Sea Area A1

Sea Area A1 is the GMDSS sea area within radiotelephone coverage of at least one VHF coast station with continuous Digital Selective Calling alerting, roughly 20 to 30 nautical miles offshore. SOLAS Chapter IV defines the four sea areas and sets carriage requirements by area: an A1 ship needs VHF with DSC on channel 70 and either a satellite EPIRB or a VHF DSC alerting capability, but not the MF or HF equipment that A2, A3, and A4 demand. The boundary is declared by the coastal administration and listed in IMO’s GMDSS Master Plan. Ships rig equipment for the most demanding area on their route.