GMDSS Sea Area A1

GMDSS Sea Area A1 is defined as the area within the radiotelephone coverage of at least one VHF coast radio station or vessel traffic service in which continuous DSC alerting is available. In practice this typically extends between 20 and 50 nautical miles from shore, depending on antenna heights and terrain. Vessels operating exclusively within Sea Area A1 may meet GMDSS carriage requirements with a VHF radiotelephone with DSC capability on Channel 70, a NAVTEX receiver or other means of receiving maritime safety information, and a 406 MHz satellite EPIRB for escape from VHF coverage. For cadets and junior officers, Sea Area A1 is the operating area of the GMDSS Short Range Certificate, which qualifies the holder to operate the VHF installation. Navigating in A1 waters does not exempt a vessel from maintaining a continuous watch on VHF Channel 16 and Channel 70. The boundaries of A1 areas are published by national maritime authorities and may be extended as coast station infrastructure is upgraded. Vessels that routinely transit beyond A1 must carry the additional equipment prescribed for Areas A2, A3, or A4 as applicable.