Innavigation,thecourseof awatercraftoraircraftis thecardinal directionin which the craft is to besteered.The course is to be distinguished from theheading,which is the direction where the watercraft'sbowor the aircraft'snoseis pointed.[1][2][3] The path that a vessel follows is called atrackor, in the case of aircraft,ground track(also known ascourse made goodorcourse over the ground).[1]The intended track is aroute.
Discussion
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For ships and aircraft, routes are typicallystraight-linesegments betweenwaypoints.A navigator determines thebearing(the compass direction from the craft's current position) of the next waypoint. Because water currents or wind can cause a craft to drift off course, a navigator sets acourse to steerthat compensates for drift. The helmsman or pilot points the craft on aheadingthat corresponds to the course to steer. If the predicted drift is correct, then the craft's track will correspond to the planned course to the next waypoint.[1][3]Course directions are specified in degrees from north, either true or magnetic. Inaviation,north is usually expressed as 360°.[4]Navigators usedordinal directions,instead of compass degrees, e.g. "northeast" instead of 45° until the mid-20th century when the use of degrees became prevalent.[5]
1 – True North
2 – Heading, the direction the vessel is "pointing towards"
3 – Magnetic north, which differs from true north by the magnetic variation.
4 – Compass north, including a two-part error; the magnetic variation (6) and the ship's own magnetic field (5)
5 – Magnetic deviation, caused by vessel's magnetic field.
6 – Magnetic variation, caused by variations in Earth's magnetic field.
7 – Compass heading or compass course, before correction for magnetic deviation or magnetic variation.
8 – Magnetic heading, the compass heading corrected for magnetic deviation but not magnetic variation; thus, the heading reliative to magnetic north.
9, 10 – Effects of crosswind and tidal current, causing the vessel's track to differ from its heading.
A, B – Vessel's track.
See also
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References
edit- ^abc Bartlett, Tim (2008),Adlard Coles Book of Navigations,Adlard Coles, p. 176,ISBN978-0713689396
- ^ Husick, Charles B. (2009).Chapman Piloting, Seamanship and Small Boat Handling.Sterling Publishing Company, Inc. p. 927.ISBN9781588167446.
- ^abFederal Aviation Administration (FAA) (2016-09-25).Pilot's Handbook of Aeronautical Knowledge: FAA-H-8083-25B.Ravenio Books.
- ^Michael Nolan (2010).Fundamentals of Air Traffic Control.Cengage Learning. p. 201.ISBN978-1-4354-8272-2.
For example, a runway heading north would have a magnetic heading of 360°.
- ^Rousmaniere, John; Smith, Mark (1999).The Annapolis Book of Seamanship: Third Edition: Completely Revised, Expanded and Updated.Simon and Schuster. p. 234.ISBN9780684854205.