/// <summary>
/// Обратная геодезическая задача (Vincenty's formula)
/// </summary>
/// <param name="B1"></param>
/// <param name="L1"></param>
/// <param name="B2"></param>
/// <param name="L2"></param>
/// <param name="S"></param>
/// <param name="A12"></param>
/// <param name="A21"></param>
public static void InverseProblemVincenty(double B1, double L1, double B2, double L2, Ellipsoid ellipsoid, out double S, out double A12, out double A21)
{
//широта, долгота в радианы
//B1 *= PI / 180;
//L1 *= PI / 180;
//B2 *= PI / 180;
//L2 *= PI / 180;
//приведенная широта
double U1 = Atan((1 - ellipsoid.f) * Tan(B1));
double U2 = Atan((1 - ellipsoid.f) * Tan(B2));
double L = L2 - L1;
double λ = L;
double λ1;
double sigma;
//косинус квадрат
double cos2_alpha;
//cos(2*sigma_m)
double cos_2sigma;
do
{
λ1 = λ;
double sin_sigma = Sqrt(Pow(Cos(U2) * Sin(λ), 2) + Pow(Cos(U1) * Sin(U2) - Sin(U1) * Cos(U2) * Cos(λ), 2));
double cos_sigma = Sin(U1) * Sin(U2) + Cos(U1) * Cos(U2) * Cos(λ);
sigma = Atan(sin_sigma / cos_sigma);
double sin_alpha = (Cos(U1) * Cos(U2) * Sin(λ)) / sin_sigma;
//косинус квадрат
cos2_alpha = 1 - Pow(sin_alpha, 2);
cos_2sigma = Cos(sigma) - (2 * Sin(U1) * Sin(U2)) / cos2_alpha;
double C = ellipsoid.f / 16 * cos2_alpha * (4 + ellipsoid.f * (4 - 3 * cos2_alpha));
λ = L + (1 - C) * ellipsoid.f * sin_alpha * (sigma + C * sin_sigma * (cos_2sigma + C * cos_sigma * (-1 + 2 * Pow(cos_2sigma, 2))));
}while (Abs(λ - λ1) > 1E-14);
double u2 = cos2_alpha * (Pow(ellipsoid.a, 2) - Pow(ellipsoid.b, 2)) / Pow(ellipsoid.b, 2);
double A = 1 + u2 / 16384 * (4096 + u2 * (-768 + u2 * (320 - 175 * u2))); //было 320 * 175
double B = u2 / 1024 * (256 + u2 * (-128 + u2 * (74 - 47 * u2)));
double deltaSigma = B * Sin(sigma) * (cos_2sigma + B / 4.0 * (
Cos(sigma) * (-1 + 2 * Pow(cos_2sigma, 2)) -
B / 6 * cos_2sigma * (-3 + 4 * Pow(Sin(sigma), 2)) * (-3 + 4 * Pow(cos_2sigma, 2))));
S = ellipsoid.b * A * (sigma - deltaSigma);
A12 = Atan((Cos(U2) * Sin(λ)) / (Cos(U1) * Sin(U2) - Sin(U1) * Cos(U2) * Cos(λ)));
A21 = Atan((Cos(U1) * Sin(λ)) / (-Sin(U1) * Cos(U2) + Cos(U1) * Sin(U2) * Cos(λ)));
A12 *= 180 / PI;
A21 = A21 * 180 / PI + 180;
}
/// <summary>
/// Инициализирует новый экземпляр класса <see cref="CoordinateConverter"/>.
/// </summary>
/// <param name="ellipsoid"> Эллипсоид, на котором выполняется преобразование координат. </param>
public CoordinateConverter(Ellipsoid ellipsoid)
{
this.ell = ellipsoid;
}