOV.DISTURBANCE LANDCOV.SOURCE LANDCOV.DISPLAY LANDCOV.RELATELANDCOV.DISPLAY is a lookup-table for displaying the land cover in ArcPlot. LANDCOV.RELATE is a relate file for performing relates (Links) between the coverage and the additional INFO files in ARC/INFO.