GMDSS A1, A2, A3, A4 Sea Areas

GMDSS (Global Maritime Distress and Safety System) divides the world’s oceans into four sea areas based on radio communication coverage. Area A1 covers nearshore regions within about 20–30 nautical miles of coastlines with reliable VHF radio coverage, used for short-range distress communication. Area A2 extends to approximately 100 nautical miles from coastlines, relying on MF radio for medium-range communication. Area A3 includes open ocean regions beyond A2, with coverage primarily via geostationary satellites (Inmarsat). Area A4 encompasses the polar regions, which currently lack satellite coverage, making communication more challenging in these remote waters.