public RadianAngle GetBearingTo(GeoCoordinate destination)
{
if (IsEmpty)
{
throw new ArgumentException("Cannot compute bearing from unknown coordinate.");
}
if (destination.IsEmpty)
{
throw new ArgumentException("Cannot compute bearing to unknown coordinate.");
}
var φ1 = LatitudeRadians;
var λ1 = LongitudeRadians;
var φ2 = destination.LatitudeRadians;
var λ2 = destination.LongitudeRadians;
var Δλ = λ2 - λ1;
number y = MathA.Sin(Δλ) * MathA.Cos(φ2);
number x = MathA.Cos(φ1) * MathA.Sin(φ2) - MathA.Sin(φ1) * MathA.Cos(φ2) * MathA.Cos(Δλ);
return(MathA.Atan2(y, x));
}
public GeoCoordinate GetDestinationPoint(Length distance, RadianAngle bearing)
{
if (IsEmpty)
{
throw new ArgumentException("Cannot compute destination point from unknown coordinate.");
}
var φ1 = LatitudeRadians;
var λ1 = LongitudeRadians;
var δ = new RadianAngle(distance / EarthRadius);
var φ2 = MathA.Asin(MathA.Sin(φ1) * MathA.Cos(δ) + MathA.Cos(φ1) * MathA.Sin(δ) * MathA.Cos(bearing));
number y = MathA.Sin(bearing) * MathA.Sin(δ) * MathA.Cos(φ1);
number x = MathA.Cos(δ) - MathA.Sin(φ1) * MathA.Sin(φ2);
var Δλ = MathA.Atan2(y, x);
var λ2 = λ1 + Δλ;
// Normalize longitude to range -π ... +π (that is, -180° ... +180°)
λ2 = (λ2 + 3 * RadianAngle.PI) % (2 * Constants.PI) - RadianAngle.PI;
return(new GeoCoordinate(φ2, λ2));
}
