A discrete global grid of photointerpretation
The Forest Inventory and Analysis (FIA) Program of the Forest Service, U.S.Department of Agriculture, collects its data in three phases. The first phase is collection of photointerpretation data or dot counts, the second phase is field collection of FIA plot data, and the third phase is collection of Forest Health Monitoring data. This paper describes the development of the Phase 2 (P2) and Phase 3 (P3) grids and discusses the creation of a new grid for Phase 1 (P1), complete with an efficient indexing scheme, which is essentially equivalent to the historical dot count grids. The P2 grid consists of one field site per approximately 6,000 acres. To create the new P1 grid, we decomposed the P2 grid by a factor of 27 to obtain new proposed P1 photointerpretation cells of about 220 acres. The new grid can be used for initial photointerpretation points to determine area estimates for forested land.