Question 1

On an AIS display, what is the difference between a "physical", "synthetic" and "virtual" Aid to Navigation (AtoN) target?

Accepted Answer

A physical AtoN is a real buoy/structure fitted with its own AIS transmitter broadcasting its actual position; a synthetic AtoN is a real buoy without its own AIS unit, whose position is broadcast by a shore station on its behalf; a virtual AtoN is broadcast by a shore station to show a mark or hazard at a location where no physical buoy exists AIS Aids to Navigation come in three forms. A physical AtoN is an actual buoy or structure equipped with its own AIS transponder transmitting its real position. A synthetic AtoN refers to a real, physical buoy that does not carry its own AIS equipment, but a shore-based AIS station transmits a message showing its known, charted position. A virtual AtoN exists only electronically — a shore station broadcasts a message showing a mark (e.g. a new wreck or hazard) at a position where no physical buoy is placed, allowing mariners to see it on ECDIS/AIS displays until a physical aid can be deployed.

Question 2

You need to send a distress alert because the vessel is taking on water faster than the pumps can cope. Which message format and channel/priority is correct?

Accepted Answer

A "Mayday" distress call on Channel 16 / DSC distress alert, giving position, nature of distress and assistance required Grave and imminent danger requiring immediate assistance (e.g. uncontrolled flooding) requires a Mayday distress call / DSC distress alert — Pan-Pan is for urgency without immediate danger to life, and Securité is for navigational safety information.

Question 3

True or False: An EPIRB should be registered with the relevant national authority, and the registration details kept up to date so that a false alarm can be quickly resolved or a real activation correctly attributed.

Accepted Answer

True True. EPIRB registration links the unique beacon ID to vessel and contact details, allowing SAR authorities to quickly verify activations (genuine or false) and contact the vessel/owner — unregistered or out-of-date beacons slow down the SAR response and waste resources.