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LatLonForCourseAndDistance(lat1, lon1, tcl, d)

Last updated May 16, 2002

author

Tom Nunamaker

Version: 1 | Requires: CF5 | Library: MathLib

Description:
Calculates the latitude and longitude for a given latitude, longitude, true course and distance. Calculates complete latitude and longitude for a given position, true course and distance in NAUTICAL MILES!

Return Values:
Returns a string containing the latitude and longitude.

Example:

<cfoutput>
Example:<br>
Suppose point 1 is LAX: (33deg 57min N, 118deg 24min W)<br>
True course = 066 degrees<br>
Distance = 100 Nautical Miles<br>

Lat1 = 33.95  // calculated from: (33 + 57/60)<br>
Lon1 = 118.4  // calculated from: (118 + 24/60)<br>
<cfset pair = LatLonForCourseAndDistance(33.95,118.4,66,100)>
#listfirst(pair)# = 34degrees 37min N<br>
Lon = #listlast(pair)# = 116 degrees 33min W<br>
</cfoutput>

Parameters:

Name Description Required
lat1 Latitude of the first point in degrees. Yes
lon1 Longitude of the first point in degrees. Yes
tcl True course. Yes
d Distance in nuatical miles from lat1/lon1. Yes

Full UDF Source:

/**
 * Calculates the latitude and longitude for a given latitude, longitude, true course and distance in nautical miles.
 * This function uses forumlae from Ed Williams Aviation Foundry website at http://williams.best.vwh.net/avform.htm.
 * 
 * @param lat1 	 Latitude of the first point in degrees. (Required)
 * @param lon1 	 Longitude of the first point in degrees. (Required)
 * @param tcl 	 True course. (Required)
 * @param d 	 Distance in nuatical miles from lat1/lon1. (Required)
 * @return Returns a string containing the latitude and longitude. 
 * @author Tom Nunamaker (tom@toshop.com) 
 * @version 1, May 16, 2002 
 */
function LatLonForCourseAndDistance(lat1,lon1,tc,d) {
	var lat = 1;
	var lon = 1;

	tc = tc * pi() / 180;
	d = d * pi()/(180*60);
	lat1 = lat1 * pi()/180;
	lon1 = lon1 * pi()/180;  
	lat = asin(sin(lat1)*cos(d)+cos(lat1)*sin(d)*cos(tc));
  
	if (abs(lat) IS pi()/2) lon = lon1;
	else lon = properMod(lon1-asin(sin(tc)*sin(d)/cos(lat))+pi(),2*pi()) - pi() ;

	lat = lat * 180/pi();
	lon = lon * 180/pi();
	
	return lat & "," & lon;
}
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