src/ATC/ground.cxx

   1 // FGGround - a class to provide ground control at larger airports.
   2 //
   3 // Written by David Luff, started March 2002.
   4 //
   5 // Copyright (C) 2002  David C. Luff - david.luff@nottingham.ac.uk
   6 //
   7 // This program is free software; you can redistribute it and/or
   8 // modify it under the terms of the GNU General Public License as
   9 // published by the Free Software Foundation; either version 2 of the
  10 // License, or (at your option) any later version.
  11 //
  12 // This program is distributed in the hope that it will be useful, but
  13 // WITHOUT ANY WARRANTY; without even the implied warranty of
  14 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15 // General Public License for more details.
  16 //
  17 // You should have received a copy of the GNU General Public License
  18 // along with this program; if not, write to the Free Software
  19 // Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  20
  21 #ifdef HAVE_CONFIG_H
  22 #  include <config.h>
  23 #endif
  24
  25 #include <simgear/misc/sg_path.hxx>
  26 #include <simgear/math/sg_random.h>
  27 #include <simgear/debug/logstream.hxx>
  28 #include <simgear/misc/sgstream.hxx>
  29 #include <simgear/constants.h>
  30 #include <Main/globals.hxx>
  31
  32 #include <stdlib.h>
  33 #include STL_FSTREAM
  34
  35 #include "ground.hxx"
  36 #include "ATCmgr.hxx"
  37 #include "ATCutils.hxx"
  38 #include "ATCdisplay.hxx"
  39 #include "AILocalTraffic.hxx"
  40
  41 SG_USING_STD(ifstream);
  42 SG_USING_STD(cout);
  43
  44 node::node() {
  45 }
  46
  47 node::~node() {
  48         for(unsigned int i=0; i < arcs.size(); ++i) {
  49                 delete arcs[i];
  50         }
  51 }
  52
  53 // Make sure that a_path.cost += distance is safe from the moment it's created.
  54 a_path::a_path() {
  55         cost = 0;
  56 }
  57
  58 FGGround::FGGround() {
  59         ATCmgr = globals->get_ATC_mgr();
  60         _type = GROUND;
  61         networkLoadOK = false;
  62         ground_traffic.erase(ground_traffic.begin(), ground_traffic.end());
  63         ground_traffic_itr = ground_traffic.begin();
  64
  65         // Init the property nodes - TODO - need to make sure we're getting surface winds.
  66         wind_from_hdg = fgGetNode("/environment/wind-from-heading-deg", true);
  67         wind_speed_knots = fgGetNode("/environment/wind-speed-kt", true);
  68
  69         // TODO - get the actual airport elevation
  70         aptElev = 0.0;
  71 }
  72
  73 FGGround::FGGround(const string& id) {
  74         ATCmgr = globals->get_ATC_mgr();
  75         networkLoadOK = false;
  76         ground_traffic.erase(ground_traffic.begin(), ground_traffic.end());
  77         ground_traffic_itr = ground_traffic.begin();
  78         ident = id;
  79
  80         // Init the property nodes - TODO - need to make sure we're getting surface winds.
  81         wind_from_hdg = fgGetNode("/environment/wind-from-heading-deg", true);
  82         wind_speed_knots = fgGetNode("/environment/wind-speed-kt", true);
  83
  84         // TODO - get the actual airport elevation
  85         aptElev = 0.0;
  86 }
  87
  88 FGGround::~FGGround() {
  89 }
  90
  91 void FGGround::ParseRwyExits(node* np, char* es) {
  92         char* token;
  93         char estr[20];
  94         strcpy(estr, es);
  95         const char delimiters[] = "-";
  96         token = strtok(estr, delimiters);
  97         while(token != NULL) {
  98                 int i = atoi(token);
  99                 //cout << "token = " << token << endl;
 100                 //cout << "rwy number = " << i << endl;
 101                 //runways[(atoi(token))].exits.push_back(np);
 102                 runways[i].exits.push_back(np);
 103                 //cout << "token = " << token << '\n';
 104                 token = strtok(NULL, delimiters);
 105         }
 106 }
 107
 108
 109 // Load the ground logical network of the current instances airport
 110 // Return true if successfull.
 111 // TODO - currently the file is assumed to reside in the base/ATC directory.
 112 // This might change to something more thought out in the future.
 113 // NOTE - currently it is assumed that all nodes are loaded before any arcs.
 114 // It won't work ATM if this doesn't hold true.
 115 bool FGGround::LoadNetwork() {
 116         node* np;
 117         arc* ap;
 118         Gate* gp;
 119
 120         int gateCount = 0;      // This is used to allocate gateID's from zero upwards
 121         // This may well change in the future - probably to reading in the real-world
 122         // gate numbers from file.
 123
 124         ifstream fin;
 125         SGPath path = globals->get_fg_root();
 126         //string taxiPath = "ATC/" + ident + ".taxi";
 127         string taxiPath = "ATC/KEMT.taxi";      // FIXME - HARDWIRED FOR TESTING
 128         path.append(taxiPath);
 129
 130         SG_LOG(SG_ATC, SG_INFO, "Trying to read taxiway data for " << ident << "...");
 131         //cout << "Trying to read taxiway data for " << ident << "..." << endl;
 132         fin.open(path.c_str(), ios::in);
 133         if(!fin) {
 134                 SG_LOG(SG_ATC, SG_ALERT, "Unable to open taxiway data input file " << path.c_str());
 135                 //cout << "Unable to open taxiway data input file " << path.c_str() << endl;
 136                 return(false);
 137         }
 138
 139         char ch;
 140         char buf[30];
 141         while(!fin.eof()) {
 142                 fin >> buf;
 143                 // Node, arc, or [End]?
 144                 //cout << "Read in ground network element type = " << buf << endl;
 145                 if(!strcmp(buf, "[End]")) {             // TODO - maybe make this more robust to spelling errors by just looking for '['
 146                         SG_LOG(SG_ATC, SG_INFO, "Done reading " << path.c_str() << endl);
 147                         break;
 148                 } else if(!strcmp(buf, "N")) {
 149                         // Node
 150                         np = new node;
 151                         np->struct_type = NODE;
 152                         fin >> buf;
 153                         np->nodeID = atoi(buf);
 154                         fin >> buf;
 155                         np->pos.setlon(atof(buf));
 156                         fin >> buf;
 157                         np->pos.setlat(atof(buf));
 158                         fin >> buf;
 159                         np->pos.setelev(atof(buf));
 160                         fin >> buf;             // node type
 161                         if(!strcmp(buf, "J")) {
 162                                 np->type = JUNCTION;
 163                         } else if(!strcmp(buf, "T")) {
 164                                 np->type = TJUNCTION;
 165                         } else if(!strcmp(buf, "H")) {
 166                                 np->type = HOLD;
 167                         } else {
 168                                 SG_LOG(SG_ATC, SG_ALERT, "**** ERROR ***** Unknown node type in taxi network...\n");
 169                                 delete np;
 170                                 return(false);
 171                         }
 172                         fin >> buf;             // rwy exit information - gets parsed later - FRAGILE - will break if buf is reused.
 173                         // Now the name
 174                         fin >> ch;      // strip the leading " off
 175                         np->name = "";
 176                         while(1) {
 177                                 fin.unsetf(ios::skipws);
 178                                 fin >> ch;
 179                                 if((ch == '"') || (ch == 0x0A)) {
 180                                         break;
 181                                 }   // we shouldn't need the 0x0A but it makes a nice safely in case someone leaves off the "
 182                                 np->name += ch;
 183                         }
 184                         fin.setf(ios::skipws);
 185                         network.push_back(np);
 186                         // FIXME - fragile - replies on buf not getting modified from exits read to here
 187                         // see if we also need to push it onto the runway exit list
 188                         //cout << "strlen(buf) = " << strlen(buf) << endl;
 189                         if(strlen(buf) > 2) {
 190                                 //cout << "Calling ParseRwyExits for " << buf << endl;
 191                                 ParseRwyExits(np, buf);
 192                         }
 193                 } else if(!strcmp(buf, "A")) {
 194                         ap = new arc;
 195                         ap->struct_type = ARC;
 196                         fin >> buf;
 197                         ap->n1 = atoi(buf);
 198                         fin >> buf;
 199                         ap->n2 = atoi(buf);
 200                         fin >> buf;
 201                         if(!strcmp(buf, "R")) {
 202                                 ap->type = RUNWAY;
 203                         } else if(!strcmp(buf, "T")) {
 204                                 ap->type = TAXIWAY;
 205                         } else {
 206                                 SG_LOG(SG_ATC, SG_ALERT, "**** ERROR ***** Unknown arc type in taxi network...\n");
 207                                 delete ap;
 208                                 return(false);
 209                         }
 210                         // directed?
 211                         fin >> buf;
 212                         if(!strcmp(buf, "Y")) {
 213                                 ap->directed = true;
 214                         } else if(!strcmp(buf, "N")) {
 215                                 ap->directed = false;
 216                         } else {
 217                                 SG_LOG(SG_ATC, SG_ALERT, "**** ERROR ***** Unknown arc directed value in taxi network - should be Y/N !!!\n");
 218                                 delete ap;
 219                                 return(false);
 220                         }
 221                         // Now the name
 222                         ap->name = "";
 223                         while(1) {
 224                                 fin.unsetf(ios::skipws);
 225                                 fin >> ch;
 226                                 ap->name += ch;
 227                                 if((ch == '"') || (ch == 0x0A)) {
 228                                         break;
 229                                 }   // we shouldn't need the 0x0A but it makes a nice safely in case someone leaves off the "
 230                         }
 231                         fin.setf(ios::skipws);
 232                         ap->distance = (int)dclGetHorizontalSeparation(network[ap->n1]->pos, network[ap->n2]->pos);
 233                         //cout << "Distance  = " << ap->distance << '\n';
 234                         network[ap->n1]->arcs.push_back(ap);
 235                         network[ap->n2]->arcs.push_back(ap);
 236                 } else if(!strcmp(buf, "G")) {
 237                         gp = new Gate;
 238                         gp->struct_type = NODE;
 239                         gp->type = GATE;
 240                         fin >> buf;
 241                         gp->nodeID = atoi(buf);
 242                         fin >> buf;
 243                         gp->pos.setlon(atof(buf));
 244                         fin >> buf;
 245                         gp->pos.setlat(atof(buf));
 246                         fin >> buf;
 247                         gp->pos.setelev(atof(buf));
 248                         fin >> buf;             // gate type - ignore this for now
 249                         fin >> buf;             // gate heading
 250                         gp->heading = atoi(buf);
 251                         // Now the name
 252                         gp->name = "";
 253                         while(1) {
 254                                 fin.unsetf(ios::skipws);
 255                                 fin >> ch;
 256                                 gp->name += ch;
 257                                 if((ch == '"') || (ch == 0x0A)) {
 258                                         break;
 259                                 }   // we shouldn't need the 0x0A but it makes a nice safely in case someone leaves off the "
 260                         }
 261                         fin.setf(ios::skipws);
 262                         gp->id = gateCount;             // Warning - this will likely change in the future.
 263                         gp->used = false;
 264                         network.push_back(gp);
 265                         gates[gateCount] = gp;
 266                         gateCount++;
 267                 } else {
 268                         // Something has gone seriously pear-shaped
 269                         SG_LOG(SG_ATC, SG_ALERT, "********* ERROR - unknown ground network element type... aborting read of " << path.c_str() << '\n');
 270                         return(false);
 271                 }
 272
 273                 fin >> skipeol;
 274         }
 275         return(true);
 276 }
 277
 278 void FGGround::Init() {
 279         untowered = false;
 280
 281         // Figure out which is the active runway - TODO - it would be better to have ground call tower
 282         // for runway operation details, but at the moment we can't guarantee that tower control at a given airport
 283         // will be initialised before ground so we can't do that.
 284         DoRwyDetails();
 285         //cout << "In FGGround::Init, active rwy is " << activeRwy << '\n';
 286         ortho.Init(rwy.threshold_pos, rwy.hdg);
 287
 288         networkLoadOK = LoadNetwork();
 289 }
 290
 291 void FGGround::Update(double dt) {
 292         // Each time step, what do we need to do?
 293         // We need to go through the list of outstanding requests and acknowedgements
 294         // and process at least one of them.
 295         // We need to go through the list of planes under our control and check if
 296         // any need to be addressed.
 297         // We need to check for planes not under our control coming within our
 298         // control area and address if necessary.
 299
 300         // Lets take the example of a plane which has just contacted ground
 301         // following landing - presumably requesting where to go?
 302         // First we need to establish the position of the plane within the logical network.
 303         // Next we need to decide where its going.
 304
 305         if(ground_traffic.size()) {
 306                 if(ground_traffic_itr == ground_traffic.end()) {
 307                         ground_traffic_itr = ground_traffic.begin();
 308                 }
 309
 310                 //Process(*ground_traffic_itr);
 311                 GroundRec* g = *ground_traffic_itr;
 312                 if(g->taxiRequestOutstanding) {
 313                         double responseTime = 10.0;             // seconds - this should get more sophisticated at some point
 314                         if(g->clearanceCounter > responseTime) {
 315                                 // DO CLEARANCE
 316                                 // TODO - move the mechanics of making up the transmission out of the main Update(...) routine.
 317                                 string trns = "";
 318                                 trns += g->plane.callsign;
 319                                 trns += " taxi holding point runway ";  // TODO - add the holding point name
 320                                 // eg " taxi holding point G2 runway "
 321                                 trns += ConvertRwyNumToSpokenString(activeRwy);
 322                                 if(_display) {
 323                                         globals->get_ATC_display()->RegisterSingleMessage(trns, 0);
 324                                 }
 325                                 g->planePtr->RegisterTransmission(1);   // cleared to taxi
 326                                 g->clearanceCounter = 0.0;
 327                                 g->taxiRequestOutstanding = false;
 328                         } else {
 329                                 g->clearanceCounter += (dt * ground_traffic.size());
 330                         }
 331                 } else if(((FGAILocalTraffic*)(g->planePtr))->AtHoldShort()) {          // That's a hack - eventually we should monitor actual position
 332                         // HACK ALERT - the automatic cast to AILocalTraffic has to go once we have other sorts working!!!!! FIXME TODO
 333                         // NOTE - we don't need to do the contact tower bit unless we have separate tower and ground
 334                         string trns = g->plane.callsign;
 335                         trns += " contact Tower ";
 336                         double f = globals->get_ATC_mgr()->GetFrequency(ident, TOWER) / 100.0;
 337                         char buf[10];
 338                         sprintf(buf, "%.2f", f);
 339                         trns += buf;
 340                         if(_display) {
 341                                 globals->get_ATC_display()->RegisterSingleMessage(trns, 0);
 342                         }
 343                         g->planePtr->RegisterTransmission(2);   // contact tower
 344                         delete *ground_traffic_itr;
 345                         ground_traffic.erase(ground_traffic_itr);
 346                         ground_traffic_itr = ground_traffic.begin();
 347                 }
 348                 ++ground_traffic_itr;
 349         }
 350
 351         // Call the base class update for the response time handling.
 352         FGATC::Update(dt);
 353 }
 354
 355 // Figure out which runways are active.
 356 // For now we'll just be simple and do one active runway - eventually this will get much more complex
 357 // Copied from FGTower - TODO - it would be better to implement this just once, and have ground call tower
 358 // for runway operation details, but at the moment we can't guarantee that tower control at a given airport
 359 // will be initialised before ground so we can't do that.
 360 void FGGround::DoRwyDetails() {
 361         //cout << "GetRwyDetails called" << endl;
 362
 363         // Based on the airport-id and wind get the active runway
 364
 365         //wind
 366         double hdg = wind_from_hdg->getDoubleValue();
 367         double speed = wind_speed_knots->getDoubleValue();
 368         hdg = (speed == 0.0 ? 270.0 : hdg);
 369         //cout << "Heading = " << hdg << '\n';
 370
 371         FGRunway runway;
 372         bool rwyGood = globals->get_runways()->search(ident, int(hdg), &runway);
 373         if(rwyGood) {
 374                 activeRwy = runway._rwy_no;
 375                 rwy.rwyID = runway._rwy_no;
 376                 SG_LOG(SG_ATC, SG_INFO, "In FGGround, active runway for airport " << ident << " is " << activeRwy);
 377
 378                 // Get the threshold position
 379                 double other_way = runway._heading - 180.0;
 380                 while(other_way <= 0.0) {
 381                         other_way += 360.0;
 382                 }
 383         // move to the +l end/center of the runway
 384                 //cout << "Runway center is at " << runway._lon << ", " << runway._lat << '\n';
 385         Point3D origin = Point3D(runway._lon, runway._lat, aptElev);
 386                 Point3D ref = origin;
 387         double tshlon, tshlat, tshr;
 388                 double tolon, tolat, tor;
 389                 rwy.length = runway._length * SG_FEET_TO_METER;
 390         geo_direct_wgs_84 ( aptElev, ref.lat(), ref.lon(), other_way,
 391                                 rwy.length / 2.0 - 25.0, &tshlat, &tshlon, &tshr );
 392         geo_direct_wgs_84 ( aptElev, ref.lat(), ref.lon(), runway._heading,
 393                                 rwy.length / 2.0 - 25.0, &tolat, &tolon, &tor );
 394                 // Note - 25 meters in from the runway end is a bit of a hack to put the plane ahead of the user.
 395                 // now copy what we need out of runway into rwy
 396         rwy.threshold_pos = Point3D(tshlon, tshlat, aptElev);
 397                 Point3D takeoff_end = Point3D(tolon, tolat, aptElev);
 398                 //cout << "Threshold position = " << tshlon << ", " << tshlat << ", " << aptElev << '\n';
 399                 //cout << "Takeoff position = " << tolon << ", " << tolat << ", " << aptElev << '\n';
 400                 rwy.hdg = runway._heading;
 401                 // Set the projection for the local area based on this active runway
 402                 ortho.Init(rwy.threshold_pos, rwy.hdg);
 403                 rwy.end1ortho = ortho.ConvertToLocal(rwy.threshold_pos);        // should come out as zero
 404                 rwy.end2ortho = ortho.ConvertToLocal(takeoff_end);
 405         } else {
 406                 SG_LOG(SG_ATC, SG_ALERT, "Help  - can't get good runway in FGTower!!");
 407                 activeRwy = "NN";
 408         }
 409 }
 410
 411 // Return a random gate ID of an unused gate.
 412 // Two error values may be returned and must be checked for by the calling function:
 413 // -2 signifies that no gates exist at this airport.
 414 // -1 signifies that all gates are currently full.
 415 int FGGround::GetRandomGateID() {
 416         // Check that this airport actually has some gates!!
 417         if(!gates.size()) {
 418                 return(-2);
 419         }
 420
 421         gate_vec_type gateVec;
 422         int num = 0;
 423         int thenum;
 424         int ID;
 425
 426         gatesItr = gates.begin();
 427         while(gatesItr != gates.end()) {
 428                 if((gatesItr->second)->used == false) {
 429                         gateVec.push_back(gatesItr->second);
 430                         num++;
 431                 }
 432                 ++gatesItr;
 433         }
 434
 435         // Check that there are some unused gates!
 436         if(!gateVec.size()) {
 437                 return(-1);
 438         }
 439
 440         // Randomly select one from the list
 441         sg_srandom_time();
 442         thenum = (int)(sg_random() * gateVec.size());
 443         ID = gateVec[thenum]->id;
 444
 445         return(ID);
 446 }
 447
 448 // Return a pointer to an unused gate node
 449 Gate* FGGround::GetGateNode() {
 450         int id = GetRandomGateID();
 451         if(id < 0) {
 452                 return(NULL);
 453         } else {
 454                 return(gates[id]);
 455         }
 456 }
 457
 458
 459 node* FGGround::GetHoldShortNode(const string& rwyID) {
 460         return(NULL);   // TODO - either implement me or remove me!!!
 461 }
 462
 463
 464 // WARNING - This is hardwired to my prototype logical network format
 465 // and will almost certainly change when Bernie's stuff comes on-line.
 466 // Returns NULL if it can't find a valid node.
 467 node* FGGround::GetThresholdNode(const string& rwyID) {
 468         // For now go through all the nodes and parse their names
 469         // Maybe in the future we'll map threshold nodes by ID
 470         //cout << "Size of network is " << network.size() << '\n';
 471         for(unsigned int i=0; i<network.size(); ++i) {
 472                 //cout << "Name = " << network[i]->name << '\n';
 473                 if(network[i]->name.size()) {
 474                         string s = network[i]->name;
 475                         // Warning - the next bit is fragile and dependent on my current naming scheme
 476                         //cout << "substr = " << s.substr(0,3) << '\n';
 477                         //cout << "size of s = " << s.size() << '\n';
 478                         if(s.substr(0,3) == "rwy") {
 479                                 //cout << "subsubstr = " << s.substr(4, s.size() - 4) << '\n';
 480                                 if(s.substr(4, s.size() - 4) == rwyID) {
 481                                         return network[i];
 482                                 }
 483                         }
 484                 }
 485         }
 486         return NULL;
 487 }
 488
 489
 490 // Get a path from a point on a runway to a gate
 491 // TODO !!
 492
 493 // Get a path from a node to another node
 494 // Eventually we will need complex algorithms for this taking other traffic,
 495 // shortest path and suitable paths into accout.
 496 // For now we'll just call the shortest path algorithm.
 497 ground_network_path_type FGGround::GetPath(node* A, node* B) {
 498         return(GetShortestPath(A, B));
 499 };
 500
 501 // Get a path from a node to a runway threshold
 502 ground_network_path_type FGGround::GetPath(node* A, const string& rwyID) {
 503         node* b = GetThresholdNode(rwyID);
 504         if(b == NULL) {
 505                 SG_LOG(SG_ATC, SG_ALERT, "ERROR - unable to find path to runway theshold in ground.cxx for airport " << ident << '\n');
 506                 ground_network_path_type emptyPath;
 507                 emptyPath.erase(emptyPath.begin(), emptyPath.end());
 508                 return(emptyPath);
 509         }
 510         return GetShortestPath(A, b);
 511 }
 512
 513 // Get a path from a node to a runway hold short point
 514 // Bit of a hack this at the moment!
 515 ground_network_path_type FGGround::GetPathToHoldShort(node* A, const string& rwyID) {
 516         ground_network_path_type path = GetPath(A, rwyID);
 517         path.pop_back();        // That should be the threshold stripped of
 518         path.pop_back();        // and that should be the arc from hold short to threshold
 519         // This isn't robust though - TODO - implement properly!
 520         return(path);
 521 }
 522
 523 // A shortest path algorithm from memory (ie. I can't find the bl&*dy book again!)
 524 // I'm sure there must be enchancements that we can make to this, such as biasing the
 525 // order in which the nodes are searched out from in favour of those geographically
 526 // closer to the destination.
 527 // Note that we are working with the master set of nodes and arcs so we mustn't change
 528 // or delete them -  we only delete the paths that we create during the algorithm.
 529 ground_network_path_type FGGround::GetShortestPath(node* A, node* B) {
 530         a_path* pathPtr;
 531         shortest_path_map_type pathMap;
 532         node_array_type nodesLeft;
 533
 534         // Debugging check
 535         int pathsCreated = 0;
 536
 537         // Initialise the algorithm
 538         nodesLeft.push_back(A);
 539         pathPtr = new a_path;
 540         pathsCreated++;
 541         pathPtr->path.push_back(A);
 542         pathPtr->cost = 0;
 543         pathMap[A->nodeID] = pathPtr;
 544         bool solution_found = false;    // Flag to indicate that at least one candidate path has been found
 545         int solution_cost = -1;                 // Cost of current best cost solution.  -1 indicates no solution found yet.
 546         a_path solution_path;
 547
 548         node* nPtr;     // nPtr is used to point to the node we are currently working with
 549
 550         while(nodesLeft.size()) {
 551                 //cout << "\n*****nodesLeft*****\n";
 552                 //for(unsigned int i=0; i<nodesLeft.size(); ++i) {
 553                         //cout << nodesLeft[i]->nodeID << '\n';
 554                 //}
 555                 //cout << "*******************\n\n";
 556                 nPtr = *nodesLeft.begin();              // Thought - definate optimization possibilities here in the choice of which nodes we process first.
 557                 nodesLeft.erase(nodesLeft.begin());
 558                 //cout << "Walking out from node " << nPtr->nodeID << '\n';
 559                 for(unsigned int i=0; i<nPtr->arcs.size(); ++i) {
 560                         //cout << "ARC TO " << ((nPtr->arcs[i]->n1 == nPtr->nodeID) ? nPtr->arcs[i]->n2 : nPtr->arcs[i]->n1) << '\n';
 561                 }
 562                 if((solution_found) && (solution_cost <= pathMap[nPtr->nodeID]->cost)) {
 563                         // Do nothing - we've already found a solution and this partial path is already more expensive
 564                 } else {
 565                         // This path could still be better than the current solution - check it out
 566                         for(unsigned int i=0; i<(nPtr->arcs.size()); i++) {
 567                                 // Map the new path against the end node, ie. *not* the one we just started with.
 568                                 unsigned int end_nodeID = ((nPtr->arcs[i]->n1 == nPtr->nodeID) ? nPtr->arcs[i]->n2 : nPtr->arcs[i]->n1);
 569                                 //cout << "end_nodeID = " << end_nodeID << '\n';
 570                                 //cout << "pathMap size is " << pathMap.size() << '\n';
 571                                 if(end_nodeID == nPtr->nodeID) {
 572                                         //cout << "Circular arc!\n";
 573                                         // Then its a circular arc - don't bother!!
 574                                         //nPtr->arcs.erase(nPtr->arcs.begin() + i);
 575                                 } else {
 576                                         // see if the end node is already in the map or not
 577                                         if(pathMap.find(end_nodeID) == pathMap.end()) {
 578                                                 //cout << "Not in the map" << endl;;
 579                                                 // Not in the map - easy!
 580                                                 pathPtr = new a_path;
 581                                                 pathsCreated++;
 582                                                 *pathPtr = *pathMap[nPtr->nodeID];      // *copy* the path
 583                                                 pathPtr->path.push_back(nPtr->arcs[i]);
 584                                                 pathPtr->path.push_back(network[end_nodeID]);
 585                                                 pathPtr->cost += nPtr->arcs[i]->distance;
 586                                                 pathMap[end_nodeID] = pathPtr;
 587                                                 nodesLeft.push_back(network[end_nodeID]);       // By definition this can't be in the list already, or
 588                                                 // it would also have been in the map and hence OR'd with this one.
 589                                                 if(end_nodeID == B->nodeID) {
 590                                                         //cout << "Solution found!!!" << endl;
 591                                                         // Since this node wasn't in the map this is by definition the first solution
 592                                                         solution_cost = pathPtr->cost;
 593                                                         solution_path = *pathPtr;
 594                                                         solution_found = true;
 595                                                 }
 596                                         } else {
 597                                                 //cout << "Already in the map" << endl;
 598                                                 // In the map - not so easy - need to get rid of an arc from the higher cost one.
 599                                                 //cout << "Current cost of node " << end_nodeID << " is " << pathMap[end_nodeID]->cost << endl;
 600                                                 int newCost = pathMap[nPtr->nodeID]->cost + nPtr->arcs[i]->distance;
 601                                                 //cout << "New cost is of node " << nPtr->nodeID << " is " << newCost << endl;
 602                                                 if(newCost >= pathMap[end_nodeID]->cost) {
 603                                                         // No need to do anything.
 604                                                         //cout << "Not doing anything!" << endl;
 605                                                 } else {
 606                                                         delete pathMap[end_nodeID];
 607                                                         pathsCreated--;
 608
 609                                                         pathPtr = new a_path;
 610                                                         pathsCreated++;
 611                                                         *pathPtr = *pathMap[nPtr->nodeID];      // *copy* the path
 612                                                         pathPtr->path.push_back(nPtr->arcs[i]);
 613                                                         pathPtr->path.push_back(network[end_nodeID]);
 614                                                         pathPtr->cost += nPtr->arcs[i]->distance;
 615                                                         pathMap[end_nodeID] = pathPtr;
 616
 617                                                         // We need to add this node to the list-to-do again to force a recalculation
 618                                                         // onwards from this node with the new lower cost to node cost.
 619                                                         nodesLeft.push_back(network[end_nodeID]);
 620
 621                                                         if(end_nodeID == B->nodeID) {
 622                                                                 //cout << "Solution found!!!" << endl;
 623                                                                 // Need to check if there is a previous better solution
 624                                                                 if((solution_cost < 0) || (pathPtr->cost < solution_cost)) {
 625                                                                         solution_cost = pathPtr->cost;
 626                                                                         solution_path = *pathPtr;
 627                                                                         solution_found = true;
 628                                                                 }
 629                                                         }
 630                                                 }
 631                                         }
 632                                 }
 633                         }
 634                 }
 635         }
 636
 637         // delete all the paths before returning
 638         shortest_path_map_iterator spItr = pathMap.begin();
 639         while(spItr != pathMap.end()) {
 640                 if(spItr->second != NULL) {
 641                         delete spItr->second;
 642                         --pathsCreated;
 643                 }
 644                 ++spItr;
 645         }
 646
 647         //cout << "pathsCreated = " << pathsCreated << '\n';
 648         if(pathsCreated > 0) {
 649                 SG_LOG(SG_ATC, SG_ALERT, "WARNING - Possible memory leak in FGGround::GetShortestPath\n\
 650                                                                           Please report to flightgear-devel@flightgear.org\n");
 651         }
 652
 653         //cout << (solution_found ? "Result: solution found\n" : "Result: no solution found\n");
 654         return(solution_path.path);             // TODO - we really ought to have a fallback position incase a solution isn't found.
 655 }
 656
 657
 658
 659 // Randomly or otherwise populate some of the gates with parked planes
 660 // (might eventually be done by the AIMgr if and when lots of AI traffic is generated)
 661
 662 // Return a list of exits from a given runway
 663 // It is up to the calling function to check for non-zero size of returned array before use
 664 node_array_type FGGround::GetExits(const string& rwyID) {
 665         // FIXME - get a 07L or similar in here and we're stuffed!!!
 666         return(runways[atoi(rwyID.c_str())].exits);
 667 }
 668
 669 void FGGround::RequestDeparture(const PlaneRec& plane, FGAIEntity* requestee) {
 670         // For now we'll just automatically clear all planes to the runway hold.
 671         // This communication needs to be delayed 20 sec or so from receiving the request.
 672         // Even if display=false we still need to start the timer in case display=true when communication starts.
 673         // We also need to bear in mind we also might have other outstanding communications, although for now we'll punt that issue!
 674         // FIXME - sort the above!
 675
 676         // HACK - assume that anything requesting departure is new for now - FIXME LATER
 677         GroundRec* g = new GroundRec;
 678         g->plane = plane;
 679         g->planePtr = requestee;
 680         g->taxiRequestOutstanding = true;
 681         g->clearanceCounter = 0;
 682         g->cleared = false;
 683         g->incoming = false;
 684         // TODO - need to handle the next 3 as well
 685     //Point3D current_pos;
 686     //node* destination;
 687     //node* last_clearance;
 688
 689         ground_traffic.push_back(g);
 690 }
 691
 692 #if 0
 693 void FGGround::NewArrival(plane_rec plane) {
 694         // What are we going to do here?
 695         // We need to start a new ground_rec and add the plane_rec to it
 696         // We need to decide what gate we are going to clear it to.
 697         // Then we need to add clearing it to that gate to the pending transmissions queue? - or simply transmit?
 698         // Probably simply transmit for now and think about a transmission queue later if we need one.
 699         // We might need one though in order to add a little delay for response time.
 700         ground_rec* g = new ground_rec;
 701         g->plane_rec = plane;
 702         g->current_pos = ConvertWGS84ToXY(plane.pos);
 703         g->node = GetNode(g->current_pos);  // TODO - might need to sort out node/arc here
 704         AssignGate(g);
 705         g->cleared = false;
 706         ground_traffic.push_back(g);
 707         NextClearance(g);
 708 }
 709
 710 void FGGround::NewContact(plane_rec plane) {
 711         // This is a bit of a convienience function at the moment and is likely to change.
 712         if(at a gate or apron)
 713                 NewDeparture(plane);
 714         else
 715                 NewArrival(plane);
 716 }
 717
 718 void FGGround::NextClearance(ground_rec &g) {
 719         // Need to work out where we can clear g to.
 720         // Assume the pilot doesn't need progressive instructions
 721         // We *should* already have a gate or holding point assigned by the time we get here
 722         // but it wouldn't do any harm to check.
 723
 724         // For now though we will hardwire it to clear to the final destination.
 725 }
 726
 727 void FGGround::AssignGate(ground_rec &g) {
 728         // We'll cheat for now - since we only have the user's aircraft and a couple of airports implemented
 729         // we'll hardwire the gate!
 730         // In the long run the logic of which gate or area to send the plane to could be somewhat non-trivial.
 731 }
 732 #endif //0
 733