A GIS-based tool for estimating tree canopy cover on fixed-radius plots using high-resolution aerial imagery

Recent changes to the Forest Inventory and Analysis (FIA) Program's definition of forest land precipitated the development of a geographic information system (GIS)-based tool for efficiently estimating tree canopy cover for all FIA plots. The FIA definition of forest land has shifted from a density-related criterion based on stocking to a 10 percent tree canopy cover threshold. This definitional change required a consistent method of estimating tree canopy cover, which is now a core FIA variable, using a combination of field-based and image-based assessments. In order to accomplish the image-interpretation task for thousands of plots annually, the FIA program, working in collaboration with the Remote Sensing Applications Center, developed a GIS-based canopy cover tool. Design considerations for the tool include the following: desired precision of the tree canopy cover estimate, seamless use across regions, compatibility with the existing Forest Service streaming image technology, and ease-of-use for image interpreters. Data from this image interpretation effort will not only serve the needs of FIA, but will also be used to update the National Land Cover Dataset tree canopy cover data layer.