/// <summary>
/// Returns new geodetic coordinate in radians
/// </summary>
/// <param name="glat1">Latitude in Radians</param>
/// <param name="glon1">Longitude in Radians</param>
/// <param name="faz">Bearing</param>
/// <param name="s">Distance</param>
/// <param name="ellipse">Earth Ellipse Values</param>
/// <returns>double[]</returns>
public static double[] Direct_Ell(double glat1, double glon1, double faz, double s, double[] ellipse)
{
glon1 *= -1; //REVERSE LONG FOR CALC 2.1.1.1
double EPS = 0.00000000005; //Used to determine if starting at pole.
double r, tu, sf, cf, b, cu, su, sa, c2a, x, c, d, y, sy = 0, cy = 0, cz = 0, e = 0;
double glat2, glon2, f;
//Determine if near pole
if ((Math.Abs(Math.Cos(glat1)) < EPS) && !(Math.Abs(Math.Sin(faz)) < EPS))
{
Debug.WriteLine("Warning: Location is at earth's pole. Only N-S courses are meaningful at this location.");
}
double a = ellipse[0]; //Equitorial Radius
f = 1 / ellipse[1]; //Flattening
r = 1 - f;
tu = r * Math.Tan(glat1);
sf = Math.Sin(faz);
cf = Math.Cos(faz);
if (cf == 0)
{
b = 0.0;
}
else
{
b = 2.0 * Math.Atan2(tu, cf);
}
cu = 1.0 / Math.Sqrt(1 + tu * tu);
su = tu * cu;
sa = cu * sf;
c2a = 1 - sa * sa;
x = 1.0 + Math.Sqrt(1.0 + c2a * (1.0 / (r * r) - 1.0));
x = (x - 2.0) / x;
c = 1.0 - x;
c = (x * x / 4.0 + 1.0) / c;
d = (0.375 * x * x - 1.0) * x;
tu = s / (r * a * c);
y = tu;
c = y + 1;
while (Math.Abs(y - c) > EPS)
{
sy = Math.Sin(y);
cy = Math.Cos(y);
cz = Math.Cos(b + y);
e = 2.0 * cz * cz - 1.0;
c = y;
x = e * cy;
y = e + e - 1.0;
y = (((sy * sy * 4.0 - 3.0) * y * cz * d / 6.0 + x) *
d / 4.0 - cz) * sy * d + tu;
}
b = cu * cy * cf - su * sy;
c = r * Math.Sqrt(sa * sa + b * b);
d = su * cy + cu * sy * cf;
glat2 = ModM.ModLat(Math.Atan2(d, c));
c = cu * cy - su * sy * cf;
x = Math.Atan2(sy * sf, c);
c = ((-3.0 * c2a + 4.0) * f + 4.0) * c2a * f / 16.0;
d = ((e * cy * c + cz) * sy * c + y) * sa;
glon2 = ModM.ModLon(glon1 + x - (1.0 - c) * d * f); //Adjust for IDL
//baz = ModM.ModCrs(Math.Atan2(sa, b) + Math.PI);
return(new double[] { glat2, glon2 });
}
