The Global Positioning System (GPS), which provides position, navigation, and timing data to users worldwide, has become essential to U.S. national security and a key tool in an expanding array of public service and commercial applications. The Air Force is in the process of modernizing GPS. In light of the importance of GPS, the modernization effort, and international efforts to develop new systems, the auditor undertook a broad review of GPS. Specifically, she assessed progress in: (1) acquiring GPS satellites; (2) acquiring the ground control and user equipment necessary to leverage GPS satellite capabilities; and (3) evaluated coordination among fed. agencies and other org. to ensure GPS missions can be accomplished. Illus.