RESCUE 21 DISTRESS SYSTEM COVERAGE
**Notice regarding VHF coverage charts below**: We plan to update the VHF coverage charts based upon the new Rescue 21 system now being deployed. However, the Rescue 21 Project office is devoting all their resources toward installing the new system and have consequently informed us that they will not be able to provide us updated charts for at least several more months. When they become available, we will quickly post them here. For now, the 1994 coverage plots are the best we have available. Thank you for your patience.
The Coast Guard currently operates a National Distress System, a network of about 300 VHF transceivers and antenna high-sites which are remotely controlled by regional communications centers to provide coverage extending out to at least 20 nautical miles from shore, and often much further. Coverage is reasonably continuous through most of the Atlantic, Gulf and Pacific Coasts, the Great Lakes, and many rivers. Many urban areas of the U.S. are also covered. This system serves as:
the primary means for mariners to contact the Coast Guard in a distress - over 20,000 distress calls are received yearly over this system,
the primary means for broadcasting urgent marine information to mariners, and
a command and control system for Coast Guard and other vessels.
Of the 25 largest U.S. cities ranked by population in the 1990 census by the Department of Commerce Census Bureau, 19 cities, i.e. 76%, are close to navigable waters and are within at least partial coverage of the U.S. Coast Guard’s VHF National Distress System.
Each National Distress System VHF site consists of a receiver guarding VHF Channel 16, the maritime distress, safety and calling channel, and a transceiver capable of operating on one of six fixed maritime channels. Two of these channels are always Channel 16 and 22A.
The system is not Global Maritime Distress & Safety System-compatible, coverage gaps exist in several locations, it cannot operate on public safety channels, it has no direction finding capability, distress calls cannot be received at a high site when the site is transmitting on any channel, and the system is near the end of its useful life. For these reasons, the Coast Guard began to modernize this system in 2003.
The National Distress System is operated by 45 Coast Guard Group and Section Command Centers, each acting as a Maritime Rescue Coordination Center having a specific area of responsibility.
VHF Distress Coverage Charts
Charts showing predicted areas of VHF National Distress System coverage can be downloaded in .jpg format. Coverage plots assume a mobile transmitter power of 1 watt or greater at sea level over water.
Predicted charts were created by C3CEN Remote Missions Systems Product Line using open source software RF Signal Propagation, Loss, and Terrain (RF SPLAT) analysis tool. The software calculates path loss based on the NTIA Longley-Rice Irregular Terrain Model (ITM) as well as the new Irregular Terrain with Obstructions Model (ITWOM v3.0). Terrain data was modeled based on the high resolution 1 arc-sec obtained from NASA’s Shuttle Radar Topography Mission (SRTM) flown in 2000. The coverage plots are displaying predicted regional coverage area based on line of sight between the Regional Fixed Facility VHF receive antenna and an antenna six feet above water level.
Coast Guard Group and Section Offices
Revised: 25 October 2016