public Coordiantes eciToEcf(Coordiantes eci, double gmst)
{
// ccar.colorado.edu/ASEN5070/handouts/coordsys.doc
//
// [X] [C -S 0][X]
// [Y] = [S C 0][Y]
// [Z]eci [0 0 1][Z]ecf
//
//
// Inverse:
// [X] [C S 0][X]
// [Y] = [-S C 0][Y]
// [Z]ecf [0 0 1][Z]eci
double x = (eci.x * Math.Cos(gmst)) + (eci.y * Math.Sin(gmst));
double y = (eci.x * (-Math.Sin(gmst))) + (eci.y * Math.Cos(gmst));
// double { z } = eci;
double z = eci.z; //TODO: Verify this line
Coordiantes ecf = new Coordiantes();
ecf.x = x;
ecf.y = y;
ecf.z = z;
return(ecf);
// return {
// x,
// y,
// z,
// };
}
public Geodetic eciToGeodetic(Coordiantes eci, double gmst)
{
// http://www.celestrak.com/columns/v02n03/
double a = 6378.137;
double b = 6356.7523142;
double R = Math.Sqrt((eci.x * eci.x) + (eci.y * eci.y));
double f = (a - b) / a;
double e2 = ((2 * f) - (f * f));
double longitude = Math.Atan2(eci.y, eci.x) - gmst;
while (longitude < -pi)
{
longitude += twoPi;
}
while (longitude > pi)
{
longitude -= twoPi;
}
double kmax = 20;
double k = 0;
double latitude = Math.Atan2(
eci.z,
Math.Sqrt((eci.x * eci.x) + (eci.y * eci.y))
);
double C = 0;
while (k < kmax)
{
C = 1 / Math.Sqrt(1 - (e2 * (Math.Sin(latitude) * Math.Sin(latitude))));
latitude = Math.Atan2(eci.z + (a * C * e2 * Math.Sin(latitude)), R);
k += 1;
}
double height = (R / Math.Cos(latitude)) - (a * C);
Geodetic geodetic = new Geodetic();
geodetic.longitude = longitude;
geodetic.latitude = latitude;
geodetic.height = height;
return(geodetic);
}
public Coordiantes ecfToEci(Coordiantes ecf, double gmst)
{
// ccar.colorado.edu/ASEN5070/handouts/coordsys.doc
//
// [X] [C -S 0][X]
// [Y] = [S C 0][Y]
// [Z]eci [0 0 1][Z]ecf
//
double X = (ecf.x * Math.Cos(gmst)) - (ecf.y * Math.Sin(gmst));
double Y = (ecf.x * (Math.Sin(gmst))) + (ecf.y * Math.Cos(gmst));
double Z = ecf.z;
Coordiantes eci = new Coordiantes();
eci.x = X;
eci.y = Y;
eci.z = Z;
return(eci);
}
public Coordiantes geodeticToEcf(Geodetic geodetic)
{
double longitude = geodetic.longitude;
double latitude = geodetic.latitude;
double height = geodetic.height;
double a = 6378.137;
double b = 6356.7523142;
double f = (a - b) / a;
double e2 = ((2 * f) - (f * f));
double normal = a / Math.Sqrt(1 - (e2 * (Math.Sin(latitude) * Math.Sin(latitude))));
double x = (normal + height) * Math.Cos(latitude) * Math.Cos(longitude);
double y = (normal + height) * Math.Cos(latitude) * Math.Sin(longitude);
double z = ((normal * (1 - e2)) + height) * Math.Sin(latitude);
Coordiantes ecf = new Coordiantes();
ecf.x = x;
ecf.y = y;
ecf.z = z;
return(ecf);
}
public PositionAndVelocity()
{
position_ECI = new Coordiantes();
velocity_ECI = new Coordiantes();
}
