lon_node = fgGetNode("/position/longitude-deg", true);
lat_node = fgGetNode("/position/latitude-deg", true);
alt_node = fgGetNode("/position/altitude-ft", true);
lon_node = fgGetNode("/position/longitude-deg", true);
lat_node = fgGetNode("/position/latitude-deg", true);
alt_node = fgGetNode("/position/altitude-ft", true);