From the Executive Summary: "The Federal Radionavigation Plan (FRP) reflects the official positioning, navigation, and timing (PNT) policy and planning for the Federal Government. Within the construct of the National PNT Architecture, the FRP covers both terrestrial- and space-based, common-use, federally operated PNT systems. Systems used exclusively by the military are covered in Chairman, Joint Chiefs of Staff Instruction 6130.01, DoD Master Positioning, Navigation, and Timing Plan (MPNTP). The FRP does not include systems that mainly perform surveillance and communication functions. The policies and operating plans described in this document cover the following PNT systems:  Global Positioning System (GPS)  Augmentations to GPS  Instrument Landing System (ILS)  Very High Frequency (VHF) Omnidirectional Range (VOR)  Distance Measuring Equipment (DME)  Tactical Air Navigation (TACAN)  Aeronautical Nondirectional Beacon (NDB)  Microwave Landing System (MLS)  Internet Time Service (ITS)  Radio Station WWVB signal  Two-Way Satellite Time Transfer (TWSTT)  Network Time Protocol (NTP). […] A major goal of DoD and DOT is to ensure that a mix of common-use (civil and military) systems is available to meet user requirements for accuracy, reliability, availability, continuity, integrity, coverage, operational utility, and cost; to provide adequate capability for growth; and to eliminate unnecessary duplication of services. The National PNT Architecture is a framework to assist United States Government (USG) organizations with investment decisions. Selecting a future PNT systems mix is a complex task, since user requirements vary widely and change with time."
U.S. Coast Guard Navigation Center: http://www.navcen.uscg.gov/