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