GREAT-CIRCLE NAVIGATION

'Great-circle navigation' is the practice of navigating a vessel (such as a ship or aircraft) along a track that follows a great circle. A great circle track is the shortest distance between two points on the surface of the earth.

Contents

Methods

See also

Resources

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 appropriate latitude.
===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 waypoints 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

★ Rhumb line

Resources

★ Great Circle – from MathWorld Great Circle description, figures, and equations. Mathworld, Wolfram Research, Inc. c1999

★ Great Circle Mapper Interactive tool for plotting great circle routes.

★ Great Circle Calculator deriving (initial) course and distance between two points.

★ Great Circle Distance Graphical tool for drawing great circles over maps. Also shows distance and azimuth in a table.