Talk:Course (navigation)

From Wikipedia, the free encyclopedia
Jump to: navigation, search
WikiProject Transport / Maritime  (Rated Start-class, Mid-importance)
WikiProject icon This article is within the scope of WikiProject Transport, a collaborative effort to improve the coverage of articles related to Transport on Wikipedia. If you would like to participate, please visit the project page, where you can join the discussion and see a list of open tasks.
Start-Class article Start  This article has been rated as Start-Class on the project's quality scale.
 Mid  This article has been rated as Mid-importance on the project's importance scale.
Taskforce icon
This article is supported by the Maritime task force.
 

I doubt if the definition is precise enough[edit]

Course is the intended path of an airplane over the ground; or the direction of a line drawn on a chart representing the intended airplane path, expressed as the angle measured from a specific reference datum clockwise from 0° through 360° to the line. The reference can be true north or magnetic north and called true course or magnetic course respectively. —The preceding unsigned comment was added by Natasha2006 (talkcontribs) 17:41, 25 April 2007 (UTC).

Differing interpretations of "course" in air navigation[edit]

The differences in interpretation of "course" are noted in the Pilot Training Manual of a major European airline, which recommends that the term be avoided because it has different meanings depending on the part of the world one is in. It does not appear in ICAO documentation, which only defines track and heading.

In the past it was simple - the vectors course/true airspeed, wind direction/wind-speed, and track/gound-speed made up the triangle of velocities used in dead reckoning navigation and illustrated in the <RAF Pilots Flying Manual AP 129 1941 edition>.

However in 1967 this illustration was changed to show "required rack", "track made good", and "heading". The term course disappeared <RAF AP 1234 2nd Edition 1967>).

For an idea of the confusion over this term see these:

<GARMIN Internet site: (2009)> Course - The direction from the beginning landmark of a course to its destination (measured in degrees, radians, or mils), or the direction from a route waypoint to the next waypoint in the route segment. Track - Your current direction of travel relative to a ground position (same as Course Over Ground). [too many courses!!]

<AMERICAN PRACTICAL NAVIGATOR (HYDROGRAPHIC DEPARTMENT, US NAVY, BOWDITCH (1938)> Course - the angle which the centreline of the vessel makes with the meridian [looks more like heading, they do not mention compass correction!!]

<MATHEMATICS AND AIR NAVIGATION (1941) H. T. H. Piaggio, The Mathematical Gazette, Vol. 25, No. 264 (May, 1941), pp. 66-71> The drift is the difference between the course and the track. [correct, but hardly a definition of course!!]

Is anyone out there interested in helping sort this out??? Robert from Canada (talk) 05:34, 18 September 2009 (UTC)

Currently ground track is written mainly for satellites while it could also serve for air navigation. A link to wind triangle has been provided to improve the description of a key navigational requirement. Currently track (navigation) redirects to this article. Given that course is going out of use, with track in its place, a switch in titles may be considered.Rgdboer (talk) 02:29, 8 December 2014 (UTC)

Is crab angle the negative of drift angle?[edit]

"Crab angle is the amount of correction an aircraft must be turned into the wind in order to maintain the desired course. It is equal in magnitude but opposite in direction to the drift angle."

I believe that this is true only approximately and for small angles.

Consider an airplane traveling east at 100 knots with a 70-knot wind from the north. The drift angle is atan(70/100) ~= 35 degrees. But, to counter that 7-knot wind, the airplane must be crabbed -asin(70/100) ~= -45 deg.

Increase the wind to 100 knots. Then the drift angle is 45 degrees and the crab angle must be -90 degrees; that is, the airplane must head directly north, just to stand still against the wind. — Preceding unsigned comment added by 38.122.49.58 (talk) 17:58, 31 March 2015 (UTC)

COG VS. SOG[edit]

please clarify these abbreviation (Course Over Ground & Speed Over Ground) in this article. At Last ... (talk) 11:51, 9 July 2016 (UTC)

Good suggestion, At Last. User:HopsonRoad 19:33, 10 July 2016 (UTC)

Reference for course[edit]

@Wouter van der Wal: Let's discuss your edit, where in you added, ", sea, or any other reference". You included a note that said, "For example; ship's use their log to display a course through water", which was formatted as a reference, but did not cite an actual reference to support your edit. We can agree that navigation is steering a vessel "through the water"; what seems to be unclear between us is whether the course has the water as a reference or the earth beneath it.

If you refer to Chapman Piloting & Seamanship, the course is defined solely by a point on the compass (i.e. over the ground). Likewise, The Allard Coles Book of Navigation cites only compass headings. If the water per se were the point of reference, that would be impractical, since in much navigation the water is a stream, not still. You may have in mind the track of a vessel, which may be conceptualized over water (when straight) or over land (as deflected by currents) or possibly a heading, the direction in which an aircraft or vessel is pointed.

If you have a different WP:Reliable source with a different definition, then let's cite it!

Sincerely, User:HopsonRoad 21:43, 19 March 2017 (UTC)

I believe that what Wouter van der Wal was referring to is the difference, for example, between "Course over the Ground" and "Course to Steer" (the latter being with reference to the water. See http://www.skysailtraining.co.uk/course_to_steer_example.htm for one explanation. --David Biddulph (talk) 22:08, 19 March 2017 (UTC)
@User:HopsonRoad
You're right, I have not elaborated fully on the use of the log. Course through water is mostly a radar principle calculated using gyro heading and log speed through water of a ship together with radar target data. As said in "Radar and ARPA manual vol. 3" by Alan Bole Alan Wall Andy Norris (I have no idea yet how to cite it correctly, my apologies for this) course through water is: "Direction of the ship’s movement through the water, defined by the angle between the meridian through its position and the direction of the ship’s movement through the water, expressed in angular units from true-north."
As David Biddulph said this is indeed also referred to as course to steer (thank you, David Biddulph ).
I hope this clears up everything. Again my apologies (for writing on your page) as I do not know my way around Wikipedia guidelines on inter-user communications yet Wouter van der Wal (talk) 22:39, 19 March 2017 (UTC)
Let's be clear, since it appears that we are all in agreement. All courses are expressed in terms of a compass direction (whether true or magnetic). The course over the ground is the path that will cause the vessel or aircraft to arrive at its destination, if adhered to in the presence of wind or water currents. The course to be steered or aircraft heading is the direction in which the bow or nose is pointed to achieve the desired course over the ground. Remember that we're including avigation, here. Is there something that I am missing in terms of a basic description? Cheers, User:HopsonRoad 22:52, 19 March 2017 (UTC)
A citation for course through the water is Bole, Alan G.; Wall, Alan D.; Norris, Andy (2013). Radar and ARPA Manual: Radar, AIS and Target Tracking for Marine Radar Users (3 ed.). Oxford: Butterworth-Heinemann. p. 552. ISBN 9780080977713.  or Fairhall, David; Peyton, Mike (2013). Pass Your Yachtmaster. London: Allard Coles Nautical. ISBN 9781408146286.  Cheers, User:HopsonRoad 00:29, 20 March 2017 (UTC)