# Course (navigation)

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{{Short description|Cardinal direction for steering}}
thumb|Instruments used to plot a course on a nautical chart.

In [navigation](/source/navigation), the '''course''' of a [watercraft](/source/watercraft) or [aircraft](/source/aircraft) is the [cardinal direction](/source/cardinal_direction) in which the craft is to be [steered](/source/Steering). The course is to be distinguished from the ''[heading](/source/Heading_(navigation))'', which is the direction where the watercraft's [bow](/source/Bow_(watercraft)) or the aircraft's [nose](/source/Nose_cone) is pointed.<ref name="Bartlett">
{{Citation|last=Bartlett|first=Tim|title=Adlard Coles Book of Navigations|year=2008|url=https://books.google.com/books?id=RWUQAAAAQBAJ&q=pilotage|page=176|publisher=Adlard Coles|isbn=978-0713689396}}</ref><ref name=Chapman>
{{cite book
 | last = Husick
 | first = Charles B.
 | title = Chapman Piloting, Seamanship and Small Boat Handling
 | publisher = Sterling Publishing Company, Inc.
 | date = 2009
 | page = 927
 | url = https://books.google.com/books?id=S4FwbS8StvEC&q=definition+nautical+course&pg=PA50 | isbn = 9781588167446 }}</ref><ref name=":0">{{Cite PHAK|year=2016}}</ref>{{pn|date=January 2025}}
The path that a vessel follows is called a '''track''' or, in the case of aircraft, '''ground track''' (also known as ''course made good'' or ''course over the ground'').<ref name="Bartlett" /> The intended track is a '''route'''.

== Discussion ==
{{further|Bearing (angle)#Arcs|Rhumb line#Introduction}}

{{multiple image
   | width1    = 200
   | footer    = True heading (left) and magnetic heading (right)
   | image1    = MISB ST 0601.8 - Platform Heading Angle.png
   | alt1      =
   | width2    = 200
   | image2    = MISB ST 0601.8 - Platform Magnetic Heading.png
   | alt2      =
   | caption2  =
  }}

For ships and aircraft, routes are typically [straight-line](/source/Great-circle_distance) segments between [waypoints](/source/Waypoint). A navigator determines the ''bearing'' (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 a ''course to steer'' that compensates for drift. The helmsman or pilot points the craft on a ''heading'' that 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.<ref name="Bartlett" /><ref name=":0" /> Course directions are specified in degrees from north, either true or magnetic. In [aviation](/source/aviation), north is usually expressed as 360°.<ref name="Nolan2010">{{cite book|author=Michael Nolan|title=Fundamentals of Air Traffic Control|url=https://books.google.com/books?id=6yhTiGC3ulcC&pg=PA201|date=2010|publisher=Cengage Learning|isbn=978-1-4354-8272-2|page=201|quote=For example, a runway heading north would have a magnetic heading of 360°.}}</ref> Navigators used [ordinal directions](/source/Cardinal_direction), instead of compass degrees, e.g. "northeast" instead of 45° until the mid-20th century when the use of degrees became prevalent.<ref>{{Cite book|url=https://books.google.com/books?id=xRqzoX04v5AC&q=cardinal+direction&pg=PA233|title=The Annapolis Book of Seamanship: Third Edition: Completely Revised, Expanded and Updated|last1=Rousmaniere|first1=John|last2=Smith|first2=Mark|date=1999|publisher=Simon and Schuster|isbn=9780684854205|pages=234|language=en}}</ref>

center|upright=3|Heading and track (A to B)<br>
1 – True North <br>
2 – Heading, the direction the vessel is "pointing towards" <br>
3 – Magnetic north, which differs from true north by the magnetic variation. <br>
4 – Compass north, including a two-part error; the magnetic variation (6) and the ship's own magnetic field (5) <br>
5 – Magnetic deviation, caused by vessel's magnetic field. <br>
6 – Magnetic variation, caused by variations in Earth's magnetic field. <br>
7 – Compass heading or compass course, before correction for magnetic deviation or magnetic variation. <br>
8 – Magnetic heading, the compass heading corrected for magnetic deviation but not magnetic variation; thus, the heading reliative to magnetic north. <br>
9, 10 – Effects of crosswind and tidal current, causing the vessel's track to differ from its heading. <br>
A, B – Vessel's track.

== See also ==
{{Portal|Geography}}
* [Acronyms and abbreviations in avionics](/source/Acronyms_and_abbreviations_in_avionics)
* [Glossary of navigation terms](/source/Glossary_of_navigation_terms)
* [Bearing (navigation)](/source/Bearing_(navigation))
* [Breton plotter](/source/Breton_plotter)
* [E6B](/source/E6B)
* [Great circle](/source/Great_circle)
* [Ground track](/source/Ground_track)
* [Navigation](/source/Navigation)
* [Navigation room](/source/Navigation_room)
* [Rhumb line](/source/Rhumb_line)

==References==
{{Reflist}}

==External links==
*[https://www.faa.gov/regulations_policies/handbooks_manuals/aviation/phak/ Pilot's Handbook of Aeronautical Knowledge]
*[https://www.faa.gov/regulations_policies/handbooks_manuals/aviation/phak/media/21_phak_glossary.pdf glossary]

{{DEFAULTSORT:Course (Navigation)}}
Category:Aircraft instruments
Category:Marine navigation
Category:Tracking
Category:Air navigation

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Adapted from the Wikipedia article [Course (navigation)](https://en.wikipedia.org/wiki/Course_(navigation)) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Course_(navigation)?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.