Distance and direction on a geoid

The simple picture of Earth is that of a sphere. However, as a result of its spinning it is somewhat flattened. distance calculations based on a spherical model can be as much as 0.5% off. 

This page contains links to download a Windows program equivalent of Ed Williams's FAI distance calculator.

FAI distance calculator: by Ed Williams. Calculations use the Vicenty Algorithm (Source: Direct and Inverse Solutions of Geodesics on the Ellipsoid with Application of Nested Equations, Survey Review, XXII, 176 (1975)). See also the Aviation Formulary (http://www.best.com/~williams/avform.htm), also by Ed Williams.

Ed Williams's code was adapted by Tony Lu to C++ classes that are used by the freeware GeoidTest program. The C++ classes are free to be used in non-commercial programs as long as Ed Williams 'sand Tony Lu's contributions are acknowledged.

Downloads updated on 29 March 2002.


Other Soaring Pilot Software programs:

  GPS_LOG,     Flight Display ESRI shape, E00 and Digital Elevation Data files to GPS_LOG WinCE map converters,   BLIPtoMAP overlay generator,and  Magellan GPS to IGC track format converter

For other things see the home page