- FGNavRecord *nav = NULL;
- Point3D station;
- double d2; // in meters squared
- double min_dist
- = FG_NAV_MAX_RANGE*SG_NM_TO_METER*FG_NAV_MAX_RANGE*SG_NM_TO_METER;
-
- // find the closest station within a sensible range (FG_NAV_MAX_RANGE)
- for ( unsigned int i = 0; i < stations.size(); ++i ) {
- // cout << "testing " << current->get_ident() << endl;
- station = Point3D( stations[i]->get_x(),
- stations[i]->get_y(),
- stations[i]->get_z() );
-
- d2 = aircraft.distance3Dsquared( station );
-
- // cout << " dist = " << sqrt(d)
- // << " range = " << current->get_range() * SG_NM_TO_METER
- // << endl;
-
- // LOC, ILS, GS, and DME antenna's could potentially be
- // installed at the opposite end of the runway. So it's not
- // enough to simply find the closest antenna with the right
- // frequency. We need the closest antenna with the right
- // frequency that is most oriented towards us. (We penalize
- // stations that are facing away from us by adding 5000 meters
- // which is further than matching stations would ever be
- // placed from each other. (Do the expensive check only for
- // directional atennas and only when there is a chance it is
- // the closest station.)
- if ( d2 < min_dist &&
- (stations[i]->get_type() == 4 || stations[i]->get_type() == 5 ||
- stations[i]->get_type() == 6 || stations[i]->get_type() == 12) )
- {
- double hdg_deg = 0.0;
- if ( stations[i]->get_type() == 4 || stations[i]->get_type() == 5 ){
- hdg_deg = stations[i]->get_multiuse();
- } else if ( stations[i]->get_type() == 6 ) {
- int tmp = (int)(stations[i]->get_multiuse() / 1000.0);
- hdg_deg = stations[i]->get_multiuse() - (tmp * 1000);
- } else if ( stations[i]->get_type() == 12 ) {
- // oops, Robin's data format doesn't give us the
- // needed information to compute a heading for a DME
- // transmitter. FIXME Robin!
- }
-
- double az1 = 0.0, az2 = 0.0, s = 0.0;
- double elev_m = 0.0, lat_rad = 0.0, lon_rad = 0.0;
- double xyz[3] = { aircraft.x(), aircraft.y(), aircraft.z() };
- sgCartToGeod( xyz, &lat_rad, &lon_rad, &elev_m );
- geo_inverse_wgs_84( elev_m,
- lat_rad * SG_RADIANS_TO_DEGREES,
- lon_rad * SG_RADIANS_TO_DEGREES,
- stations[i]->get_lat(), stations[i]->get_lon(),
- &az1, &az2, &s);
- az1 = az1 - stations[i]->get_multiuse();
- if ( az1 > 180.0) az1 -= 360.0;
- if ( az1 < -180.0) az1 += 360.0;
- // penalize opposite facing stations by adding 5000 meters
- // (squared) which is further than matching stations would
- // ever be placed from each other.
- if ( fabs(az1) > 90.0 ) {
- double dist = sqrt(d2);
- d2 = (dist + 5000) * (dist + 5000);
- }
- }
-
- if ( d2 < min_dist ) {
- min_dist = d2;
- nav = stations[i];
- }