DGS GP Rating Exit Exam key terms

The direction in which a ship's bow is pointing at any moment, measured in degrees clockwise from true or magnetic north. It differs from the course actually made good over the ground.

The horizontal angle from a reference direction, usually north, to a visible object such as a lighthouse or another vessel, measured clockwise and used to plot position lines on a chart.

A method of estimating a ship's position by applying the courses steered and speeds run since the last known fix, allowing for known current, without using new external position observations.

The horizontal reference level, normally lowest astronomical tide, from which depths and drying heights on a nautical chart are measured, so that charted soundings show the least water expected.

The lowest internal space of a ship's hull, where water from leaks, condensation and washing collects; it is drained by the bilge pumping system and must be kept free of oil contamination.

Measuring the depth of liquid in a tank or hold, by tape, gauge or float, to determine the quantity on board. Regular soundings detect leaks and must be recorded before and after transfers.

A high-speed centrifugal machine that separates water and solid impurities from fuel oil or lubricating oil so that the cleaned oil can be burned or reused safely in the machinery.

A boiler producing steam for services such as fuel heating, hot water and tank cleaning, separate from the main propulsion plant. Its water level, pressure and burner need regular checks.

A watertight compartment space between the ship's outer bottom shell and an inner watertight floor, used to carry ballast or fuel and to give strength and protection against grounding damage.

A narrow empty watertight space between two bulkheads or tanks that prevents leakage or contamination passing from one compartment to another, for example between fuel oil and fresh water tanks.

A block of a less noble metal, usually zinc or aluminium alloy, bolted to the hull or inside tanks; it corrodes instead of the steel, protecting it from rust, and is renewed when wasted.

A hinged or sliding steel door in a watertight bulkhead that can be closed to stop flooding spreading between compartments; it must be kept closed at sea unless in immediate use.

Loose timber, matting or similar material placed under and between cargo to spread weight, allow ventilation, separate parcels and protect the cargo and the ship's structure from damage.

Securing cargo with ropes, wires, chains or webbing to deck fittings or to other cargo so that it cannot shift in heavy weather or during the voyage.

The volume in cubic metres occupied by one tonne of a particular cargo in its stowed condition, used to plan how much space that cargo will need in a hold.

The space in a hold that is wasted and cannot be filled by cargo, caused by the shape of the compartment, the shape of the cargo, or by dunnage and securing arrangements.

The three things a fire needs to keep burning: fuel, oxygen and heat. Removing any one of them, for example by cooling, smothering or shutting off the fuel, puts the fire out.

A fire involving flammable liquids such as fuel oil, diesel or paint. It is best fought by smothering with foam, dry powder or carbon dioxide, never with a straight water jet.

A piped water system running through the ship, fed by fire pumps and fitted with hydrants and isolating valves, that supplies hoses and monitors for firefighting.

The lowest temperature at which a liquid gives off enough vapour to form an ignitable mixture near its surface; liquids with low flash points are the most dangerous to handle.

The marked area where crew and passengers assemble after the general alarm so that they can be counted, briefed and, if necessary, directed to the survival craft.

A waterproof suit that keeps a person's body dry and slows the loss of body heat in cold water; it must be donned quickly and checked for damage before use.

Emergency position-indicating radio beacon. When activated, by water or by hand, it transmits a distress alert carrying the ship's identity on 406 MHz to satellites so rescuers can locate the vessel.

A device that holds a liferaft to its cradle and releases it automatically when the ship sinks to about four metres, allowing the raft to float free and inflate.

Cardiopulmonary resuscitation: cycles of chest compressions and, if trained and willing, rescue breaths, given to a person who is not breathing normally to keep blood and oxygen moving until help arrives.

A stable side-lying position for an unconscious person who is breathing, which keeps the airway open and lets fluid drain from the mouth while waiting for further help.

A life-threatening condition in which the circulation fails to supply enough blood to the body's organs, shown by pale cold clammy skin, rapid weak pulse, thirst and confusion; keep the casualty warm and still.

Entering a tank, hold, duct or similar space with restricted access and poor natural ventilation, allowed only after atmosphere testing, with a permit, a standby man and rescue equipment ready.

A written authorisation for a specific high-risk job, recording the hazards, precautions, isolation and time limits, and signed by the responsible person before work starts.

Personal protective equipment: items worn by a worker such as helmet, gloves, safety shoes, goggles, ear protection and coveralls, chosen to reduce the risk of injury for the task.

The International Convention for the Prevention of Pollution from Ships, which sets rules on discharges of oil, noxious liquid substances, garbage, sewage and air emissions, and requires records and equipment on board.

A mandatory logbook in which all movements of oil, oily water transfers, discharges and disposal operations on board are recorded and signed for inspection by authorities.

Water taken on board to give stability, trim and draft; because it can carry invasive species between ports, it must be managed, exchanged or treated according to the Ballast Water Management Convention.

The international radiotelephony distress signal, spoken three times, used only when a ship or person is in grave and imminent danger and needs immediate assistance.

The international radiotelephony urgency signal, spoken three times, used when a vessel has a serious problem but is not yet in grave and imminent danger, for example engine failure.

Standard Marine Communication Phrases: a set of agreed English phrases and message formats used at sea so that vessels and shore stations with different first languages can understand each other clearly.

The designated maritime radiotelephone distress, safety and calling frequency; it is monitored continuously and used to call another station before moving to a working channel.