Nautical Glossary

12 terms, every one tied to its primary source where applicable.

• Abeam

  Off the side of the vessel; perpendicular to the keel.

• Aft

  Toward or near the stern of the vessel.

• Bearing

  The horizontal direction of one terrestrial point from another, expressed as an angle measured clockwise from a reference direction (true, magnetic, or relative).

• Closest Point of Approach (CPA)

  The minimum predicted distance between two vessels on their current courses and speeds.

• Dead Reckoning (DR)

  A method of determining position by applying course steered and distance run from a known starting point, without external fixes.

• Deviation

  The angle between magnetic north and compass north, caused by the vessel's own magnetism.

• EPIRB

  Emergency Position-Indicating Radio Beacon — a 406 MHz satellite-monitored distress beacon that transmits the vessel's identity and position when activated.

• Gross Tonnage

  A measure of a vessel's overall internal volume, used to determine credentialing thresholds (OUPV is for vessels <100 GT carrying ≤6 passengers).

• Not Under Command (NUC)

  A vessel which through some exceptional circumstance is unable to maneuver as required by the Rules and is therefore unable to keep out of the way of another vessel (Rule 3(f)).

• Restricted in Ability to Maneuver (RAM)

  A vessel which from the nature of her work is restricted in her ability to maneuver as required by the Rules and is therefore unable to keep out of the way of another vessel (Rule 3(g)).

• Scope (anchoring)

  The ratio of the length of anchor rode deployed to the depth of water plus the height of the bow above the water; typical 7:1 in good conditions.

• Variation

  The angle between true north and magnetic north at a given location; published on charts and changes slowly with time.