/// <summary>
/// 由测站地心地固大地坐标计算在天球空间直角坐标的位置和速度。
/// </summary>
/// <param name="geo">大地坐标</param>
/// <param name="date">时间</param>
/// <param name="ellipsoid">参考椭球</param>
/// <param name="isKm">是否是千米</param>
/// <returns></returns>
public static MotionState GetMovingState(
GeoCoord geo,
Julian date,
Geo.Referencing.Ellipsoid ellipsoid = null,
bool isKm = true
)
{
double lat = geo.Lat;
double lon = geo.Lon;
double alt = geo.Altitude;
if (geo.Unit == AngleUnit.Degree)
{
lat = AngularConvert.DegToRad(lat);
lon = AngularConvert.DegToRad(lon);
}
if (ellipsoid == null)
{
ellipsoid = Geo.Referencing.Ellipsoid.WGS84;
}
double f = ellipsoid.Flattening;
double a = ellipsoid.SemiMajorAxis;
if (isKm)
{
a = ellipsoid.SemiMajorAxis / 1000.0;
}
// Calculate Local Mean Sidereal Time (theta)
double theta = date.GetLocalMeanSiderealTime(lon);
double c = 1.0 / Math.Sqrt(1.0 + f * (f - 2.0) * GeoMath.Sqr(Math.Sin(lat)));
double s = GeoMath.Sqr(1.0 - f) * c;
double achcp = (a * c + alt) * Math.Cos(lat);
XYZ pos = new XYZ();
pos.X = achcp * Math.Cos(theta);
pos.Y = achcp * Math.Sin(theta);
pos.Z = (a * s + alt) * Math.Sin(lat);
XYZ vel = GetVelocityInCelestialSphere(pos);
return(new MotionState(pos, vel));
}
public XYZ GetSatPos(OrbitParam param, double time, Geo.Referencing.Ellipsoid ellipsoid = null)
{
if (ellipsoid == null)
{
ellipsoid = Geo.Referencing.Ellipsoid.WGS84;
}
double u = ellipsoid.GM;
double a = param.SemiMajor;
double tao = param.EpochOfPerigee;
double e = param.Eccentricity;
double omega = param.ArgumentOfPerigee;
double bigOmega = param.LongOfAscension;
double i = param.Inclination;
//1.由 a 计算平均角速度
double n = Math.Sqrt(u / a / a / a);
//2.计算平近点角 M
double M = n * (time - tao);
//3.计算偏近点角，解开普勒方程。
double E = KeplerEqForEccAnomaly(M, e);
double sinE = Math.Sin(E);
double cosE = Math.Cos(E);
//4.计算矢径 r 和真近点角 f。则已经在极坐标中确定了卫星位置
double r = a * (1.0 - e * Math.Cos(E));
double f = 2.0 * Math.Atan(Math.Sqrt((1 + e) / (1 - e)) * Math.Tan(E / 2));
//5.计算轨道平面坐标（x’,y’）
double theta = f + omega;
double x1 = r * Math.Cos(theta);
double y1 = r * Math.Sin(theta);
XYZ xyz1 = new XYZ(x1, y1, 0);
//6.计算天球空间直角坐标（x，y，z）
XYZ rotation = new XYZ(-i, 0, -bigOmega);
XYZ xyz = xyz1.Rotate(rotation);
//7.计算瞬时地球坐标系
//Z轴旋转对应时刻的平格林尼治子午面的春分点时角
//8.计算到协议地球坐标系里,如WGS84
return(xyz);
}
