The U. S. Geological Survey has completed the performance evaluation flight tests of the Aerial Profiling of Terrain System (APTS) and is now performing a series of application tests to determine its effectiveness and efficiency as an earth-science data collection tool. These tests are designed to evaluate the APTS at such tasks as positioning water wells, testing reliability of older maps, measuring elevations of kettle ponds, and profiling stream valleys for flood studies. The results of three application tests in Massachusetts are discussed: positioning water wells and measuring elevations along the Charles River; testing four older 1:24,000-scale quadrangle maps in the Plymouth area; and measuring elevations of several hundred kettle ponds near the Cape Cod Canal.