AnMaster wrote:
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I was working on trying to find the cause why tower altitude set to 70 in
apt.dat wasn't correct and
caused ATC aircraft to end up under ground.
As far as I understood we use same format as x-plane for apt.dat? Then the
tower elevation in
apt.dat should be ft above ground.
FlightGear stores the tower altitude under /sim/tower/altitude-ft. ATC use this
as absolute altitude.
Shouldn't that property be renamed to "altitude-agl-ft" in order to indicate
that it is relative to
ground? That naming scheme is used under /position.
Or the property could be changed to give the altitude above sea level maybe?
Regards,
Arvid Norlander
This patch solves it but should be tested
-> it introduces /sim/tower/height-ft (which is /sim/tower/altitude-ft
under a new name) - this is the *height* of the tower, not the altitude
-> /sim/tower/altitude-ft now contains the "proper" altitude of the top
of tower ASL. This altitude is the height plus the ground elevation ASL(
so it's top of the tower ASL).
All things i could find referencing this property (tower view and atc
control aircraft) should be improved by the change
How it works:
when fg loads, the old code executes (before the scenery is loaded) and
uses the airport elevation as ground elevation
the new function is called after scenery loading, and will attempt to
obtain the scenery's ground elevation at the tower position. If it fails
, the airport elevation prevails.
Potential problems:
->the intended scenery tile may for some reason not be loaded and
get_elevation_m fails (there's an alert level warning for this)
-> given that the towers are an obstruction, i'm not sure if
globals->get_scenery()->get_elevation_m will return ground level or the
top of the tower. Can someone shed some light here?
Cheers,
Tiago
Index: fg_init.cxx
===================================================================
RCS file: /var/cvs/FlightGear-0.9/source/src/Main/fg_init.cxx,v
retrieving revision 1.192
diff -u -p -u -r1.192 fg_init.cxx
--- fg_init.cxx 14 Dec 2007 22:51:57 -0000 1.192
+++ fg_init.cxx 5 Jan 2008 23:25:52 -0000
@@ -729,19 +729,34 @@ static bool fgSetPosFromAirportID( const
#endif
-// Set current tower position lon/lat given an airport id
+// Set current tower position lon/lat and altitude given an airport id
static bool fgSetTowerPosFromAirportID( const string& id) {
const FGAirport *a = fgFindAirportID( id);
if (a) {
SGGeod tower = a->getTowerLocation();
fgSetDouble("/sim/tower/longitude-deg", tower.getLongitudeDeg());
fgSetDouble("/sim/tower/latitude-deg", tower.getLatitudeDeg());
- fgSetDouble("/sim/tower/altitude-ft", tower.getElevationFt());
- return true;
- } else {
- return false;
- }
+ fgSetDouble("/sim/tower/height-ft", tower.getElevationFt());
+ fgSetDouble("/sim/tower/altitude-ft", tower.getElevationFt() +
a->getElevation());
+ return true;
+ }
+ return false;
+}
+// calculates a more precise tower altitude (separated because it needs the
scenery loaded)
+static void fgSetTowerAltitudeAirportID( )
+{
+ double ground;
+
if(globals->get_scenery()->get_elevation_m(fgGetDouble("/sim/tower/latitude-deg"),
fgGetDouble("/sim/tower/longitude-deg"), 999999, ground, NULL))
+ {
+ ground+=fgGetDouble("/sim/tower/height-ft");
+ fgSetDouble("/sim/tower/altitude-ft",
fgGetDouble("/sim/tower/height-ft") + ground);
+ }
+ else
+ {
+ SG_LOG( SG_GENERAL, SG_ALERT,
+ "Unable to obtain exact elevation for tower, Using airport elevation"
<< '\n' );
+ }
}
struct FGTowerLocationListener : SGPropertyChangeListener {
@@ -751,9 +766,19 @@ struct FGTowerLocationListener : SGPrope
}
};
+struct FGTowerElevationListener : SGPropertyChangeListener {
+ void valueChanged(SGPropertyNode* node) {
+ if(node->getBoolValue()==true) fgSetTowerAltitudeAirportID();
+ }
+};
+
+
void fgInitTowerLocationListener() {
fgGetNode("/sim/tower/airport-id", true)
->addChangeListener( new FGTowerLocationListener(), true );
+ fgGetNode("/sim/sceneryloaded", true)
+ ->addChangeListener( new FGTowerElevationListener(), true );
+
}
// Set current_options lon/lat given an airport id and heading (degrees)
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