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This calculator computes the great circle distance between two points on the
earth's surface.
The program is operated by entering two geographic points and then pressing
the Calculate button. The entry form allows you to enter geographic
position in degrees, minutes, and seconds. The calculator computes distance in
kilometers and also computes the true bearing from the origin to the
destination. All entries are cleared by pressing the Clear button
| Notes
A great circle is the intersection of a sphere with a plane passing through the center of the sphere. Arcs of great circles represent the shorest route between two points on the surface of the sphere. The equator is a great circle as are all meridians of longitude. The great circle distance and bearing between two points can be calculated easily given the latitudes and longitudes of the origin and destination using the following formula from spherical trigonometry:
In applying the above formula, south latitudes and west longitudes are treated as negative angles. Note: When the origin is exactly at a pole, the bearing or course to the destination cannot be determined, why? The
formulas above assume that the earth is spherical. To obtain more
accurate distances, this calculator implements a method shown in
chapter 10 of [1]. I've used the WGS 1984 parameters for the earth's
equatorial radius and ellipsoid flattening given in [2]. |