]> git.mxchange.org Git - flightgear.git/blobdiff - src/ATC/trafficcontrol.cxx
functional radio signal attenuation
[flightgear.git] / src / ATC / trafficcontrol.cxx
index 43859b1883d8e7cbca7ef9b6a50c8cdd82dd44e1..15520295a5ec24296b6b9fd84acfa95c08c80406 100644 (file)
@@ -25,6 +25,9 @@
 #endif
 
 #include <algorithm>
+#include <math.h>
+#include <stdlib.h>
+#include <deque>
 
 #include <osg/Geode>
 #include <osg/Geometry>
@@ -47,6 +50,8 @@
 #include <Airports/groundnetwork.hxx>
 #include <Airports/dynamics.hxx>
 #include <Airports/simple.hxx>
+#define WITH_POINT_TO_POINT
+#include "itm.cpp"
 
 using std::sort;
 
@@ -86,7 +91,7 @@ time_t ActiveRunway::requestTimeSlot(time_t eta)
                 }
             } else {
                 if ((((*j) - (*i)) > (separation * 2))) {       // found a potential slot
-                    // now check whether this slow is usable:
+                    // now check whether this slot is usable:
                     // 1) eta should fall between the two points
                     //    i.e. eta > i AND eta < j
                     //
@@ -193,6 +198,11 @@ void FGTrafficRecord::setPositionAndIntentions(int pos,
     }
     //exit(1);
 }
+/**
+ * Check if another aircraft is ahead of the current one, and on the same 
+ * return true / false is the is/isn't the case.
+ *
+ ****************************************************************************/
 
 bool FGTrafficRecord::checkPositionAndIntentions(FGTrafficRecord & other)
 {
@@ -469,7 +479,7 @@ bool FGATCInstruction::hasInstruction()
 
 FGATCController::FGATCController()
 {
-    cerr << "running FGATController constructor" << endl;
+    //cerr << "running FGATController constructor" << endl;
     dt_count = 0;
     available = true;
     lastTransmission = 0;
@@ -478,7 +488,7 @@ FGATCController::FGATCController()
 
 FGATCController::~FGATCController()
 {
-     cerr << "running FGATController destructor" << endl;
+     //cerr << "running FGATController destructor" << endl;
 }
 
 string FGATCController::getGateName(FGAIAircraft * ref)
@@ -491,16 +501,18 @@ bool FGATCController::isUserAircraft(FGAIAircraft* ac)
     return (ac->getCallSign() == fgGetString("/sim/multiplay/callsign")) ? true : false; 
 };
 
-void FGATCController::transmit(FGTrafficRecord * rec, AtcMsgId msgId,
+void FGATCController::transmit(FGTrafficRecord * rec, FGAirportDynamics *parent, AtcMsgId msgId,
                                AtcMsgDir msgDir, bool audible)
 {
     string sender, receiver;
     int stationFreq = 0;
     int taxiFreq = 0;
+    int towerFreq = 0;
     int freqId = 0;
     string atisInformation;
     string text;
     string taxiFreqStr;
+    string towerFreqStr;
     double heading = 0;
     string activeRunway;
     string fltType;
@@ -509,28 +521,38 @@ void FGATCController::transmit(FGTrafficRecord * rec, AtcMsgId msgId,
     string transponderCode;
     FGAIFlightPlan *fp;
     string fltRules;
+    string instructionText;
+    int ground_to_air=0;
 
     //double commFreqD;
     sender = rec->getAircraft()->getTrafficRef()->getCallSign();
+    if (rec->getAircraft()->getTaxiClearanceRequest()) {
+        instructionText = "push-back and taxi";
+    } else {
+        instructionText = "taxi";
+    }
     //cerr << "transmitting for: " << sender << "Leg = " << rec->getLeg() << endl;
     switch (rec->getLeg()) {
+    case 1:
     case 2:
-    case 3:
         freqId = rec->getNextFrequency();
         stationFreq =
             rec->getAircraft()->getTrafficRef()->getDepartureAirport()->
             getDynamics()->getGroundFrequency(rec->getLeg() + freqId);
         taxiFreq =
             rec->getAircraft()->getTrafficRef()->getDepartureAirport()->
-            getDynamics()->getGroundFrequency(3);
+            getDynamics()->getGroundFrequency(2);
+        towerFreq = 
+            rec->getAircraft()->getTrafficRef()->getDepartureAirport()->
+            getDynamics()->getTowerFrequency(2);
         receiver =
             rec->getAircraft()->getTrafficRef()->getDepartureAirport()->
             getName() + "-Ground";
         atisInformation =
             rec->getAircraft()->getTrafficRef()->getDepartureAirport()->
-            getDynamics()->getAtisInformation();
+            getDynamics()->getAtisSequence();
         break;
-    case 4:
+    case 3:
         receiver =
             rec->getAircraft()->getTrafficRef()->getDepartureAirport()->
             getName() + "-Tower";
@@ -541,6 +563,7 @@ void FGATCController::transmit(FGTrafficRecord * rec, AtcMsgId msgId,
         string tmp = sender;
         sender = receiver;
         receiver = tmp;
+        ground_to_air=1;
     }
     switch (msgId) {
     case MSG_ANNOUNCE_ENGINE_START:
@@ -588,7 +611,7 @@ void FGATCController::transmit(FGTrafficRecord * rec, AtcMsgId msgId,
             receiver + ". Start-up approved. " + atisInformation +
             " correct, runway " + activeRunway + ", " + SID + ", squawk " +
             transponderCode + ". " +
-            "For push-back and taxi clearance call " + taxiFreqStr + ". " +
+            "For "+ instructionText + " clearance call " + taxiFreqStr + ". " +
             sender + " control.";
         break;
     case MSG_DENY_ENGINE_START:
@@ -606,11 +629,12 @@ void FGATCController::transmit(FGTrafficRecord * rec, AtcMsgId msgId,
         taxiFreqStr = formatATCFrequency3_2(taxiFreq);
         activeRunway = rec->getAircraft()->GetFlightPlan()->getRunway();
         transponderCode = rec->getAircraft()->GetTransponderCode();
+
         text =
             receiver + ". Start-up approved. " + atisInformation +
             " correct, runway " + activeRunway + ", " + SID + ", squawk " +
             transponderCode + ". " +
-            "For push-back and taxi clearance call " + taxiFreqStr + ". " +
+            "For " + instructionText + " clearance call " + taxiFreqStr + ". " +
             sender;
         break;
     case MSG_ACKNOWLEDGE_SWITCH_GROUND_FREQUENCY:
@@ -624,10 +648,18 @@ void FGATCController::transmit(FGTrafficRecord * rec, AtcMsgId msgId,
         text = receiver + ". Roger. " + sender;
         break;
     case MSG_REQUEST_PUSHBACK_CLEARANCE:
-        text = receiver + ". Request push-back. " + sender;
+        if (rec->getAircraft()->getTaxiClearanceRequest()) {
+            text = receiver + ". Request push-back. " + sender;
+        } else {
+            text = receiver + ". Request Taxi clearance. " + sender;
+        }
         break;
     case MSG_PERMIT_PUSHBACK_CLEARANCE:
-        text = receiver + ". Push-back approved. " + sender;
+        if (rec->getAircraft()->getTaxiClearanceRequest()) {
+            text = receiver + ". Push-back approved. " + sender;
+        } else {
+            text = receiver + ". Cleared to Taxi." + sender;
+        }
         break;
     case MSG_HOLD_PUSHBACK_CLEARANCE:
         text = receiver + ". Standby. " + sender;
@@ -653,7 +685,37 @@ void FGATCController::transmit(FGTrafficRecord * rec, AtcMsgId msgId,
     case MSG_ACKNOWLEDGE_RESUME_TAXI:
         text = receiver + ". Continuing Taxi. " + sender;
         break;
+    case MSG_REPORT_RUNWAY_HOLD_SHORT:
+        activeRunway = rec->getAircraft()->GetFlightPlan()->getRunway();
+        //activeRunway = "test";
+        text = receiver + ". Holding short runway " 
+                        + activeRunway 
+                        + ". " + sender;
+        //text = "test1";
+        //cerr << "1 Currently at leg " << rec->getLeg() << endl;
+        break;
+    case MSG_ACKNOWLEDGE_REPORT_RUNWAY_HOLD_SHORT:
+        activeRunway = rec->getAircraft()->GetFlightPlan()->getRunway();
+        text = receiver + "Roger. Holding short runway " 
+        //                + activeRunway 
+                        + ". " + sender;
+        //text = "test2";
+        //cerr << "2 Currently at leg " << rec->getLeg() << endl;
+        break;
+    case MSG_SWITCH_TOWER_FREQUENCY:
+        towerFreqStr = formatATCFrequency3_2(towerFreq);
+        text = receiver + "Contact Tower at " + towerFreqStr + ". " + sender;
+        //text = "test3";
+        //cerr << "3 Currently at leg " << rec->getLeg() << endl;
+        break;
+    case MSG_ACKNOWLEDGE_SWITCH_TOWER_FREQUENCY:
+        towerFreqStr = formatATCFrequency3_2(towerFreq);
+        text = receiver + "Roger, switching to tower at " + towerFreqStr + ". " + sender;
+        //text = "test4";
+        //cerr << "4 Currently at leg " << rec->getLeg() << endl;
+        break;
     default:
+        //text = "test3";
         text = text + sender + ". Transmitting unknown Message";
         break;
     }
@@ -669,8 +731,25 @@ void FGATCController::transmit(FGTrafficRecord * rec, AtcMsgId msgId,
         // Display ATC message only when one of the radios is tuned
         // the relevant frequency.
         // Note that distance attenuation is currently not yet implemented
+                
         if ((onBoardRadioFreqI0 == stationFreq)
             || (onBoardRadioFreqI1 == stationFreq)) {
+               double snr = calculate_attenuation(rec, parent, ground_to_air);
+               if (snr <= 0)
+                       return;
+               if (snr > 0 && snr < 12) {
+                       //for low SNR values implement a way to make the conversation
+                       //hard to understand but audible
+                       string hash_noise = " ";
+                       int reps = fabs((int)snr - 11);
+                       int t_size = text.size();
+                       for (int n=1;n<=reps * 2;n++) {
+                               int pos = rand() % t_size -1;
+                               text.replace(pos,1, hash_noise);
+                       }
+                       
+               }
+               
             if (rec->allowTransmissions()) {
                 fgSetString("/sim/messages/atc", text.c_str());
             }
@@ -682,6 +761,165 @@ void FGATCController::transmit(FGTrafficRecord * rec, AtcMsgId msgId,
     }
 }
 
+double FGATCController::calculate_attenuation(FGTrafficRecord * rec, FGAirportDynamics *parent,
+                               int ground_to_air) {
+       //////////////////////////////////////////////////
+        ///  Implement radio attenuation               //
+        ///  based on the Longley-Rice propagation model//
+        //////////////////////////////////////////////////
+        
+        FGScenery * scenery = globals->get_scenery();
+        // player aircraft position
+        double own_lat = fgGetDouble("/position/latitude-deg");
+        double own_lon = fgGetDouble("/position/longitude-deg");
+        double own_alt_ft = fgGetDouble("/position/altitude-ft");
+        double own_alt= own_alt_ft * SG_FEET_TO_METER;
+        
+        cerr << "ITM:: pilot Lat: " << own_lat << ", Lon: " << own_lon << ", Alt: " << own_alt << endl;
+        
+        SGGeod own_pos = SGGeod::fromDegM( own_lon, own_lat, own_alt );
+        SGGeod max_own_pos = SGGeod::fromDegM( own_lon, own_lat, SG_MAX_ELEVATION_M );
+        SGGeoc center = SGGeoc::fromGeod( max_own_pos );
+        SGGeoc own_pos_c = SGGeoc::fromGeod( own_pos );
+        
+        // position of sender radio antenna (HAAT)
+        // sender can be aircraft or ground station
+        double ATC_HAAT = 30.0;
+        double Aircraft_HAAT = 7.0;
+        double sender_alt_ft,sender_alt;
+        double transceiver_height=0.0;
+        double receiver_height=0.0;
+        SGGeod sender_pos;
+        if(ground_to_air) {
+               sender_alt_ft = parent->getElevation();
+               sender_alt = sender_alt_ft * SG_FEET_TO_METER + ATC_HAAT;
+               sender_pos= SGGeod::fromDegM( parent->getLongitude(),
+                       parent->getLatitude(), sender_alt );
+       }
+       else {
+               sender_alt_ft = rec->getAltitude();
+               sender_alt = sender_alt_ft * SG_FEET_TO_METER + Aircraft_HAAT;
+               sender_pos= SGGeod::fromDegM( rec->getLongitude(),
+                       rec->getLatitude(), sender_alt );
+       }
+       SGGeoc sender_pos_c = SGGeoc::fromGeod( sender_pos );
+       cerr << "ITM:: sender Lat: " << parent->getLatitude() << ", Lon: " << parent->getLongitude() << ", Alt: " << sender_alt << endl;
+       
+        double point_distance= 90.0; // regular SRTM is 90 meters
+        double course = SGGeodesy::courseRad(own_pos_c, sender_pos_c);
+        double distance_m = SGGeodesy::distanceM(own_pos, sender_pos);
+        double probe_distance = 0.0;
+        
+        cerr << "ITM:: Distance: " << distance_m << endl;
+        
+        double max_points = distance_m / point_distance;
+        deque<double> _elevations;
+        
+        SGGeod probe_pilot = SGGeod::fromGeoc(center.advanceRadM( course, 0 ));
+        double elevation_under_pilot = 0.0;
+       if (scenery->get_elevation_m( probe_pilot, elevation_under_pilot, NULL )) {
+               receiver_height = own_alt - elevation_under_pilot;
+       }
+       _elevations.push_front(receiver_height);
+       
+       SGGeod probe_sender = SGGeod::fromGeoc(center.advanceRadM( course, distance_m ));
+        double elevation_under_sender = 0.0;
+       if (scenery->get_elevation_m( probe_sender, elevation_under_sender, NULL )) {
+               transceiver_height = sender_alt - elevation_under_sender;
+       }
+        
+        // If distance larger than this value (400 km), assume reception imposssible
+        // technically 400 km is no problem if LOS conditions exist,
+        // but we do this to spare resources
+        if (distance_m > 400000)
+               return -1.0;
+        
+        int e_size = (deque<unsigned>::size_type)max_points;
+        
+        while (_elevations.size() < e_size) {
+               probe_distance += point_distance;
+               SGGeod probe = SGGeod::fromGeoc(center.advanceRadM( course, probe_distance ));
+               
+               double elevation_m = 0.0;
+       
+               if (scenery->get_elevation_m( probe, elevation_m, NULL )) {
+                        _elevations.push_front(elevation_m);
+                        //cerr << "ITM:: Probe elev: " << elevation_m << endl;
+               }
+       }
+       
+       _elevations.push_front(transceiver_height);
+       double max_alt_between=0.0;
+       for( deque<double>::size_type i = 0; i < _elevations.size(); i++ ) {
+               if (_elevations[i] > max_alt_between) {
+                       max_alt_between = _elevations[i];
+               }
+       }
+       
+       double num_points= (double)_elevations.size();
+       cerr << "ITM:: Max alt between: " << max_alt_between << ", num points:" << num_points << endl;
+       _elevations.push_front(point_distance);
+       _elevations.push_front(num_points -1);
+       int size = _elevations.size();
+       double itm_elev[size];
+       for(int i=0;i<size;i++) {
+               itm_elev[i]=_elevations[i];
+               //cerr << "ITM:: itm_elev: " << _elevations[i] << endl;
+       }
+       
+       ////////////// ITM default parameters //////////////
+       // later perhaps take them from tile materials?
+       double eps_dielect=15.0;
+       double sgm_conductivity = 0.005;
+       double eno = 301.0;
+       double frq_mhz = 125.0;         // middle of bandplan
+       int radio_climate = 5;          // continental temperate
+       int pol=1;      // assuming vertical polarization
+       double conf = 0.90;     // my own tests in Radiomobile have worked best with these values
+       double rel = 0.80;      // ^^
+       double dbloss;
+       char strmode[150];
+       int errnum;
+       
+       /////////// radio parameters ///////////
+       double receiver_sensitivity = -112.0;   // typical AM receiver sensitivity in dBm
+       // AM transmitter power in dBm.
+       // Note this value is calculated from the typical final transistor stage output
+       // !!! small aircraft have portable transmitters which operate at 36 dBm output (4 Watts)
+       // later store this value in aircraft description
+       // ATC comms usually operate high power equipment, thus making the link asymetrical; this is ignored for now
+       if(ground_to_air)
+               double transmitter_power = 49.0;
+       else
+               double transmitter_power = 43.0;
+       if(ground_to_air)
+               double antenna_gain = 5.0; //pilot plane's antenna gain + Controller antenna gain
+       else
+               double antenna_gain = 2.0; //pilot plane's antenna gain + AI aircraft antenna gain
+       double link_budget = transmitter_power - receiver_sensitivity + antenna_gain;   
+       
+       
+       // first Fresnel zone radius
+       // frequency in the middle of the bandplan, more accuracy is not necessary
+       double fz_clr= 8.657 * sqrt(distance_m / 0.125);
+       
+       // TODO: If we clear the first Fresnel zone, we are into line of sight teritory
+
+       // else we need to calculate point to point link loss
+
+       point_to_point(itm_elev, sender_alt, own_alt,
+               eps_dielect, sgm_conductivity, eno, frq_mhz, radio_climate,
+               pol, conf, rel, dbloss, strmode, errnum);
+
+       cerr << "ITM:: Attenuation: " << dbloss << " dBm, " << strmode << ", Error: " << errnum << endl;
+       
+       //if (errnum !=0 && errnum !=1)
+       //      return -1;
+       double snr = link_budget - dbloss;
+       return snr;
+
+}
+
 string FGATCController::formatATCFrequency3_2(int freq)
 {
     char buffer[7];
@@ -716,9 +954,10 @@ void FGATCController::init()
  * class FGTowerController
  *
  **************************************************************************/
-FGTowerController::FGTowerController():
+FGTowerController::FGTowerController(FGAirportDynamics *par) :
 FGATCController()
 {
+    parent = par;
 }
 
 // 
@@ -752,8 +991,29 @@ void FGTowerController::announcePosition(int id,
         rec.setRunway(intendedRoute->getRunway());
         rec.setLeg(leg);
         //rec.setCallSign(callsign);
+        rec.setRadius(radius);
         rec.setAircraft(ref);
         activeTraffic.push_back(rec);
+        // Don't just schedule the aircraft for the tower controller, also assign if to the correct active runway. 
+        ActiveRunwayVecIterator rwy = activeRunways.begin();
+        if (activeRunways.size()) {
+            while (rwy != activeRunways.end()) {
+                if (rwy->getRunwayName() == intendedRoute->getRunway()) {
+                    break;
+                }
+                rwy++;
+            }
+        }
+        if (rwy == activeRunways.end()) {
+            ActiveRunway aRwy(intendedRoute->getRunway(), id);
+            aRwy.addToDepartureCue(ref);
+            activeRunways.push_back(aRwy);
+            rwy = (activeRunways.end()-1);
+        } else {
+            rwy->addToDepartureCue(ref);
+        }
+
+        //cerr << ref->getTrafficRef()->getCallSign() << " You are number " << rwy->getDepartureCueSize() <<  " for takeoff " << endl;
     } else {
         i->setPositionAndHeading(lat, lon, heading, speed, alt);
     }
@@ -786,29 +1046,43 @@ void FGTowerController::updateAircraftInformation(int id, double lat, double lon
     }
     setDt(getDt() + dt);
 
-//    // see if we already have a clearance record for the currently active runway
+    // see if we already have a clearance record for the currently active runway
+    // NOTE: dd. 2011-08-07: Because the active runway has been constructed in the announcePosition function, we may safely assume that is
+    // already exists here. So, we can simplify the current code. 
     ActiveRunwayVecIterator rwy = activeRunways.begin();
-    // again, a map might be more efficient here
-    if (activeRunways.size()) {
-        //while ((rwy->getRunwayName() != current->getRunway()) && (rwy != activeRunways.end())) {
-        while (rwy != activeRunways.end()) {
-            if (rwy->getRunwayName() == current->getRunway()) {
-                break;
-            }
-            rwy++;
+    while (rwy != activeRunways.end()) {
+        if (rwy->getRunwayName() == current->getRunway()) {
+            break;
         }
+        rwy++;
     }
-    if (rwy == activeRunways.end()) {
-        ActiveRunway aRwy(current->getRunway(), id);
-        activeRunways.push_back(aRwy);  // Since there are no clearance records for this runway yet
-        current->setHoldPosition(false);        // Clear the current aircraft to continue
-    } else {
-        // Okay, we have a clearance record for this runway, so check
-        // whether the clearence ID matches that of the current aircraft
-        if (id == rwy->getCleared()) {
-            current->setHoldPosition(false);
+
+    // only bother running the following code if the current aircraft is the
+    // first in line for depature
+    /* if (current->getAircraft() == rwy->getFirstAircraftInDepartureCue()) {
+        if (rwy->getCleared()) {
+            if (id == rwy->getCleared()) {
+                current->setHoldPosition(false);
+            } else {
+                current->setHoldPosition(true);
+            }
+        } else {
+            // For now. At later stages, this will probably be the place to check for inbound traffc.
+            rwy->setCleared(id);
+        }
+    } */
+    // only bother with aircraft that have a takeoff status of 2, since those are essentially under tower control
+    if (current->getAircraft()->getTakeOffStatus() == 2) {
+        current->setHoldPosition(true);
+        int clearanceId = rwy->getCleared();
+        if (clearanceId) {
+            if (id == clearanceId) {
+                current->setHoldPosition(false);
+            }
         } else {
-            current->setHoldPosition(true);
+            if (current->getAircraft() == rwy->getFirstAircraftInDepartureCue()) {
+                rwy->setCleared(id);
+            }
         }
     }
 }
@@ -839,7 +1113,8 @@ void FGTowerController::signOff(int id)
             rwy++;
         }
         if (rwy != activeRunways.end()) {
-            rwy = activeRunways.erase(rwy);
+            rwy->setCleared(0);
+            rwy->updateDepartureCue();
         } else {
             SG_LOG(SG_GENERAL, SG_ALERT,
                    "AI error: Attempting to erase non-existing runway clearance record in FGTowerController::signoff");
@@ -849,7 +1124,9 @@ void FGTowerController::signOff(int id)
         SG_LOG(SG_GENERAL, SG_ALERT,
                "AI error: Aircraft without traffic record is signing off from tower");
     } else {
+        i->getAircraft()->resetTakeOffStatus();
         i = activeTraffic.erase(i);
+        //cerr << "Signing off from tower controller" << endl;
     }
 }
 
@@ -906,11 +1183,16 @@ FGATCInstruction FGTowerController::getInstruction(int id)
     return FGATCInstruction();
 }
 
-void FGTowerController::render() {
-    cerr << "FGTowerController::render function not yet implemented" << endl;
+void FGTowerController::render(bool visible) {
+    //cerr << "FGTowerController::render function not yet implemented" << endl;
+}
+
+string FGTowerController::getName() {
+    return string(parent->getId() + "-tower");
 }
 
 
+
 /***************************************************************************
  * class FGStartupController
  *
@@ -1033,6 +1315,7 @@ void FGStartupController::signOff(int id)
         SG_LOG(SG_GENERAL, SG_ALERT,
                "AI error: Aircraft without traffic record is signing off from tower");
     } else {
+        //cerr << i->getAircraft()->getCallSign() << " signing off from startupcontroller" << endl;
         i = activeTraffic.erase(i);
     }
 }
@@ -1044,24 +1327,24 @@ bool FGStartupController::checkTransmissionState(int st, time_t now, time_t star
     if ((state == st) && available) {
         if ((msgDir == ATC_AIR_TO_GROUND) && isUserAircraft(i->getAircraft())) {
             
-            cerr << "Checking state " << st << " for " << i->getAircraft()->getCallSign() << endl;
+            //cerr << "Checking state " << st << " for " << i->getAircraft()->getCallSign() << endl;
             static SGPropertyNode_ptr trans_num = globals->get_props()->getNode("/sim/atc/transmission-num", true);
             int n = trans_num->getIntValue();
-            if (n >= 0) {
+            if (n == 0) {
                 trans_num->setIntValue(-1);
                  // PopupCallback(n);
-                 cerr << "Selected transmission message" << n << endl;
+                 //cerr << "Selected transmission message " << n << endl;
                  FGATCManager *atc = (FGATCManager*) globals->get_subsystem("atc");
                  atc->getATCDialog()->removeEntry(1);
             } else {
-                cerr << "creading message for " << i->getAircraft()->getCallSign() << endl;
-                transmit(&(*i), msgId, msgDir, false);
+                //cerr << "creading message for " << i->getAircraft()->getCallSign() << endl;
+                transmit(&(*i), &(*parent), msgId, msgDir, false);
                 return false;
             }
         }
         if (now > startTime) {
             //cerr << "Transmitting startup msg" << endl;
-            transmit(&(*i), msgId, msgDir, true);
+            transmit(&(*i), &(*parent), msgId, msgDir, true);
             i->updateState();
             lastTransmission = now;
             available = false;
@@ -1130,11 +1413,11 @@ void FGStartupController::updateAircraftInformation(int id, double lat, double l
         if (now > startTime + 200) {
             if (i->pushBackAllowed()) {
                 i->allowRepeatedTransmissions();
-                transmit(&(*i), MSG_PERMIT_PUSHBACK_CLEARANCE,
+                transmit(&(*i), &(*parent), MSG_PERMIT_PUSHBACK_CLEARANCE,
                          ATC_GROUND_TO_AIR, true);
                 i->updateState();
             } else {
-                transmit(&(*i), MSG_HOLD_PUSHBACK_CLEARANCE,
+                transmit(&(*i), &(*parent), MSG_HOLD_PUSHBACK_CLEARANCE,
                          ATC_GROUND_TO_AIR, true);
                 i->suppressRepeatedTransmissions();
             }
@@ -1149,7 +1432,7 @@ void FGStartupController::updateAircraftInformation(int id, double lat, double l
 
 // Note that this function is copied from simgear. for maintanance purposes, it's probabtl better to make a general function out of that.
 static void WorldCoordinate(osg::Matrix& obj_pos, double lat,
-                            double lon, double elev, double hdg)
+                            double lon, double elev, double hdg, double slope)
 {
     SGGeod geod = SGGeod::fromDegM(lon, lat, elev);
     obj_pos = geod.makeZUpFrame();
@@ -1157,10 +1440,12 @@ static void WorldCoordinate(osg::Matrix& obj_pos, double lat,
     // around the Z axis
     obj_pos.preMult(osg::Matrix::rotate(hdg * SGD_DEGREES_TO_RADIANS,
                                         0.0, 0.0, 1.0));
+    obj_pos.preMult(osg::Matrix::rotate(slope * SGD_DEGREES_TO_RADIANS,
+                                        0.0, 1.0, 0.0));
 }
 
 
-void FGStartupController::render()
+void FGStartupController::render(bool visible)
 {
 
     SGMaterialLib *matlib = globals->get_matlib();
@@ -1169,78 +1454,80 @@ void FGStartupController::render()
         globals->get_scenery()->get_scene_graph()->removeChild(group);
         //while (group->getNumChildren()) {
         //  cerr << "Number of children: " << group->getNumChildren() << endl;
-        simgear::EffectGeode* geode = (simgear::EffectGeode*) group->getChild(0);
+        //simgear::EffectGeode* geode = (simgear::EffectGeode*) group->getChild(0);
           //osg::MatrixTransform *obj_trans = (osg::MatrixTransform*) group->getChild(0);
            //geode->releaseGLObjects();
            //group->removeChild(geode);
            //delete geode;
+        group = 0;
     }
-    group = new osg::Group;
-
-    //for ( FGTaxiSegmentVectorIterator i = segments.begin(); i != segments.end(); i++) {
-    double dx = 0;
-    for   (TrafficVectorIterator i = activeTraffic.begin(); i != activeTraffic.end(); i++) {
-        // Handle start point
-        int pos = i->getCurrentPosition();
-        if (pos > 0) {
-            FGTaxiSegment *segment  = parent->getGroundNetwork()->findSegment(pos);
-            SGGeod start(SGGeod::fromDeg((i->getLongitude()), (i->getLatitude())));
-            SGGeod end  (SGGeod::fromDeg(segment->getEnd()->getLongitude(), segment->getEnd()->getLatitude()));
-
-            double length = SGGeodesy::distanceM(start, end);
-            //heading = SGGeodesy::headingDeg(start->getGeod(), end->getGeod());
-
-            double az2, heading; //, distanceM;
-            SGGeodesy::inverse(start, end, heading, az2, length);
-            double coveredDistance = length * 0.5;
-            SGGeod center;
-            SGGeodesy::direct(start, heading, coveredDistance, center, az2);
-            //cerr << "Active Aircraft : Centerpoint = (" << center.getLatitudeDeg() << ", " << center.getLongitudeDeg() << "). Heading = " << heading << endl;
-            ///////////////////////////////////////////////////////////////////////////////
-            // Make a helper function out of this
-            osg::Matrix obj_pos;
+    if (visible) {
+        group = new osg::Group;
+        FGScenery * local_scenery = globals->get_scenery();
+        double elevation_meters = 0.0;
+        double elevation_feet = 0.0;
+
+
+        //for ( FGTaxiSegmentVectorIterator i = segments.begin(); i != segments.end(); i++) {
+        double dx = 0;
+        for   (TrafficVectorIterator i = activeTraffic.begin(); i != activeTraffic.end(); i++) {
+            // Handle start point
+            int pos = i->getCurrentPosition();
+            //cerr << "rendering for " << i->getAircraft()->getCallSign() << "pos = " << pos << endl;
+            if (pos > 0) {
+                FGTaxiSegment *segment  = parent->getGroundNetwork()->findSegment(pos);
+                SGGeod start(SGGeod::fromDeg((i->getLongitude()), (i->getLatitude())));
+                SGGeod end  (SGGeod::fromDeg(segment->getEnd()->getLongitude(), segment->getEnd()->getLatitude()));
+
+                double length = SGGeodesy::distanceM(start, end);
+                //heading = SGGeodesy::headingDeg(start->getGeod(), end->getGeod());
+
+                double az2, heading; //, distanceM;
+                SGGeodesy::inverse(start, end, heading, az2, length);
+                double coveredDistance = length * 0.5;
+                SGGeod center;
+                SGGeodesy::direct(start, heading, coveredDistance, center, az2);
+                //cerr << "Active Aircraft : Centerpoint = (" << center.getLatitudeDeg() << ", " << center.getLongitudeDeg() << "). Heading = " << heading << endl;
+                ///////////////////////////////////////////////////////////////////////////////
+                // Make a helper function out of this
+                osg::Matrix obj_pos;
                 osg::MatrixTransform *obj_trans = new osg::MatrixTransform;
                 obj_trans->setDataVariance(osg::Object::STATIC);
+                // Experimental: Calculate slope here, based on length, and the individual elevations
+                double elevationStart;
+                if (isUserAircraft((i)->getAircraft())) {
+                    elevationStart = fgGetDouble("/position/ground-elev-m");
+                } else {
+                    elevationStart = ((i)->getAircraft()->_getAltitude()); 
+                }
+                double elevationEnd   = segment->getEnd()->getElevation();
+                if (elevationEnd == 0) {
+                    SGGeod center2 = end;
+                    center2.setElevationM(SG_MAX_ELEVATION_M);
+                    if (local_scenery->get_elevation_m( center2, elevationEnd, NULL )) {
+                        elevation_feet = elevationEnd * SG_METER_TO_FEET + 0.5;
+                            //elevation_meters += 0.5;
+                    }
+                    else { 
+                        elevationEnd = parent->getElevation()+8+dx;
+                    }
+                    segment->getEnd()->setElevation(elevationEnd);
+                }
 
-                WorldCoordinate( obj_pos, center.getLatitudeDeg(), center.getLongitudeDeg(), parent->getElevation()+8+dx, -(heading) );
-
-                obj_trans->setMatrix( obj_pos );
-                //osg::Vec3 center(0, 0, 0)
+                double elevationMean  = (elevationStart + elevationEnd) / 2.0;
+                double elevDiff       = elevationEnd - elevationStart;
+               
+               double slope = atan2(elevDiff, length) * SGD_RADIANS_TO_DEGREES;
+                
+               //cerr << "1. Using mean elevation : " << elevationMean << " and " << slope << endl;
 
-                float width = length /2.0;
-                osg::Vec3 corner(-width, 0, 0.25f);
-                osg::Vec3 widthVec(2*width + 1, 0, 0);
-                osg::Vec3 heightVec(0, 1, 0);
-                osg::Geometry* geometry;
-                geometry = osg::createTexturedQuadGeometry(corner, widthVec, heightVec);
-                simgear::EffectGeode* geode = new simgear::EffectGeode;
-                geode->setName("test");
-                geode->addDrawable(geometry);
-                //osg::Node *custom_obj;
-                SGMaterial *mat = matlib->find("UnidirectionalTaper");
-                if (mat)
-                    geode->setEffect(mat->get_effect());
-                obj_trans->addChild(geode);
-                // wire as much of the scene graph together as we can
-                //->addChild( obj_trans );
-                group->addChild( obj_trans );
-        /////////////////////////////////////////////////////////////////////
-        } else {
-             cerr << "BIG FAT WARNING: current position is here : " << pos << endl;
-        }
-        for(intVecIterator j = (i)->getIntentions().begin(); j != (i)->getIntentions().end(); j++) {
-             osg::Matrix obj_pos;
-            int k = (*j);
-            if (k > 0) {
-                osg::MatrixTransform *obj_trans = new osg::MatrixTransform;
-                obj_trans->setDataVariance(osg::Object::STATIC);
-                FGTaxiSegment *segment  = parent->getGroundNetwork()->findSegment(k);
-                WorldCoordinate( obj_pos, segment->getLatitude(), segment->getLongitude(), parent->getElevation()+8+dx, -(segment->getHeading()) );
+                WorldCoordinate( obj_pos, center.getLatitudeDeg(), center.getLongitudeDeg(), elevationMean + 0.5, -(heading), slope );
+;
 
                 obj_trans->setMatrix( obj_pos );
                 //osg::Vec3 center(0, 0, 0)
 
-                float width = segment->getLength() /2.0;
+                float width = length /2.0;
                 osg::Vec3 corner(-width, 0, 0.25f);
                 osg::Vec3 widthVec(2*width + 1, 0, 0);
                 osg::Vec3 heightVec(0, 1, 0);
@@ -1257,13 +1544,90 @@ void FGStartupController::render()
                 // wire as much of the scene graph together as we can
                 //->addChild( obj_trans );
                 group->addChild( obj_trans );
+                /////////////////////////////////////////////////////////////////////
             } else {
-                cerr << "BIG FAT WARNING: k is here : " << pos << endl;
+                //cerr << "BIG FAT WARNING: current position is here : " << pos << endl;
             }
+            for(intVecIterator j = (i)->getIntentions().begin(); j != (i)->getIntentions().end(); j++) {
+                osg::Matrix obj_pos;
+                int k = (*j);
+                if (k > 0) {
+                    //cerr << "rendering for " << i->getAircraft()->getCallSign() << "intention = " << k << endl;
+                    osg::MatrixTransform *obj_trans = new osg::MatrixTransform;
+                    obj_trans->setDataVariance(osg::Object::STATIC);
+                    FGTaxiSegment *segment  = parent->getGroundNetwork()->findSegment(k);
+
+                    double elevationStart = segment->getStart()->getElevation();
+                    double elevationEnd   = segment->getEnd  ()->getElevation();
+                    if (elevationStart == 0) {
+                        SGGeod center2 = segment->getStart()->getGeod();
+                        center2.setElevationM(SG_MAX_ELEVATION_M);
+                        if (local_scenery->get_elevation_m( center2, elevationStart, NULL )) {
+                            elevation_feet = elevationStart * SG_METER_TO_FEET + 0.5;
+                            //elevation_meters += 0.5;
+                        }
+                        else { 
+                            elevationStart = parent->getElevation()+8+dx;
+                        }
+                        segment->getStart()->setElevation(elevationStart);
+                    }
+                    if (elevationEnd == 0) {
+                        SGGeod center2 = segment->getEnd()->getGeod();
+                        center2.setElevationM(SG_MAX_ELEVATION_M);
+                        if (local_scenery->get_elevation_m( center2, elevationEnd, NULL )) {
+                            elevation_feet = elevationEnd * SG_METER_TO_FEET + 0.5;
+                            //elevation_meters += 0.5;
+                        }
+                        else { 
+                            elevationEnd = parent->getElevation()+8+dx;
+                        }
+                        segment->getEnd()->setElevation(elevationEnd);
+                    }
+                    double elevationMean  = (elevationStart + elevationEnd) / 2.0;
+                    double elevDiff       = elevationEnd - elevationStart;
+                    double length         = segment->getLength();
+                    double slope = atan2(elevDiff, length) * SGD_RADIANS_TO_DEGREES;
+                
+                    //cerr << "2. Using mean elevation : " << elevationMean << " and " << slope << endl;
+
+
+                    WorldCoordinate( obj_pos, segment->getLatitude(), segment->getLongitude(), elevationMean + 0.5, -(segment->getHeading()), slope );
+
+                    //WorldCoordinate( obj_pos, segment->getLatitude(), segment->getLongitude(), parent->getElevation()+8+dx, -(segment->getHeading()) );
+
+                    obj_trans->setMatrix( obj_pos );
+                    //osg::Vec3 center(0, 0, 0)
+
+                    float width = segment->getLength() /2.0;
+                    osg::Vec3 corner(-width, 0, 0.25f);
+                    osg::Vec3 widthVec(2*width + 1, 0, 0);
+                    osg::Vec3 heightVec(0, 1, 0);
+                    osg::Geometry* geometry;
+                    geometry = osg::createTexturedQuadGeometry(corner, widthVec, heightVec);
+                    simgear::EffectGeode* geode = new simgear::EffectGeode;
+                    geode->setName("test");
+                    geode->addDrawable(geometry);
+                    //osg::Node *custom_obj;
+                    SGMaterial *mat = matlib->find("UnidirectionalTaper");
+                    if (mat)
+                        geode->setEffect(mat->get_effect());
+                    obj_trans->addChild(geode);
+                    // wire as much of the scene graph together as we can
+                    //->addChild( obj_trans );
+                    group->addChild( obj_trans );
+                } else {
+                    //cerr << "BIG FAT WARNING: k is here : " << pos << endl;
+                }
+            }
+            //dx += 0.1;
         }
-        dx += 0.1;
+        globals->get_scenery()->get_scene_graph()->addChild(group);
     }
-    globals->get_scenery()->get_scene_graph()->addChild(group);
+}
+
+string FGStartupController::getName() {
+    return string(parent->getId() + "-startup");
 }
 
 
@@ -1271,9 +1635,10 @@ void FGStartupController::render()
  * class FGApproachController
  *
  **************************************************************************/
-FGApproachController::FGApproachController():
+FGApproachController::FGApproachController(FGAirportDynamics *par):
 FGATCController()
 {
+    parent = par;
 }
 
 // 
@@ -1458,6 +1823,12 @@ ActiveRunway *FGApproachController::getRunway(string name)
     return &(*rwy);
 }
 
-void FGApproachController::render() {
-    cerr << "FGApproachController::render function not yet implemented" << endl;
+void FGApproachController::render(bool visible) {
+    //cerr << "FGApproachController::render function not yet implemented" << endl;
+}
+
+
+
+string FGApproachController::getName() {
+    return string(parent->getId() + "-approach");
 }