/// <summary>
/// Great circle distance between two positions.
///
/// From http://williams.best.vwh.net/avform.htm:
/// d=2*asin(sqrt((sin((lat1-lat2)/2))^2 +
/// cos(lat1)*cos(lat2)*(sin((lon1-lon2)/2))^2))
/// </summary>
/// <param name="coordinate"></param>
/// <returns>Angular distance along a great circle</returns>
public Angle Distance(Coordinate coordinate)
{
return(2 * Angle.Asin(Math.Sqrt(Math.Pow(((Latitude - coordinate.Latitude) / 2).Sin(), 2)
+ Latitude.Cos() * coordinate.Latitude.Cos() * Math.Pow(((Longitude - coordinate.Longitude) / 2).Sin(), 2))));
}
/// <summary>
/// Initial course of great circle going to coordinate
///
/// From http://williams.best.vwh.net/avform.htm:
///
/// mod
/// ( atan2
/// ( sin(lon1-lon2) * cos(lat2)
/// , cos(lat1)*sin(lat2) - sin(lat1)*cos(lat2)*cos(lon1-lon2)
/// )
/// , 2*pi
/// )
/// </summary>
/// <param name="coordinate">Target coordinate that we want to travel to</param>
/// <returns>initial bearing</returns>
public Bearing InitialCourse(Coordinate coordinate)
{
// TODO: resolve edge case: close to the poles
// if (Latitude.Cos() < .0001)
// return Latitude.Hemisphere == Latitude.HemisphereType.North ? Bearing.South : Bearing.North;
return(new Bearing(Angle.Atan2((Longitude - coordinate.Longitude).Sin() * coordinate.Latitude.Cos(), Latitude.Cos() * coordinate.Latitude.Sin() -
Latitude.Sin() * coordinate.Latitude.Cos() * (Longitude - coordinate.Longitude).Cos())));
}
public Coordinate(Latitude latitude, Longitude longitude)
{
Latitude = latitude;
Longitude = longitude;
}