MARITIME – COMMUNICATION & REGULATION CALCULATOR
Gmdss Sea Area
A precise tool.
What is the Gmdss Sea Area & How does it work?
The Global Maritime Distress and Safety System (GMDSS) divides the world’s oceans into four sea areas (A1‑A4) based on the range of radio equipment that a vessel must carry to ensure continuous distress communication. Sea Area A1 covers waters within 150 nm of a coast station equipped with VHF, MF/HF, and digital selective calling (DSC). Vessels operating solely in this zone need only VHF with DSC, an EPIRB, and a SART. As the required communication range increases, additional equipment such as MF/HF radiotelephones, INMARSAT satellite terminals, and high‑frequency direction‑finding (HF‑DF) become mandatory, moving the vessel into Sea Areas A2, A3, or A4.
\text{SeaArea}=\begin{cases}
A1 & \text{if } \text{INMARSAT}\land\text{MF/HF}\land\text{VHF}\land\text{EPIRB}\land\text{SART}\\
A2 & \text{if } \text{MF/HF}\land\text{VHF}\land\text{EPIRB}\land\text{SART}\\
A3 & \text{if } \text{VHF}\land\text{EPIRB}\land\text{SART}\\
A4 & \text{otherwise}
\end{cases}
SeaArea = GMDSS sea‑area classification based on equipment
Parameters
Result
—
Frequently Asked Questions
What is GMDSS Sea Area A1?
Sea Area A1 covers waters within 150 nm of a coast station equipped with VHF, MF/HF, and DSC. Vessels in this area need only VHF with DSC, an EPIRB, and a SART.
What equipment is required for Sea Area A2?
Sea Area A2 requires additional equipment such as MF/HF radio and Inmarsat-B satellite phone beyond what is needed in Sea Area A1.
How does Sea Area A3 differ from A2?
Sea Area A3 includes the requirements of A2 but also mandates a satellite distress beacon (SART) and an Inmarsat-C satellite phone for enhanced communication capabilities.
What is the primary difference between Sea Area A4 and other areas?
Sea Area A4 covers all waters beyond Sea Areas A1, A2, and A3. It requires the most advanced equipment including Inmarsat-A satellite phone and a high-frequency (HF) radio for long-range communication.
Can a vessel operate in multiple GMDSS Sea Areas?
Yes, vessels can operate in multiple Sea Areas depending on their route. They must carry the equipment required for the most demanding area they will enter.
What is the purpose of DSC in GMDSS Sea Areas?
DSC (Digital Selective Calling) is used to alert nearby ships and coast stations in case of distress, allowing for quicker response times.
How does a vessel determine which GMDSS Sea Area it is operating in?
A vessel determines its Sea Area based on its proximity to coast stations equipped with different communication technologies and the specific equipment it carries.
Results are for informational purposes only and do not constitute professional advice.