GreatCircleCoordinates( )

Purpose

Determines the coordinates of a point a given distance and bearing along a great circle.

*Author*	*Date of code (original)*	*Updated on*	*Date of page (original)*	*Updated on*
Bill Thoen bthoen@ctmap.com	29Dec2000	29Dec2000	5Jan2001	10Jan2001

Restrictions on use

This module is distributed under the terms of the Lesser GNU General Public License. Restrictions on the use of this work in a commercial application or derivative work is described in the Lesser GNU General Public License page at: http://www.fsf.org/copyleft/lesser.html

Description

Calculates lat/lon coordinates from origin, azimuth and distance from origin. Destination coordinates are returned in decimal degrees. fDistance and fRadius must be in the same units.

External resources

none

Declare statement of sub_function. Include in your program. Copy/Paste if needed.

declare sub GreatCircleCoords (
       byval fLon0 as float,      'Origin longitude
       byval fLat0 as float,      'Origin latitude
       byval fAzimuth as float,   'Azimuth
       byval fDistance as float,  'Distance
       byval fRadius as float,    'Radius of earth
       fLon1 as float,            'Destination longitude
       fLat1 as float)            'Destination latitude

Returned value(s) (function only)

Other required declare statement(s). Include in your program. Copy/Paste if needed.

include "GC_Constants.def"
include "GC_Coordinates.def"

MapBasic Code. Copy/Paste if needed.

View code in separate window

Availability for download

GreatCircleFn.zip

Example

include "GC_Constants.def"
include "GC_Coordinates.def"

   dim fLat1, fLon1 as float

   call GreatCircleCoords (-105, 40, 30, 25,
      EARTH_RADIUS, fLon1, fLat1)

   'Now (fLon1, fLat1) are the coordinates of
   'the point 25 miles bearing 30 degrees (NNE)
   'from the origin at (-105,40).

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