public static GeoPoint3 EcefToGeodetic(Vector3 ecef, GeoDatum datum)
{
const double precision2 = 1e-6;
const int maxIterations = 16;
var norm = ecef.Norm;
var phi = Math.Atan2(ecef.Y, ecef.X);
var theta0 = BasicMath.Asin(ecef.Z / ecef.Norm); // first approximation
var h0 = norm - datum.Semiminor; // first approximation
var theta = theta0;
var h = h0;
var error2 = double.PositiveInfinity;
for (var i = 0; i < maxIterations && error2 > precision2; i++)
{
var ecefPrime = new GeoPoint3(theta, phi, h).ToEcef(datum);
var normPrime = ecefPrime.Norm;
var thetaSphere = BasicMath.Asin(ecefPrime.Z / normPrime);
var hSphere = normPrime - datum.Semiminor;
theta += theta0 - thetaSphere;
h += h0 - hSphere;
error2 = Vector3.Distance2(ecef, ecefPrime);
}
return(new GeoPoint3(theta, phi, h));
}