private static ICoordinate GetV(ICoordinate p1, ICoordinate p2, double disNm)
{
return(EarthGeometry.GetV(
p1.ToVector3D(),
p2.ToVector3D(),
disNm / EarthRadiusNm).ToLatLon());
}
/// <summary>
/// Calculates the great circle path from x to y, and returns heading departing x.
/// x and y should be unique.
/// </summary>
/// <exception cref="ArgumentException"></exception>
public static double TrueHeading(ICoordinate x, ICoordinate y)
{
if (x.LatLonEquals(y))
{
throw new ArgumentException();
}
return(TrueHeading(GetW(x.ToVector3D(), y.ToVector3D()), x));
}
/// <summary>
/// Calculates the true heading of the given vector, at the given coordinate.
/// Return value is larger than 0 and smaller or equal to 360. Note: If v is
/// orthogonal to the earth surface, the return value may be any number
/// in that range.
/// </summary>
/// <exception cref="ArgumentException"></exception>
public static double TrueHeading(Vector3D v, ICoordinate c)
{
if (v.R == 0)
{
throw new ArgumentException("Length of v cannot be 0.");
}
if (c.Lat >= 90.0)
{
return(180);
}
if (c.Lat <= -90.0)
{
return(360);
}
// Normal vector to tangent plane of earth at c
var normal = c.ToVector3D();
// Projection of v onto the tangent plane
var projection = ProjectOnPlane(v, normal);
if (projection.R == 0)
{
return(360);
}
// vector that points towards north on the tangent plane
var north = ProjectOnPlane(new Vector3D(0, 0, 1), normal).Normalize();
var east = (-normal).Cross(new Vector3D(0, 0, 1)).Normalize();
// Calculate angle
var x = north.Dot(projection);
var y = east.Dot(projection);
var heading = Angles.ToDegree(Atan2(y, x));
var headingDeg = heading.Mod(360);
return(headingDeg == 0.0 ? 360.0 : headingDeg);
Vector3D ProjectOnPlane(Vector3D p, Vector3D unitNormalVec)
{
return(p - p.Dot(unitNormalVec) * unitNormalVec);
}
}
// delta: in degrees
public double GetAirDistance(ICoordinate point1, ICoordinate point2, double delta = 1.0)
{
if (point1.LatLonEquals(point2, 1E-5))
{
return(0.0);
}
v1 = point1.ToVector3D();
v2 = point2.ToVector3D();
double deltaAlpha = ToRadian(delta);
// Total distance
double r = EarthRadiusNm * SafeAcos(v1.Dot(v2));
// Total time required
double time = Integrate(GetOneOverGS, 0.0, r, deltaAlpha * EarthRadiusNm);
return(time * Ktas);
}
