National Land Cover Database 2011 (NLCD 2011) is the most recent national land cover product created by the Multi-Resolution Land Characteristics (MRLC) Consortium. NLCD 2011 provides the capability to assess wall-to-wall, spatially explicit, national land cover changes and trends across the United States from 2001 to 2011. As with two previous NLCD land cover products NLCD 2011 keeps the same 16-class land cover classification scheme that has been applied consistently across the United States at a spatial resolution of 30 meters. NLCD 2011 is based primarily on a decision-tree classification of circa 2011 Landsat satellite data.
Tree cover data is obtained from the NLCD 2011 USFS Tree Canopy cartographic (3.2 GB) link on the NLCD site.
The U.S. Forest Service cartographic canopy product is designed for the standard user who requires the single best representation of tree canopy designed for most applications. This product consists of a single layer, percent tree canopy cover, with file pixel values ranging from 0 to 100 percent, with each individual value representing the area or proportion of that 30m cell covered by tree canopy. The product is then filtered and masked to eliminate obvious non-tree areas, and to create a more cartographically useful product. Although this approach more closely resembles the NLCD 2001 tree canopy protocol, the products still used different mapping methods and are not designed to be directly comparable for change analysis. The percent tree canopy cover layer was produced using a Random Forests (trademarked by Leo Breiman and Adele Cutler) regression algorithm.