- Great-circle navigation
**Great-circle navigation**is the practice of navigating a vessel (such as aship oraircraft ) along a track that follows agreat circle . A great circle track is the shortest distance between two points on the surface of theearth .**Methods**In order to construct a great circle track, the

navigator of a ship may employ several methods.**Gnomonic chart**A straight line drawn on this chart would represent a great circle track. When this is transferred to a Mercator chart, it becomes a curve. The positions are transferred at a convenient interval of

longitude and this is plotted on the Mercator chart with the appropriatelatitude .Spherical trigonometry Mathematically, it is possible to determine the distance of a great circle track between two known positions. Other features of the great circle track may also be calculated.

**Computer**software Software is available that allows a navigator to input a departure and arrival position to create a list of

waypoint s which follow a great circle track. Normally, such programs will also calculate the total distance, the distance between successive waypoints, and the courses to be followed between successive waypoints.**See also***

Great circle

*Great circle distance

*Rhumb line **Resources*** [

*http://mathworld.wolfram.com/GreatCircle.html Great Circle – from MathWorld*] Great Circle description, figures, and equations. Mathworld, Wolfram Research, Inc. c1999

* [*http://gc.kls2.com/ Great Circle Mapper*] Interactive tool for plotting great circle routes.

* [*http://williams.best.vwh.net/gccalc.htm Great Circle Calculator*] deriving (initial) course and distance between two points.

* [*http://www.acscdg.com/ Great Circle Distance*] Graphical tool for drawing great circles over maps. Also shows distance and azimuth in a table.

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