GreatCircleAzimuth( )

Purpose

Determines the azimuth that the first point bears to the second.

*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

Returns the azimuth that the first point bears to the second along the great circle route between the two points. Points must be decimal degrees of Latitude and Longitude.

External resources

none

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

declare function GreatCircleAzimuth (
   byval fLon0 as float,  'Origin longitude
   byval fLat0 as float,  'Origin latitude
   byval fLon1 as float,  'Destination longitude
   byval fLat1 as float   'Destination latitude
   ) as float

Returned value(s) (function only)

Azimuth in decimal degrees

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

include "GC_Azimuth.def"
include "GC_Constants.def" '(Optional for caller)

MapBasic Code. Copy/Paste if needed.

View code in separate window

Availability for download

GreatCircleFn.zip

Example

dim fLat0, fLon0, fLat1, fLon1 as float
dim fAzimuth as float

   fLat0 = 40  fLon0 = -105
   fLat1 = 42  fLon1 = -72

   fAzimuth = GreatCircleAzimuth (fLon0, fLat0, fLon1, fLat1)

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