public static HorizontalCoordinate From(Vector3 vector)
{
Angle altitude = Angle.Zero;
altitude.Sine = vector.Z;
// Make X and Y components negative for zero azimuth at south
// with westward increasing values.
// Then change x and y calculations likewise in ToVector method
// and remove adjustment in From(EquatorialCoordinates) method.
Angle azimuth = Angle.ArcTangent(vector.X, vector.Y);
return(new HorizontalCoordinate(azimuth, altitude));
}
// Time not used in current calculation, but might be need in future refinements
public static EquatorialCoordinate From(EclipticCoordinate eclipticCoordinate, Time time)
{
// Calculate right ascension and declination
Angle angleEpsilon = Angle.FromDegrees(23.4392911); // obliquity of the ecliptic -- see Meeus, pg. 92
Angle angleRightAscension = Angle.ArcTangent(eclipticCoordinate.Longitude.Sine * angleEpsilon.Cosine - eclipticCoordinate.Latitude.Tangent * angleEpsilon.Sine, eclipticCoordinate.Longitude.Cosine);
angleRightAscension.NormalizePositive();
Angle angleDeclination = Angle.Zero;
angleDeclination.Sine = eclipticCoordinate.Latitude.Sine * angleEpsilon.Cosine + eclipticCoordinate.Latitude.Cosine * angleEpsilon.Sine * eclipticCoordinate.Longitude.Sine;
angleDeclination.NormalizeAroundZero();
return(new EquatorialCoordinate(angleRightAscension, angleDeclination));
}
public void GetAngleOffsets(HorizontalCoordinate objectCoord, ref Angle horzAngle, ref Angle vertAngle)
{
Vector3 objectVector = objectCoord.ToVector();
Vector3 horzObjectCross = Vector3.Cross(objectVector, -horzAxis);
Vector3 vertObjectCross = Vector3.Cross(objectVector, vertAxis);
horzObjectCross.Normalize();
vertObjectCross.Normalize();
double x = Vector3.Dot(horzObjectCross, vertAxis);
double y = Vector3.Dot(horzObjectCross, this.ViewCenterVector);
horzAngle = -Angle.ArcTangent(y, x);
x = Vector3.Dot(vertObjectCross, horzAxis);
y = Vector3.Dot(vertObjectCross, this.ViewCenterVector);
vertAngle = -Angle.ArcTangent(y, x);
}
public static HorizontalCoordinate From(EquatorialCoordinate equatorialCoordinate, GeographicCoordinate geographicCoordinate, Time time)
{
// Calculate hour angle
Angle localHourAngle = time.GreenwichSiderealTime - geographicCoordinate.Longitude - equatorialCoordinate.RightAscension;
// Calculate azimuth
Angle azimuth = Angle.ArcTangent(localHourAngle.Sine, localHourAngle.Cosine * geographicCoordinate.Latitude.Sine - equatorialCoordinate.Declination.Tangent * geographicCoordinate.Latitude.Cosine);
// Adjustment for azimuth eastward from north
azimuth += Angle.Straight;
azimuth.NormalizeAroundZero();
// Calculate altitude
Angle altitude = Angle.Zero;
altitude.Sine = geographicCoordinate.Latitude.Sine * equatorialCoordinate.Declination.Sine + geographicCoordinate.Latitude.Cosine * equatorialCoordinate.Declination.Cosine * localHourAngle.Cosine;
altitude.NormalizeAroundZero();
return(new HorizontalCoordinate(azimuth, altitude));
}
