GMDSS Sea Areas:
Sea Area A1:
This area is within coverage of VHF coast stations where digital selective calling alert (DSC) is available (CH. 70/156.525 MHz) so you must use VHF capable transceivers with DSC capabilities. Typically, this area could extend 30 to 40 nautical miles (56 to 74 km) from a coastal radio station.
Sea Area A2:
This excludes Sea Area A1 and provides coverage of at least one MF coast station and continuous DSC (2187.5kHz) alerting is available so a VHF and MF radio station set up is required. This area typically extends up to 180 nautical miles (330 km) offshore during daylight hours and 150 nautical miles (280 km) offshore during night time hours.
Sea Area A3:
Excluding Sea Areas A1 & A2, this area is within coverage of INMARSAT geostationary satellites. Here a complete VHF radio and either a MF/HF radio or INMARSAT station is required. This area covers 70-degrees North Latitude and 70-degrees South Latitude.
Sea Area A4:
This area excludes Sea Area’s A1, A2 & A3 and is essentially the polar regions. A complete VHF and MF/HF radio station must be used in this area. This covers 71-degrees North Latitude and above 71-degrees South Latitude.
RCC (rescue coordination center) - a unit responsible for promoting the efficient organisation of search and rescue operations within a search and rescue region.
Rescue Coordination Centre (RCC) means a designated coordination centre that acts as the national Search and Rescue Region's coordination centre and the international point of contact for search and rescue (SAR) services and that takes care of the continuous maintenance of coordination and communication preparedness and coordinates SAR operations within its Search and Rescue Sub-Region (SRS).