/**
* Get the look angle for the observers position to the object
* @param[in] eci the object to find the look angle to
* @returns the lookup angle
*/
public CoordTopocentric GetLookAngle(Eci eci)
{
/*
* update the observers Eci to match the time of the Eci passed in
* if necessary
*/
Update(eci.GetDateTime());
/*
* calculate differences
*/
Vector range_rate = eci.Velocity() - m_eci.Velocity();
Vector range = eci.Position() - m_eci.Position();
range.w = range.Magnitude();
/*
* Calculate Local Mean Sidereal Time for observers longitude
*/
double theta = eci.GetDateTime().ToLocalMeanSiderealTime(m_geo.longitude);
double sin_lat = Math.Sin(m_geo.latitude);
double cos_lat = Math.Cos(m_geo.latitude);
double sin_theta = Math.Sin(theta);
double cos_theta = Math.Cos(theta);
double top_s = sin_lat * cos_theta * range.x
+ sin_lat * sin_theta * range.y - cos_lat * range.z;
double top_e = -sin_theta * range.x
+ cos_theta * range.y;
double top_z = cos_lat * cos_theta * range.x
+ cos_lat * sin_theta * range.y + sin_lat * range.z;
double az = Math.Atan(-top_e / top_s);
if (top_s > 0.0)
{
az += Global.kPI;
}
if (az < 0.0)
{
az += 2.0 * Global.kPI;
}
double el = Math.Asin(top_z / range.w);
double rate = range.Dot(range_rate) / range.w;
/*
* azimuth in radians
* elevation in radians
* range in km
* range rate in km/s
*/
return(new CoordTopocentric(az, el, range.w, rate));
}
/**
* Set the observers location
* @param[in] geo the observers position
*/
public void SetLocation(CoordGeodetic geo)
{
m_geo = geo;
m_eci.Update(m_eci.GetDateTime(), m_geo);
}