Recognising the need for standardisation of navigational terms used by the nautical profession, a Nautical Institute working party was set up to agree a number of basic definitions which could be used universally for teaching and in practice. The Department of Trade, Royal Navy, Royal Institute of Navigation and a nautical college contributed to the working party.
In 1981 the Marine Division of the Department of Trade accepted the new "Navigational Terms", and the following list indicates the terms that will be gradually phased in to DoT Navigational and Chartwork examinations over a period of time. During the phasing in period candidates may use either the old or new terminology in their examination answers. Other terms, not specifically mentioned in the DoT list, are subsequently defined as appropriate.
This booklet has been revised where necessary and the new terminology is used throughout. It is worth noting that course through the water becomes water track, and course made good becomes ground track.
The path followed or to be followed, between one position and another. This path may be that over the ground (Ground Track) or through the water (Water Track).
Ground Track is indicated by a double arrow in the direction of motion of the vessel.
The direction of a track, i.e. the angle that the track makes with true north.
The mean ground track actually achieved over a given period.
Heading (Ship's Head)
The horizontal direction of the ship's head, at any given moment. (This term does not necessarily require movement of the vessel.)
Course (Co)
The intended heading.
The course related to the compass used by the helmsman.
The direction towards which, a current and/or tidal stream flows. This is indicated by a triple arrow in the direction of motion, of the tidal stream
The distance covered in a given time due solely to the movement of a current and/or tidal stream.
The angular difference between the ground track and water track.
The effect of the wind in moving a vessel bodily to leeward.
The angular difference between the water track and the ship's heading.
Dead Reckoning
The process of maintaining, or predicting, an approximate record of progress by projecting course and distance from a known position.
DR Position (DR)
The general term for a position obtained by dead reckoning.
Specifically a position obtained using true course and distance run, the latter derived from the log or engine revolutions as considered most appropriate. This should take account of any effect due to the wind.
Estimated Position (EP)
The best possible approximation of a present or future position. It is based on course and distance since the last known position with an estimation made for leeway, set and drift, or by extrapolation from earlier fixes.
Directions
Heading, Courses and Track Angles should be given in degrees from 0° to 359° with North as zero.
Bearings may be given relative to North (0° to 359°), or they may be related to the ship's head from 0° to 359° relative.
The following suffixes should be used:
T if relative to True North
C if relative to Magnetic Compass North
M if relative to Magnetic North
G if relative to Gyro North
Navigational terms
Finding an Estimated Position
Making good an intended track
Note: If leeway is contained in a question, it must be applied on the answer paper so that only the water track (not the heading) is drawn on the chart.
Lesson 1.doc Navigational Terms DGR1999
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