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    Re: distance with atan2
    From: Charles Seitz
    Date: 2005 Nov 12, 14:37 -0500

    If for whatever reason you cannot use Atan2,  this equation will
    compute the great circle distance between two places on a spherical
    earth. Everything is expressed in radians.
    
    These are Borland Delphi (Pascal) functions and the extended data
    type has precision much greater than rquired for practical usage.
    
    ////////////// Great circle navigation /////////////////////
    
    function GcDis(const Lat1, Lon1, Lat2, Lon2: Extended): Extended;
    
    begin
    
         Result := 2*ArcSin(Sqrt(Sqr(Sin((Lat1-Lat2)/2)) +
    
          Cos(Lat1)*Cos(Lat2)*Sqr(Sin((Lon1-Lon2)/2))));
    
    end;
    
    function DegToRad(const Degrees: Extended): Extended;
    
    begin   Result := Degrees*(pi/180)   end;
    
    
    function RadToNm(const Radians: Extended): Extended;
    
    begin   Result := (60*180/pi)*Radians   end;
    
    
    
    ---  CHAS
    
    
    

       
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