Availability. Availability of 99.7% is specified in general and 99.9% is specified for critical waterways. This higher availability is achieved through redundant coverage. The availability may be further increased by decreasing the distance between reference stations.
Coverage Area. The system is designed to provide coverage for all harbor/harbor approach areas and other critical waterways for which the USCG provides aids to navigation. As a result, complete coverage of the coast line of the continental U.S. (CONUS) is provided and extends out to 37 km (20 nautical miles). It is expected that in the near future this coverage will be extended to cover the complete CONUS Coastal Navigation Zone which extends out to 93 km (50 nautical miles). Figure 3-2 shows the expected coverage area for the system as currently planned for deployment.