flightgear/src/AIModel/AIAircraft.cxx

// FGAIAircraft - FGAIBase-derived class creates an AI airplane
//
// Written by David Culp, started October 2003.
//
// Copyright (C) 2003  David P. Culp - davidculp2@comcast.net
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License as
// published by the Free Software Foundation; either version 2 of the
// License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful, but
// WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.

#ifdef HAVE_CONFIG_H
#  include <config.h>
#endif

#include <simgear/math/point3d.hxx>
#include <simgear/route/waypoint.hxx>
#include <Main/fg_props.hxx>
#include <Main/globals.hxx>
#include <Main/viewer.hxx>
#include <Scenery/scenery.hxx>
#include <Scenery/tilemgr.hxx>

#include <string>
#include <math.h>
#include <time.h>
#ifdef _MSC_VER
#  include <float.h>
#  define finite _finite
#elif defined(__sun) || defined(sgi)
#  include <ieeefp.h>
#endif

SG_USING_STD(string);

#include "AIAircraft.hxx"
   static string tempReg;
//
// accel, decel, climb_rate, descent_rate, takeoff_speed, climb_speed,
// cruise_speed, descent_speed, land_speed
//
const FGAIAircraft::PERF_STRUCT FGAIAircraft::settings[] = {
    // light aircraft
    {2.0, 2.0,  450.0, 1000.0,  70.0,  80.0, 100.0,  80.0,  60.0},
    // ww2_fighter
    {4.0, 2.0, 3000.0, 1500.0, 110.0, 180.0, 250.0, 200.0, 100.0},
    // jet_transport
    {5.0, 2.0, 3000.0, 1500.0, 140.0, 300.0, 430.0, 300.0, 130.0},
    // jet_fighter
    {7.0, 3.0, 4000.0, 2000.0, 150.0, 350.0, 500.0, 350.0, 150.0},
    // tanker
    {5.0, 2.0, 3000.0, 1500.0, 140.0, 300.0, 430.0, 300.0, 130.0},
    // ufo (extreme accel/decel)
    {30.0, 30.0, 6000.0, 6000.0, 150.0, 300.0, 430.0, 300.0, 130.0}
};


FGAIAircraft::FGAIAircraft(FGAISchedule *ref) :
    FGAIBase(otAircraft)
{
    trafficRef = ref;
    if (trafficRef)
        groundOffset = trafficRef->getGroundOffset();
    else
        groundOffset = 0;

    fp = 0;
    dt_count = 0;
    dt_elev_count = 0;
    use_perf_vs = true;
    isTanker = false;

    // set heading and altitude locks
    hdg_lock = false;
    alt_lock = false;
    roll = 0;
    headingChangeRate = 0.0;
}


FGAIAircraft::~FGAIAircraft() {
    //delete fp;
}


void FGAIAircraft::readFromScenario(SGPropertyNode* scFileNode) {
    if (!scFileNode)
        return;

    FGAIBase::readFromScenario(scFileNode);

    setPerformance(scFileNode->getStringValue("class", "jet_transport"));
    setFlightPlan(scFileNode->getStringValue("flightplan"),
                  scFileNode->getBoolValue("repeat", false));
    setCallSign(scFileNode->getStringValue("callsign"));
    setTACANChannelID(scFileNode->getStringValue("TACAN-channel-ID"));
}


bool FGAIAircraft::init() {
    //refuel_node = fgGetNode("systems/refuel/contact", true);
    return FGAIBase::init();
}


void FGAIAircraft::bind() {
    FGAIBase::bind();

    props->tie("controls/gear/gear-down",
               SGRawValueMethods<FGAIAircraft,bool>(*this,
                                              &FGAIAircraft::_getGearDown));
    props->tie("refuel/contact", SGRawValuePointer<bool>(&contact));
    props->setStringValue("callsign", callsign.c_str());
    props->setStringValue("navaids/tacan/channel-ID", TACAN_channel_id.c_str());
    props->setBoolValue("tanker",isTanker);
}


void FGAIAircraft::unbind() {
    FGAIBase::unbind();

    props->untie("controls/gear/gear-down");
    props->untie("refuel/contact");
}


void FGAIAircraft::update(double dt) {
    FGAIBase::update(dt);
    Run(dt);
    Transform();
}


void FGAIAircraft::setPerformance(const std::string& acclass) {
    if (acclass == "light") {
        SetPerformance(&FGAIAircraft::settings[FGAIAircraft::LIGHT]);
    } else if (acclass == "ww2_fighter") {
        SetPerformance(&FGAIAircraft::settings[FGAIAircraft::WW2_FIGHTER]);
    } else if (acclass == "jet_transport") {
        SetPerformance(&FGAIAircraft::settings[FGAIAircraft::JET_TRANSPORT]);
    } else if (acclass == "jet_fighter") {
        SetPerformance(&FGAIAircraft::settings[FGAIAircraft::JET_FIGHTER]);
    } else if (acclass == "tanker") {
        SetPerformance(&FGAIAircraft::settings[FGAIAircraft::JET_TRANSPORT]);
        SetTanker(true);
    } else if (acclass == "ufo") {
        SetPerformance(&FGAIAircraft::settings[FGAIAircraft::UFO]);
    } else {
        SetPerformance(&FGAIAircraft::settings[FGAIAircraft::JET_TRANSPORT]);
    }
}


void FGAIAircraft::SetPerformance(const PERF_STRUCT *ps) {

   performance = ps;
}


void FGAIAircraft::Run(double dt) {

    FGAIAircraft::dt = dt;
    
    if (fp) {
        time_t now = time(NULL) + fgGetLong("/sim/time/warp");
        ProcessFlightPlan(dt, now);
        if (now < fp->getStartTime()) {
            // Do execute Ground elev for inactive aircraft, so they
            // Are repositioned to the correct ground altitude when the user flies within visibility range.
            if (no_roll) {
                Transform();       // make sure aip is initialized.
                getGroundElev(dt); // make sure it's exectuted first time around, so force a large dt value
                //getGroundElev(dt); // Need to do this twice.
                //cerr << trafficRef->getRegistration() << " Setting altitude to " << tgt_altitude;
                doGroundAltitude();
                //cerr << " Actual altitude " << altitude << endl;
                // Transform();
                pos.setElevationFt(altitude_ft);
            }
            return;
        }
    } else {
        // no flight plan, update target heading, speed, and altitude
        // from control properties.  These default to the initial
        // settings in the config file, but can be changed "on the
        // fly".
        string lat_mode = props->getStringValue("controls/flight/lateral-mode");
        if ( lat_mode == "roll" ) {
            double angle
                = props->getDoubleValue("controls/flight/target-roll" );
            RollTo( angle );
        } else {
             double angle
                = props->getDoubleValue("controls/flight/target-hdg" );
            TurnTo( angle );
        }

        string lon_mode
            = props->getStringValue("controls/flight/longitude-mode");
        if ( lon_mode == "alt" ) {
            double alt = props->getDoubleValue("controls/flight/target-alt" );
            ClimbTo( alt );
        } else {
            double angle
                = props->getDoubleValue("controls/flight/target-pitch" );
            PitchTo( angle );
        }

        AccelTo( props->getDoubleValue("controls/flight/target-spd" ) );
    }
      
    double turn_radius_ft;
    double turn_circum_ft;
    double speed_north_deg_sec;
    double speed_east_deg_sec;
    double dist_covered_ft;
    double alpha;

    // adjust speed
    double speed_diff; //= tgt_speed - speed;
    if (!no_roll) {
        speed_diff = tgt_speed - speed;
    } else {
        speed_diff = groundTargetSpeed - speed;
    }

    if (speed_diff > 0.0) {
        speed += performance->accel * dt;
	if (no_roll) { // apply overshoot correction
	  if ( speed > groundTargetSpeed ) speed = groundTargetSpeed;
	}else {
	  if ( speed > tgt_speed ) speed = tgt_speed;
	}
    } else if (speed_diff < 0.0) {
        if (no_roll) {
            // on ground (aircraft can't roll)
	    // deceleration performance is better due to wheel brakes.
            speed -= performance->decel * dt * 3;
        } else {
            speed -= performance->decel * dt;
        }
	if (no_roll) { // apply overshoot correction
        if (speed < groundTargetSpeed ) speed = groundTargetSpeed;
	} else { 
	  if ( speed < tgt_speed ) speed = tgt_speed;
	}
    }
    
    
    // convert speed to degrees per second
    speed_north_deg_sec = cos( hdg * SGD_DEGREES_TO_RADIANS )
                          * speed * 1.686 / ft_per_deg_lat;
    speed_east_deg_sec  = sin( hdg * SGD_DEGREES_TO_RADIANS )
                          * speed * 1.686 / ft_per_deg_lon;

    // set new position
    pos.setLatitudeDeg( pos.getLatitudeDeg() + speed_north_deg_sec * dt);
    pos.setLongitudeDeg( pos.getLongitudeDeg() + speed_east_deg_sec * dt); 

    /* printf("%.7f %0.4f %.7f %.5f %.7f %.7f %.8f %.8f %.9f %.9f\n",
           dt, hdg, speed, ft_per_deg_lat,
           cos( hdg * SGD_DEGREES_TO_RADIANS ),
           speed * 1.686 / ft_per_deg_lat,
           speed_north_deg_sec, speed_east_deg_sec,
           pos.getLatitudeDeg(), pos.getLongitudeDeg()); */

    //if (!(finite(pos.lat()) && finite(pos.lon())))
    //  {
    //    cerr << "Position is not finite" << endl;
    //    cerr << "speed = " << speed << endl;
    //    cerr << "dt" << dt << endl;
    //    cerr << "heading " << hdg << endl;
    //    cerr << "speed east " << speed_east_deg_sec << endl;
    //    cerr << "speed nrth " << speed_north_deg_sec << endl;
    //    cerr << "deg_lat    " << ft_per_deg_lat << endl;
    //    cerr << "deg_lon    " << ft_per_deg_lon << endl;
    //  }

    // adjust heading based on current bank angle
    if (roll == 0.0)
        roll = 0.01;

    if (roll != 0.0) {
        // double turnConstant;
        //if (no_roll)
        //  turnConstant = 0.0088362;
        //else
        //  turnConstant = 0.088362;
        // If on ground, calculate heading change directly
        if (no_roll) {
            double headingDiff = fabs(hdg-tgt_heading);

            if (headingDiff > 180)
                headingDiff = fabs(headingDiff - 360);

            groundTargetSpeed = tgt_speed - (tgt_speed * (headingDiff/45));
            if (sign(groundTargetSpeed) != sign(tgt_speed))
                groundTargetSpeed = 0.21 * sign(tgt_speed); // to prevent speed getting stuck in 'negative' mode

            if (headingDiff > 30.0) {
                headingChangeRate += dt * sign(roll); // invert if pushed backward
                // Print some debug statements to find out why aircraft may get stuck
                // forever turning
                //if (trafficRef->getDepartureAirport()->getId() == string("EHAM")) {
                //    cerr << "Turning : " << trafficRef->getRegistration()
                //    cerr <<  " Speed = " << speed << " Heading " << hdg
                //         << " Target Heading " << tgt_heading
                //         << " Lead Distance " <<  fp->getLeadDistance()
                //         << " Distance to go "
                //         << fp->getDistanceToGo(pos.lat(), pos.lon(), fp->getCurrentWaypoint())
                //         << "waypoint name " << fp->getCurrentWaypoint()->name
                //         << endl;
                //}
                if (headingChangeRate > 30)
                    headingChangeRate = 30;
                else if (headingChangeRate < -30)
                    headingChangeRate = -30;

            } else {
                if (fabs(headingChangeRate) > headingDiff)
                    headingChangeRate = headingDiff*sign(roll);
                else
                    headingChangeRate += dt * sign(roll);
            }
            hdg += headingChangeRate * dt;
            //cerr << "On ground. Heading: " << hdg << ". Target Heading: " << tgt_heading
            //     << ". Target speed: " << groundTargetSpeed << ". heading change rate"
            //     << headingChangeRate << endl;

        } else {
            if (fabs(speed) > 1.0) {
                turn_radius_ft = 0.088362 * speed * speed
                        / tan( fabs(roll) / SG_RADIANS_TO_DEGREES );
            } else {
                turn_radius_ft = 1.0; // Check if turn_radius_ft == 0; this might lead to a division by 0.
            }
            turn_circum_ft = SGD_2PI * turn_radius_ft;
            dist_covered_ft = speed * 1.686 * dt;
            alpha = dist_covered_ft / turn_circum_ft * 360.0;
            hdg += alpha * sign(roll);
        }
        while ( hdg > 360.0 ) {
            hdg -= 360.0;
            spinCounter++;
        }
        while ( hdg < 0.0) {
            hdg += 360.0;
            spinCounter--;
        }
    }


    // adjust target bank angle if heading lock engaged
    if (hdg_lock) {
        double bank_sense = 0.0;
        double diff = fabs(hdg - tgt_heading);
        if (diff > 180)
            diff = fabs(diff - 360);

        double sum = hdg + diff;
        if (sum > 360.0)
            sum -= 360.0;
        if (fabs(sum - tgt_heading) < 1.0) {
            bank_sense = 1.0;   // right turn
        } else {
            bank_sense = -1.0;  // left turn
        }
        if (diff < 30) {
            tgt_roll = diff * bank_sense;
        } else {
            tgt_roll = 30.0 * bank_sense;
        }
        if ((fabs((double) spinCounter) > 1) && (diff > 30)) {
            tgt_speed *= 0.999; // Ugly hack: If aircraft get stuck, they will continually spin around.
            // The only way to resolve this is to make them slow down.
            //if (tempReg.empty())
            //  tempReg = trafficRef->getRegistration();
            //if (trafficRef->getRegistration() == tempReg) {
            //    cerr << trafficRef->getRegistration()
            //         << " appears to be spinning: " << spinCounter << endl
            //         << " speed          " << speed << endl
            //         << " heading        " << hdg << endl
            //         << " lead distance  " << fp->getLeadDistance() << endl
            //         << " waypoint       " << fp->getCurrentWaypoint()->name
            //         << " target heading " << tgt_heading << endl
            //         << " lead in angle  " << fp->getLeadInAngle()<< endl
            //         << " roll           " << roll << endl
            //         << " target_roll    " << tgt_roll << endl;
            //}
        }
    }

    // adjust bank angle, use 9 degrees per second
    double bank_diff = tgt_roll - roll;
    if (fabs(bank_diff) > 0.2) {
        if (bank_diff > 0.0)
            roll += 9.0 * dt;

        if (bank_diff < 0.0)
            roll -= 9.0 * dt;
        //while (roll > 180) roll -= 360;
        //while (roll < 180) roll += 360;
    }

    // adjust altitude (meters) based on current vertical speed (fpm)
    altitude_ft += vs / 60.0 * dt;
    pos.setElevationFt(altitude_ft);  

    // adjust target Altitude, based on ground elevation when on ground
    if (no_roll) {
        getGroundElev(dt);
        doGroundAltitude();
    } else {
        // find target vertical speed if altitude lock engaged
        if (alt_lock && use_perf_vs) {
            if (altitude_ft < tgt_altitude_ft) {
                tgt_vs = tgt_altitude_ft - altitude_ft;
                if (tgt_vs > performance->climb_rate)
                    tgt_vs = performance->climb_rate;
            } else {
                tgt_vs = tgt_altitude_ft - altitude_ft;
                if (tgt_vs  < (-performance->descent_rate))
                    tgt_vs = -performance->descent_rate;
            }
        }

        if (alt_lock && !use_perf_vs) {
            double max_vs = 4*(tgt_altitude_ft - altitude_ft);
            double min_vs = 100;
            if (tgt_altitude_ft < altitude_ft)
                min_vs = -100.0;
            if ((fabs(tgt_altitude_ft - altitude_ft) < 1500.0)
                    && (fabs(max_vs) < fabs(tgt_vs)))
                tgt_vs = max_vs;

            if (fabs(tgt_vs) < fabs(min_vs))
                tgt_vs = min_vs;
        }
    }
    // adjust vertical speed
    double vs_diff = tgt_vs - vs;
    if (fabs(vs_diff) > 10.0) {
        if (vs_diff > 0.0) {
            vs += 900.0 * dt;

            if (vs > tgt_vs)
                vs = tgt_vs;
        } else {
            vs -= 400.0 * dt;

           if (vs < tgt_vs)
               vs = tgt_vs;
        }
    }

    // match pitch angle to vertical speed
    if (vs > 0) {
        pitch = vs * 0.005;
    } else {
        pitch = vs * 0.002;
    }

    //###########################//
    // do calculations for radar //
    //###########################//
    double range_ft2 = UpdateRadar(manager);

    //************************************//
    // Tanker code                        //
    //************************************//

    if ( isTanker) {
        if ( (range_ft2 < 250.0 * 250.0) && (y_shift > 0.0)
                && (elevation > 0.0) ) {
            //refuel_node->setBoolValue(true);
            contact = true;
        } else {
            //refuel_node->setBoolValue(false);
            contact = false;
        }
    } else {
        contact = false;
    }
}


void FGAIAircraft::AccelTo(double speed) {
    tgt_speed = speed;
}


void FGAIAircraft::PitchTo(double angle) {
    tgt_pitch = angle;
    alt_lock = false;
}


void FGAIAircraft::RollTo(double angle) {
    tgt_roll = angle;
    hdg_lock = false;
}


void FGAIAircraft::YawTo(double angle) {
    tgt_yaw = angle;
}


void FGAIAircraft::ClimbTo(double alt_ft ) {
    tgt_altitude_ft = alt_ft;
    alt_lock = true;
}


void FGAIAircraft::TurnTo(double heading) {
    tgt_heading = heading;
    hdg_lock = true;
}


double FGAIAircraft::sign(double x) {
    if ( x < 0.0 )
        return -1.0;
    else
        return 1.0;
}


void FGAIAircraft::setFlightPlan(const std::string& flightplan, bool repeat) {
    if (!flightplan.empty()) {
        FGAIFlightPlan* fp = new FGAIFlightPlan(flightplan);
        fp->setRepeat(repeat);
        SetFlightPlan(fp);
    }
}


void FGAIAircraft::SetFlightPlan(FGAIFlightPlan *f) {
    delete fp;
    fp = f;
}


void FGAIAircraft::ProcessFlightPlan( double dt, time_t now ) {
    bool eraseWaypoints;
    if (trafficRef) {
//      FGAirport *arr;
//      FGAirport *dep;
        eraseWaypoints = true;
//      cerr << trafficRef->getRegistration();
//      cerr << "Departure airport " << endl;
//      dep = trafficRef->getDepartureAirport();
//      if (dep)
//          cerr << dep->getId() << endl;
//      cerr << "Arrival   airport " << endl;
//      arr = trafficRef->getArrivalAirport();
//      if (arr)
//          cerr << arr->getId() <<endl << endl;;
    } else
        eraseWaypoints = false;

    //cerr << "Processing Flightplan" << endl;
    FGAIFlightPlan::waypoint* prev = 0; // the one behind you
    FGAIFlightPlan::waypoint* curr = 0; // the one ahead
    FGAIFlightPlan::waypoint* next = 0; // the next plus 1
    prev = fp->getPreviousWaypoint();
    curr = fp->getCurrentWaypoint();
    next = fp->getNextWaypoint();
    dt_count += dt;

    if (!prev) {  //beginning of flightplan, do this initialization once
        //setBank(0.0);
        spinCounter = 0;
        tempReg = "";
        //prev_dist_to_go = HUGE;
        //cerr << "Before increment " << curr-> name << endl;
        fp->IncrementWaypoint(eraseWaypoints);
        //prev = fp->getPreviousWaypoint(); //first waypoint
        //curr = fp->getCurrentWaypoint();  //second waypoint
        //next = fp->getNextWaypoint();     //third waypoint (might not exist!)
        //cerr << "After increment " << prev-> name << endl;
        if (!(fp->getNextWaypoint()) && trafficRef)
            loadNextLeg();

        //cerr << "After load " << prev-> name << endl;
        prev = fp->getPreviousWaypoint(); //first waypoint
        curr = fp->getCurrentWaypoint();  //second waypoint
        next = fp->getNextWaypoint();     //third waypoint (might not exist!)
        //cerr << "After load " << prev-> name << endl;
        setLatitude(prev->latitude);
        setLongitude(prev->longitude);
        setSpeed(prev->speed);
        setAltitude(prev->altitude);

        if (prev->speed > 0.0)
            setHeading(fp->getBearing(prev->latitude, prev->longitude, curr));
        else
            setHeading(fp->getBearing(curr->latitude, curr->longitude, prev));

        // If next doesn't exist, as in incrementally created flightplans for
        // AI/Trafficmanager created plans,
        // Make sure lead distance is initialized otherwise
        if (next)
            fp->setLeadDistance(speed, hdg, curr, next);

        if (curr->crossat > -1000.0) { //use a calculated descent/climb rate
            use_perf_vs = false;
            tgt_vs = (curr->crossat - prev->altitude)
                    / (fp->getDistanceToGo(pos.getLatitudeDeg(), pos.getLongitudeDeg(), curr)
                    / 6076.0 / prev->speed*60.0);
            tgt_altitude_ft = curr->crossat;
        } else {
            use_perf_vs = true;
            tgt_altitude_ft = prev->altitude;
        }
        alt_lock = hdg_lock = true;
        no_roll = prev->on_ground;
        if (no_roll) {
            Transform();         // make sure aip is initialized.
            getGroundElev(60.1); // make sure it's exectuted first time around, so force a large dt value
            //getGroundElev(60.1); // Need to do this twice.
            //cerr << trafficRef->getRegistration() << " Setting altitude to " << tgt_altitude << endl;
            doGroundAltitude(); //(tgt_altitude);
        }
        prevSpeed = 0;
        //cout << "First waypoint:  " << prev->name << endl;
        //cout << "  Target speed:    " << tgt_speed << endl;
        //cout << "  Target altitude: " << tgt_altitude << endl;
        //cout << "  Target heading:  " << tgt_heading << endl << endl;
        //cerr << "Done Flightplan init" << endl;
        return;
    } // end of initialization

    // let's only process the flight plan every 100 ms.
    if ((dt_count < 0.1) || (now < fp->getStartTime())) {
        //cerr  << "done fp dt" << endl;
        return;
    } else {
        dt_count = 0;
    }
    // check to see if we've reached the lead point for our next turn
    double dist_to_go = fp->getDistanceToGo(pos.getLatitudeDeg(), pos.getLongitudeDeg(), curr);

    //cerr << "2" << endl;
    double lead_dist = fp->getLeadDistance();
    //cerr << " Distance : " << dist_to_go << ": Lead distance " << lead_dist << endl;
    // experimental: Use fabs, because speed can be negative (I hope) during push_back.

    if (lead_dist < fabs(2*speed)) {
        lead_dist = fabs(2*speed);  //don't skip over the waypoint
        //cerr << "Extending lead distance to " << lead_dist << endl;
    }
//  FGAirport * apt = trafficRef->getDepartureAirport();
//  if ((dist_to_go > prev_dist_to_go) && trafficRef && apt) {
//      if (apt->getId() == string("EHAM"))
//          cerr << "Alert: " << trafficRef->getRegistration() << " is moving away from waypoint " << curr->name  << endl
//               << "Target heading : " << tgt_heading << "act heading " << hdg << " Tgt speed : " << tgt_speed << endl
//               << "Lead distance : " << lead_dist  << endl
//               << "Distance to go: " << dist_to_go << endl;
//  }

    prev_dist_to_go = dist_to_go;
    //cerr << "2" << endl;
    //if (no_roll)
    //  lead_dist = 10.0;
    //cout << "Leg : " << (fp->getLeg()-1) << ". dist_to_go: " << dist_to_go << ",  lead_dist: "
    //     << lead_dist << ", tgt_speed " << tgt_speed << ", tgt_heading " << tgt_heading
    //     << " speed " << speed << " hdg " << hdg << ". Altitude "  << altitude << " TAget alt :"
    //     << tgt_altitude << endl;

    if ( dist_to_go < lead_dist ) {
        //prev_dist_to_go = HUGE;
        // For traffic manager generated aircraft:
        // check if the aircraft flies of of user range. And adjust the
        // Current waypoint's elevation according to Terrain Elevation
        if (curr->finished) {  //end of the flight plan
            if (fp->getRepeat())
                fp->restart();
            else
                setDie(true);

            //cerr << "Done die end of fp" << endl;
            return;
        }

        // we've reached the lead-point for the waypoint ahead
        //cerr << "4" << endl;
        //cerr << "Situation after lead point" << endl;
        //cerr << "Prviious: " << prev->name << endl;
        //cerr << "Current : " << curr->name << endl;
        //cerr << "Next    : " << next->name << endl;
        if (next) {
            tgt_heading = fp->getBearing(curr, next);
            spinCounter = 0;
        }

        fp->IncrementWaypoint(eraseWaypoints);
        if (!(fp->getNextWaypoint()) && trafficRef)
            loadNextLeg();

        prev = fp->getPreviousWaypoint();
        curr = fp->getCurrentWaypoint();
        next = fp->getNextWaypoint();

        // Now that we have incremented the waypoints, excute some traffic manager specific code
        // based on the name of the waypoint we just passed.
        if (trafficRef) {
            double userLatitude  = fgGetDouble("/position/latitude-deg");
            double userLongitude = fgGetDouble("/position/longitude-deg");
            double course, distance;
            SGWayPoint current(pos.getLongitudeDeg(), pos.getLatitudeDeg(), 0);
            SGWayPoint user (userLongitude, userLatitude, 0);
            user.CourseAndDistance(current, &course, &distance);
            if ((distance * SG_METER_TO_NM) > TRAFFICTOAIDIST) {
                setDie(true);
                //cerr << "done fp die out of range" << endl;
                return;
            }

            FGAirport * dep = trafficRef->getDepartureAirport();
            FGAirport * arr = trafficRef->getArrivalAirport();
            // At parking the beginning of the airport
            if (!( dep && arr)) {
                setDie(true);
                return;
            }

            //if ((dep->getId() == string("EHAM") || (arr->getId() == string("EHAM")))) {
            //    cerr << trafficRef->getRegistration()
            //         << " Enroute from " << dep->getId()
            //         << " to "           << arr->getId()
            //         << " just crossed " << prev->name
            //         << " Assigned rwy     " << fp->getRunwayId()
            //         << " " << fp->getRunway() << endl;
            // }
            //if ((dep->getId() == string("EHAM")) && (prev->name == "park2")) {
            //    cerr << "Schiphol ground "
            //         << trafficRef->getCallSign();
            //    if (trafficRef->getHeavy())
            //        cerr << "Heavy";
            //    cerr << ", is type "
            //         << trafficRef->getAircraft()
            //         << " ready to go. IFR to "
            //         << arr->getId() <<endl;
            // }

            if (prev->name == "park2")
                dep->getDynamics()->releaseParking(fp->getGate());

            // Some debug messages, specific to testing the Logical networks.
            // if ((arr->getId() == string("EHAM")) && (prev->name  == "Center")) {
            //     cerr << "Schiphol ground "
            //          << trafficRef->getRegistration() << " "
            //          << trafficRef->getCallSign();
            //     if (trafficRef->getHeavy())
            //         cerr << "Heavy";
            //     cerr << ", arriving from " << dep->getName() ;
            //     cerr << " landed runway "
            //          << fp->getRunway()
            //          << " request taxi to gate "
            //          << arr->getDynamics()->getParkingName(fp->getGate())
            //          << endl;
            // }
            if (prev->name == "END")
                fp->setTime(trafficRef->getDepartureTime());
            //cerr << "5" << endl;
        }

        if (next) {
            //cerr << "Current waypoint" << curr->name << endl;
            //cerr << "Next waypoint" << next->name << endl;
            fp->setLeadDistance(speed, tgt_heading, curr, next);
        }

        //cerr << "5.1" << endl;
        if (!(prev->on_ground)) { // only update the tgt altitude from flightplan if not on the ground
            tgt_altitude_ft = prev->altitude;
            if (curr->crossat > -1000.0) {
                //cerr << "5.1a" << endl;
                use_perf_vs = false;
                tgt_vs = (curr->crossat - altitude_ft) / (fp->getDistanceToGo(pos.getLatitudeDeg(), pos.getLongitudeDeg(), curr)
                        / 6076.0 / speed*60.0);
                //cerr << "5.1b" << endl;
                tgt_altitude_ft = curr->crossat;
            } else {
                //cerr << "5.1c" << endl;
                use_perf_vs = true;
                //cerr << "5.1d" << endl;
                //cerr << "Setting target altitude : " <<tgt_altitude_ft << endl;
            }
        }
        //cerr << "6" << endl;
        tgt_speed = prev->speed;
        hdg_lock = alt_lock = true;
        no_roll = prev->on_ground;
        //cout << "Crossing waypoint: " << prev->name << endl;
        //cout << "  Target speed:    " << tgt_speed << endl;
        //cout << "  Target altitude: " << tgt_altitude_ft << endl;
        //cout << "  Target heading:  " << tgt_heading << endl << endl;

    } else {
        double calc_bearing = fp->getBearing(pos.getLatitudeDeg(), pos.getLongitudeDeg(), curr);
        //cerr << "Bearing = " << calc_bearing << endl;
        if (speed < 0) {
            calc_bearing +=180;
            if (calc_bearing > 360)
                calc_bearing -= 360;
        }

        if (finite(calc_bearing)) {
            double hdg_error = calc_bearing - tgt_heading;
            if (fabs(hdg_error) > 1.0) {
                TurnTo( calc_bearing );
            }

        } else {
            cerr << "calc_bearing is not a finite number : "
                 << "Speed " << speed
                 << "pos : " << pos.getLatitudeDeg() << ", " << pos.getLongitudeDeg()
                 << "waypoint " << curr->latitude << ", " << curr->longitude << endl;
            cerr << "waypoint name " << curr->name;
            exit(1);  // FIXME
        }

        double speed_diff = speed - prevSpeed;
        // Update the lead distance calculation if speed has changed sufficiently
        // to prevent spinning (hopefully);
        if (fabs(speed_diff) > 10) {
            prevSpeed = speed;
            fp->setLeadDistance(speed, tgt_heading, curr, next);
        }

        //cerr << "Done Processing FlightPlan"<< endl;
    }
}


bool FGAIAircraft::_getGearDown() const {
    return ((props->getFloatValue("position/altitude-agl-ft") < 900.0)
            && (props->getFloatValue("velocities/airspeed-kt")
            < performance->land_speed*1.25));
}


void FGAIAircraft::loadNextLeg() {
    //delete fp;
    //time_t now = time(NULL) + fgGetLong("/sim/time/warp");

    //FGAIModelEntity entity;
    //entity.m_class = "jet_transport";
    //entity.path = modelPath.c_str();
    //entity.flightplan = "none";
    //entity.latitude = _getLatitude();
    //entity.longitude = _getLongitude();
    //entity.altitude = trafficRef->getCruiseAlt() * 100; // convert from FL to feet
    //entity.speed = 450; // HACK ALERT
    //entity.fp = new FGAIFlightPlan(&entity, courseToDest, i->getDepartureTime(), dep, arr);
    int leg;
    if ((leg = fp->getLeg())  == 10) {
        trafficRef->next();
        leg = 1;
        fp->setLeg(leg);
        //cerr << "Resetting leg : " << leg << endl;
    }
    //leg++;
    //fp->setLeg(leg);
    //cerr << "Creating leg number : " << leg << endl;
    FGAirport *dep = trafficRef->getDepartureAirport();
    FGAirport *arr = trafficRef->getArrivalAirport();
    if (!(dep && arr)) {
        setDie(true);
        //cerr << "Failed to get airport in AIAircraft::ProcessFlightplan()" << endl;
        //if (dep)
        //  cerr << "Departure " << dep->getId() << endl;
        //if (arr)
        //  cerr << "Arrival   " << arr->getId() << endl;

    } else {
        double cruiseAlt = trafficRef->getCruiseAlt() * 100;
        //cerr << "Creating new leg using " << cruiseAlt << " as cruise altitude."<< endl;

        fp->create (dep,
                    arr,
                    leg,
                    cruiseAlt, //(trafficRef->getCruiseAlt() * 100), // convert from FL to feet
                    trafficRef->getSpeed(),
                    _getLatitude(),
                    _getLongitude(),
                    false,
                    trafficRef->getRadius(),
                    trafficRef->getFlightType(),
                    acType,
                    company);
        //prev = fp->getPreviousWaypoint();
        //curr = fp->getCurrentWaypoint();
        //next = fp->getNextWaypoint();
        //cerr << "25" << endl;
        //if (next)
        //        {
        //  //cerr << "Next waypoint" << next->name << endl;
        //          fp->setLeadDistance(speed, tgt_heading, curr, next);
        //        }
        //cerr << "25.1" << endl;
        //if (curr->crossat > -1000.0) {
        //        //cerr << "25.1a" << endl;
        //        use_perf_vs = false;
        //
        //        tgt_vs = (curr->crossat - altitude_ft)/
        //          (fp->getDistanceToGo(pos.lat(), pos.lon(), curr)/6076.0/speed*60.0);
        //        //cerr << "25.1b" << endl;
        //        tgt_altitude_ft = curr->crossat;
        //} else {
        //        //cerr << "25.1c" << endl;
        //        use_perf_vs = true;
        //        //cerr << "25.1d" << endl;
        //        tgt_altitude_ft = prev->altitude;
        //        //cerr << "Setting target altitude : " <<tgt_altitude_ft << endl;
        // }
        //cerr << "26" << endl;
        //tgt_speed = prev->speed;
        //hdg_lock = alt_lock = true;
        //no_roll = prev->on_ground;
    }
    //else
    //{
    //delete entity.fp;
    //entity.fp = new FGAIFlightPlan(&entity,
    //                                 999,  // A hack
    //                                 trafficRef->getDepartureTime(),
    //                                 trafficRef->getDepartureAirport(),
    //                                 trafficRef->getArrivalAirport(),
    //                                 false,
    //                                 acType,
    //                                 company);
    //SetFlightPlan(entity.fp);
}


// Note: This code is copied from David Luff's AILocalTraffic
// Warning - ground elev determination is CPU intensive
// Either this function or the logic of how often it is called
// will almost certainly change.

void FGAIAircraft::getGroundElev(double dt) {
    dt_elev_count += dt;

    // Update minimally every three secs, but add some randomness
    // to prevent all IA objects doing this in synchrony
    if (dt_elev_count < (3.0) + (rand() % 10))
        return;
    else
       dt_elev_count = 0;

    // Only do the proper hitlist stuff if we are within visible range of the viewer.
    if (!invisible) {
        double visibility_meters = fgGetDouble("/environment/visibility-m");

        FGViewer* vw = globals->get_current_view();
        double course, distance;

        SGWayPoint current(pos.getLongitudeDeg(), pos.getLatitudeDeg(), 0);
        SGWayPoint view (vw->getLongitude_deg(), vw->getLatitude_deg(), 0);
        view.CourseAndDistance(current, &course, &distance);
        if(distance > visibility_meters) {
            //aip.getSGLocation()->set_cur_elev_m(aptElev);
            return;
        }

        // FIXME: make sure the pos.lat/pos.lon values are in degrees ...
        double range = 500.0;
        if (!globals->get_tile_mgr()->scenery_available(pos.getLatitudeDeg(), pos.getLongitudeDeg(), range)) {
            // Try to shedule tiles for that position.
            globals->get_tile_mgr()->update( aip.getSGLocation(), range );
        }

        // FIXME: make sure the pos.lat/pos.lon values are in degrees ...
        double alt;
        if (globals->get_scenery()->get_elevation_m(pos.getLatitudeDeg(), pos.getLongitudeDeg(), 20000.0, alt, 0))
            tgt_altitude_ft = alt * SG_METER_TO_FEET;

        //cerr << "Target altitude : " << tgt_altitude_ft << endl;
        // if (globals->get_scenery()->get_elevation_m(pos.lat(), pos.lon(),
        //                                            20000.0, alt))
        //    tgt_altitude_ft = alt * SG_METER_TO_FEET;
        //cerr << "Target altitude : " << tgt_altitude_ft << endl;
    }
}


void FGAIAircraft::setCallSign(const string& s) {
    callsign = s;
}


void FGAIAircraft::setTACANChannelID(const string& id) {
    TACAN_channel_id = id;
}


void FGAIAircraft::doGroundAltitude() {
   if (fabs(altitude_ft - (tgt_altitude_ft+groundOffset)) > 1000.0)
       altitude_ft = (tgt_altitude_ft + groundOffset);
   else
      altitude_ft += 0.1 * ((tgt_altitude_ft+groundOffset) - altitude_ft);
}