/**
* Calculate satellite visibility.
*
* @param Predict_Sat $sat The satellite structure.
* @param Predict_QTH $qth The QTH
* @param float $jul_utc The time at which the visibility should be calculated.
*
* @return int The visiblity constant, 0, 1, 2, or 3 (see above)
*/
public function get_sat_vis(Predict_Sat $sat, Predict_QTH $qth, $jul_utc)
{
/* gboolean sat_sun_status;
gdouble sun_el;
gdouble threshold;
gdouble eclipse_depth;
sat_vis_t vis = SAT_VIS_NONE; */
$eclipse_depth = 0.0;
$zero_vector = new Predict_Vector();
$obs_geodetic = new Predict_Geodetic();
/* Solar ECI position vector */
$solar_vector = new Predict_Vector();
/* Solar observed az and el vector */
$solar_set = new Predict_ObsSet();
/* FIXME: could be passed as parameter */
$obs_geodetic->lon = $qth->lon * self::de2ra;
$obs_geodetic->lat = $qth->lat * self::de2ra;
$obs_geodetic->alt = $qth->alt / 1000.0;
$obs_geodetic->theta = 0;
Predict_Solar::Calculate_Solar_Position($jul_utc, $solar_vector);
Predict_SGPObs::Calculate_Obs($jul_utc, $solar_vector, $zero_vector, $obs_geodetic, $solar_set);
if (Predict_Solar::Sat_Eclipsed($sat->pos, $solar_vector, $eclipse_depth)) {
/* satellite is eclipsed */
$sat_sun_status = false;
} else {
/* satellite in sunlight => may be visible */
$sat_sun_status = true;
}
if ($sat_sun_status) {
$sun_el = Predict_Math::Degrees($solar_set->el);
if ($sun_el <= $this->threshold && $sat->el >= 0.0) {
$vis = self::SAT_VIS_VISIBLE;
} else {
$vis = self::SAT_VIS_DAYLIGHT;
}
} else {
$vis = self::SAT_VIS_ECLIPSED;
}
return $vis;
}
