/// <summary>
/// Reverse projection, from Cassini-Soldner to geographic.
/// </summary>
/// <param name="x">easting of point (meters).</param>
/// <param name="y">northing of point (meters).</param>
/// <param name="azi">azimuth of easting direction at point (degrees).</param>
/// <param name="rk">reciprocal of azimuthal northing scale at point.</param>
/// <returns>
/// <i>lat</i>, latitude of point and <i>lon</i>, longitude of point, in degress.
/// </returns>
/// <remarks>
/// A call to <see cref="Reverse(double, double, out double, out double)"/> followed
/// by a call to <see cref="Forward(double, double, out double, out double)"/> will
/// return the original (<paramref name="x"/>, <paramref name="y"/>) (to within roundoff),
/// provided that <paramref name="x"/> and <paramref name="y"/> are sufficiently small not to "wrap around" the earth.
/// The routine does nothing if the origin has not been set.
/// </remarks>
public (double lat, double lon) Reverse(double x, double y, out double azi, out double rk)
{
_meridian.Position(y, out var lat1, out var lon1, out var azi0);
_earth.Direct(lat1, lon1, azi0 + 90, x, out var lat, out var lon, out azi, out rk, out _);
return(lat, lon);
}
