The USDA Forest Service Forest Inventory and Analysis (FIA) is the primary source of authoritative information on status, condition, and trends of U.S. forests and the products and services they provide. FIA’s Resource Use Monitoring component consist of two data collection efforts- the Timber Products Output (TPO) and the Harvest Utilization (HU) studies. Through HU, FIA generates estimates of harvested volume left on site (logging residue).