+ // 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.)
+ int type = station->get_type();
+ if ( d2 < min_dist &&
+ (type == 4 || type == 5 || type == 6 || type == 12 || type == 13) )
+ {
+ double hdg_deg = 0.0;
+ if ( type == 4 || type == 5 ){
+ hdg_deg = station->get_multiuse();
+
+ } else if ( type == 6 ) {
+ int tmp = (int)(station->get_multiuse() / 1000.0);
+ hdg_deg = station->get_multiuse() - (tmp * 1000);
+
+ } else if ( type == 12 || type == 13 ) {
+ // 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;
+ SGGeod geod = SGGeod::fromCart(aircraft);
+ geo_inverse_wgs_84( geod, station->get_pos(), &az1, &az2, &s);
+ az1 = az1 - station->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 = station;
+ }
+ }
+
+ return nav;
+}
+
+
+// returns the closest entry to the give lon/lat/elev
+FGNavRecord *FGNavList::findClosest( double lon_rad, double lat_rad,
+ double elev_m, fg_nav_types type)
+{
+ FGNavRecord *result = NULL;
+ double diff;
+
+ double lon_deg = lon_rad * SG_RADIANS_TO_DEGREES;
+ double lat_deg = lat_rad * SG_RADIANS_TO_DEGREES;
+ int lonidx = (int)lon_deg;
+ diff = lon_deg - (double)lonidx;
+ if ( (lon_deg < 0.0) && (fabs(diff) > SG_EPSILON) ) {
+ lonidx -= 1;
+ }
+ lonidx += 180;
+
+ int latidx = (int)lat_deg;
+ diff = lat_deg - (double)latidx;
+ if ( (lat_deg < 0.0) && (fabs(diff) > SG_EPSILON) ) {
+ latidx -= 1;