src/ATC/AILocalTraffic.cxx

   1 // FGAILocalTraffic - AIEntity derived class with enough logic to
   2 // fly and interact with the traffic pattern.
   3 //
   4 // Written by David Luff, started March 2002.
   5 //
   6 // Copyright (C) 2002  David C. Luff - david.luff@nottingham.ac.uk
   7 //
   8 // This program is free software; you can redistribute it and/or
   9 // modify it under the terms of the GNU General Public License as
  10 // published by the Free Software Foundation; either version 2 of the
  11 // License, or (at your option) any later version.
  12 //
  13 // This program is distributed in the hope that it will be useful, but
  14 // WITHOUT ANY WARRANTY; without even the implied warranty of
  15 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  16 // General Public License for more details.
  17 //
  18 // You should have received a copy of the GNU General Public License
  19 // along with this program; if not, write to the Free Software
  20 // Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  21
  22 #ifdef HAVE_CONFIG_H
  23 #  include <config.h>
  24 #endif
  25
  26 #include <simgear/scene/model/location.hxx>
  27
  28 #include <Airports/runways.hxx>
  29 #include <Main/globals.hxx>
  30 #include <Scenery/scenery.hxx>
  31 #include <Scenery/tilemgr.hxx>
  32 #include <simgear/math/point3d.hxx>
  33 #include <simgear/math/sg_geodesy.hxx>
  34 #include <simgear/misc/sg_path.hxx>
  35 #include <string>
  36 #include <math.h>
  37
  38 SG_USING_STD(string);
  39
  40 #include "ATCmgr.hxx"
  41 #include "AILocalTraffic.hxx"
  42 #include "ATCutils.hxx"
  43
  44 FGAILocalTraffic::FGAILocalTraffic() {
  45         ATC = globals->get_ATC_mgr();
  46
  47         // TODO - unhardwire this - possibly let the AI manager set the callsign
  48         plane.callsign = "Trainer-two-five-charlie";
  49         plane.type = GA_SINGLE;
  50
  51         roll = 0.0;
  52         pitch = 0.0;
  53         hdg = 270.0;
  54
  55         //Hardwire initialisation for now - a lot of this should be read in from config eventually
  56         Vr = 70.0;
  57         best_rate_of_climb_speed = 70.0;
  58         //best_rate_of_climb;
  59         //nominal_climb_speed;
  60         //nominal_climb_rate;
  61         //nominal_circuit_speed;
  62         //min_circuit_speed;
  63         //max_circuit_speed;
  64         nominal_descent_rate = 500.0;
  65         nominal_final_speed = 65.0;
  66         //nominal_approach_speed;
  67         //stall_speed_landing_config;
  68         nominalTaxiSpeed = 8.0;
  69         taxiTurnRadius = 8.0;
  70         wheelOffset = 1.45;     // Warning - hardwired to the C172 - we need to read this in from file.
  71         elevInitGood = false;
  72         // Init the property nodes
  73         wind_from_hdg = fgGetNode("/environment/wind-from-heading-deg", true);
  74         wind_speed_knots = fgGetNode("/environment/wind-speed-kts", true);
  75         circuitsToFly = 0;
  76         liningUp = false;
  77         taxiRequestPending = false;
  78         taxiRequestCleared = false;
  79         holdingShort = false;
  80         clearedToLineUp = false;
  81         clearedToTakeOff = false;
  82         reportReadyForDeparture = false;
  83         contactTower = false;
  84         contactGround = false;
  85 }
  86
  87 FGAILocalTraffic::~FGAILocalTraffic() {
  88 }
  89
  90
  91 // Get details of the active runway
  92 // It is assumed that by the time this is called the tower control and airport code will have been set up.
  93 void FGAILocalTraffic::GetRwyDetails() {
  94         //cout << "GetRwyDetails called" << endl;
  95
  96         rwy.rwyID = tower->GetActiveRunway();
  97
  98         // Now we need to get the threshold position and rwy heading
  99
 100         SGPath path( globals->get_fg_root() );
 101         path.append( "Airports" );
 102         path.append( "runways.mk4" );
 103         FGRunways runways( path.c_str() );
 104
 105         FGRunway runway;
 106         bool rwyGood = runways.search(airportID, rwy.rwyID, &runway);
 107         if(rwyGood) {
 108                 // Get the threshold position
 109         hdg = runway.heading;   // TODO - check - is this our heading we are setting here, and if so should we be?
 110                 //cout << "hdg reset to " << hdg << '\n';
 111                 double other_way = hdg - 180.0;
 112                 while(other_way <= 0.0) {
 113                         other_way += 360.0;
 114                 }
 115
 116         // move to the +l end/center of the runway
 117                 //cout << "Runway center is at " << runway.lon << ", " << runway.lat << '\n';
 118         Point3D origin = Point3D(runway.lon, runway.lat, aptElev);
 119                 Point3D ref = origin;
 120         double tshlon, tshlat, tshr;
 121                 double tolon, tolat, tor;
 122                 rwy.length = runway.length * SG_FEET_TO_METER;
 123         geo_direct_wgs_84 ( aptElev, ref.lat(), ref.lon(), other_way,
 124                                 rwy.length / 2.0 - 25.0, &tshlat, &tshlon, &tshr );
 125         geo_direct_wgs_84 ( aptElev, ref.lat(), ref.lon(), hdg,
 126                                 rwy.length / 2.0 - 25.0, &tolat, &tolon, &tor );
 127                 // Note - 25 meters in from the runway end is a bit of a hack to put the plane ahead of the user.
 128                 // now copy what we need out of runway into rwy
 129         rwy.threshold_pos = Point3D(tshlon, tshlat, aptElev);
 130                 Point3D takeoff_end = Point3D(tolon, tolat, aptElev);
 131                 //cout << "Threshold position = " << tshlon << ", " << tshlat << ", " << aptElev << '\n';
 132                 //cout << "Takeoff position = " << tolon << ", " << tolat << ", " << aptElev << '\n';
 133                 rwy.hdg = hdg;
 134                 // Set the projection for the local area
 135                 ortho.Init(rwy.threshold_pos, rwy.hdg);
 136                 rwy.end1ortho = ortho.ConvertToLocal(rwy.threshold_pos);        // should come out as zero
 137                 rwy.end2ortho = ortho.ConvertToLocal(takeoff_end);
 138         } else {
 139                 SG_LOG(SG_ATC, SG_ALERT, "Help  - can't get good runway in FGAILocalTraffic!!\n");
 140         }
 141 }
 142
 143 /*
 144 There are two possible scenarios during initialisation:
 145 The first is that the user is flying towards the airport, and hence the traffic
 146 could be initialised anywhere, as long as the AI planes are consistent with
 147 each other.
 148 The second is that the user has started the sim at or close to the airport, and
 149 hence the traffic must be initialised with respect to the user as well as each other.
 150 To a certain extent it's FGAIMgr that has to worry about this, but we need to provide
 151 sufficient initialisation functionality within the plane classes to allow the manager
 152 to initialy position them where and how required.
 153 */
 154 bool FGAILocalTraffic::Init(string ICAO, OperatingState initialState, PatternLeg initialLeg) {
 155         //cout << "FGAILocalTraffic.Init(...) called" << endl;
 156         // Hack alert - Hardwired path!!
 157         string planepath = "Aircraft/c172/Models/c172-dpm.ac";
 158         SGPath path = globals->get_fg_root();
 159         path.append(planepath);
 160         ssgBranch *model = sgLoad3DModel( path.str(),
 161                                           planepath.c_str(),
 162                                           globals->get_props(),
 163                                           globals->get_sim_time_sec() );
 164         aip.init( model );
 165         aip.setVisible(false);          // This will be set to true once a valid ground elevation has been determined
 166         globals->get_scenery()->get_scene_graph()->addKid(aip.getSceneGraph());
 167
 168         // Find the tower frequency - this is dependent on the ATC system being initialised before the AI system
 169         airportID = ICAO;
 170         AirportATC a;
 171         if(ATC->GetAirportATCDetails(airportID, &a)) {
 172                 if(a.tower_freq) {      // Has a tower
 173                         tower = (FGTower*)ATC->GetATCPointer((string)airportID, TOWER); // Maybe need some error checking here
 174                         if(tower == NULL) {
 175                                 // Something has gone wrong - abort or carry on with un-towered operation?
 176                                 return(false);
 177                         }
 178                         freq = (double)tower->get_freq() / 100.0;
 179                         ground = tower->GetGroundPtr();
 180                         if(ground == NULL) {
 181                                 // Something has gone wrong :-(
 182                                 SG_LOG(SG_ATC, SG_ALERT, "ERROR - can't get a ground pointer from tower control in FGAILocalTraffic::Init() :-(");
 183                                 return(false);
 184                         } else if((initialState == PARKED) || (initialState == TAXIING)) {
 185                                 freq = (double)ground->get_freq() / 100.0;
 186                         }
 187                         //cout << "AILocalTraffic freq is " << freq << '\n';
 188                 } else {
 189                         // Check CTAF, unicom etc
 190                 }
 191         } else {
 192                 //cout << "Unable to find airport details in FGAILocalTraffic::Init()\n";
 193         }
 194
 195         // Get the airport elevation
 196         aptElev = dclGetAirportElev(airportID.c_str()) * SG_FEET_TO_METER;
 197         //cout << "Airport elev in AILocalTraffic = " << aptElev << '\n';
 198         // WARNING - we use this elev for the whole airport - some assumptions in the code
 199         // might fall down with very slopey airports.
 200
 201         //cout << "In Init(), initialState = " << initialState << endl;
 202         operatingState = initialState;
 203         switch(operatingState) {
 204         case PARKED:
 205                 ourGate = ground->GetGateNode();
 206                 if(ourGate == NULL) {
 207                         // Implies no available gates - what shall we do?
 208                         // For now just vanish the plane - possibly we can make this more elegant in the future
 209                         SG_LOG(SG_ATC, SG_ALERT, "No gate found by FGAILocalTraffic whilst attempting Init at " << airportID << '\n');
 210                         return(false);
 211                 }
 212                 pitch = 0.0;
 213                 roll = 0.0;
 214                 vel = 0.0;
 215                 slope = 0.0;
 216                 pos = ourGate->pos;
 217                 pos.setelev(aptElev);
 218                 hdg = ourGate->heading;
 219
 220                 // Now we've set the position we can do the ground elev
 221                 elevInitGood = false;
 222                 inAir = false;
 223                 DoGroundElev();
 224
 225                 Transform();
 226                 break;
 227         case TAXIING:
 228                 // FIXME - implement this case properly
 229                 return(false);  // remove this line when fixed!
 230                 break;
 231         case IN_PATTERN:
 232                 // For now we'll always start the in_pattern case on the threshold ready to take-off
 233                 // since we've got the implementation for this case already.
 234                 // TODO - implement proper generic in_pattern startup.
 235
 236                 // Get the active runway details (and copy them into rwy)
 237                 GetRwyDetails();
 238
 239                 // Initial position on threshold for now
 240                 pos.setlat(rwy.threshold_pos.lat());
 241                 pos.setlon(rwy.threshold_pos.lon());
 242                 pos.setelev(rwy.threshold_pos.elev());
 243                 hdg = rwy.hdg;
 244
 245                 // Now we've set the position we can do the ground elev
 246                 // This might not always be necessary if we implement in-air start
 247                 elevInitGood = false;
 248                 inAir = false;
 249                 DoGroundElev();
 250
 251                 pitch = 0.0;
 252                 roll = 0.0;
 253                 leg = TAKEOFF_ROLL;
 254                 vel = 0.0;
 255                 slope = 0.0;
 256
 257                 circuitsToFly = 0;              // ie just fly this circuit and then stop
 258                 touchAndGo = false;
 259                 // FIXME TODO - pattern direction is still hardwired
 260                 patternDirection = -1;          // Left
 261                 // At the bare minimum we ought to make sure it goes the right way at dual parallel rwy airports!
 262                 if(rwy.rwyID.size() == 3) {
 263                         patternDirection = (rwy.rwyID.substr(2,1) == "R" ? 1 : -1);
 264                 }
 265
 266                 operatingState = IN_PATTERN;
 267
 268                 Transform();
 269                 break;
 270         default:
 271                 SG_LOG(SG_ATC, SG_ALERT, "Attempt to set unknown operating state in FGAILocalTraffic.Init(...)\n");
 272                 return(false);
 273         }
 274
 275
 276         return(true);
 277 }
 278
 279 // Commands to do something from higher level logic
 280 void FGAILocalTraffic::FlyCircuits(int numCircuits, bool tag) {
 281         //cout << "FlyCircuits called" << endl;
 282
 283         switch(operatingState) {
 284         case IN_PATTERN:
 285                 circuitsToFly += numCircuits;
 286                 return;
 287                 break;
 288         case TAXIING:
 289                 // For now we'll punt this and do nothing
 290                 break;
 291         case PARKED:
 292                 circuitsToFly = numCircuits;    // Note that one too many circuits gets flown because we only test and decrement circuitsToFly after landing
 293                                                                                 // thus flying one too many circuits.  TODO - Need to sort this out better!
 294                 touchAndGo = tag;
 295 #if 0
 296                 // Get the active runway details (and copy them into rwy)
 297                 GetRwyDetails();
 298
 299                 // Get the takeoff node for the active runway, get a path to it and start taxiing
 300                 path = ground->GetPath(ourGate, rwy.rwyID);
 301                 if(path.size() < 2) {
 302                         // something has gone wrong
 303                         SG_LOG(SG_ATC, SG_ALERT, "Invalid path from gate to theshold in FGAILocalTraffic::FlyCircuits\n");
 304                         return;
 305                 }
 306                 /*
 307                 cout << "path returned was:" << endl;
 308                 for(unsigned int i=0; i<path.size(); ++i) {
 309                         switch(path[i]->struct_type) {
 310                         case NODE:
 311                                 cout << "NODE " << ((node*)(path[i]))->nodeID << endl;
 312                                 break;
 313                         case ARC:
 314                                 cout << "ARC\n";
 315                                 break;
 316                         }
 317                 }
 318                 */
 319                 // pop the gate - we're here already!
 320                 path.erase(path.begin());
 321                 //path.erase(path.begin());
 322                 /*
 323                 cout << "path after popping front is:" << endl;
 324                 for(unsigned int i=0; i<path.size(); ++i) {
 325                         switch(path[i]->struct_type) {
 326                         case NODE:
 327                                 cout << "NODE " << ((node*)(path[i]))->nodeID << endl;
 328                                 break;
 329                         case ARC:
 330                                 cout << "ARC\n";
 331                                 break;
 332                         }
 333                 }
 334                 */
 335
 336                 taxiState = TD_OUTBOUND;
 337                 StartTaxi();
 338
 339                 // Maybe the below should be set when we get to the threshold and prepare for TO?
 340                 // FIXME TODO - pattern direction is still hardwired
 341                 patternDirection = -1;          // Left
 342                 // At the bare minimum we ought to make sure it goes the right way at dual parallel rwy airports!
 343                 if(rwy.rwyID.size() == 3) {
 344                         patternDirection = (rwy.rwyID.substr(2,1) == "R" ? 1 : -1);
 345                 }
 346
 347                 Transform();
 348 #endif
 349                 break;
 350         }
 351 }
 352
 353 // Run the internal calculations
 354 void FGAILocalTraffic::Update(double dt) {
 355         //cout << "A" << flush;
 356         double responseTime = 10.0;             // seconds - this should get more sophisticated at some point
 357         responseCounter += dt;
 358         if((contactTower) && (responseCounter >= 8.0)) {
 359                 // Acknowledge request before changing frequency so it gets rendered if the user is on the same freq
 360                 string trns = "Tower ";
 361                 double f = globals->get_ATC_mgr()->GetFrequency(airportID, TOWER) / 100.0;
 362                 char buf[10];
 363                 sprintf(buf, "%f", f);
 364                 trns += buf;
 365                 trns += " ";
 366                 trns += plane.callsign;
 367                 Transmit(trns);
 368                 responseCounter = 0.0;
 369                 contactTower = false;
 370                 changeFreq = true;
 371                 changeFreqType = TOWER;
 372         }
 373
 374         if((changeFreq) && (responseCounter > 8.0)) {
 375                 switch(changeFreqType) {
 376                 case TOWER:
 377                         freq = (double)tower->get_freq() / 100.0;
 378                         //Transmit("DING!");
 379                         // Contact the tower, even if only virtually
 380                         changeFreq = false;
 381                         tower->ContactAtHoldShort(plane, this, CIRCUIT);
 382                         break;
 383                 case GROUND:
 384                         freq = (double)ground->get_freq() / 100.0;
 385                         break;
 386                 // And to avoid compiler warnings...
 387                 case APPROACH:
 388                         break;
 389                 case ATIS:
 390                         break;
 391                 case ENROUTE:
 392                         break;
 393                 case DEPARTURE:
 394                         break;
 395                 case INVALID:
 396                         break;
 397                 }
 398         }
 399
 400         //cout << "." << flush;
 401
 402         switch(operatingState) {
 403         case IN_PATTERN:
 404                 //cout << "In IN_PATTERN\n";
 405                 if(!inAir) DoGroundElev();
 406                 if(!elevInitGood) {
 407                         if(aip.getSGLocation()->get_cur_elev_m() > -9990.0) {
 408                                 pos.setelev(aip.getSGLocation()->get_cur_elev_m() + wheelOffset);
 409                                 //cout << "TAKEOFF_ROLL, POS = " << pos.lon() << ", " << pos.lat() << ", " << pos.elev() << '\n';
 410                                 //Transform();
 411                                 aip.setVisible(true);
 412                                 //cout << "Making plane visible!\n";
 413                                 elevInitGood = true;
 414                         }
 415                 }
 416                 FlyTrafficPattern(dt);
 417                 Transform();
 418                 break;
 419         case TAXIING:
 420                 //cout << "In TAXIING\n";
 421                 //cout << "*" << flush;
 422                 if(!elevInitGood) {
 423                         //DoGroundElev();
 424                         if(aip.getSGLocation()->get_cur_elev_m() > -9990.0) {
 425                                 pos.setelev(aip.getSGLocation()->get_cur_elev_m() + wheelOffset);
 426                                 //Transform();
 427                                 aip.setVisible(true);
 428                                 //Transform();
 429                                 //cout << "Making plane visible!\n";
 430                                 elevInitGood = true;
 431                         }
 432                 }
 433                 DoGroundElev();
 434                 //cout << "," << flush;
 435                 if(!((holdingShort) && (!clearedToLineUp))) {
 436                         //cout << "|" << flush;
 437                         Taxi(dt);
 438                 }
 439                 //cout << ";" << flush;
 440                 if((clearedToTakeOff) && (responseCounter >= 8.0)) {
 441                         // possible assumption that we're at the hold short here - may not always hold
 442                         // TODO - sort out the case where we're cleared to line-up first and then cleared to take-off on the rwy.
 443                         taxiState = TD_LINING_UP;
 444                         path = ground->GetPath(holdShortNode, rwy.rwyID);
 445                         /*
 446                         cout << "path returned was:" << endl;
 447                         for(unsigned int i=0; i<path.size(); ++i) {
 448                                 switch(path[i]->struct_type) {
 449                                         case NODE:
 450                                         cout << "NODE " << ((node*)(path[i]))->nodeID << endl;
 451                                         break;
 452                                         case ARC:
 453                                         cout << "ARC\n";
 454                                         break;
 455                                 }
 456                         }
 457                         */
 458                         clearedToTakeOff = false;       // We *are* still cleared - this simply stops the response recurring!!
 459                         holdingShort = false;
 460                         string trns = "Cleared for take-off ";
 461                         trns += plane.callsign;
 462                         Transmit(trns);
 463                         StartTaxi();
 464                 }
 465                 //cout << "^" << flush;
 466                 Transform();
 467                 break;
 468                 case PARKED:
 469                 //cout << "In PARKED\n";
 470                 if(!elevInitGood) {
 471                         DoGroundElev();
 472                         if(aip.getSGLocation()->get_cur_elev_m() > -9990.0) {
 473                                 pos.setelev(aip.getSGLocation()->get_cur_elev_m() + wheelOffset);
 474                                 //Transform();
 475                                 aip.setVisible(true);
 476                                 //Transform();
 477                                 //cout << "Making plane visible!\n";
 478                                 elevInitGood = true;
 479                         }
 480                 }
 481
 482                 if(circuitsToFly) {
 483                         if((taxiRequestPending) && (taxiRequestCleared)) {
 484                                 //cout << "&" << flush;
 485                                 // Get the active runway details (and copy them into rwy)
 486                                 GetRwyDetails();
 487
 488                                 // Get the takeoff node for the active runway, get a path to it and start taxiing
 489                                 path = ground->GetPathToHoldShort(ourGate, rwy.rwyID);
 490                                 if(path.size() < 2) {
 491                                         // something has gone wrong
 492                                         SG_LOG(SG_ATC, SG_ALERT, "Invalid path from gate to theshold in FGAILocalTraffic::FlyCircuits\n");
 493                                         return;
 494                                 }
 495                                 /*
 496                                 cout << "path returned was:\n";
 497                                 for(unsigned int i=0; i<path.size(); ++i) {
 498                                         switch(path[i]->struct_type) {
 499                                                 case NODE:
 500                                                 cout << "NODE " << ((node*)(path[i]))->nodeID << endl;
 501                                                 break;
 502                                                 case ARC:
 503                                                 cout << "ARC\n";
 504                                                 break;
 505                                         }
 506                                 }
 507                                 */
 508                                 path.erase(path.begin());       // pop the gate - we're here already!
 509                                 taxiState = TD_OUTBOUND;
 510                                 taxiRequestPending = false;
 511                                 holdShortNode = (node*)(*(path.begin() + path.size()));
 512                                 StartTaxi();
 513                         } else if(!taxiRequestPending) {
 514                                 //cout << "(" << flush;
 515                                 ground->RequestDeparture(plane, this);
 516                                 // Do some communication
 517                                 // airport name + tower + airplane callsign + location + request taxi for + operation type + ?
 518                                 string trns = "";
 519                                 trns += tower->get_name();
 520                                 trns += " tower ";
 521                                 trns += plane.callsign;
 522                                 trns += " on apron parking request taxi for traffic pattern";
 523                                 //cout << "trns = " << trns << endl;
 524                                 Transmit(trns);
 525                                 taxiRequestCleared = false;
 526                                 taxiRequestPending = true;
 527                         }
 528                 }
 529
 530                 //cout << "!" << flush;
 531
 532                 // Maybe the below should be set when we get to the threshold and prepare for TO?
 533                 // FIXME TODO - pattern direction is still hardwired
 534                 patternDirection = -1;          // Left
 535                 // At the bare minimum we ought to make sure it goes the right way at dual parallel rwy airports!
 536                 if(rwy.rwyID.size() == 3) {
 537                         patternDirection = (rwy.rwyID.substr(2,1) == "R" ? 1 : -1);
 538                 }
 539                 // Do nothing
 540                 Transform();
 541                 //cout << ")" << flush;
 542                 break;
 543         default:
 544                 break;
 545         }
 546         //cout << "I " << flush;
 547 }
 548
 549 void FGAILocalTraffic::RegisterTransmission(int code) {
 550         switch(code) {
 551         case 1: // taxi request cleared
 552                 taxiRequestCleared = true;
 553                 SG_LOG(SG_ATC, SG_INFO, "AI local traffic " << plane.callsign << " cleared to taxi...");
 554                 break;
 555         case 2: // contact tower
 556                 responseCounter = 0;
 557                 contactTower = true;
 558                 SG_LOG(SG_ATC, SG_INFO, "AI local traffic " << plane.callsign << " told to contact tower...");
 559                 break;
 560         case 3: // Cleared to line up
 561                 responseCounter = 0;
 562                 clearedToLineUp = true;
 563                 SG_LOG(SG_ATC, SG_INFO, "AI local traffic " << plane.callsign << " cleared to line-up...");
 564                 break;
 565         case 4: // cleared to take-off
 566                 responseCounter = 0;
 567                 clearedToTakeOff = true;
 568                 SG_LOG(SG_ATC, SG_INFO, "AI local traffic " << plane.callsign << " cleared to take-off...");
 569                 break;
 570         default:
 571                 break;
 572         }
 573 }
 574
 575 // Fly a traffic pattern
 576 // FIXME - far too much of the mechanics of turning, rolling, accellerating, descending etc is in here.
 577 //         Move it out to FGAIPlane and have FlyTrafficPattern just specify what to do, not the implementation.
 578 void FGAILocalTraffic::FlyTrafficPattern(double dt) {
 579         // Need to differentiate between in-air (IAS governed) and on-ground (vel governed)
 580         // Take-off is an interesting case - we are on the ground but takeoff speed is IAS governed.
 581
 582         static bool transmitted = false;        // FIXME - this is a hack
 583
 584         // WIND
 585         // Wind has two effects - a mechanical one in that IAS translates to a different vel, and the hdg != track,
 586         // but also a piloting effect, in that the AI must be able to descend at a different rate in order to hit the threshold.
 587
 588         //cout << "dt = " << dt << '\n';
 589         double dist = 0;
 590         // ack - I can't remember how long a rate 1 turn is meant to take.
 591         double turn_time = 60.0;        // seconds - TODO - check this guess
 592         double turn_circumference;
 593         double turn_radius;
 594         Point3D orthopos = ortho.ConvertToLocal(pos);   // ortho position of the plane
 595         //cout << "runway elev = " << rwy.threshold_pos.elev() << ' ' << rwy.threshold_pos.elev() * SG_METER_TO_FEET << '\n';
 596         //cout << "elev = " << pos.elev() << ' ' << pos.elev() * SG_METER_TO_FEET << '\n';
 597
 598         // HACK FOR TESTING - REMOVE
 599         //cout << "Calling ExitRunway..." << endl;
 600         //ExitRunway(orthopos);
 601         //return;
 602         // END HACK
 603
 604         //wind
 605         double wind_from = wind_from_hdg->getDoubleValue();
 606         double wind_speed = wind_speed_knots->getDoubleValue();
 607
 608         switch(leg) {
 609         case TAKEOFF_ROLL:
 610                 //inAir = false;
 611                 track = rwy.hdg;
 612                 if(vel < 80.0) {
 613                         double dveldt = 5.0;
 614                         vel += dveldt * dt;
 615                 }
 616                 if(aip.getSGLocation()->get_cur_elev_m() > -9990.0) {
 617                         pos.setelev(aip.getSGLocation()->get_cur_elev_m() + wheelOffset);
 618                 }
 619                 IAS = vel + (cos((hdg - wind_from) * DCL_DEGREES_TO_RADIANS) * wind_speed);
 620                 if(IAS >= 70) {
 621                         leg = CLIMBOUT;
 622                         pitch = 10.0;
 623                         IAS = best_rate_of_climb_speed;
 624                         slope = 7.0;
 625                         inAir = true;
 626                 }
 627                 break;
 628         case CLIMBOUT:
 629                 track = rwy.hdg;
 630                 if((pos.elev() - rwy.threshold_pos.elev()) * SG_METER_TO_FEET > 600) {
 631                         cout << "Turning to crosswind, distance from threshold = " << orthopos.y() << '\n';
 632                         leg = TURN1;
 633                 }
 634                 break;
 635         case TURN1:
 636                 track += (360.0 / turn_time) * dt * patternDirection;
 637                 Bank(25.0 * patternDirection);
 638                 if((track < (rwy.hdg - 89.0)) || (track > (rwy.hdg + 89.0))) {
 639                         leg = CROSSWIND;
 640                 }
 641                 break;
 642         case CROSSWIND:
 643                 LevelWings();
 644                 track = rwy.hdg + (90.0 * patternDirection);
 645                 if((pos.elev() - rwy.threshold_pos.elev()) * SG_METER_TO_FEET > 1000) {
 646                         slope = 0.0;
 647                         pitch = 0.0;
 648                         IAS = 80.0;             // FIXME - use smooth transistion to new speed
 649                 }
 650                 // turn 1000m out for now
 651                 if(fabs(orthopos.x()) > 980) {
 652                         leg = TURN2;
 653                 }
 654                 break;
 655         case TURN2:
 656                 track += (360.0 / turn_time) * dt * patternDirection;
 657                 Bank(25.0 * patternDirection);
 658                 // just in case we didn't make height on crosswind
 659                 if((pos.elev() - rwy.threshold_pos.elev()) * SG_METER_TO_FEET > 1000) {
 660                         slope = 0.0;
 661                         pitch = 0.0;
 662                         IAS = 80.0;             // FIXME - use smooth transistion to new speed
 663                 }
 664                 if((track < (rwy.hdg - 179.0)) || (track > (rwy.hdg + 179.0))) {
 665                         leg = DOWNWIND;
 666                         transmitted = false;
 667                         //roll = 0.0;
 668                 }
 669                 break;
 670         case DOWNWIND:
 671                 LevelWings();
 672                 track = rwy.hdg - (180 * patternDirection);     //should tend to bring track back into the 0->360 range
 673                 // just in case we didn't make height on crosswind
 674                 if((pos.elev() - rwy.threshold_pos.elev()) * SG_METER_TO_FEET > 1000) {
 675                         slope = 0.0;
 676                         pitch = 0.0;
 677                         IAS = 90.0;             // FIXME - use smooth transistion to new speed
 678                 }
 679                 if((orthopos.y() < 0) && (!transmitted)) {
 680                         TransmitPatternPositionReport();
 681                         transmitted = true;
 682                 }
 683                 if(orthopos.y() < -480) {
 684                         slope = -4.0;   // FIXME - calculate to descent at 500fpm and hit the threshold (taking wind into account as well!!)
 685                         pitch = -3.0;
 686                         IAS = 85.0;
 687                 }
 688                 if(orthopos.y() < -980) {
 689                         //roll = -20;
 690                         leg = TURN3;
 691                         transmitted = false;
 692                         IAS = 80.0;
 693                 }
 694                 break;
 695         case TURN3:
 696                 track += (360.0 / turn_time) * dt * patternDirection;
 697                 Bank(25.0 * patternDirection);
 698                 if(fabs(rwy.hdg - track) < 91.0) {
 699                         leg = BASE;
 700                 }
 701                 break;
 702         case BASE:
 703                 LevelWings();
 704                 if(!transmitted) {
 705                         TransmitPatternPositionReport();
 706                         transmitted = true;
 707                 }
 708                 track = rwy.hdg - (90 * patternDirection);
 709                 slope = -6.0;   // FIXME - calculate to descent at 500fpm and hit the threshold
 710                 pitch = -4.0;
 711                 IAS = 70.0;     // FIXME - slowdown gradually
 712                 // Try and arrange to turn nicely onto base
 713                 turn_circumference = IAS * 0.514444 * turn_time;
 714                 //Hmmm - this is an interesting one - ground vs airspeed in relation to turn radius
 715                 //We'll leave it as a hack with IAS for now but it needs revisiting.
 716
 717                 turn_radius = turn_circumference / (2.0 * DCL_PI);
 718                 if(fabs(orthopos.x()) < (turn_radius + 50)) {
 719                         leg = TURN4;
 720                         transmitted = false;
 721                         //roll = -20;
 722                 }
 723                 break;
 724         case TURN4:
 725                 track += (360.0 / turn_time) * dt * patternDirection;
 726                 Bank(25.0 * patternDirection);
 727                 if(fabs(track - rwy.hdg) < 0.6) {
 728                         leg = FINAL;
 729                         vel = nominal_final_speed;
 730                 }
 731                 break;
 732         case FINAL:
 733                 LevelWings();
 734                 if(!transmitted) {
 735                         TransmitPatternPositionReport();
 736                         transmitted = true;
 737                 }
 738                 // Try and track the extended centreline
 739                 track = rwy.hdg - (0.2 * orthopos.x());
 740                 //cout << "orthopos.x() = " << orthopos.x() << " hdg = " << hdg << '\n';
 741                 if(pos.elev() < (rwy.threshold_pos.elev()+20.0+wheelOffset)) {
 742                         DoGroundElev(); // Need to call it here expicitly on final since it's only called
 743                                         // for us in update(...) when the inAir flag is false.
 744                 }
 745                 if(pos.elev() < (rwy.threshold_pos.elev()+10.0+wheelOffset)) {
 746                         if(aip.getSGLocation()->get_cur_elev_m() > -9990.0) {
 747                                 if((aip.getSGLocation()->get_cur_elev_m() + wheelOffset) > pos.elev()) {
 748                                         slope = 0.0;
 749                                         pitch = 0.0;
 750                                         leg = LANDING_ROLL;
 751                                         inAir = false;
 752                                 }
 753                         }       // else need a fallback position based on arpt elev in case ground elev determination fails?
 754                 }
 755                 break;
 756         case LANDING_ROLL:
 757                 //inAir = false;
 758                 if(aip.getSGLocation()->get_cur_elev_m() > -9990.0) {
 759                         pos.setelev(aip.getSGLocation()->get_cur_elev_m() + wheelOffset);
 760                 }
 761                 track = rwy.hdg;
 762                 double dveldt = -5.0;
 763                 vel += dveldt * dt;
 764                 // FIXME - differentiate between touch and go and full stops
 765                 if(vel <= 15.0) {
 766                         //cout << "Vel <= 15.0, circuitsToFly = " << circuitsToFly << endl;
 767                         if(circuitsToFly <= 0) {
 768                                 //cout << "Calling ExitRunway..." << endl;
 769                                 ExitRunway(orthopos);
 770                                 return;
 771                         } else {
 772                                 //cout << "Taking off again..." << endl;
 773                                 leg = TAKEOFF_ROLL;
 774                                 --circuitsToFly;
 775                         }
 776                 }
 777                 break;
 778     }
 779
 780         if(inAir) {
 781                 // FIXME - at the moment this is a bit screwy
 782                 // The velocity correction is applied based on the relative headings.
 783                 // Then the heading is changed based on the velocity.
 784                 // Which comes first, the chicken or the egg?
 785                 // Does it really matter?
 786
 787                 // Apply wind to ground-relative velocity if in the air
 788                 vel = IAS - (cos((hdg - wind_from) * DCL_DEGREES_TO_RADIANS) * wind_speed);
 789                 //crab = f(track, wind, vel);
 790                 // The vector we need to fly is our desired vector minus the wind vector
 791                 // TODO - we probably ought to use plib's built in vector types and operations for this
 792                 // ie.  There's almost *certainly* a better way to do this!
 793                 double gxx = vel * sin(track * DCL_DEGREES_TO_RADIANS); // Plane desired velocity x component wrt ground
 794                 double gyy = vel * cos(track * DCL_DEGREES_TO_RADIANS); // Plane desired velocity y component wrt ground
 795                 double wxx = wind_speed * sin((wind_from + 180.0) * DCL_DEGREES_TO_RADIANS);    // Wind velocity x component
 796                 double wyy = wind_speed * cos((wind_from + 180.0) * DCL_DEGREES_TO_RADIANS);    // Wind velocity y component
 797                 double axx = gxx - wxx; // Plane in-air velocity x component
 798                 double ayy = gyy - wyy; // Plane in-air velocity y component
 799                 // Now we want the angle between gxx and axx (which is the crab)
 800                 double maga = sqrt(axx*axx + ayy*ayy);
 801                 double magg = sqrt(gxx*gxx + gyy*gyy);
 802                 crab = acos((axx*gxx + ayy*gyy) / (maga * magg));
 803                 // At this point this works except we're getting the modulus of the angle
 804                 //cout << "crab = " << crab << '\n';
 805
 806                 // Make sure both headings are in the 0->360 circle in order to get sane differences
 807                 dclBoundHeading(wind_from);
 808                 dclBoundHeading(track);
 809                 if(track > wind_from) {
 810                         if((track - wind_from) <= 180) {
 811                                 crab *= -1.0;
 812                         }
 813                 } else {
 814                         if((wind_from - track) >= 180) {
 815                                 crab *= -1.0;
 816                         }
 817                 }
 818         } else {        // on the ground - crab dosen't apply
 819                 crab = 0.0;
 820         }
 821
 822         hdg = track + crab;
 823         dist = vel * 0.514444 * dt;
 824         pos = dclUpdatePosition(pos, track, slope, dist);
 825 }
 826
 827 void FGAILocalTraffic::TransmitPatternPositionReport(void) {
 828         // airport name + "traffic" + airplane callsign + pattern direction + pattern leg + rwy + ?
 829         string trns = "";
 830
 831         trns += tower->get_name();
 832         trns += " Traffic ";
 833         trns += plane.callsign;
 834         if(patternDirection == 1) {
 835                 trns += " right ";
 836         } else {
 837                 trns += " left ";
 838         }
 839
 840         // We could probably get rid of this whole switch statement and just pass a string containing the leg from the FlyPattern function.
 841         switch(leg) {   // We'll assume that transmissions in turns are intended for next leg - do pilots ever call out that they are in the turn?
 842         case TURN1:
 843                 // Fall through to CROSSWIND
 844         case CROSSWIND: // I don't think this case will be used here but it can't hurt to leave it in
 845                 trns += "crosswind ";
 846                 break;
 847         case TURN2:
 848                 // Fall through to DOWNWIND
 849         case DOWNWIND:
 850                 trns += "downwind ";
 851                 break;
 852         case TURN3:
 853                 // Fall through to BASE
 854         case BASE:
 855                 trns += "base ";
 856                 break;
 857         case TURN4:
 858                 // Fall through to FINAL
 859         case FINAL:             // maybe this should include long/short final if appropriate?
 860                 trns += "final ";
 861                 break;
 862         default:                // Hopefully this won't be used
 863                 trns += "pattern ";
 864                 break;
 865         }
 866         // FIXME - I've hardwired the runway call as well!! (We could work this out from rwy heading and mag deviation)
 867         trns += ConvertRwyNumToSpokenString(1);
 868
 869         // And add the airport name again
 870         trns += tower->get_name();
 871
 872         Transmit(trns);
 873 }
 874
 875 void FGAILocalTraffic::ExitRunway(Point3D orthopos) {
 876         //cout << "In ExitRunway" << endl;
 877         //cout << "Runway ID is " << rwy.ID << endl;
 878         node_array_type exitNodes = ground->GetExits(rwy.rwyID);        //I suppose we ought to have some fallback for rwy with no defined exits?
 879         /*
 880         cout << "Node ID's of exits are ";
 881         for(unsigned int i=0; i<exitNodes.size(); ++i) {
 882                 cout << exitNodes[i]->nodeID << ' ';
 883         }
 884         cout << endl;
 885         */
 886         if(exitNodes.size()) {
 887                 //Find the next exit from orthopos.y
 888                 double d;
 889                 double dist = 100000;   //ie. longer than any runway in existance
 890                 double backdist = 100000;
 891                 node_array_iterator nItr = exitNodes.begin();
 892                 node* rwyExit = *(exitNodes.begin());
 893                 //int gateID;           //This might want to be more persistant at some point
 894                 while(nItr != exitNodes.end()) {
 895                         d = ortho.ConvertToLocal((*nItr)->pos).y() - ortho.ConvertToLocal(pos).y();     //FIXME - consider making orthopos a class variable
 896                         if(d > 0.0) {
 897                                 if(d < dist) {
 898                                         dist = d;
 899                                         rwyExit = *nItr;
 900                                 }
 901                         } else {
 902                                 if(fabs(d) < backdist) {
 903                                         backdist = d;
 904                                         //TODO - need some logic here that if we don't get a forward exit we turn round and store the backwards one
 905                                 }
 906                         }
 907                         ++nItr;
 908                 }
 909                 ourGate = ground->GetGateNode();
 910                 if(ourGate == NULL) {
 911                         // Implies no available gates - what shall we do?
 912                         // For now just vanish the plane - possibly we can make this more elegant in the future
 913                         SG_LOG(SG_ATC, SG_ALERT, "No gate found by FGAILocalTraffic whilst landing at " << airportID << '\n');
 914                         aip.setVisible(false);
 915                         operatingState = PARKED;
 916                         return;
 917                 }
 918                 path = ground->GetPath(rwyExit, ourGate);
 919                 /*
 920                 cout << "path returned was:" << endl;
 921                 for(unsigned int i=0; i<path.size(); ++i) {
 922                         switch(path[i]->struct_type) {
 923                         case NODE:
 924                                 cout << "NODE " << ((node*)(path[i]))->nodeID << endl;
 925                                 break;
 926                         case ARC:
 927                                 cout << "ARC\n";
 928                                 break;
 929                         }
 930                 }
 931                 */
 932                 taxiState = TD_INBOUND;
 933                 StartTaxi();
 934         } else {
 935                 // Something must have gone wrong with the ground network file - or there is only a rwy here and no exits defined
 936                 SG_LOG(SG_ATC, SG_ALERT, "No exits found by FGAILocalTraffic from runway " << rwy.rwyID << " at " << airportID << '\n');
 937                 // What shall we do - just remove the plane from sight?
 938                 aip.setVisible(false);
 939                 operatingState = PARKED;
 940         }
 941 }
 942
 943 // Set the class variable nextTaxiNode to the next node in the path
 944 // and update taxiPathPos, the class variable path iterator position
 945 // TODO - maybe should return error codes to the calling function if we fail here
 946 void FGAILocalTraffic::GetNextTaxiNode() {
 947         //cout << "GetNextTaxiNode called " << endl;
 948         //cout << "taxiPathPos = " << taxiPathPos << endl;
 949         ground_network_path_iterator pathItr = path.begin() + taxiPathPos;
 950         if(pathItr == path.end()) {
 951                 SG_LOG(SG_ATC, SG_ALERT, "ERROR IN AILocalTraffic::GetNextTaxiNode - no more nodes in path\n");
 952         } else {
 953                 if((*pathItr)->struct_type == NODE) {
 954                         //cout << "ITS A NODE" << endl;
 955                         //*pathItr = new node;
 956                         nextTaxiNode = (node*)*pathItr;
 957                         ++taxiPathPos;
 958                         //delete pathItr;
 959                 } else {
 960                         //cout << "ITS NOT A NODE" << endl;
 961                         //The first item in found must have been an arc
 962                         //Assume for now that it was straight
 963                         pathItr++;
 964                         taxiPathPos++;
 965                         if(pathItr == path.end()) {
 966                                 SG_LOG(SG_ATC, SG_ALERT, "ERROR IN AILocalTraffic::GetNextTaxiNode - path ended with an arc\n");
 967                         } else if((*pathItr)->struct_type == NODE) {
 968                                 nextTaxiNode = (node*)*pathItr;
 969                                 ++taxiPathPos;
 970                         } else {
 971                                 //OOPS - two non-nodes in a row - that shouldn't happen ATM
 972                                 SG_LOG(SG_ATC, SG_ALERT, "ERROR IN AILocalTraffic::GetNextTaxiNode - two non-nodes in sequence\n");
 973                         }
 974                 }
 975         }
 976 }
 977
 978 // StartTaxi - set up the taxiing state - call only at the start of taxiing
 979 void FGAILocalTraffic::StartTaxi() {
 980         //cout << "StartTaxi called" << endl;
 981         operatingState = TAXIING;
 982         taxiPathPos = 0;
 983
 984         //Set the desired heading
 985         //Assume we are aiming for first node on path
 986         //Eventually we may need to consider the fact that we might start on a curved arc and
 987         //not be able to head directly for the first node.
 988         GetNextTaxiNode();      // sets the class variable nextTaxiNode to the next taxi node!
 989         desiredTaxiHeading = GetHeadingFromTo(pos, nextTaxiNode->pos);
 990         //cout << "First taxi heading is " << desiredTaxiHeading << endl;
 991 }
 992
 993 // speed in knots, headings in degrees, radius in meters.
 994 static double TaxiTurnTowardsHeading(double current_hdg, double desired_hdg, double speed, double radius, double dt) {
 995         // wrap heading - this prevents a logic bug where the plane would just go round in circles!!
 996         while(current_hdg < 0.0) {
 997                 current_hdg += 360.0;
 998         }
 999         while(current_hdg > 360.0) {
1000                 current_hdg -= 360.0;
1001         }
1002         if(fabs(current_hdg - desired_hdg) > 0.1) {
1003                 // Which is the quickest direction to turn onto heading?
1004                 if(desired_hdg > current_hdg) {
1005                         if((desired_hdg - current_hdg) <= 180) {
1006                                 // turn right
1007                                 current_hdg += ((speed * 0.514444 * dt) / (radius * DCL_PI)) * 180.0;
1008                                 // TODO - check that increments are less than the delta that we check for the right direction
1009                                 // Probably need to reduce convergence speed as convergence is reached
1010                         } else {
1011                                 current_hdg -= ((speed * 0.514444 * dt) / (radius * DCL_PI)) * 180.0;
1012                         }
1013                 } else {
1014                         if((current_hdg - desired_hdg) <= 180) {
1015                                 // turn left
1016                                 current_hdg -= ((speed * 0.514444 * dt) / (radius * DCL_PI)) * 180.0;
1017                                 // TODO - check that increments are less than the delta that we check for the right direction
1018                                 // Probably need to reduce convergence speed as convergence is reached
1019                         } else {
1020                                 current_hdg += ((speed * 0.514444 * dt) / (radius * DCL_PI)) * 180.0;
1021                         }
1022                 }
1023         }
1024         return(current_hdg);
1025 }
1026
1027 void FGAILocalTraffic::Taxi(double dt) {
1028         //cout << "Taxi called" << endl;
1029         // Logic - if we are further away from next point than turn radius then head for it
1030         // If we have reached turning point then get next point and turn onto that heading
1031         // Look out for the finish!!
1032
1033         //Point3D orthopos = ortho.ConvertToLocal(pos); // ortho position of the plane
1034         desiredTaxiHeading = GetHeadingFromTo(pos, nextTaxiNode->pos);
1035
1036         bool lastNode = (taxiPathPos == path.size() ? true : false);
1037         if(lastNode) {
1038                 //cout << "LAST NODE\n";
1039         }
1040
1041         // HACK ALERT! - for now we will taxi at constant speed for straights and turns
1042
1043         // Remember that hdg is always equal to track when taxiing so we don't have to consider them both
1044         double dist_to_go = dclGetHorizontalSeparation(pos, nextTaxiNode->pos); // we may be able to do this more cheaply using orthopos
1045         //cout << "dist_to_go = " << dist_to_go << endl;
1046         if((nextTaxiNode->type == GATE) && (dist_to_go <= 0.1)) {
1047                 // This might be more robust to outward paths starting with a gate if we check for either
1048                 // last node or TD_INBOUND ?
1049                 // park up
1050                 operatingState = PARKED;
1051         } else if(((dist_to_go > taxiTurnRadius) || (nextTaxiNode->type == GATE)) && (!liningUp)){
1052                 // if the turn radius is r, and speed is s, then in a time dt we turn through
1053                 // ((s.dt)/(PI.r)) x 180 degrees
1054                 // or alternatively (s.dt)/r radians
1055                 //cout << "hdg = " << hdg << " desired taxi heading = " << desiredTaxiHeading << '\n';
1056                 hdg = TaxiTurnTowardsHeading(hdg, desiredTaxiHeading, nominalTaxiSpeed, taxiTurnRadius, dt);
1057                 double vel = nominalTaxiSpeed;
1058                 //cout << "vel = " << vel << endl;
1059                 double dist = vel * 0.514444 * dt;
1060                 //cout << "dist = " << dist << endl;
1061                 double track = hdg;
1062                 //cout << "track = " << track << endl;
1063                 double slope = 0.0;
1064                 pos = dclUpdatePosition(pos, track, slope, dist);
1065                 //cout << "Updated position...\n";
1066                 if(aip.getSGLocation()->get_cur_elev_m() > -9990) {
1067                         pos.setelev(aip.getSGLocation()->get_cur_elev_m() + wheelOffset);
1068                 } // else don't change the elev until we get a valid ground elev again!
1069         } else if(lastNode) {
1070                 if(taxiState == TD_LINING_UP) {
1071                         if((!liningUp) && (dist_to_go <= taxiTurnRadius)) {
1072                                 liningUp = true;
1073                         }
1074                         if(liningUp) {
1075                                 hdg = TaxiTurnTowardsHeading(hdg, rwy.hdg, nominalTaxiSpeed, taxiTurnRadius, dt);
1076                                 double vel = nominalTaxiSpeed;
1077                                 //cout << "vel = " << vel << endl;
1078                                 double dist = vel * 0.514444 * dt;
1079                                 //cout << "dist = " << dist << endl;
1080                                 double track = hdg;
1081                                 //cout << "track = " << track << endl;
1082                                 double slope = 0.0;
1083                                 pos = dclUpdatePosition(pos, track, slope, dist);
1084                                 //cout << "Updated position...\n";
1085                                 if(aip.getSGLocation()->get_cur_elev_m() > -9990) {
1086                                         pos.setelev(aip.getSGLocation()->get_cur_elev_m() + wheelOffset);
1087                                 } // else don't change the elev until we get a valid ground elev again!
1088                                 if(fabs(hdg - rwy.hdg) <= 1.0) {
1089                                         operatingState = IN_PATTERN;
1090                                         leg = TAKEOFF_ROLL;
1091                                         inAir = false;
1092                                         liningUp = false;
1093                                 }
1094                         }
1095                 } else if(taxiState == TD_OUTBOUND) {
1096                         // Pause awaiting further instructions
1097                         // and for now assume we've reached the hold-short node
1098                         holdingShort = true;
1099                 } // else at the moment assume TD_INBOUND always ends in a gate in which case we can ignore it
1100         } else {
1101                 // Time to turn (we've already checked it's not the end we're heading for).
1102                 // set the target node to be the next node which will prompt automatically turning onto
1103                 // the right heading in the stuff above, with the usual provisos applied.
1104                 GetNextTaxiNode();
1105                 // For now why not just recursively call this function?
1106                 Taxi(dt);
1107         }
1108 }
1109
1110
1111 // Warning - ground elev determination is CPU intensive
1112 // Either this function or the logic of how often it is called
1113 // will almost certainly change.
1114 void FGAILocalTraffic::DoGroundElev() {
1115
1116         // It would be nice if we could set the correct tile center here in order to get a correct
1117         // answer with one call to the function, but what I tried in the two commented-out lines
1118         // below only intermittently worked, and I haven't quite groked why yet.
1119         //SGBucket buck(pos.lon(), pos.lat());
1120         //aip.getSGLocation()->set_tile_center(Point3D(buck.get_center_lon(), buck.get_center_lat(), 0.0));
1121
1122         double visibility_meters = fgGetDouble("/environment/visibility-m");
1123         //globals->get_tile_mgr()->prep_ssg_nodes( acmodel_location,
1124         globals->get_tile_mgr()->prep_ssg_nodes( aip.getSGLocation(),   visibility_meters );
1125         Point3D scenery_center = globals->get_scenery()->get_center();
1126         globals->get_tile_mgr()->update( aip.getSGLocation(), visibility_meters, (aip.getSGLocation())->get_absolute_view_pos( scenery_center ) );
1127         // save results of update in SGLocation for fdm...
1128
1129         //if ( globals->get_scenery()->get_cur_elev() > -9990 ) {
1130         //      acmodel_location->
1131         //      set_cur_elev_m( globals->get_scenery()->get_cur_elev() );
1132         //}
1133
1134         // The need for this here means that at least 2 consecutive passes are needed :-(
1135         aip.getSGLocation()->set_tile_center( globals->get_scenery()->get_next_center() );
1136
1137         //cout << "Transform Elev is " << globals->get_scenery()->get_cur_elev() << '\n';
1138         aip.getSGLocation()->set_cur_elev_m(globals->get_scenery()->get_cur_elev());
1139         //return(globals->get_scenery()->get_cur_elev());
1140 }
1141