Preparing now for the future: U.S. civil radionavigation policy and planning

The United States expects to transition to space-based navigation in the next century. The Global Positioning System (GPS) is the system of choice for this transition. The Coast Guard differential GPS (DGPS) service is now operational and the Federal Aviation Administration plans to implement the Wide Area Augmentation System (WAAS) and the Local Area Augmentation System (LAAS) for civil aviation. The Federal Government is also planning to establish a nationwide DGPS service for land use based on the Coast Guard's system. The 1996 Federal Radionavigation Plan (FRP), the official source of U.S. dual-use radionavigation policy, sets forth the timetable for transitioning from land-based systems to GPS. The Presidential Decision Directive (PDD) on GPS, signed by President Clinton on March 28, 1996, sets forth a comprehensive national policy on the future management and use of GPS and related U.S. Government augmentations and presents a strategic vision that addresses a broad range of military, civil, commercial, and scientific interests, both in the U.S. and internationally. A major thrust of the PDD is to promote international cooperation in using GPS for peaceful purposes, and the acceptance of GPS and U.S. Government augmentations as standards for international use. The PDD directed the establishment of an Interagency GPS Executive Board (IGEB) to manage GPS and U.S. augmentations to GPS. In recognition of civil needs for GPS dual frequency correlation, the U.S. Is planning to implement a second GPS coded signal on the future Block IIF satellites. In the meantime, civil users will be allowed access to the carrier phase signal on the L2 frequency to satisfy two frequency applications. The U.S. Department of Transportation (DOT) and the U.S. Department of Defense (DOD) signed a Memorandum of Agreement in July 1997 documenting that an implementation plan would be jointly developed by March 1998 and that DOD would not interfere with civil use of the L2 carrier signal until the second coded civil signal is operational. In addressing the future GPS architecture, DOD, in cooperation with DOT, is also developing what is called a Capstone Requirements Document (CRD) for near, mid, and far term modernization of GPS.