/// <summary>
/// ''' The along-track distance, calculated from the start point to the closest point on the path to the given point.
/// ''' </summary>
/// ''' <param name="at">The <see cref="Position">position</see> to caclulate the on track distance for.</param>
/// ''' <returns>The on track distance from the start of the stretch.</returns>
/// ''' <remarks></remarks>
public static Distance OnTrackDistance(this Stretch me, Position at)
{
const double r = EarthMeanRadiusMeters / 1000;
var s = Stretch.Between(me.From, at);
var d13 = s.Distance.Meters;
var dXt = me.CrossTrackDistance(at).Meters;
var d = Acos(Cos(d13 / r) / Cos(dXt / r)) * r;
return(Distance.FromMeters(Abs(d)));
}
public static bool IsOnTrack(this Stretch me, Position at, Distance maxOffTrackDistance) => me.CrossTrackDistance(at) <= maxOffTrackDistance;