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-kts", true);
  64 }
  65
  66 FGGround::FGGround(string id) {
  67         ATCmgr = globals->get_ATC_mgr();
  68         display = false;
  69         networkLoadOK = false;
  70         ground_traffic.erase(ground_traffic.begin(), ground_traffic.end());
  71         ground_traffic_itr = ground_traffic.begin();
  72         ident = id;
  73
  74         // Init the property nodes - TODO - need to make sure we're getting surface winds.
  75         wind_from_hdg = fgGetNode("/environment/wind-from-heading-deg", true);
  76         wind_speed_knots = fgGetNode("/environment/wind-speed-kts", true);
  77 }
  78
  79 FGGround::~FGGround() {
  80 }
  81
  82 void FGGround::ParseRwyExits(node* np, char* es) {
  83         char* token;
  84         char estr[20];
  85         strcpy(estr, es);
  86         const char delimiters[] = "-";
  87         token = strtok(estr, delimiters);
  88         while(token != NULL) {
  89                 int i = atoi(token);
  90                 //cout << "token = " << token << endl;
  91                 //cout << "rwy number = " << i << endl;
  92                 //runways[(atoi(token))].exits.push_back(np);
  93                 runways[i].exits.push_back(np);
  94                 //cout << "token = " << token << '\n';
  95                 token = strtok(NULL, delimiters);
  96         }
  97 }
  98
  99
 100 // Load the ground logical network of the current instances airport
 101 // Return true if successfull.
 102 // TODO - currently the file is assumed to reside in the base/ATC directory.
 103 // This might change to something more thought out in the future.
 104 // NOTE - currently it is assumed that all nodes are loaded before any arcs.
 105 // It won't work ATM if this doesn't hold true.
 106 bool FGGround::LoadNetwork() {
 107         node* np;
 108         arc* ap;
 109         Gate* gp;
 110
 111         int gateCount = 0;      // This is used to allocate gateID's from zero upwards
 112         // This may well change in the future - probably to reading in the real-world
 113         // gate numbers from file.
 114
 115         ifstream fin;
 116         SGPath path = globals->get_fg_root();
 117         //string taxiPath = "ATC/" + ident + ".taxi";
 118         string taxiPath = "ATC/KEMT.taxi";      // FIXME - HARDWIRED FOR TESTING
 119         path.append(taxiPath);
 120
 121         SG_LOG(SG_ATC, SG_INFO, "Trying to read taxiway data for " << ident << "...");
 122         //cout << "Trying to read taxiway data for " << ident << "..." << endl;
 123         fin.open(path.c_str(), ios::in);
 124         if(!fin) {
 125                 SG_LOG(SG_ATC, SG_ALERT, "Unable to open taxiway data input file " << path.c_str());
 126                 //cout << "Unable to open taxiway data input file " << path.c_str() << endl;
 127                 return(false);
 128         }
 129
 130         char ch;
 131         char buf[30];
 132         while(!fin.eof()) {
 133                 fin >> buf;
 134                 // Node, arc, or [End]?
 135                 //cout << "Read in ground network element type = " << buf << endl;
 136                 if(!strcmp(buf, "[End]")) {             // TODO - maybe make this more robust to spelling errors by just looking for '['
 137                         SG_LOG(SG_ATC, SG_INFO, "Done reading " << path.c_str() << endl);
 138                         break;
 139                 } else if(!strcmp(buf, "N")) {
 140                         // Node
 141                         np = new node;
 142                         np->struct_type = NODE;
 143                         fin >> buf;
 144                         np->nodeID = atoi(buf);
 145                         fin >> buf;
 146                         np->pos.setlon(atof(buf));
 147                         fin >> buf;
 148                         np->pos.setlat(atof(buf));
 149                         fin >> buf;
 150                         np->pos.setelev(atof(buf));
 151                         fin >> buf;             // node type
 152                         if(!strcmp(buf, "J")) {
 153                                 np->type = JUNCTION;
 154                         } else if(!strcmp(buf, "T")) {
 155                                 np->type = TJUNCTION;
 156                         } else if(!strcmp(buf, "H")) {
 157                                 np->type = HOLD;
 158                         } else {
 159                                 SG_LOG(SG_ATC, SG_ALERT, "**** ERROR ***** Unknown node type in taxi network...\n");
 160                                 delete np;
 161                                 return(false);
 162                         }
 163                         fin >> buf;             // rwy exit information - gets parsed later - FRAGILE - will break if buf is reused.
 164                         // Now the name
 165                         fin >> ch;      // strip the leading " off
 166                         np->name = "";
 167                         while(1) {
 168                                 fin.unsetf(ios::skipws);
 169                                 fin >> ch;
 170                                 if((ch == '"') || (ch == 0x0A)) {
 171                                         break;
 172                                 }   // we shouldn't need the 0x0A but it makes a nice safely in case someone leaves off the "
 173                                 np->name += ch;
 174                         }
 175                         fin.setf(ios::skipws);
 176                         network.push_back(np);
 177                         // FIXME - fragile - replies on buf not getting modified from exits read to here
 178                         // see if we also need to push it onto the runway exit list
 179                         //cout << "strlen(buf) = " << strlen(buf) << endl;
 180                         if(strlen(buf) > 2) {
 181                                 //cout << "Calling ParseRwyExits for " << buf << endl;
 182                                 ParseRwyExits(np, buf);
 183                         }
 184                 } else if(!strcmp(buf, "A")) {
 185                         ap = new arc;
 186                         ap->struct_type = ARC;
 187                         fin >> buf;
 188                         ap->n1 = atoi(buf);
 189                         fin >> buf;
 190                         ap->n2 = atoi(buf);
 191                         fin >> buf;
 192                         if(!strcmp(buf, "R")) {
 193                                 ap->type = RUNWAY;
 194                         } else if(!strcmp(buf, "T")) {
 195                                 ap->type = TAXIWAY;
 196                         } else {
 197                                 SG_LOG(SG_ATC, SG_ALERT, "**** ERROR ***** Unknown arc type in taxi network...\n");
 198                                 delete ap;
 199                                 return(false);
 200                         }
 201                         // directed?
 202                         fin >> buf;
 203                         if(!strcmp(buf, "Y")) {
 204                                 ap->directed = true;
 205                         } else if(!strcmp(buf, "N")) {
 206                                 ap->directed = false;
 207                         } else {
 208                                 SG_LOG(SG_ATC, SG_ALERT, "**** ERROR ***** Unknown arc directed value in taxi network - should be Y/N !!!\n");
 209                                 delete ap;
 210                                 return(false);
 211                         }
 212                         // Now the name
 213                         ap->name = "";
 214                         while(1) {
 215                                 fin.unsetf(ios::skipws);
 216                                 fin >> ch;
 217                                 ap->name += ch;
 218                                 if((ch == '"') || (ch == 0x0A)) {
 219                                         break;
 220                                 }   // we shouldn't need the 0x0A but it makes a nice safely in case someone leaves off the "
 221                         }
 222                         fin.setf(ios::skipws);
 223                         ap->distance = (int)dclGetHorizontalSeparation(network[ap->n1]->pos, network[ap->n2]->pos);
 224                         //cout << "Distance  = " << ap->distance << '\n';
 225                         network[ap->n1]->arcs.push_back(ap);
 226                         network[ap->n2]->arcs.push_back(ap);
 227                 } else if(!strcmp(buf, "G")) {
 228                         gp = new Gate;
 229                         gp->struct_type = NODE;
 230                         gp->type = GATE;
 231                         fin >> buf;
 232                         gp->nodeID = atoi(buf);
 233                         fin >> buf;
 234                         gp->pos.setlon(atof(buf));
 235                         fin >> buf;
 236                         gp->pos.setlat(atof(buf));
 237                         fin >> buf;
 238                         gp->pos.setelev(atof(buf));
 239                         fin >> buf;             // gate type - ignore this for now
 240                         fin >> buf;             // gate heading
 241                         gp->heading = atoi(buf);
 242                         // Now the name
 243                         gp->name = "";
 244                         while(1) {
 245                                 fin.unsetf(ios::skipws);
 246                                 fin >> ch;
 247                                 gp->name += ch;
 248                                 if((ch == '"') || (ch == 0x0A)) {
 249                                         break;
 250                                 }   // we shouldn't need the 0x0A but it makes a nice safely in case someone leaves off the "
 251                         }
 252                         fin.setf(ios::skipws);
 253                         gp->id = gateCount;             // Warning - this will likely change in the future.
 254                         gp->used = false;
 255                         network.push_back(gp);
 256                         gates[gateCount] = gp;
 257                         gateCount++;
 258                 } else {
 259                         // Something has gone seriously pear-shaped
 260                         SG_LOG(SG_ATC, SG_ALERT, "********* ERROR - unknown ground network element type... aborting read of " << path.c_str() << '\n');
 261                         return(false);
 262                 }
 263
 264                 fin >> skipeol;
 265         }
 266         return(true);
 267 }
 268
 269 void FGGround::Init() {
 270         display = false;
 271         untowered = false;
 272
 273         // Figure out which is the active runway - TODO - it would be better to have ground call tower
 274         // for runway operation details, but at the moment we can't guarantee that tower control at a given airport
 275         // will be initialised before ground so we can't do that.
 276         DoRwyDetails();
 277         //cout << "In FGGround::Init, active rwy is " << activeRwy << '\n';
 278         ortho.Init(rwy.threshold_pos, rwy.hdg);
 279
 280         networkLoadOK = LoadNetwork();
 281 }
 282
 283 void FGGround::Update(double dt) {
 284         // Each time step, what do we need to do?
 285         // We need to go through the list of outstanding requests and acknowedgements
 286         // and process at least one of them.
 287         // We need to go through the list of planes under our control and check if
 288         // any need to be addressed.
 289         // We need to check for planes not under our control coming within our
 290         // control area and address if necessary.
 291
 292         // Lets take the example of a plane which has just contacted ground
 293         // following landing - presumably requesting where to go?
 294         // First we need to establish the position of the plane within the logical network.
 295         // Next we need to decide where its going.
 296
 297         if(ground_traffic.size()) {
 298                 if(ground_traffic_itr == ground_traffic.end()) {
 299                         ground_traffic_itr = ground_traffic.begin();
 300                 }
 301
 302                 //Process(*ground_traffic_itr);
 303                 GroundRec* g = *ground_traffic_itr;
 304                 if(g->taxiRequestOutstanding) {
 305                         double responseTime = 10.0;             // seconds - this should get more sophisticated at some point
 306                         if(g->clearanceCounter > responseTime) {
 307                                 // DO CLEARANCE
 308                                 // TODO - move the mechanics of making up the transmission out of the main Update(...) routine.
 309                                 string trns = "";
 310                                 trns += g->plane.callsign;
 311                                 trns += " taxi holding point runway ";  // TODO - add the holding point name
 312                                 // eg " taxi holding point G2 runway "
 313                                 trns += ConvertRwyNumToSpokenString(activeRwy);
 314                                 if(display) {
 315                                         globals->get_ATC_display()->RegisterSingleMessage(trns, 0);
 316                                 }
 317                                 g->planePtr->RegisterTransmission(1);   // cleared to taxi
 318                                 g->clearanceCounter = 0.0;
 319                                 g->taxiRequestOutstanding = false;
 320                         } else {
 321                                 g->clearanceCounter += (dt * ground_traffic.size());
 322                         }
 323                 } else if(((FGAILocalTraffic*)(g->planePtr))->AtHoldShort()) {          // That's a hack - eventually we should monitor actual position
 324                         // HACK ALERT - the automatic cast to AILocalTraffic has to go once we have other sorts working!!!!! FIXME TODO
 325                         // NOTE - we don't need to do the contact tower bit unless we have separate tower and ground
 326                         string trns = g->plane.callsign;
 327                         trns += " contact Tower ";
 328                         double f = globals->get_ATC_mgr()->GetFrequency(ident, TOWER);
 329                         char buf[10];
 330                         sprintf(buf, "%f", f);
 331                         trns += buf;
 332                         if(display) {
 333                                 globals->get_ATC_display()->RegisterSingleMessage(trns, 0);
 334                         }
 335                         g->planePtr->RegisterTransmission(2);   // contact tower
 336                         delete *ground_traffic_itr;
 337                         ground_traffic.erase(ground_traffic_itr);
 338                         ground_traffic_itr = ground_traffic.begin();
 339                 }
 340                 ++ground_traffic_itr;
 341         }
 342 }
 343
 344 // Figure out which runways are active.
 345 // For now we'll just be simple and do one active runway - eventually this will get much more complex
 346 // Copied from FGTower - TODO - it would be better to implement this just once, and have ground call tower
 347 // for runway operation details, but at the moment we can't guarantee that tower control at a given airport
 348 // will be initialised before ground so we can't do that.
 349 void FGGround::DoRwyDetails() {
 350         //cout << "GetRwyDetails called" << endl;
 351
 352         // Based on the airport-id and wind get the active runway
 353         SGPath path( globals->get_fg_root() );
 354         path.append( "Airports" );
 355         path.append( "runways.mk4" );
 356         FGRunways r_ways( path.c_str() );
 357
 358         //wind
 359         double hdg = wind_from_hdg->getDoubleValue();
 360         double speed = wind_speed_knots->getDoubleValue();
 361         hdg = (speed == 0.0 ? 270.0 : hdg);
 362         //cout << "Heading = " << hdg << '\n';
 363
 364         FGRunway runway;
 365         bool rwyGood = r_ways.search(ident, int(hdg), &runway);
 366         if(rwyGood) {
 367                 activeRwy = runway.rwy_no;
 368                 rwy.rwyID = runway.rwy_no;
 369                 SG_LOG(SG_ATC, SG_INFO, "In FGGround, active runway for airport " << ident << " is " << activeRwy);
 370
 371                 // Get the threshold position
 372                 double other_way = runway.heading - 180.0;
 373                 while(other_way <= 0.0) {
 374                         other_way += 360.0;
 375                 }
 376         // move to the +l end/center of the runway
 377                 //cout << "Runway center is at " << runway.lon << ", " << runway.lat << '\n';
 378         Point3D origin = Point3D(runway.lon, runway.lat, aptElev);
 379                 Point3D ref = origin;
 380         double tshlon, tshlat, tshr;
 381                 double tolon, tolat, tor;
 382                 rwy.length = runway.length * SG_FEET_TO_METER;
 383         geo_direct_wgs_84 ( aptElev, ref.lat(), ref.lon(), other_way,
 384                                 rwy.length / 2.0 - 25.0, &tshlat, &tshlon, &tshr );
 385         geo_direct_wgs_84 ( aptElev, ref.lat(), ref.lon(), runway.heading,
 386                                 rwy.length / 2.0 - 25.0, &tolat, &tolon, &tor );
 387                 // Note - 25 meters in from the runway end is a bit of a hack to put the plane ahead of the user.
 388                 // now copy what we need out of runway into rwy
 389         rwy.threshold_pos = Point3D(tshlon, tshlat, aptElev);
 390                 Point3D takeoff_end = Point3D(tolon, tolat, aptElev);
 391                 //cout << "Threshold position = " << tshlon << ", " << tshlat << ", " << aptElev << '\n';
 392                 //cout << "Takeoff position = " << tolon << ", " << tolat << ", " << aptElev << '\n';
 393                 rwy.hdg = runway.heading;
 394                 // Set the projection for the local area based on this active runway
 395                 ortho.Init(rwy.threshold_pos, rwy.hdg);
 396                 rwy.end1ortho = ortho.ConvertToLocal(rwy.threshold_pos);        // should come out as zero
 397                 rwy.end2ortho = ortho.ConvertToLocal(takeoff_end);
 398         } else {
 399                 SG_LOG(SG_ATC, SG_ALERT, "Help  - can't get good runway in FGTower!!");
 400                 activeRwy = "NN";
 401         }
 402 }
 403
 404 // Return a random gate ID of an unused gate.
 405 // Two error values may be returned and must be checked for by the calling function:
 406 // -2 signifies that no gates exist at this airport.
 407 // -1 signifies that all gates are currently full.
 408 int FGGround::GetRandomGateID() {
 409         // Check that this airport actually has some gates!!
 410         if(!gates.size()) {
 411                 return(-2);
 412         }
 413
 414         gate_vec_type gateVec;
 415         int num = 0;
 416         int thenum;
 417         int ID;
 418
 419         gatesItr = gates.begin();
 420         while(gatesItr != gates.end()) {
 421                 if((gatesItr->second)->used == false) {
 422                         gateVec.push_back(gatesItr->second);
 423                         num++;
 424                 }
 425                 ++gatesItr;
 426         }
 427
 428         // Check that there are some unused gates!
 429         if(!gateVec.size()) {
 430                 return(-1);
 431         }
 432
 433         // Randomly select one from the list
 434         sg_srandom_time();
 435         thenum = (int)(sg_random() * gateVec.size());
 436         ID = gateVec[thenum]->id;
 437
 438         return(ID);
 439 }
 440
 441 // Return a pointer to an unused gate node
 442 Gate* FGGround::GetGateNode() {
 443         int id = GetRandomGateID();
 444         if(id < 0) {
 445                 return(NULL);
 446         } else {
 447                 return(gates[id]);
 448         }
 449 }
 450
 451
 452 // WARNING - This is hardwired to my prototype logical network format
 453 // and will almost certainly change when Bernie's stuff comes on-line.
 454 node* FGGround::GetThresholdNode(string rwyID) {
 455         // For now go through all the nodes and parse their names
 456         // Maybe in the future we'll map threshold nodes by ID
 457         //cout << "Size of network is " << network.size() << '\n';
 458         for(unsigned int i=0; i<network.size(); ++i) {
 459                 //cout << "Name = " << network[i]->name << '\n';
 460                 if(network[i]->name.size()) {
 461                         string s = network[i]->name;
 462                         // Warning - the next bit is fragile and dependent on my current naming scheme
 463                         //cout << "substr = " << s.substr(0,3) << '\n';
 464                         //cout << "size of s = " << s.size() << '\n';
 465                         if(s.substr(0,3) == "rwy") {
 466                                 //cout << "subsubstr = " << s.substr(4, s.size() - 4) << '\n';
 467                                 if(s.substr(4, s.size() - 4) == rwyID) {
 468                                         return network[i];
 469                                 }
 470                         }
 471                 }
 472         }
 473         return NULL;
 474 }
 475
 476
 477 // Get a path from a point on a runway to a gate
 478 // TODO !!
 479
 480 // Get a path from a node to another node
 481 // Eventually we will need complex algorithms for this taking other traffic,
 482 // shortest path and suitable paths into accout.
 483 // For now we'll just call the shortest path algorithm.
 484 ground_network_path_type FGGround::GetPath(node* A, node* B) {
 485         return(GetShortestPath(A, B));
 486 };
 487
 488 // Get a path from a node to a runway threshold
 489 ground_network_path_type FGGround::GetPath(node* A, string rwyID) {
 490         node* b = GetThresholdNode(rwyID);
 491         if(b == NULL) {
 492                 SG_LOG(SG_ATC, SG_ALERT, "ERROR - unable to find path to runway theshold in ground.cxx\n");
 493                 ground_network_path_type emptyPath;
 494                 emptyPath.erase(emptyPath.begin(), emptyPath.end());
 495                 return(emptyPath);
 496         }
 497         return GetShortestPath(A, b);
 498 }
 499
 500 // Get a path from a node to a runway hold short point
 501 // Bit of a hack this at the moment!
 502 ground_network_path_type FGGround::GetPathToHoldShort(node* A, string rwyID) {
 503         ground_network_path_type path = GetPath(A, rwyID);
 504         path.pop_back();        // That should be the threshold stripped of
 505         path.pop_back();        // and that should be the arc from hold short to threshold
 506         // This isn't robust though - TODO - implement properly!
 507         return(path);
 508 }
 509
 510 // A shortest path algorithm from memory (ie. I can't find the bl&*dy book again!)
 511 // I'm sure there must be enchancements that we can make to this, such as biasing the
 512 // order in which the nodes are searched out from in favour of those geographically
 513 // closer to the destination.
 514 // Note that we are working with the master set of nodes and arcs so we mustn't change
 515 // or delete them -  we only delete the paths that we create during the algorithm.
 516 ground_network_path_type FGGround::GetShortestPath(node* A, node* B) {
 517         a_path* pathPtr;
 518         shortest_path_map_type pathMap;
 519         node_array_type nodesLeft;
 520
 521         // Debugging check
 522         int pathsCreated = 0;
 523
 524         // Initialise the algorithm
 525         nodesLeft.push_back(A);
 526         pathPtr = new a_path;
 527         pathsCreated++;
 528         pathPtr->path.push_back(A);
 529         pathPtr->cost = 0;
 530         pathMap[A->nodeID] = pathPtr;
 531         bool solution_found = false;    // Flag to indicate that at least one candidate path has been found
 532         int solution_cost = -1;                 // Cost of current best cost solution.  -1 indicates no solution found yet.
 533         a_path solution_path;
 534
 535         node* nPtr;     // nPtr is used to point to the node we are currently working with
 536
 537         while(nodesLeft.size()) {
 538                 //cout << "\n*****nodesLeft*****\n";
 539                 //for(unsigned int i=0; i<nodesLeft.size(); ++i) {
 540                         //cout << nodesLeft[i]->nodeID << '\n';
 541                 //}
 542                 //cout << "*******************\n\n";
 543                 nPtr = *nodesLeft.begin();              // Thought - definate optimization possibilities here in the choice of which nodes we process first.
 544                 nodesLeft.erase(nodesLeft.begin());
 545                 //cout << "Walking out from node " << nPtr->nodeID << '\n';
 546                 for(unsigned int i=0; i<nPtr->arcs.size(); ++i) {
 547                         //cout << "ARC TO " << ((nPtr->arcs[i]->n1 == nPtr->nodeID) ? nPtr->arcs[i]->n2 : nPtr->arcs[i]->n1) << '\n';
 548                 }
 549                 if((solution_found) && (solution_cost <= pathMap[nPtr->nodeID]->cost)) {
 550                         // Do nothing - we've already found a solution and this partial path is already more expensive
 551                 } else {
 552                         // This path could still be better than the current solution - check it out
 553                         for(unsigned int i=0; i<(nPtr->arcs.size()); i++) {
 554                                 // Map the new path against the end node, ie. *not* the one we just started with.
 555                                 unsigned int end_nodeID = ((nPtr->arcs[i]->n1 == nPtr->nodeID) ? nPtr->arcs[i]->n2 : nPtr->arcs[i]->n1);
 556                                 //cout << "end_nodeID = " << end_nodeID << '\n';
 557                                 //cout << "pathMap size is " << pathMap.size() << '\n';
 558                                 if(end_nodeID == nPtr->nodeID) {
 559                                         //cout << "Circular arc!\n";
 560                                         // Then its a circular arc - don't bother!!
 561                                         //nPtr->arcs.erase(nPtr->arcs.begin() + i);
 562                                 } else {
 563                                         // see if the end node is already in the map or not
 564                                         if(pathMap.find(end_nodeID) == pathMap.end()) {
 565                                                 //cout << "Not in the map" << endl;;
 566                                                 // Not in the map - easy!
 567                                                 pathPtr = new a_path;
 568                                                 pathsCreated++;
 569                                                 *pathPtr = *pathMap[nPtr->nodeID];      // *copy* the path
 570                                                 pathPtr->path.push_back(nPtr->arcs[i]);
 571                                                 pathPtr->path.push_back(network[end_nodeID]);
 572                                                 pathPtr->cost += nPtr->arcs[i]->distance;
 573                                                 pathMap[end_nodeID] = pathPtr;
 574                                                 nodesLeft.push_back(network[end_nodeID]);       // By definition this can't be in the list already, or
 575                                                 // it would also have been in the map and hence OR'd with this one.
 576                                                 if(end_nodeID == B->nodeID) {
 577                                                         //cout << "Solution found!!!" << endl;
 578                                                         // Since this node wasn't in the map this is by definition the first solution
 579                                                         solution_cost = pathPtr->cost;
 580                                                         solution_path = *pathPtr;
 581                                                         solution_found = true;
 582                                                 }
 583                                         } else {
 584                                                 //cout << "Already in the map" << endl;
 585                                                 // In the map - not so easy - need to get rid of an arc from the higher cost one.
 586                                                 //cout << "Current cost of node " << end_nodeID << " is " << pathMap[end_nodeID]->cost << endl;
 587                                                 int newCost = pathMap[nPtr->nodeID]->cost + nPtr->arcs[i]->distance;
 588                                                 //cout << "New cost is of node " << nPtr->nodeID << " is " << newCost << endl;
 589                                                 if(newCost >= pathMap[end_nodeID]->cost) {
 590                                                         // No need to do anything.
 591                                                         //cout << "Not doing anything!" << endl;
 592                                                 } else {
 593                                                         delete pathMap[end_nodeID];
 594                                                         pathsCreated--;
 595
 596                                                         pathPtr = new a_path;
 597                                                         pathsCreated++;
 598                                                         *pathPtr = *pathMap[nPtr->nodeID];      // *copy* the path
 599                                                         pathPtr->path.push_back(nPtr->arcs[i]);
 600                                                         pathPtr->path.push_back(network[end_nodeID]);
 601                                                         pathPtr->cost += nPtr->arcs[i]->distance;
 602                                                         pathMap[end_nodeID] = pathPtr;
 603
 604                                                         // We need to add this node to the list-to-do again to force a recalculation
 605                                                         // onwards from this node with the new lower cost to node cost.
 606                                                         nodesLeft.push_back(network[end_nodeID]);
 607
 608                                                         if(end_nodeID == B->nodeID) {
 609                                                                 //cout << "Solution found!!!" << endl;
 610                                                                 // Need to check if there is a previous better solution
 611                                                                 if((solution_cost < 0) || (pathPtr->cost < solution_cost)) {
 612                                                                         solution_cost = pathPtr->cost;
 613                                                                         solution_path = *pathPtr;
 614                                                                         solution_found = true;
 615                                                                 }
 616                                                         }
 617                                                 }
 618                                         }
 619                                 }
 620                         }
 621                 }
 622         }
 623
 624         // delete all the paths before returning
 625         shortest_path_map_iterator spItr = pathMap.begin();
 626         while(spItr != pathMap.end()) {
 627                 if(spItr->second != NULL) {
 628                         delete spItr->second;
 629                         --pathsCreated;
 630                 }
 631                 ++spItr;
 632         }
 633
 634         //cout << "pathsCreated = " << pathsCreated << '\n';
 635         if(pathsCreated > 0) {
 636                 SG_LOG(SG_ATC, SG_ALERT, "WARNING - Possible memory leak in FGGround::GetShortestPath\n\
 637                                                                           Please report to flightgear-devel@flightgear.org\n");
 638         }
 639
 640         //cout << (solution_found ? "Result: solution found\n" : "Result: no solution found\n");
 641         return(solution_path.path);             // TODO - we really ought to have a fallback position incase a solution isn't found.
 642 }
 643
 644
 645
 646 // Randomly or otherwise populate some of the gates with parked planes
 647 // (might eventually be done by the AIMgr if and when lots of AI traffic is generated)
 648
 649 // Return a list of exits from a given runway
 650 // It is up to the calling function to check for non-zero size of returned array before use
 651 node_array_type FGGround::GetExits(string rwyID) {
 652         // FIXME - get a 07L or similar in here and we're stuffed!!!
 653         return(runways[atoi(rwyID.c_str())].exits);
 654 }
 655
 656 void FGGround::RequestDeparture(PlaneRec plane, FGAIEntity* requestee) {
 657         // For now we'll just automatically clear all planes to the runway hold.
 658         // This communication needs to be delayed 20 sec or so from receiving the request.
 659         // Even if display=false we still need to start the timer in case display=true when communication starts.
 660         // We also need to bear in mind we also might have other outstanding communications, although for now we'll punt that issue!
 661         // FIXME - sort the above!
 662
 663         // HACK - assume that anything requesting departure is new for now - FIXME LATER
 664         GroundRec* g = new GroundRec;
 665         g->plane = plane;
 666         g->planePtr = requestee;
 667         g->taxiRequestOutstanding = true;
 668         g->clearanceCounter = 0;
 669         g->cleared = false;
 670         g->incoming = false;
 671         // TODO - need to handle the next 3 as well
 672     //Point3D current_pos;
 673     //node* destination;
 674     //node* last_clearance;
 675
 676         ground_traffic.push_back(g);
 677 }
 678
 679 #if 0
 680 void FGGround::NewArrival(plane_rec plane) {
 681         // What are we going to do here?
 682         // We need to start a new ground_rec and add the plane_rec to it
 683         // We need to decide what gate we are going to clear it to.
 684         // Then we need to add clearing it to that gate to the pending transmissions queue? - or simply transmit?
 685         // Probably simply transmit for now and think about a transmission queue later if we need one.
 686         // We might need one though in order to add a little delay for response time.
 687         ground_rec* g = new ground_rec;
 688         g->plane_rec = plane;
 689         g->current_pos = ConvertWGS84ToXY(plane.pos);
 690         g->node = GetNode(g->current_pos);  // TODO - might need to sort out node/arc here
 691         AssignGate(g);
 692         g->cleared = false;
 693         ground_traffic.push_back(g);
 694         NextClearance(g);
 695 }
 696
 697 void FGGround::NewContact(plane_rec plane) {
 698         // This is a bit of a convienience function at the moment and is likely to change.
 699         if(at a gate or apron)
 700                 NewDeparture(plane);
 701         else
 702                 NewArrival(plane);
 703 }
 704
 705 void FGGround::NextClearance(ground_rec &g) {
 706         // Need to work out where we can clear g to.
 707         // Assume the pilot doesn't need progressive instructions
 708         // We *should* already have a gate or holding point assigned by the time we get here
 709         // but it wouldn't do any harm to check.
 710
 711         // For now though we will hardwire it to clear to the final destination.
 712 }
 713
 714 void FGGround::AssignGate(ground_rec &g) {
 715         // We'll cheat for now - since we only have the user's aircraft and a couple of airports implemented
 716         // we'll hardwire the gate!
 717         // In the long run the logic of which gate or area to send the plane to could be somewhat non-trivial.
 718 }
 719 #endif //0
 720