The Triton


Devices keep track of yachts on the water


As we continue to watch the tragic events surrounding Malaysia Airlines Flight 370, the news headlines continue to blast the same message: How does a jet just disappear?


In general, the safety regulations that affect the airline and maritime industries parallel each other in many ways. While the specific requirements are polar opposites in most cases, the major areas of concern are not. These areas include rules for design, construction, operation, safety, environmental protection, crew certification, and emergency response.



So what type of devices does a yacht carry to notify others of its position? Let us take a look at the most common ones.



Automatic Identification System (AIS). Following the terrorist events of Sept. 11, 2001, the member-states of the International Maritime Organization (IMO) enacted a series of safety and security regulations with a revision to the International Convention for the Safety of Life at Sea (SOLAS). These new rules included the requirement for all international trading vessels of 300 gross tons and greater to be equipped with AIS.

AIS works through a transponder. The unit automatically broadcasts information, such as a vessel’s position, speed and navigational status. This data is sent at regular intervals via a VHF transmitter that is built into the transponder. The yacht’s information originates from navigational sensors, typically a GPS unit and gyrocompass or satellite compass.



Other important information, such as the yacht’s name and call sign, is programmed into the AIS unit. The signals are received by AIS transponders fitted on other ships, yachts or on land-based systems, such as those used by Vessel Traffic Services. The received information is displayed on a screen or chart plotter, showing the other vessels’ positions in a format similar to that observed on a radar screen.

AIS provides many positive benefits. These include collision avoidance, search and rescue, and accident investigation.



Emergency Position-Indicating Radio Beacon (EPIRB). EPIRBs are tracking devices that aid in the detection and location of vessels in distress. In simplest terms, they are radio beacons that interface with the worldwide system known as COSPAS-SARSAT. This service is a satellite-based search and rescue (SAR) distress alert system. It was established in 1979 by the governments of Canada, France, the United States, and the former Soviet Union.



When manually activated, or automatically activated upon immersion, EPIRBs actively send out a distress signal. The signals are monitored worldwide at dedicated rescue centers. Non-geostationary satellites detect the location of the distress.



The ideal location for an EPIRB to be stored on a yacht is the open deck, unobstructed from any overhead structure. It should be attached to the yacht via a hydrostatic release unit (HRU). The HRU is a pressure-activated mechanism designed to automatically deploy when certain conditions are met. This occurs when the HRU is submerged to a maximum depth of four meters. The pressure of the water against a diaphragm within the sealed casing causes a plastic pin to be cut. Following this designed action, the containment bracket releases the casing and allows the EPIRB to float free.



Search and Rescue Transponder (SART). A SART is a self-contained, waterproof transponder intended for emergency use at sea. The device may be one of two types. It will be either a Radar-SART or a GPS-based AIS-SART.



The Radar-SART is used to locate a survival craft, life raft or distressed vessel. It does this by creating a series of dots on a rescuing ship’s radar display. The radar observer will see a distinct pattern on the radar screen that provides a bearing toward the distress location. Unlike an EPIRB, a Radar-SART will only respond to a 9 GHz X-band (3 cm) radar. It will not be seen on the S-band (10 cm) or any other type of radar.

The AIS-SART calculates position and time from a built-in GPS receiver. At an interval of once per minute, the position is actively sent as a series of eight identical position report messages. This scheme creates a high probability that at least one of the messages is sent on the highest point of a wave. The receiving rescue ship or aircraft is then provided an exact position, in addition to the visual bearing exhibited on the radar display.



Long Range Identification and Tracking (LRIT). LRIT equipment must carried by internationally trading ships of 300 gross tons or greater. This includes commercial yachts.



The LRIT information that is transmitted includes the vessel’s identity, location, date, and time of the position. Unlike AIS, which is limited to VHF-type of range, LRIT signals are received via satellite. While similar in function, there is no interface between LRIT and AIS equipment. They are independent of each other.

One of the more important distinctions between the two systems, apart from the obvious one of range, is that, where AIS is an open broadcast system, data derived through LRIT is available only to the recipients who are entitled to receive such information. In most cases, this is the government of a sovereign nation. Safeguards concerning the confidentiality of this data are built into the regulatory provisions. Governments are entitled to receive information about ships and yachts navigating within a distance not exceeding 1,000 nautical miles off their coast.



Voyage Data Recorder (VDR). A VDR is a data recording system designed for all vessels required to comply with the IMO’s regulations. The unit is designed to collect data from various sensors on board the vessel.



The VDR then digitizes, compresses and stores this information in an externally mounted protective storage unit. The protective storage unit is a tamper-proof unit designed to withstand extreme shock, impact, pressure and heat. The external factors are normally associated with a marine incident such as a fire, explosion, collision or sinking.



The protective storage unit may be in a retrievable fixed unit or free float unit (or combined with an EPIRB). The VDR is designed to store the last 24 hours of data. The idea is to recover this information for use in any incident investigation.



Beside the protective storage unit, the VDR system may consist of other recording control units, such as microphones, to store conversation made in the wheelhouse. The VDR is the maritime industry’s equivalent of a “black box” installed on commercial aircraft. VDRs are required to be installed on ships and yachts of 3,000 gross tons and greater.



Much of the above equipment can be considered intrusive, especially when dealing with the privacy issues of a yacht. However, knowing that these systems are active, functioning and transmitting when you need help can be reassuring if an emergency were to develop.


Capt. Jake DesVergers is chief surveyor for International Yacht Bureau (IYB), an organization that provides flag-state inspection services to yachts on behalf of several administrations. A deck officer graduate of the U.S. Merchant Marine Academy at Kings Point, he previously sailed as master on merchant ships, acted as designated person for a shipping company, and served as regional manager for an international classification society. Contact him at +1 954-596-2728 or Comments on this column are welcome at

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