]> git.mxchange.org Git - flightgear.git/blobdiff - src/Airports/groundnetwork.cxx
std namespace fixes in headers.
[flightgear.git] / src / Airports / groundnetwork.cxx
index 321a3af68833c7212d8f67d037e6b3e651d872e5..62449b0cb13fe04cc6c499e0131630ec21609e27 100644 (file)
 
 #include <math.h>
 #include <algorithm>
+#include <fstream>
+
+
+#include <osg/Geode>
+#include <osg/Geometry>
+#include <osg/MatrixTransform>
+#include <osg/Shape>
 
 #include <simgear/debug/logstream.hxx>
-#include <simgear/route/waypoint.hxx>
+#include <simgear/scene/material/EffectGeode.hxx>
+#include <simgear/scene/material/matlib.hxx>
+#include <simgear/scene/material/mat.hxx>
+#include <simgear/scene/util/OsgMath.hxx>
 
+#include <Airports/simple.hxx>
 #include <Airports/dynamics.hxx>
 
+#include <AIModel/AIAircraft.hxx>
+#include <AIModel/performancedata.hxx>
 #include <AIModel/AIFlightPlan.hxx>
 
+#include <ATC/atc_mgr.hxx>
+
+#include <Scenery/scenery.hxx>
+
 #include "groundnetwork.hxx"
 
+using std::string;
+
 /***************************************************************************
  * FGTaxiSegment
  **************************************************************************/
 
-void FGTaxiSegment::setStart(FGTaxiNodeVector *nodes)
+void FGTaxiSegment::setStart(FGTaxiNodeVector * nodes)
 {
-  FGTaxiNodeVectorIterator i = nodes->begin();
-  while (i != nodes->end())
-    {
-      //cerr << "Scanning start node index" << (*i)->getIndex() << endl;
-      if ((*i)->getIndex() == startNode)
-       {
-         start = (*i)->getAddress();
-         (*i)->addSegment(this);
-         return;
-       }
-      i++;
+    FGTaxiNodeVectorIterator i = nodes->begin();
+    while (i != nodes->end()) {
+        //cerr << "Scanning start node index" << (*i)->getIndex() << endl;
+        if ((*i)->getIndex() == startNode) {
+            start = (*i)->getAddress();
+            (*i)->addSegment(this);
+            return;
+        }
+        i++;
     }
-  SG_LOG(SG_GENERAL, SG_ALERT,  "Could not find start node " << startNode << endl);
+    SG_LOG(SG_GENERAL, SG_ALERT,
+           "Could not find start node " << startNode << endl);
 }
 
-void FGTaxiSegment::setEnd(FGTaxiNodeVector *nodes)
+void FGTaxiSegment::setEnd(FGTaxiNodeVector * nodes)
 {
-  FGTaxiNodeVectorIterator i = nodes->begin();
-  while (i != nodes->end())
-    {
-      //cerr << "Scanning end node index" << (*i)->getIndex() << endl;
-      if ((*i)->getIndex() == endNode)
-       {
-         end = (*i)->getAddress();
-         return;
-       }
-      i++;
+    FGTaxiNodeVectorIterator i = nodes->begin();
+    while (i != nodes->end()) {
+        //cerr << "Scanning end node index" << (*i)->getIndex() << endl;
+        if ((*i)->getIndex() == endNode) {
+            end = (*i)->getAddress();
+            return;
+        }
+        i++;
     }
-  SG_LOG(SG_GENERAL, SG_ALERT,  "Could not find end node " << endNode << endl);
+    SG_LOG(SG_GENERAL, SG_ALERT,
+           "Could not find end node " << endNode << endl);
 }
 
 
 
-// There is probably a computationally cheaper way of 
+// There is probably a computationally cheaper way of
 // doing this.
-void FGTaxiSegment::setTrackDistance()
+void FGTaxiSegment::setDimensions(double elevation)
 {
-  length = SGGeodesy::distanceM(start->getGeod(), end->getGeod());
+    length = SGGeodesy::distanceM(start->getGeod(), end->getGeod());
+    //heading = SGGeodesy::headingDeg(start->getGeod(), end->getGeod());
+
+    double az2; //, distanceM;
+    SGGeodesy::inverse(start->getGeod(), end->getGeod(), heading, az2, length);
+    double coveredDistance = length * 0.5;
+    SGGeodesy::direct(start->getGeod(), heading, coveredDistance, center, az2);
+    //start->setElevation(elevation);
+    //end->setElevation(elevation);
+    //cerr << "Centerpoint = (" << center.getLatitudeDeg() << ", " << center.getLongitudeDeg() << "). Heading = " << heading << endl;
 }
 
 
-void FGTaxiSegment::setCourseDiff(double crse)
+//void FGTaxiSegment::setCourseDiff(double crse)
+//{
+//    headingDiff = fabs(course - crse);
+
+//    if (headingDiff > 180)
+//        headingDiff = fabs(headingDiff - 360);
+//}
+
+void FGTaxiSegment::block(int id, time_t blockTime, time_t now)
 {
-  headingDiff = fabs(course-crse);
-  
-  if (headingDiff > 180)
-    headingDiff = fabs(headingDiff - 360);
+    BlockListIterator i = blockTimes.begin();
+    while (i != blockTimes.end()) {
+        if (i->getId() == id) 
+            break;
+        i++;
+    }
+    if (i == blockTimes.end()) {
+        blockTimes.push_back(Block(id, blockTime, now));
+        sort(blockTimes.begin(), blockTimes.end());
+    } else {
+        i->updateTimeStamps(blockTime, now);
+    }
 }
 
+// The segment has a block if any of the block times listed in the block list is
+// smaller than the current time.
+bool FGTaxiSegment::hasBlock(time_t now)
+{
+    for (BlockListIterator i = blockTimes.begin(); i != blockTimes.end(); i++) {
+        if (i->getBlockTime() < now)
+            return true;
+    }
+    return false;
+}
+
+void FGTaxiSegment::unblock(time_t now)
+{
+    if (blockTimes.size()) {
+        BlockListIterator i = blockTimes.begin();
+        if (i->getTimeStamp() < (now - 30)) {
+            blockTimes.erase(i);
+        }
+    }
+}
+
+
 
 /***************************************************************************
  * FGTaxiRoute
  **************************************************************************/
-bool FGTaxiRoute::next(int *nde) 
-{ 
-  //for (intVecIterator i = nodes.begin(); i != nodes.end(); i++)
-  //  cerr << "FGTaxiRoute contains : " << *(i) << endl;
-  //cerr << "Offset from end: " << nodes.end() - currNode << endl;
-  //if (currNode != nodes.end())
-  //  cerr << "true" << endl;
-  //else
-  //  cerr << "false" << endl;
-  //if (nodes.size() != (routes.size()) +1)
-  //  cerr << "ALERT: Misconfigured TaxiRoute : " << nodes.size() << " " << routes.size() << endl;
-      
-  if (currNode == nodes.end())
-    return false;
-  *nde = *(currNode); 
-  if (currNode != nodes.begin()) // make sure route corresponds to the end node
-    currRoute++;
-  currNode++;
-  return true;
+bool FGTaxiRoute::next(int *nde)
+{
+    //for (intVecIterator i = nodes.begin(); i != nodes.end(); i++)
+    //  cerr << "FGTaxiRoute contains : " << *(i) << endl;
+    //cerr << "Offset from end: " << nodes.end() - currNode << endl;
+    //if (currNode != nodes.end())
+    //  cerr << "true" << endl;
+    //else
+    //  cerr << "false" << endl;
+    //if (nodes.size() != (routes.size()) +1)
+    //  cerr << "ALERT: Misconfigured TaxiRoute : " << nodes.size() << " " << routes.size() << endl;
+
+    if (currNode == nodes.end())
+        return false;
+    *nde = *(currNode);
+    if (currNode != nodes.begin())      // make sure route corresponds to the end node
+        currRoute++;
+    currNode++;
+    return true;
 };
 
-bool FGTaxiRoute::next(int *nde, int *rte) 
-{ 
-  //for (intVecIterator i = nodes.begin(); i != nodes.end(); i++)
-  //  cerr << "FGTaxiRoute contains : " << *(i) << endl;
-  //cerr << "Offset from end: " << nodes.end() - currNode << endl;
-  //if (currNode != nodes.end())
-  //  cerr << "true" << endl;
-  //else
-  //  cerr << "false" << endl;
-  if (nodes.size() != (routes.size()) +1) {
-    SG_LOG(SG_GENERAL, SG_ALERT, "ALERT: Misconfigured TaxiRoute : " << nodes.size() << " " << routes.size());
-    exit(1);
-  }
-  if (currNode == nodes.end())
-    return false;
-  *nde = *(currNode); 
-  //*rte = *(currRoute);
-  if (currNode != nodes.begin()) // Make sure route corresponds to the end node
-    {
-      *rte = *(currRoute);
-      currRoute++;
+bool FGTaxiRoute::next(int *nde, int *rte)
+{
+    //for (intVecIterator i = nodes.begin(); i != nodes.end(); i++)
+    //  cerr << "FGTaxiRoute contains : " << *(i) << endl;
+    //cerr << "Offset from end: " << nodes.end() - currNode << endl;
+    //if (currNode != nodes.end())
+    //  cerr << "true" << endl;
+    //else
+    //  cerr << "false" << endl;
+    if (nodes.size() != (routes.size()) + 1) {
+        SG_LOG(SG_GENERAL, SG_ALERT,
+               "ALERT: Misconfigured TaxiRoute : " << nodes.
+               size() << " " << routes.size());
+        exit(1);
     }
-  else
+    if (currNode == nodes.end())
+        return false;
+    *nde = *(currNode);
+    //*rte = *(currRoute);
+    if (currNode != nodes.begin())      // Make sure route corresponds to the end node
     {
-      // If currNode points to the first node, this means the aircraft is not on the taxi node
-      // yet. Make sure to return a unique identifyer in this situation though, because otherwise
-      // the speed adjust AI code may be unable to resolve whether two aircraft are on the same 
-      // taxi route or not. the negative of the preceding route seems a logical choice, as it is 
-      // unique for any starting location. 
-      // Note that this is probably just a temporary fix until I get Parking / tower control working.
-      *rte = -1 * *(currRoute); 
-    }
-  currNode++;
-  return true;
+        *rte = *(currRoute);
+        currRoute++;
+    } else {
+        // If currNode points to the first node, this means the aircraft is not on the taxi node
+        // yet. Make sure to return a unique identifyer in this situation though, because otherwise
+        // the speed adjust AI code may be unable to resolve whether two aircraft are on the same
+        // taxi route or not. the negative of the preceding route seems a logical choice, as it is
+        // unique for any starting location.
+        // Note that this is probably just a temporary fix until I get Parking / tower control working.
+        *rte = -1 * *(currRoute);
+    }
+    currNode++;
+    return true;
 };
 
+
 void FGTaxiRoute::rewind(int route)
 {
-  int currPoint;
-  int currRoute;
-  first();
-  do {
-    if (!(next(&currPoint, &currRoute))) { 
-      SG_LOG(SG_GENERAL,SG_ALERT, "Error in rewinding TaxiRoute: current" << currRoute 
-            << " goal " << route);
-    }
-  } while (currRoute != route);
+    int currPoint;
+    int currRoute;
+    first();
+    do {
+        if (!(next(&currPoint, &currRoute))) {
+            SG_LOG(SG_GENERAL, SG_ALERT,
+                   "Error in rewinding TaxiRoute: current" << currRoute <<
+                   " goal " << route);
+        }
+    } while (currRoute != route);
 }
 
 
@@ -171,67 +237,148 @@ void FGTaxiRoute::rewind(int route)
 /***************************************************************************
  * FGGroundNetwork()
  **************************************************************************/
-bool compare_nodes(FGTaxiNode *a, FGTaxiNode *b) {
-return (*a) < (*b);
+bool compare_nodes(FGTaxiNode * a, FGTaxiNode * b)
+{
+    return (*a) < (*b);
+}
+
+bool compare_segments(FGTaxiSegment * a, FGTaxiSegment * b)
+{
+    return (*a) < (*b);
 }
 
-bool compare_segments(FGTaxiSegment *a, FGTaxiSegment *b) {
-return (*a) < (*b);
+bool compare_trafficrecords(FGTrafficRecord a, FGTrafficRecord b)
+{
+    return (a.getIntentions().size() < b.getIntentions().size());
 }
 
-FGGroundNetwork::FGGroundNetwork()
+FGGroundNetwork::FGGroundNetwork() :
+  parent(NULL)
 {
-  hasNetwork = false;
-  foundRoute = false;
-  totalDistance = 0;
-  maxDistance = 0;
-  //maxDepth    = 1000;
-  count       = 0;
-  currTraffic = activeTraffic.begin();
+    hasNetwork = false;
+    foundRoute = false;
+    totalDistance = 0;
+    maxDistance = 0;
+    //maxDepth    = 1000;
+    count = 0;
+    currTraffic = activeTraffic.begin();
+    group = 0;
+    version = 0;
+    networkInitialized = false;
 
 }
 
 FGGroundNetwork::~FGGroundNetwork()
 {
-  for (FGTaxiNodeVectorIterator node = nodes.begin();
-       node != nodes.end();
-       node++)
-    {
-      delete (*node);
+// JMT 2012-09-8 - disabling the groundnet-caching as part of enabling the
+// navcache. The problem isn't the NavCache - it's that for the past few years,
+// we have not being running destructors on FGPositioned classes, and hence,
+// not running this code.
+// When I fix FGPositioned lifetimes (unloading-at-runtime support), this
+// will need to be re-visited so it can run safely during shutdown.
+#if 0
+    //cerr << "Running Groundnetwork Destructor " << endl;
+    bool saveData = false;
+    ofstream cachefile;
+    if (fgGetBool("/sim/ai/groundnet-cache")) {
+        SGPath cacheData(globals->get_fg_home());
+        cacheData.append("ai");
+        string airport = parent->getId();
+
+        if ((airport) != "") {
+            char buffer[128];
+            ::snprintf(buffer, 128, "%c/%c/%c/",
+                       airport[0], airport[1], airport[2]);
+            cacheData.append(buffer);
+            if (!cacheData.exists()) {
+                cacheData.create_dir(0777);
+            }
+            cacheData.append(airport + "-groundnet-cache.txt");
+            cachefile.open(cacheData.str().c_str());
+            saveData = true;
+        }
     }
-  nodes.clear();
-  pushBackNodes.clear();
-  for (FGTaxiSegmentVectorIterator seg = segments.begin();
-       seg != segments.end();
-       seg++)
-    {
-      delete (*seg);
+    cachefile << "[GroundNetcachedata:ref:2011:09:04]" << endl;
+    for (FGTaxiNodeVectorIterator node = nodes.begin();
+            node != nodes.end(); node++) {
+        if (saveData) {
+            cachefile << (*node)->getIndex     () << " "
+            << (*node)->getElevationM (parent->getElevation()*SG_FEET_TO_METER)   << " "
+            << endl;
+        }
+        delete(*node);
+    }
+    nodes.clear();
+    pushBackNodes.clear();
+    for (FGTaxiSegmentVectorIterator seg = segments.begin();
+            seg != segments.end(); seg++) {
+        delete(*seg);
+    }
+    segments.clear();
+    if (saveData) {
+        cachefile.close();
     }
-  segments.clear();
+#endif
 }
 
-void FGGroundNetwork::addSegment(const FGTaxiSegment &seg)
-{
-  segments.push_back(new FGTaxiSegment(seg));
+void FGGroundNetwork::saveElevationCache() {
+    //cerr << "Running Groundnetwork Destructor " << endl;
+    bool saveData = false;
+    ofstream cachefile;
+    if (fgGetBool("/sim/ai/groundnet-cache")) {
+        SGPath cacheData(globals->get_fg_home());
+        cacheData.append("ai");
+        string airport = parent->getId();
+
+        if ((airport) != "") {
+            char buffer[128];
+            ::snprintf(buffer, 128, "%c/%c/%c/",
+                       airport[0], airport[1], airport[2]);
+            cacheData.append(buffer);
+            if (!cacheData.exists()) {
+                cacheData.create_dir(0777);
+            }
+            cacheData.append(airport + "-groundnet-cache.txt");
+            cachefile.open(cacheData.str().c_str());
+            saveData = true;
+        }
+    }
+    cachefile << "[GroundNetcachedata:ref:2011:09:04]" << endl;
+    for (FGTaxiNodeVectorIterator node = nodes.begin();
+            node != nodes.end(); node++) {
+        if (saveData) {
+            cachefile << (*node)->getIndex     () << " "
+            << (*node)->getElevationM (parent->getElevation()*SG_FEET_TO_METER) << " "
+            << endl;
+        }
+    }
+    if (saveData) {
+        cachefile.close();
+    }
 }
 
-void FGGroundNetwork::addNode(const FGTaxiNode &node)
+void FGGroundNetwork::addSegment(const FGTaxiSegment & seg)
 {
-  nodes.push_back(new FGTaxiNode(node));
+    segments.push_back(new FGTaxiSegment(seg));
 }
 
-void FGGroundNetwork::addNodes(FGParkingVec *parkings)
+void FGGroundNetwork::addNode(const FGTaxiNode & node)
 {
-  FGTaxiNode n;
-  FGParkingVecIterator i = parkings->begin();
-  while (i != parkings->end())
-    {
-      n.setIndex(i->getIndex());
-      n.setLatitude(i->getLatitude());
-      n.setLongitude(i->getLongitude());
-      nodes.push_back(new FGTaxiNode(n));
+    nodes.push_back(new FGTaxiNode(node));
+}
 
-      i++;
+void FGGroundNetwork::addNodes(FGParkingVec * parkings)
+{
+    FGTaxiNode n;
+    FGParkingVecIterator i = parkings->begin();
+    while (i != parkings->end()) {
+        n.setIndex(i->getIndex());
+        n.setLatitude(i->getLatitude());
+        n.setLongitude(i->getLongitude());
+        n.setElevation(parent->getElevation()*SG_FEET_TO_METER);
+        nodes.push_back(new FGTaxiNode(n));
+
+        i++;
     }
 }
 
@@ -239,120 +386,188 @@ void FGGroundNetwork::addNodes(FGParkingVec *parkings)
 
 void FGGroundNetwork::init()
 {
-  hasNetwork = true;
-  int index = 1;
-  sort(nodes.begin(), nodes.end(), compare_nodes);
-  //sort(segments.begin(), segments.end(), compare_segments());
-  FGTaxiSegmentVectorIterator i = segments.begin();
-  while(i != segments.end()) {
-    (*i)->setStart(&nodes);
-    (*i)->setEnd  (&nodes);
-    (*i)->setTrackDistance();
-    (*i)->setIndex(index);
-    if ((*i)->isPushBack()) {
-          pushBackNodes.push_back((*i)->getEnd());
-    }
-    //SG_LOG(SG_GENERAL, SG_BULK,  "initializing segment " << (*i)->getIndex() << endl);
-    //SG_LOG(SG_GENERAL, SG_BULK, "Track distance = "     << (*i)->getLength() << endl);
-    //SG_LOG(SG_GENERAL, SG_BULK, "Track runs from "      << (*i)->getStart()->getIndex() << " to "
-    //                                                    << (*i)->getEnd()->getIndex() << endl);
-    i++;
-    index++;
-  }
-  i = segments.begin();
-  while(i != segments.end()) {
-    FGTaxiSegmentVectorIterator j = (*i)->getEnd()->getBeginRoute(); 
-    while (j != (*i)->getEnd()->getEndRoute())
-      {
-       if ((*j)->getEnd()->getIndex() == (*i)->getStart()->getIndex())
-         {
-//         int start1 = (*i)->getStart()->getIndex();
-//         int end1   = (*i)->getEnd()  ->getIndex();
-//         int start2 = (*j)->getStart()->getIndex();
-//         int end2   = (*j)->getEnd()->getIndex();
-//         int oppIndex = (*j)->getIndex();
-           //cerr << "Opposite of  " << (*i)->getIndex() << " (" << start1 << "," << end1 << ") "
-           //   << "happens to be " << oppIndex      << " (" << start2 << "," << end2 << ") " << endl;
-           (*i)->setOpposite(*j);
-           break;
-         }
-         j++;
-      }
-    i++;
-  }
-  //FGTaxiNodeVectorIterator j = nodes.begin();
-  //while (j != nodes.end()) {
-  //    if ((*j)->getHoldPointType() == 3) {
-  //        pushBackNodes.push_back((*j));
-  //    }
-  //    j++;
-  //}
-  //cerr << "Done initializing ground network" << endl;
-  //exit(1);
-}
-
-int FGGroundNetwork::findNearestNode(const SGGeod& aGeod)
-{
-  double minDist = HUGE_VAL;
-  int index = -1;
-  
-  for (FGTaxiNodeVectorIterator itr = nodes.begin(); itr != nodes.end(); itr++)
-  {
-    double d = SGGeodesy::distanceM(aGeod, (*itr)->getGeod());
-    if (d < minDist)
-    {
-      minDist = d;
-      index = (*itr)->getIndex();
-      //cerr << "Minimum distance of " << minDist << " for index " << index << endl;
+    if (networkInitialized) {
+        FGATCController::init();
+        //cerr << "FGground network already initialized" << endl;
+        return;
+    }
+    hasNetwork = true;
+    nextSave = 0;
+    int index = 1;
+    sort(nodes.begin(), nodes.end(), compare_nodes);
+    //sort(segments.begin(), segments.end(), compare_segments());
+    FGTaxiSegmentVectorIterator i = segments.begin();
+    while (i != segments.end()) {
+        (*i)->setStart(&nodes);
+        (*i)->setEnd(&nodes);
+        (*i)->setDimensions(parent->getElevation() * SG_FEET_TO_METER);
+        (*i)->setIndex(index);
+        if ((*i)->isPushBack()) {
+            pushBackNodes.push_back((*i)->getEnd());
+        }
+        //SG_LOG(SG_GENERAL, SG_BULK,  "initializing segment " << (*i)->getIndex() << endl);
+        //SG_LOG(SG_GENERAL, SG_BULK, "Track distance = "     << (*i)->getLength() << endl);
+        //SG_LOG(SG_GENERAL, SG_BULK, "Track runs from "      << (*i)->getStart()->getIndex() << " to "
+        //                                                    << (*i)->getEnd()->getIndex() << endl);
+        i++;
+        index++;
+    }
+
+    i = segments.begin();
+    while (i != segments.end()) {
+        FGTaxiSegmentVectorIterator j = (*i)->getEnd()->getBeginRoute();
+        while (j != (*i)->getEnd()->getEndRoute()) {
+            if ((*j)->getEnd()->getIndex() == (*i)->getStart()->getIndex()) {
+//          int start1 = (*i)->getStart()->getIndex();
+//          int end1   = (*i)->getEnd()  ->getIndex();
+//          int start2 = (*j)->getStart()->getIndex();
+//          int end2   = (*j)->getEnd()->getIndex();
+//          int oppIndex = (*j)->getIndex();
+                //cerr << "Opposite of  " << (*i)->getIndex() << " (" << start1 << "," << end1 << ") "
+                //   << "happens to be " << oppIndex      << " (" << start2 << "," << end2 << ") " << endl;
+                (*i)->setOpposite(*j);
+                break;
+            }
+            j++;
+        }
+        i++;
     }
-  }
-  
-  return index;
+    //FGTaxiNodeVectorIterator j = nodes.begin();
+    //while (j != nodes.end()) {
+    //    if ((*j)->getHoldPointType() == 3) {
+    //        pushBackNodes.push_back((*j));
+    //    }
+    //    j++;
+    //}
+    //cerr << "Done initializing ground network" << endl;
+    //exit(1);
+    if (fgGetBool("/sim/ai/groundnet-cache")) {
+        SGPath cacheData(globals->get_fg_home());
+        cacheData.append("ai");
+        string airport = parent->getId();
+
+        if ((airport) != "") {
+            char buffer[128];
+            ::snprintf(buffer, 128, "%c/%c/%c/",
+                       airport[0], airport[1], airport[2]);
+            cacheData.append(buffer);
+            if (!cacheData.exists()) {
+                cacheData.create_dir(0777);
+            }
+            int index;
+            double elev;
+            cacheData.append(airport + "-groundnet-cache.txt");
+            if (cacheData.exists()) {
+                ifstream data(cacheData.c_str());
+                string revisionStr;
+                data >> revisionStr;
+                if (revisionStr != "[GroundNetcachedata:ref:2011:09:04]") {
+                    SG_LOG(SG_GENERAL, SG_ALERT,"GroundNetwork Warning: discarding outdated cachefile " <<
+                           cacheData.c_str() << " for Airport " << airport);
+                } else {
+                    for (FGTaxiNodeVectorIterator i = nodes.begin();
+                            i != nodes.end();
+                            i++) {
+                        (*i)->setElevation(parent->getElevation() * SG_FEET_TO_METER);
+                        data >> index >> elev;
+                        if (data.eof())
+                            break;
+                        if (index != (*i)->getIndex()) {
+                            SG_LOG(SG_GENERAL, SG_ALERT, "Index read from ground network cache at airport " << airport << " does not match index in the network itself");
+                        } else {
+                            (*i)->setElevation(elev);
+                        }
+                    }
+                }
+            }
+        }
+    }
+    //cerr << "Finished initializing " << parent->getId() << " groundnetwork " << endl;
+    networkInitialized = true;
+}
+
+int FGGroundNetwork::findNearestNode(const SGGeod & aGeod)
+{
+    double minDist = HUGE_VAL;
+    int index = -1;
+
+    for (FGTaxiNodeVectorIterator itr = nodes.begin(); itr != nodes.end();
+            itr++) {
+        double d = SGGeodesy::distanceM(aGeod, (*itr)->getGeod());
+        if (d < minDist) {
+            minDist = d;
+            index = (*itr)->getIndex();
+            //cerr << "Minimum distance of " << minDist << " for index " << index << endl;
+        }
+    }
+
+    return index;
 }
 
+int FGGroundNetwork::findNearestNodeOnRunway(const SGGeod & aGeod)
+{
+    double minDist = HUGE_VAL;
+    int index = -1;
+
+    for (FGTaxiNodeVectorIterator itr = nodes.begin(); itr != nodes.end();
+            itr++) {
+        if (!((*itr)->getIsOnRunway())) {
+            continue;
+        }
+        double d = SGGeodesy::distanceM(aGeod, (*itr)->getGeod());
+        if (d < minDist) {
+            minDist = d;
+            index = (*itr)->getIndex();
+            //cerr << "Minimum distance of " << minDist << " for index " << index << endl;
+        }
+    }
+
+    return index;
+}
+
+
 int FGGroundNetwork::findNearestNode(double lat, double lon)
 {
-  return findNearestNode(SGGeod::fromDeg(lon, lat));
+    return findNearestNode(SGGeod::fromDeg(lon, lat));
 }
 
 FGTaxiNode *FGGroundNetwork::findNode(unsigned idx)
-{ /*
-    for (FGTaxiNodeVectorIterator 
-    itr = nodes.begin();
-    itr != nodes.end(); itr++)
-    {
-    if (itr->getIndex() == idx)
-    return itr->getAddress();
-    }*/
-  
-  if ((idx >= 0) && (idx < nodes.size())) 
-    return nodes[idx]->getAddress();
-  else
-    return 0;
+{                               /*
+                                   for (FGTaxiNodeVectorIterator
+                                   itr = nodes.begin();
+                                   itr != nodes.end(); itr++)
+                                   {
+                                   if (itr->getIndex() == idx)
+                                   return itr->getAddress();
+                                   } */
+
+    if (idx < nodes.size())
+        return nodes[idx]->getAddress();
+    else
+        return 0;
 }
 
 FGTaxiSegment *FGGroundNetwork::findSegment(unsigned idx)
-{/*
-  for (FGTaxiSegmentVectorIterator 
-        itr = segments.begin();
-       itr != segments.end(); itr++)
-    {
-      if (itr->getIndex() == idx)
-       return itr->getAddress();
-    } 
- */
-  if ((idx > 0) && (idx <= segments.size()))
-    return segments[idx-1]->getAddress();
-  else
-    {
-      //cerr << "Alert: trying to find invalid segment " << idx << endl;
-      return 0;
+{                               /*
+                                   for (FGTaxiSegmentVectorIterator
+                                   itr = segments.begin();
+                                   itr != segments.end(); itr++)
+                                   {
+                                   if (itr->getIndex() == idx)
+                                   return itr->getAddress();
+                                   }
+                                 */
+    if ((idx > 0) && (idx <= segments.size()))
+        return segments[idx - 1]->getAddress();
+    else {
+        //cerr << "Alert: trying to find invalid segment " << idx << endl;
+        return 0;
     }
 }
 
 
-FGTaxiRoute FGGroundNetwork::findShortestRoute(int start, int end, bool fullSearch) 
+FGTaxiRoute FGGroundNetwork::findShortestRoute(int start, int end,
+        bool fullSearch)
 {
 //implements Dijkstra's algorithm to find shortest distance route from start to end
 //taken from http://en.wikipedia.org/wiki/Dijkstra's_algorithm
@@ -362,54 +577,76 @@ FGTaxiRoute FGGroundNetwork::findShortestRoute(int start, int end, bool fullSear
     int nParkings = parent->getDynamics()->getNrOfParkings();
     FGTaxiNodeVector *currNodesSet;
     if (fullSearch) {
-         currNodesSet = &nodes;
+        currNodesSet = &nodes;
     } else {
-         currNodesSet = &pushBackNodes;
+        currNodesSet = &pushBackNodes;
     }
 
     for (FGTaxiNodeVectorIterator
-         itr = currNodesSet->begin();
-         itr != currNodesSet->end(); itr++) {
-            (*itr)->setPathScore(HUGE_VAL); //infinity by all practical means
-            (*itr)->setPreviousNode(0); //
-            (*itr)->setPreviousSeg (0); //
-         }
+            itr = currNodesSet->begin(); itr != currNodesSet->end(); itr++) {
+        (*itr)->setPathScore(HUGE_VAL); //infinity by all practical means
+        (*itr)->setPreviousNode(0);     //
+        (*itr)->setPreviousSeg(0);      //
+    }
 
     FGTaxiNode *firstNode = findNode(start);
+    if (!firstNode)
+    {
+        SG_LOG(SG_GENERAL, SG_ALERT,
+               "Error in ground network. Failed to find first waypoint: " << start
+               << " at " << ((parent) ? parent->getId() : "<unknown>"));
+        return FGTaxiRoute();
+    }
     firstNode->setPathScore(0);
 
-    FGTaxiNode *lastNode  = findNode(end);
+    FGTaxiNode *lastNode = findNode(end);
+    if (!lastNode)
+    {
+        SG_LOG(SG_GENERAL, SG_ALERT,
+               "Error in ground network. Failed to find last waypoint: " << end
+               << " at " << ((parent) ? parent->getId() : "<unknown>"));
+        return FGTaxiRoute();
+    }
 
-    FGTaxiNodeVector unvisited(*currNodesSet); // working copy
+    FGTaxiNodeVector unvisited(*currNodesSet);  // working copy
 
     while (!unvisited.empty()) {
-        FGTaxiNodebest = *(unvisited.begin());
+        FGTaxiNode *best = *(unvisited.begin());
         for (FGTaxiNodeVectorIterator
-             itr = unvisited.begin();
-             itr != unvisited.end(); itr++) {
-                 if ((*itr)->getPathScore() < best->getPathScore())
-                     best = (*itr);
+                itr = unvisited.begin(); itr != unvisited.end(); itr++) {
+            if ((*itr)->getPathScore() < best->getPathScore())
+                best = (*itr);
         }
 
-        FGTaxiNodeVectorIterator newend = remove(unvisited.begin(), unvisited.end(), best);
+        FGTaxiNodeVectorIterator newend =
+            remove(unvisited.begin(), unvisited.end(), best);
         unvisited.erase(newend, unvisited.end());
-        
+
         if (best == lastNode) { // found route or best not connected
             break;
         } else {
             for (FGTaxiSegmentVectorIterator
-                 seg = best->getBeginRoute();
-                 seg != best->getEndRoute(); seg++) {
+                    seg = best->getBeginRoute();
+                    seg != best->getEndRoute(); seg++) {
                 if (fullSearch || (*seg)->isPushBack()) {
-                    FGTaxiNode* tgt = (*seg)->getEnd();
-                    double alt = best->getPathScore() + (*seg)->getLength() + (*seg)->getPenalty(nParkings);
-                    if (alt < tgt->getPathScore()) {              // Relax (u,v)
+                    FGTaxiNode *tgt = (*seg)->getEnd();
+                    if (!tgt)
+                    {
+                        SG_LOG(SG_GENERAL, SG_ALERT,
+                               "Error in ground network. Found empty segment "
+                               << " at " << ((parent) ? parent->getId() : "<unknown>"));
+                        return FGTaxiRoute();
+                    }
+                    double alt =
+                        best->getPathScore() + (*seg)->getLength() +
+                        (*seg)->getPenalty(nParkings);
+                    if (alt < tgt->getPathScore()) {    // Relax (u,v)
                         tgt->setPathScore(alt);
                         tgt->setPreviousNode(best);
-                        tgt->setPreviousSeg(*seg); //
-                   }
+                        tgt->setPreviousSeg(*seg);      //
+                    }
                 } else {
-                //   // cerr << "Skipping TaxiSegment " << (*seg)->getIndex() << endl;
+                    //   // cerr << "Skipping TaxiSegment " << (*seg)->getIndex() << endl;
                 }
             }
         }
@@ -417,17 +654,18 @@ FGTaxiRoute FGGroundNetwork::findShortestRoute(int start, int end, bool fullSear
 
     if (lastNode->getPathScore() == HUGE_VAL) {
         // no valid route found
-       if (fullSearch) {
-            SG_LOG( SG_GENERAL, SG_ALERT, "Failed to find route from waypoint " << start << " to " << end << " at " <<
-                    parent->getId());
+        if (fullSearch) {
+            SG_LOG(SG_GENERAL, SG_ALERT,
+                   "Failed to find route from waypoint " << start << " to "
+                   << end << " at " << parent->getId());
         }
-       FGTaxiRoute empty;
-       return empty;
+        FGTaxiRoute empty;
+        return empty;
         //exit(1); //TODO exit more gracefully, no need to stall the whole sim with broken GN's
     } else {
         // assemble route from backtrace information
         intVec nodes, routes;
-        FGTaxiNodebt = lastNode;
+        FGTaxiNode *bt = lastNode;
         while (bt->getPreviousNode() != 0) {
             nodes.push_back(bt->getIndex());
             routes.push_back(bt->getPreviousSegment()->getIndex());
@@ -441,116 +679,206 @@ FGTaxiRoute FGGroundNetwork::findShortestRoute(int start, int end, bool fullSear
     }
 }
 
-int FGTaxiSegment::getPenalty(int nGates) {
-     int penalty = 0;
-     if (end->getIndex() < nGates) {
-         penalty += 10000;
-     }
-     if (end->getIsOnRunway()) { // For now. In future versions, need to find out whether runway is active.
-         penalty += 1000;
-     }
-     return penalty;
+int FGTaxiSegment::getPenalty(int nGates)
+{
+    int penalty = 0;
+    if (end->getIndex() < nGates) {
+        penalty += 10000;
+    }
+    if (end->getIsOnRunway()) { // For now. In future versions, need to find out whether runway is active.
+        penalty += 1000;
+    }
+    return penalty;
 }
 
 /* ATC Related Functions */
 
-void FGGroundNetwork::announcePosition(int id, FGAIFlightPlan *intendedRoute, int currentPosition,
-                                      double lat, double lon, double heading, 
-                                      double speed, double alt, double radius, int leg,
-                                      FGAIAircraft *aircraft)
-{
-   TrafficVectorIterator i = activeTraffic.begin();
-   // Search search if the current id alread has an entry
-   // This might be faster using a map instead of a vector, but let's start by taking a safe route
-   if (activeTraffic.size()) {
-     //while ((i->getId() != id) && i != activeTraffic.end()) {
-     while (i != activeTraffic.end()) {
-       if (i->getId() == id) {
-        break;
-       }
-       i++;
-     }
-   }
-   // Add a new TrafficRecord if no one exsists for this aircraft.
-   if (i == activeTraffic.end() || (activeTraffic.size() == 0)) {
-     FGTrafficRecord rec;
-     rec.setId(id);
-     rec.setPositionAndIntentions(currentPosition, intendedRoute);
-     rec.setPositionAndHeading(lat, lon, heading, speed, alt);
-     rec.setRadius(radius); // only need to do this when creating the record.
-     rec.setAircraft(aircraft);
-     activeTraffic.push_back(rec);
-   } else {
-     i->setPositionAndIntentions(currentPosition, intendedRoute); 
-     i->setPositionAndHeading(lat, lon, heading, speed, alt);
-   }
-}
-
-void FGGroundNetwork::signOff(int id) {
-  TrafficVectorIterator i = activeTraffic.begin();
-   // Search search if the current id alread has an entry
-   // This might be faster using a map instead of a vector, but let's start by taking a safe route
-   if (activeTraffic.size()) {
-     //while ((i->getId() != id) && i != activeTraffic.end()) {
-     while (i != activeTraffic.end()) {
-       if (i->getId() == id) {
-        break;
-       }
-       i++;
-     }
-   }
-   if (i == activeTraffic.end() || (activeTraffic.size() == 0)) {
-     SG_LOG(SG_GENERAL, SG_ALERT, "AI error: Aircraft without traffic record is signing off");
-   } else {
-       i = activeTraffic.erase(i);
-   }
-}
-
-void FGGroundNetwork::update(int id, double lat, double lon, double heading, double speed, double alt, 
-                            double dt) {
-   // Check whether aircraft are on hold due to a preceding pushback. If so, make sure to 
-   // Transmit air-to-ground "Ready to taxi request:
-   // Transmit ground to air approval / hold
-   // Transmit confirmation ... 
-   // Probably use a status mechanism similar to the Engine start procedure in the startup controller.
-
-
-   TrafficVectorIterator i = activeTraffic.begin();
-   // Search search if the current id has an entry
-   // This might be faster using a map instead of a vector, but let's start by taking a safe route
-   TrafficVectorIterator current, closest;
-   if (activeTraffic.size()) {
-     //while ((i->getId() != id) && i != activeTraffic.end()) {
-     while (i != activeTraffic.end()) {
-       if (i->getId() == id) {
-        break;
-       }
-       i++;
-     }
-   }
-   // update position of the current aircraft
-   if (i == activeTraffic.end() || (activeTraffic.size() == 0)) {
-     SG_LOG(SG_GENERAL, SG_ALERT, "AI error: updating aircraft without traffic record");
-   } else {
-     i->setPositionAndHeading(lat, lon, heading, speed, alt);
-     current = i;
-   }
-  
-   setDt(getDt() + dt);
-  
-   // Update every three secs, but add some randomness
-   // to prevent all IA objects doing this in synchrony
-   //if (getDt() < (3.0) + (rand() % 10))
-   //  return;
-   //else
-   //  setDt(0);
-   current->clearResolveCircularWait();
-   current->setWaitsForId(0);
-   checkSpeedAdjustment(id, lat, lon, heading, speed, alt);
-   checkHoldPosition   (id, lat, lon, heading, speed, alt);
-   if (checkForCircularWaits(id)) {
-       i->setResolveCircularWait();
-   }
+void FGGroundNetwork::announcePosition(int id,
+                                       FGAIFlightPlan * intendedRoute,
+                                       int currentPosition, double lat,
+                                       double lon, double heading,
+                                       double speed, double alt,
+                                       double radius, int leg,
+                                       FGAIAircraft * aircraft)
+{
+    init();
+    TrafficVectorIterator i = activeTraffic.begin();
+    // Search search if the current id alread has an entry
+    // This might be faster using a map instead of a vector, but let's start by taking a safe route
+    if (activeTraffic.size()) {
+        //while ((i->getId() != id) && i != activeTraffic.end()) {
+        while (i != activeTraffic.end()) {
+            if (i->getId() == id) {
+                break;
+            }
+            i++;
+        }
+    }
+    // Add a new TrafficRecord if no one exsists for this aircraft.
+    if (i == activeTraffic.end() || (activeTraffic.size() == 0)) {
+        FGTrafficRecord rec;
+        rec.setId(id);
+        rec.setLeg(leg);
+        rec.setPositionAndIntentions(currentPosition, intendedRoute);
+        rec.setPositionAndHeading(lat, lon, heading, speed, alt);
+        rec.setRadius(radius);  // only need to do this when creating the record.
+        rec.setAircraft(aircraft);
+        if (leg == 2) {
+            activeTraffic.push_front(rec);
+        } else {
+            activeTraffic.push_back(rec);   
+        }
+        
+    } else {
+        i->setPositionAndIntentions(currentPosition, intendedRoute);
+        i->setPositionAndHeading(lat, lon, heading, speed, alt);
+    }
+}
+
+
+void FGGroundNetwork::signOff(int id)
+{
+    TrafficVectorIterator i = activeTraffic.begin();
+    // Search search if the current id alread has an entry
+    // This might be faster using a map instead of a vector, but let's start by taking a safe route
+    if (activeTraffic.size()) {
+        //while ((i->getId() != id) && i != activeTraffic.end()) {
+        while (i != activeTraffic.end()) {
+            if (i->getId() == id) {
+                break;
+            }
+            i++;
+        }
+    }
+    if (i == activeTraffic.end() || (activeTraffic.size() == 0)) {
+        SG_LOG(SG_GENERAL, SG_ALERT,
+               "AI error: Aircraft without traffic record is signing off at " << SG_ORIGIN);
+    } else {
+        i = activeTraffic.erase(i);
+    }
+}
+/**
+ * The ground network can deal with the following states:
+ * 0 =  Normal; no action required
+ * 1 = "Acknowledge "Hold position
+ * 2 = "Acknowledge "Resume taxi".
+ * 3 = "Issue TaxiClearance"
+ * 4 = Acknowledge Taxi Clearance"
+ * 5 = Post acknowlegde taxiclearance: Start taxiing
+ * 6 = Report runway
+ * 7 = Acknowledge report runway
+ * 8 = Switch tower frequency
+ * 9 = Acknowledge switch tower frequency
+ *************************************************************************************************************************/
+bool FGGroundNetwork::checkTransmissionState(int minState, int maxState, TrafficVectorIterator i, time_t now, AtcMsgId msgId,
+        AtcMsgDir msgDir)
+{
+    int state = i->getState();
+    if ((state >= minState) && (state <= maxState) && available) {
+        if ((msgDir == ATC_AIR_TO_GROUND) && isUserAircraft(i->getAircraft())) {
+            //cerr << "Checking state " << state << " for " << i->getAircraft()->getCallSign() << endl;
+            static SGPropertyNode_ptr trans_num = globals->get_props()->getNode("/sim/atc/transmission-num", true);
+            int n = trans_num->getIntValue();
+            if (n == 0) {
+                trans_num->setIntValue(-1);
+                // PopupCallback(n);
+                //cerr << "Selected transmission message " << n << endl;
+                //FGATCManager *atc = (FGATCManager*) globals->get_subsystem("atc");
+                FGATCDialogNew::instance()->removeEntry(1);
+            } else {
+                //cerr << "creating message for " << i->getAircraft()->getCallSign() << endl;
+                transmit(&(*i), &(*parent->getDynamics()), msgId, msgDir, false);
+                return false;
+            }
+        }
+        transmit(&(*i), &(*parent->getDynamics()), msgId, msgDir, true);
+        i->updateState();
+        lastTransmission = now;
+        available = false;
+        return true;
+    }
+    return false;
+}
+
+void FGGroundNetwork::updateAircraftInformation(int id, double lat, double lon,
+        double heading, double speed, double alt,
+        double dt)
+{
+    time_t currentTime = time(NULL);
+    if (nextSave < currentTime) {
+        saveElevationCache();
+        nextSave = currentTime + 100 + rand() % 200;
+    }
+    // Check whether aircraft are on hold due to a preceding pushback. If so, make sure to
+    // Transmit air-to-ground "Ready to taxi request:
+    // Transmit ground to air approval / hold
+    // Transmit confirmation ...
+    // Probably use a status mechanism similar to the Engine start procedure in the startup controller.
+
+
+    TrafficVectorIterator i = activeTraffic.begin();
+    // Search search if the current id has an entry
+    // This might be faster using a map instead of a vector, but let's start by taking a safe route
+    TrafficVectorIterator current, closest;
+    if (activeTraffic.size()) {
+        //while ((i->getId() != id) && i != activeTraffic.end()) {
+        while (i != activeTraffic.end()) {
+            if (i->getId() == id) {
+                break;
+            }
+            i++;
+        }
+    }
+    // update position of the current aircraft
+    if (i == activeTraffic.end() || (activeTraffic.size() == 0)) {
+        SG_LOG(SG_GENERAL, SG_ALERT,
+               "AI error: updating aircraft without traffic record at " << SG_ORIGIN);
+    } else {
+        i->setPositionAndHeading(lat, lon, heading, speed, alt);
+        current = i;
+    }
+
+    setDt(getDt() + dt);
+
+    // Update every three secs, but add some randomness
+    // to prevent all IA objects doing this in synchrony
+    //if (getDt() < (3.0) + (rand() % 10))
+    //  return;
+    //else
+    //  setDt(0);
+    current->clearResolveCircularWait();
+    current->setWaitsForId(0);
+    checkSpeedAdjustment(id, lat, lon, heading, speed, alt);
+    bool needsTaxiClearance = current->getAircraft()->getTaxiClearanceRequest();
+    if (!needsTaxiClearance) {
+        checkHoldPosition(id, lat, lon, heading, speed, alt);
+        //if (checkForCircularWaits(id)) {
+        //    i->setResolveCircularWait();
+        //}
+    } else {
+        current->setHoldPosition(true);
+        int state = current->getState();
+        time_t now = time(NULL) + fgGetLong("/sim/time/warp");
+        if ((now - lastTransmission) > 15) {
+            available = true;
+        }
+        if (checkTransmissionState(0,2, current, now, MSG_REQUEST_TAXI_CLEARANCE, ATC_AIR_TO_GROUND)) {
+            current->setState(3);
+        }
+        if (checkTransmissionState(3,3, current, now, MSG_ISSUE_TAXI_CLEARANCE, ATC_GROUND_TO_AIR)) {
+            current->setState(4);
+        }
+        if (checkTransmissionState(4,4, current, now, MSG_ACKNOWLEDGE_TAXI_CLEARANCE, ATC_AIR_TO_GROUND)) {
+            current->setState(5);
+        }
+        if ((state == 5) && available) {
+            current->setState(0);
+            current->getAircraft()->setTaxiClearanceRequest(false);
+            current->setHoldPosition(false);
+            available = false;
+        }
+
+    }
 }
 
 /**
@@ -560,136 +888,151 @@ void FGGroundNetwork::update(int id, double lat, double lon, double heading, dou
    aircraft. For traffic that is on other routes we need to issue a "HOLD Position"
    instruction. See below for the hold position instruction.
 
-   Note that there currently still is one flaw in the logic that needs to be addressed. 
+   Note that there currently still is one flaw in the logic that needs to be addressed.
    There can be situations where one aircraft is in front of the current aircraft, on a separate
    route, but really close after an intersection coming off the current route. This
    aircraft is still close enough to block the current aircraft. This situation is currently
    not addressed yet, but should be.
 */
 
-void FGGroundNetwork::checkSpeedAdjustment(int id, double lat, 
-                                          double lon, double heading, 
-                                          double speed, double alt)
+void FGGroundNetwork::checkSpeedAdjustment(int id, double lat,
+        double lon, double heading,
+        double speed, double alt)
 {
-  
-  TrafficVectorIterator current, closest;
-  TrafficVectorIterator i = activeTraffic.begin();
-  bool otherReasonToSlowDown = false;
-  bool previousInstruction;
-  if (activeTraffic.size()) 
-    {
-      //while ((i->getId() != id) && (i != activeTraffic.end()))
-      while (i != activeTraffic.end()) {
-       if (i->getId() == id) {
-         break;
-       }
-       i++;
-      }
-    }
-  else
-    {
-      return;
-    }
-  if (i == activeTraffic.end() || (activeTraffic.size() == 0)) {
-    SG_LOG(SG_GENERAL, SG_ALERT, "AI error: Trying to access non-existing aircraft in FGGroundNetwork::checkSpeedAdjustment");
-  }
-  current = i;
-  //closest = current;
-  
-  previousInstruction = current->getSpeedAdjustment();
-  double mindist = HUGE_VAL;
-  if (activeTraffic.size()) 
-    {
-      double course, dist, bearing, minbearing, az2;
-      SGGeod curr(SGGeod::fromDegM(lon, lat, alt));
-      //TrafficVector iterator closest;
-      closest = current;
-      for (TrafficVectorIterator i = activeTraffic.begin(); 
-          i != activeTraffic.end(); i++)
-       {
-         if (i == current) {
-        continue;
-      }
-      
-        SGGeod other(SGGeod::fromDegM(i->getLongitude(),
-          i->getLatitude(), i->getAltitude()));
-        SGGeodesy::inverse(curr, other, course, az2, dist);
-        bearing = fabs(heading-course);
-           if (bearing > 180)
-             bearing = 360-bearing;
-           if ((dist < mindist) && (bearing < 60.0))
-             {
-               mindist = dist;
-               closest = i;
-               minbearing = bearing;
-             }
-       }
-      //Check traffic at the tower controller
-      if (towerController->hasActiveTraffic())
-       {
-         for (TrafficVectorIterator i = towerController->getActiveTraffic().begin(); 
-              i != towerController->getActiveTraffic().end(); i++)
-           {
-             //cerr << "Comparing " << current->getId() << " and " << i->getId() << endl;
-             SGGeod other(SGGeod::fromDegM(i->getLongitude(),
-                                            i->getLatitude(), 
-                                            i->getAltitude()));
-        SGGeodesy::inverse(curr, other, course, az2, dist);
-        bearing = fabs(heading-course);
-             if (bearing > 180)
-          bearing = 360-bearing;
-             if ((dist < mindist) && (bearing < 60.0))
-               {
-                 mindist = dist;
-                 closest = i;
-                 minbearing = bearing;
-                 otherReasonToSlowDown = true;
-               }
-           }
-       }
-      // Finally, check UserPosition
-      double userLatitude  = fgGetDouble("/position/latitude-deg");
-      double userLongitude = fgGetDouble("/position/longitude-deg");
-      SGGeod user(SGGeod::fromDeg(userLongitude,userLatitude));
-      SGGeodesy::inverse(curr, user, course, az2, dist);
-
-      bearing = fabs(heading-course);
-      if (bearing > 180)
-      bearing = 360-bearing;
-      if ((dist < mindist) && (bearing < 60.0))
-       {
-         mindist = dist;
-         //closest = i;
-         minbearing = bearing;
-         otherReasonToSlowDown = true;
-       }
-
-      current->clearSpeedAdjustment();
-    
-      if (current->checkPositionAndIntentions(*closest) || otherReasonToSlowDown) 
-       {
-          double maxAllowableDistance = (1.1*current->getRadius()) + (1.1*closest->getRadius());
-          if (mindist < 2*maxAllowableDistance)
-            {
-              if (current->getId() == closest->getWaitsForId())
-                return;
-              else 
-                current->setWaitsForId(closest->getId());
-              if (closest->getId() != current->getId())
-                current->setSpeedAdjustment(closest->getSpeed()* (mindist/100));
-              else
-                current->setSpeedAdjustment(0); // This can only happen when the user aircraft is the one closest
-              if (mindist < maxAllowableDistance)
-                {
-                  //double newSpeed = (maxAllowableDistance-mindist);
-                  //current->setSpeedAdjustment(newSpeed);
-                  //if (mindist < 0.5* maxAllowableDistance)
-                  //  {
-                      current->setSpeedAdjustment(0);
-                      //  }
-                }
-            }
-       }
+
+    TrafficVectorIterator current, closest, closestOnNetwork;
+    TrafficVectorIterator i = activeTraffic.begin();
+    bool otherReasonToSlowDown = false;
+//    bool previousInstruction;
+    if (activeTraffic.size()) {
+        //while ((i->getId() != id) && (i != activeTraffic.end()))
+        while (i != activeTraffic.end()) {
+            if (i->getId() == id) {
+                break;
+            }
+            i++;
+        }
+    } else {
+        return;
+    }
+    if (i == activeTraffic.end() || (activeTraffic.size() == 0)) {
+        SG_LOG(SG_GENERAL, SG_ALERT,
+               "AI error: Trying to access non-existing aircraft in FGGroundNetwork::checkSpeedAdjustment at " << SG_ORIGIN);
+    }
+    current = i;
+    //closest = current;
+
+//    previousInstruction = current->getSpeedAdjustment();
+    double mindist = HUGE_VAL;
+    if (activeTraffic.size()) {
+        double course, dist, bearing, az2; // minbearing,
+        SGGeod curr(SGGeod::fromDegM(lon, lat, alt));
+        //TrafficVector iterator closest;
+        closest = current;
+        closestOnNetwork = current;
+        for (TrafficVectorIterator i = activeTraffic.begin();
+                i != activeTraffic.end(); i++) {
+            if (i == current) {
+                continue;
+            }
+
+            SGGeod other(SGGeod::fromDegM(i->getLongitude(),
+                                          i->getLatitude(),
+                                          i->getAltitude()));
+            SGGeodesy::inverse(curr, other, course, az2, dist);
+            bearing = fabs(heading - course);
+            if (bearing > 180)
+                bearing = 360 - bearing;
+            if ((dist < mindist) && (bearing < 60.0)) {
+                mindist = dist;
+                closest = i;
+                closestOnNetwork = i;
+//                minbearing = bearing;
+                
+            }
+        }
+        //Check traffic at the tower controller
+        if (towerController->hasActiveTraffic()) {
+            for (TrafficVectorIterator i =
+                        towerController->getActiveTraffic().begin();
+                    i != towerController->getActiveTraffic().end(); i++) {
+                //cerr << "Comparing " << current->getId() << " and " << i->getId() << endl;
+                SGGeod other(SGGeod::fromDegM(i->getLongitude(),
+                                              i->getLatitude(),
+                                              i->getAltitude()));
+                SGGeodesy::inverse(curr, other, course, az2, dist);
+                bearing = fabs(heading - course);
+                if (bearing > 180)
+                    bearing = 360 - bearing;
+                if ((dist < mindist) && (bearing < 60.0)) {
+                    //cerr << "Current aircraft " << current->getAircraft()->getTrafficRef()->getCallSign()
+                    //     << " is closest to " << i->getAircraft()->getTrafficRef()->getCallSign()
+                    //     << ", which has status " << i->getAircraft()->isScheduledForTakeoff()
+                    //     << endl;
+                    mindist = dist;
+                    closest = i;
+//                    minbearing = bearing;
+                    otherReasonToSlowDown = true;
+                }
+            }
+        }
+        // Finally, check UserPosition
+        // Note, as of 2011-08-01, this should no longer be necessecary.
+        /*
+        double userLatitude = fgGetDouble("/position/latitude-deg");
+        double userLongitude = fgGetDouble("/position/longitude-deg");
+        SGGeod user(SGGeod::fromDeg(userLongitude, userLatitude));
+        SGGeodesy::inverse(curr, user, course, az2, dist);
+
+        bearing = fabs(heading - course);
+        if (bearing > 180)
+            bearing = 360 - bearing;
+        if ((dist < mindist) && (bearing < 60.0)) {
+            mindist = dist;
+            //closest = i;
+            minbearing = bearing;
+            otherReasonToSlowDown = true;
+        }
+        */
+        current->clearSpeedAdjustment();
+        bool needBraking = false;
+        if (current->checkPositionAndIntentions(*closest)
+                || otherReasonToSlowDown) {
+            double maxAllowableDistance =
+                (1.1 * current->getRadius()) +
+                (1.1 * closest->getRadius());
+            if (mindist < 2 * maxAllowableDistance) {
+                if (current->getId() == closest->getWaitsForId())
+                    return;
+                else
+                    current->setWaitsForId(closest->getId());
+                if (closest->getId() != current->getId()) {
+                    current->setSpeedAdjustment(closest->getSpeed() *
+                                                (mindist / 100));
+                    needBraking = true;
+                    
+//                     if (
+//                         closest->getAircraft()->getTakeOffStatus() &&
+//                         (current->getAircraft()->getTrafficRef()->getDepartureAirport() ==  closest->getAircraft()->getTrafficRef()->getDepartureAirport()) &&
+//                         (current->getAircraft()->GetFlightPlan()->getRunway() == closest->getAircraft()->GetFlightPlan()->getRunway())
+//                     )
+//                         current->getAircraft()->scheduleForATCTowerDepartureControl(1);
+                } else {
+                    current->setSpeedAdjustment(0);     // This can only happen when the user aircraft is the one closest
+                }
+                if (mindist < maxAllowableDistance) {
+                    //double newSpeed = (maxAllowableDistance-mindist);
+                    //current->setSpeedAdjustment(newSpeed);
+                    //if (mindist < 0.5* maxAllowableDistance)
+                    //  {
+                    current->setSpeedAdjustment(0);
+                    //  }
+                }
+            }
+        }
+        if ((closest->getId() == closestOnNetwork->getId()) && (current->getPriority() < closest->getPriority()) && needBraking) {
+            swap(current, closest);
+        }
     }
 }
 
@@ -701,123 +1044,145 @@ void FGGroundNetwork::checkSpeedAdjustment(int id, double lat,
    3) For crossing or merging taxiroutes.
 */
 
-void FGGroundNetwork::checkHoldPosition(int id, double lat, 
-                                       double lon, double heading, 
-                                       double speed, double alt)
+void FGGroundNetwork::checkHoldPosition(int id, double lat,
+                                        double lon, double heading,
+                                        double speed, double alt)
 {
-  
-  TrafficVectorIterator current;
-  TrafficVectorIterator i = activeTraffic.begin();
-  if (activeTraffic.size()) 
-    {
-      //while ((i->getId() != id) && i != activeTraffic.end()) 
-      while (i != activeTraffic.end()) {
-       if (i->getId() == id) {
-         break;
-       }
-       i++;
-      }
-    }
-  else
-    {
-      return ;
-    } 
-  if (i == activeTraffic.end() || (activeTraffic.size() == 0)) {
-    SG_LOG(SG_GENERAL, SG_ALERT, "AI error: Trying to access non-existing aircraft in FGGroundNetwork::checkHoldPosition");
-  }
-  current = i;
-  current->setHoldPosition(false);
-  SGGeod curr(SGGeod::fromDegM(lon, lat, alt));
-  
-  for (i = activeTraffic.begin(); 
-       i != activeTraffic.end(); i++)
-    {
-      if (i->getId() != current->getId()) 
-       {
-         int node = current->crosses(this, *i);
-         if (node != -1)
-           {
-          FGTaxiNode* taxiNode = findNode(node);
-          
-             // Determine whether it's save to continue or not. 
-             // If we have a crossing route, there are two possibilities:
-             // 1) This is an interestion
-             // 2) This is oncoming two-way traffic, using the same taxiway.
-             //cerr << "Hold check 1 : " << id << " has common node " << node << endl;
-            
-        SGGeod other(SGGeod::fromDegM(i->getLongitude(), i->getLatitude(), i->getAltitude()));
-        bool needsToWait;
-             bool opposing;
-             if (current->isOpposing(this, *i, node))
-               {
-                 needsToWait = true;
-                 opposing    = true;
-                 //cerr << "Hold check 2 : " << node << "  has opposing segment " << endl;
-                 // issue a "Hold Position" as soon as we're close to the offending node
-                 // For now, I'm doing this as long as the other aircraft doesn't
-                 // have a hold instruction as soon as we're within a reasonable 
-                 // distance from the offending node.
-                 // This may be a bit of a conservative estimate though, as it may
-                 // be well possible that both aircraft can both continue to taxi 
-                 // without crashing into each other.
-               } 
-             else 
-               {
-                 opposing = false;
-                 if (SGGeodesy::distanceM(other, taxiNode->getGeod()) > 200) // 2.0*i->getRadius())
-                   {
-                     needsToWait = false; 
-                     //cerr << "Hold check 3 : " << id <<"  Other aircraft approaching node is still far away. (" << dist << " nm). Can safely continue " 
-                     //           << endl;
-                   }
-                 else 
-                   {
-                     needsToWait = true;
-                     //cerr << "Hold check 4: " << id << "  Would need to wait for other aircraft : distance = " << dist << " meters" << endl;
-                   }
-               }
-      
-      double dist = SGGeodesy::distanceM(curr, taxiNode->getGeod());
-      if (!(i->hasHoldPosition()))
-               {
-                 
-                 if ((dist < 200) && //2.5*current->getRadius()) && 
-                     (needsToWait) &&
-                     (i->onRoute(this, *current)) &&
-                     //((i->onRoute(this, *current)) || ((!(i->getSpeedAdjustment())))) &&
-                     (!(current->getId() == i->getWaitsForId())))
-                     //(!(i->getSpeedAdjustment()))) // &&
-                     //(!(current->getSpeedAdjustment())))
-                   
-                   {
-                     current->setHoldPosition(true);
-                     current->setWaitsForId(i->getId());
-                     //cerr << "Hold check 5: " << current->getCallSign() <<"  Setting Hold Position: distance to node ("  << node << ") "
-                     //           << dist << " meters. Waiting for " << i->getCallSign();
-                     //if (opposing)
-                     //cerr <<" [opposing] " << endl;
-                     //else
-                     //        cerr << "[non-opposing] " << endl;
-                     //if (i->hasSpeefAdjustment())
-                     //        {
-                     //          cerr << " (which in turn waits for ) " << i->
-                   }
-                 else
-                   {
-                     //cerr << "Hold check 6: " << id << "  No need to hold yet: Distance to node : " << dist << " nm"<< endl;
-                   }
-               }
-           }
-       }
+    TrafficVectorIterator current;
+    TrafficVectorIterator i = activeTraffic.begin();
+    if (activeTraffic.size()) {
+        //while ((i->getId() != id) && i != activeTraffic.end())
+        while (i != activeTraffic.end()) {
+            if (i->getId() == id) {
+                break;
+            }
+            i++;
+        }
+    } else {
+        return;
     }
+    time_t now = time(NULL) + fgGetLong("/sim/time/warp");
+    if (i == activeTraffic.end() || (activeTraffic.size() == 0)) {
+        SG_LOG(SG_GENERAL, SG_ALERT,
+               "AI error: Trying to access non-existing aircraft in FGGroundNetwork::checkHoldPosition at " << SG_ORIGIN);
+    }
+    current = i;
+    // 
+    if (current->getAircraft()->getTakeOffStatus() == 1) {
+        current->setHoldPosition(true);
+        return;
+    }
+    if (current->getAircraft()->getTakeOffStatus() == 2) {
+        //cerr << current->getAircraft()->getCallSign() << ". Taxi in position and hold" << endl;
+        current->setHoldPosition(false);
+        current->clearSpeedAdjustment();
+        return;
+    }
+    bool origStatus = current->hasHoldPosition();
+    current->setHoldPosition(false);
+    SGGeod curr(SGGeod::fromDegM(lon, lat, alt));
+    int currentRoute = i->getCurrentPosition();
+    int nextRoute;
+    if (i->getIntentions().size()) {
+        nextRoute    = (*(i->getIntentions().begin()));
+    } else {
+        nextRoute = 0;
+    }       
+    if (currentRoute > 0) {
+        FGTaxiSegment *tx = findSegment(currentRoute);
+        FGTaxiSegment *nx;
+        if (nextRoute) {
+            nx = findSegment(nextRoute);
+        } else {
+            nx = tx;
+        }
+        //if (tx->hasBlock(now) || nx->hasBlock(now) ) {
+        //   current->setHoldPosition(true);
+        //}
+        SGGeod start(SGGeod::fromDeg((i->getLongitude()), (i->getLatitude())));
+        SGGeod end  (SGGeod::fromDeg(nx->getStart()->getLongitude(), nx->getStart()->getLatitude()));
+
+        double distance = SGGeodesy::distanceM(start, end);
+        if (nx->hasBlock(now) && (distance < i->getRadius() * 4)) {
+            current->setHoldPosition(true);
+        } else {
+            intVecIterator ivi = i->getIntentions().begin();
+            while (ivi != i->getIntentions().end()) {
+                if ((*ivi) > 0) {
+                    distance += segments[(*ivi)-1]->getLength();
+                    if ((segments[(*ivi)-1]->hasBlock(now)) && (distance < i->getRadius() * 4)) {
+                        current->setHoldPosition(true);
+                        break;
+                    }
+                }
+                ivi++;
+            }
+        } 
+    }
+    bool currStatus = current->hasHoldPosition();
+    current->setHoldPosition(origStatus);
+    // Either a Hold Position or a resume taxi transmission has been issued
+    if ((now - lastTransmission) > 2) {
+        available = true;
+    }
+    if (current->getState() == 0) {
+        if ((origStatus != currStatus) && available) {
+            //cerr << "Issueing hold short instrudtion " << currStatus << " " << available << endl;
+            if (currStatus == true) { // No has a hold short instruction
+                transmit(&(*current), &(*parent->getDynamics()), MSG_HOLD_POSITION, ATC_GROUND_TO_AIR, true);
+                //cerr << "Transmittin hold short instrudtion " << currStatus << " " << available << endl;
+                current->setState(1);
+            } else {
+                transmit(&(*current), &(*parent->getDynamics()), MSG_RESUME_TAXI, ATC_GROUND_TO_AIR, true);
+                //cerr << "Transmittig resume instrudtion " << currStatus << " " << available << endl;
+                current->setState(2);
+            }
+            lastTransmission = now;
+            available = false;
+            // Don't act on the changed instruction until the transmission is confirmed
+            // So set back to original status
+            //cerr << "Current state " << current->getState() << endl;
+        }
+
+    }
+    // 6 = Report runway
+    // 7 = Acknowledge report runway
+    // 8 = Switch tower frequency
+    //9 = Acknowledge switch tower frequency
+
+    //int state = current->getState();
+    if (checkTransmissionState(1,1, current, now, MSG_ACKNOWLEDGE_HOLD_POSITION, ATC_AIR_TO_GROUND)) {
+        current->setState(0);
+        current->setHoldPosition(true);
+    }
+    if (checkTransmissionState(2,2, current, now, MSG_ACKNOWLEDGE_RESUME_TAXI, ATC_AIR_TO_GROUND)) {
+        current->setState(0);
+        current->setHoldPosition(false);
+    }
+    if (current->getAircraft()->getTakeOffStatus() && (current->getState() == 0)) {
+        //cerr << "Scheduling " << current->getAircraft()->getCallSign() << " for hold short" << endl;
+        current->setState(6);
+    }
+    if (checkTransmissionState(6,6, current, now, MSG_REPORT_RUNWAY_HOLD_SHORT, ATC_AIR_TO_GROUND)) {
+    }
+    if (checkTransmissionState(7,7, current, now, MSG_ACKNOWLEDGE_REPORT_RUNWAY_HOLD_SHORT, ATC_GROUND_TO_AIR)) {
+    }
+    if (checkTransmissionState(8,8, current, now, MSG_SWITCH_TOWER_FREQUENCY, ATC_GROUND_TO_AIR)) {
+    }
+    if (checkTransmissionState(9,9, current, now, MSG_ACKNOWLEDGE_SWITCH_TOWER_FREQUENCY, ATC_AIR_TO_GROUND)) {
+    }
+
+
+
+    //current->setState(0);
 }
 
 /**
  * Check whether situations occur where the current aircraft is waiting for itself
- * due to higher order interactions. 
+ * due to higher order interactions.
  * A 'circular' wait is a situation where a waits for b, b waits for c, and c waits
- * for a. Ideally each aircraft only waits for one other aircraft, so by tracing 
- * through this list of waiting aircraft, we can check if we'd eventually end back 
+ * for a. Ideally each aircraft only waits for one other aircraft, so by tracing
+ * through this list of waiting aircraft, we can check if we'd eventually end back
  * at the current aircraft.
  *
  * Note that we should consider the situation where we are actually checking aircraft
@@ -827,142 +1192,452 @@ void FGGroundNetwork::checkHoldPosition(int id, double lat,
  */
 
 bool FGGroundNetwork::checkForCircularWaits(int id)
-{  
-   //cerr << "Performing Wait check " << id << endl;
-   int target = 0;
-   TrafficVectorIterator current, other;
-   TrafficVectorIterator i = activeTraffic.begin();
-   int trafficSize = activeTraffic.size();
-   if (trafficSize)  {
+{
+    //cerr << "Performing Wait check " << id << endl;
+    int target = 0;
+    TrafficVectorIterator current, other;
+    TrafficVectorIterator i = activeTraffic.begin();
+    int trafficSize = activeTraffic.size();
+    if (trafficSize) {
         while (i != activeTraffic.end()) {
-        if (i->getId() == id) {
-           break;
-       }
-       i++;
-    }
-  }
-  else {
-      return false;
-  }
-  if (i == activeTraffic.end() || (trafficSize == 0)) {
-    SG_LOG(SG_GENERAL, SG_ALERT, "AI error: Trying to access non-existing aircraft in FGGroundNetwork::checkForCircularWaits");
-  }
-   
-   current = i;
-   target = current->getWaitsForId();
-   //bool printed = false; // Note that this variable is for debugging purposes only.
-   int counter = 0;
-
-   if (id == target) {
-       //cerr << "aircraft waits for user" << endl;
-       return false;
-   }
-
-
-   while ((target > 0) && (target != id) && counter++ < trafficSize) {
-    //printed = true;
-     TrafficVectorIterator i = activeTraffic.begin();
-     if (trafficSize)  {
-          //while ((i->getId() != id) && i != activeTraffic.end()) 
-          while (i != activeTraffic.end()) {
-          if (i->getId() == target) {
-             break;
-         }
-         i++;
-        }
-      }
-      else {
+            if (i->getId() == id) {
+                break;
+            }
+            i++;
+        }
+    } else {
         return false;
-    } 
+    }
     if (i == activeTraffic.end() || (trafficSize == 0)) {
-       //cerr << "[Waiting for traffic at Runway: DONE] " << endl << endl;;
-      // The target id is not found on the current network, which means it's at the tower
-      //SG_LOG(SG_GENERAL, SG_ALERT, "AI error: Trying to access non-existing aircraft in FGGroundNetwork::checkForCircularWaits");
-      return false;
-    }
-    other = i;
-    target = other->getWaitsForId();
-
-    // actually this trap isn't as impossible as it first seemed:
-    // the setWaitsForID(id) is set to current when the aircraft
-    // is waiting for the user controlled aircraft. 
-    //if (current->getId() == other->getId()) {
-    //    cerr << "Caught the impossible trap" << endl;
-    //    cerr << "Current = " << current->getId() << endl;
-    //    cerr << "Other   = " << other  ->getId() << endl;
-    //    for (TrafficVectorIterator at = activeTraffic.begin();
-    //          at != activeTraffic.end();
-    //          at++) {
-    //        cerr << "currently active aircraft : " << at->getCallSign() << " with Id " << at->getId() << " waits for " << at->getWaitsForId() << endl;
-    //    }
-    //    exit(1);
-    if (current->getId() == other->getId())
-       return false;
-    //}
-    //cerr << current->getCallSign() << " (" << current->getId()  << ") " << " -> " << other->getCallSign() 
-    //     << " (" << other->getId()  << "); " << endl;;
-    //current = other;
-   }
+        SG_LOG(SG_GENERAL, SG_ALERT,
+               "AI error: Trying to access non-existing aircraft in FGGroundNetwork::checkForCircularWaits at " << SG_ORIGIN);
+    }
 
+    current = i;
+    target = current->getWaitsForId();
+    //bool printed = false; // Note that this variable is for debugging purposes only.
+    int counter = 0;
 
+    if (id == target) {
+        //cerr << "aircraft waits for user" << endl;
+        return false;
+    }
 
 
+    while ((target > 0) && (target != id) && counter++ < trafficSize) {
+        //printed = true;
+        TrafficVectorIterator i = activeTraffic.begin();
+        if (trafficSize) {
+            //while ((i->getId() != id) && i != activeTraffic.end())
+            while (i != activeTraffic.end()) {
+                if (i->getId() == target) {
+                    break;
+                }
+                i++;
+            }
+        } else {
+            return false;
+        }
+        if (i == activeTraffic.end() || (trafficSize == 0)) {
+            //cerr << "[Waiting for traffic at Runway: DONE] " << endl << endl;;
+            // The target id is not found on the current network, which means it's at the tower
+            //SG_LOG(SG_GENERAL, SG_ALERT, "AI error: Trying to access non-existing aircraft in FGGroundNetwork::checkForCircularWaits");
+            return false;
+        }
+        other = i;
+        target = other->getWaitsForId();
+
+        // actually this trap isn't as impossible as it first seemed:
+        // the setWaitsForID(id) is set to current when the aircraft
+        // is waiting for the user controlled aircraft.
+        //if (current->getId() == other->getId()) {
+        //    cerr << "Caught the impossible trap" << endl;
+        //    cerr << "Current = " << current->getId() << endl;
+        //    cerr << "Other   = " << other  ->getId() << endl;
+        //    for (TrafficVectorIterator at = activeTraffic.begin();
+        //          at != activeTraffic.end();
+        //          at++) {
+        //        cerr << "currently active aircraft : " << at->getCallSign() << " with Id " << at->getId() << " waits for " << at->getWaitsForId() << endl;
+        //    }
+        //    exit(1);
+        if (current->getId() == other->getId())
+            return false;
+        //}
+        //cerr << current->getCallSign() << " (" << current->getId()  << ") " << " -> " << other->getCallSign()
+        //     << " (" << other->getId()  << "); " << endl;;
+        //current = other;
+    }
 
 
-   //if (printed)
-   //   cerr << "[done] " << endl << endl;;
-   if (id == target) {
-       SG_LOG(SG_GENERAL, SG_WARN, "Detected circular wait condition: Id = " << id << "target = " << target);
-       return true;
-   } else {
-   return false;
-   }
+
+
+
+
+    //if (printed)
+    //   cerr << "[done] " << endl << endl;;
+    if (id == target) {
+        SG_LOG(SG_GENERAL, SG_WARN,
+               "Detected circular wait condition: Id = " << id <<
+               "target = " << target);
+        return true;
+    } else {
+        return false;
+    }
 }
 
 // Note that this function is probably obsolete...
 bool FGGroundNetwork::hasInstruction(int id)
 {
     TrafficVectorIterator i = activeTraffic.begin();
-   // Search search if the current id has an entry
-   // This might be faster using a map instead of a vector, but let's start by taking a safe route
-   if (activeTraffic.size()) 
-     {
-       //while ((i->getId() != id) && i != activeTraffic.end()) {
-       while (i != activeTraffic.end()) {
-        if (i->getId() == id) {
-          break;
-        }
-        i++;
-       }
-     }
-   if (i == activeTraffic.end() || (activeTraffic.size() == 0)) {
-     SG_LOG(SG_GENERAL, SG_ALERT, "AI error: checking ATC instruction for aircraft without traffic record");
-   } else {
-     return i->hasInstruction();
-   }
-  return false;
+    // Search search if the current id has an entry
+    // This might be faster using a map instead of a vector, but let's start by taking a safe route
+    if (activeTraffic.size()) {
+        //while ((i->getId() != id) && i != activeTraffic.end()) {
+        while (i != activeTraffic.end()) {
+            if (i->getId() == id) {
+                break;
+            }
+            i++;
+        }
+    }
+    if (i == activeTraffic.end() || (activeTraffic.size() == 0)) {
+        SG_LOG(SG_GENERAL, SG_ALERT,
+               "AI error: checking ATC instruction for aircraft without traffic record at " << SG_ORIGIN);
+    } else {
+        return i->hasInstruction();
+    }
+    return false;
 }
 
 FGATCInstruction FGGroundNetwork::getInstruction(int id)
 {
-  TrafficVectorIterator i = activeTraffic.begin();
-  // Search search if the current id has an entry
-   // This might be faster using a map instead of a vector, but let's start by taking a safe route
-   if (activeTraffic.size()) {
-     //while ((i->getId() != id) && i != activeTraffic.end()) {
-     while (i != activeTraffic.end()) {
-       if (i->getId() == id) {
-        break;
-       }
-       i++;
-     }
-   }
-   if (i == activeTraffic.end() || (activeTraffic.size() == 0)) {
-     SG_LOG(SG_GENERAL, SG_ALERT, "AI error: requesting ATC instruction for aircraft without traffic record");
-   } else {
-     return i->getInstruction();
-   }
-  return FGATCInstruction();
+    TrafficVectorIterator i = activeTraffic.begin();
+    // Search search if the current id has an entry
+    // This might be faster using a map instead of a vector, but let's start by taking a safe route
+    if (activeTraffic.size()) {
+        //while ((i->getId() != id) && i != activeTraffic.end()) {
+        while (i != activeTraffic.end()) {
+            if (i->getId() == id) {
+                break;
+            }
+            i++;
+        }
+    }
+    if (i == activeTraffic.end() || (activeTraffic.size() == 0)) {
+        SG_LOG(SG_GENERAL, SG_ALERT,
+               "AI error: requesting ATC instruction for aircraft without traffic record at " << SG_ORIGIN);
+    } else {
+        return i->getInstruction();
+    }
+    return FGATCInstruction();
+}
+
+// Note that this function is copied from simgear. for maintanance purposes, it's probabtl better to make a general function out of that.
+static void WorldCoordinate(osg::Matrix& obj_pos, double lat,
+                            double lon, double elev, double hdg, double slope)
+{
+    SGGeod geod = SGGeod::fromDegM(lon, lat, elev);
+    obj_pos = makeZUpFrame(geod);
+    // hdg is not a compass heading, but a counter-clockwise rotation
+    // around the Z axis
+    obj_pos.preMult(osg::Matrix::rotate(hdg * SGD_DEGREES_TO_RADIANS,
+                                        0.0, 0.0, 1.0));
+    obj_pos.preMult(osg::Matrix::rotate(slope * SGD_DEGREES_TO_RADIANS,
+                                        0.0, 1.0, 0.0));
 }
 
 
+
+
+void FGGroundNetwork::render(bool visible)
+{
+
+    SGMaterialLib *matlib = globals->get_matlib();
+    if (group) {
+        //int nr = ;
+        globals->get_scenery()->get_scene_graph()->removeChild(group);
+        //while (group->getNumChildren()) {
+        //  cerr << "Number of children: " << group->getNumChildren() << endl;
+        //simgear::EffectGeode* geode = (simgear::EffectGeode*) group->getChild(0);
+        //osg::MatrixTransform *obj_trans = (osg::MatrixTransform*) group->getChild(0);
+        //geode->releaseGLObjects();
+        //group->removeChild(geode);
+        //delete geode;
+        group = 0;
+    }
+    if (visible) {
+        group = new osg::Group;
+        FGScenery * local_scenery = globals->get_scenery();
+        // double elevation_meters = 0.0;
+//        double elevation_feet = 0.0;
+        time_t now = time(NULL) + fgGetLong("/sim/time/warp");
+        //for ( FGTaxiSegmentVectorIterator i = segments.begin(); i != segments.end(); i++) {
+        //double dx = 0;
+        for   (TrafficVectorIterator i = activeTraffic.begin(); i != activeTraffic.end(); i++) {
+            // Handle start point
+            int pos = i->getCurrentPosition() - 1;
+            if (pos >= 0) {
+
+                SGGeod start(SGGeod::fromDeg((i->getLongitude()), (i->getLatitude())));
+                SGGeod end  (SGGeod::fromDeg(segments[pos]->getEnd()->getLongitude(), segments[pos]->getEnd()->getLatitude()));
+
+                double length = SGGeodesy::distanceM(start, end);
+                //heading = SGGeodesy::headingDeg(start->getGeod(), end->getGeod());
+
+                double az2, heading; //, distanceM;
+                SGGeodesy::inverse(start, end, heading, az2, length);
+                double coveredDistance = length * 0.5;
+                SGGeod center;
+                SGGeodesy::direct(start, heading, coveredDistance, center, az2);
+                //cerr << "Active Aircraft : Centerpoint = (" << center.getLatitudeDeg() << ", " << center.getLongitudeDeg() << "). Heading = " << heading << endl;
+                ///////////////////////////////////////////////////////////////////////////////
+                // Make a helper function out of this
+                osg::Matrix obj_pos;
+                osg::MatrixTransform *obj_trans = new osg::MatrixTransform;
+                obj_trans->setDataVariance(osg::Object::STATIC);
+                // Experimental: Calculate slope here, based on length, and the individual elevations
+                double elevationStart;
+                if (isUserAircraft((i)->getAircraft())) {
+                    elevationStart = fgGetDouble("/position/ground-elev-m");
+                } else {
+                    elevationStart = ((i)->getAircraft()->_getAltitude());
+                }
+                double elevationEnd   = segments[pos]->getEnd()->getElevationM(parent->getElevation()*SG_FEET_TO_METER);
+                //cerr << "Using elevation " << elevationEnd << endl;
+
+                if ((elevationEnd == 0) || (elevationEnd = parent->getElevation())) {
+                    SGGeod center2 = end;
+                    center2.setElevationM(SG_MAX_ELEVATION_M);
+                    if (local_scenery->get_elevation_m( center2, elevationEnd, NULL )) {
+//                        elevation_feet = elevationEnd * SG_METER_TO_FEET + 0.5;
+                        //elevation_meters += 0.5;
+                    }
+                    else {
+                        elevationEnd = parent->getElevation();
+                    }
+                    segments[pos]->getEnd()->setElevation(elevationEnd);
+                }
+                double elevationMean  = (elevationStart + elevationEnd) / 2.0;
+                double elevDiff       = elevationEnd - elevationStart;
+
+                double slope = atan2(elevDiff, length) * SGD_RADIANS_TO_DEGREES;
+
+                //cerr << "1. Using mean elevation : " << elevationMean << " and " << slope << endl;
+
+                WorldCoordinate( obj_pos, center.getLatitudeDeg(), center.getLongitudeDeg(), elevationMean+ 0.5, -(heading), slope );
+
+                obj_trans->setMatrix( obj_pos );
+                //osg::Vec3 center(0, 0, 0)
+
+                float width = length /2.0;
+                osg::Vec3 corner(-width, 0, 0.25f);
+                osg::Vec3 widthVec(2*width + 1, 0, 0);
+                osg::Vec3 heightVec(0, 1, 0);
+                osg::Geometry* geometry;
+                geometry = osg::createTexturedQuadGeometry(corner, widthVec, heightVec);
+                simgear::EffectGeode* geode = new simgear::EffectGeode;
+                geode->setName("test");
+                geode->addDrawable(geometry);
+                //osg::Node *custom_obj;
+                SGMaterial *mat;
+                if (segments[pos]->hasBlock(now)) {
+                    mat = matlib->find("UnidirectionalTaperRed");
+                } else {
+                    mat = matlib->find("UnidirectionalTaperGreen");
+                }
+                if (mat)
+                    geode->setEffect(mat->get_effect());
+                obj_trans->addChild(geode);
+                // wire as much of the scene graph together as we can
+                //->addChild( obj_trans );
+                group->addChild( obj_trans );
+                /////////////////////////////////////////////////////////////////////
+            } else {
+                //cerr << "BIG FAT WARNING: current position is here : " << pos << endl;
+            }
+            for (intVecIterator j = (i)->getIntentions().begin(); j != (i)->getIntentions().end(); j++) {
+                osg::Matrix obj_pos;
+                int k = (*j)-1;
+                if (k >= 0) {
+                    osg::MatrixTransform *obj_trans = new osg::MatrixTransform;
+                    obj_trans->setDataVariance(osg::Object::STATIC);
+
+                    // Experimental: Calculate slope here, based on length, and the individual elevations
+                    double elevationStart = segments[k]->getStart()->getElevationM(parent->getElevation()*SG_FEET_TO_METER);
+                    double elevationEnd   = segments[k]->getEnd  ()->getElevationM(parent->getElevation()*SG_FEET_TO_METER);
+                    if ((elevationStart == 0)  || (elevationStart == parent->getElevation())) {
+                        SGGeod center2 = segments[k]->getStart()->getGeod();
+                        center2.setElevationM(SG_MAX_ELEVATION_M);
+                        if (local_scenery->get_elevation_m( center2, elevationStart, NULL )) {
+//                            elevation_feet = elevationStart * SG_METER_TO_FEET + 0.5;
+                            //elevation_meters += 0.5;
+                        }
+                        else {
+                            elevationStart = parent->getElevation();
+                        }
+                        segments[k]->getStart()->setElevation(elevationStart);
+                    }
+                    if ((elevationEnd == 0) || (elevationEnd == parent->getElevation())) {
+                        SGGeod center2 = segments[k]->getEnd()->getGeod();
+                        center2.setElevationM(SG_MAX_ELEVATION_M);
+                        if (local_scenery->get_elevation_m( center2, elevationEnd, NULL )) {
+//                            elevation_feet = elevationEnd * SG_METER_TO_FEET + 0.5;
+                            //elevation_meters += 0.5;
+                        }
+                        else {
+                            elevationEnd = parent->getElevation();
+                        }
+                        segments[k]->getEnd()->setElevation(elevationEnd);
+                    }
+
+                    double elevationMean  = (elevationStart + elevationEnd) / 2.0;
+                    double elevDiff       = elevationEnd - elevationStart;
+                    double length         = segments[k]->getLength();
+                    double slope = atan2(elevDiff, length) * SGD_RADIANS_TO_DEGREES;
+
+                    // cerr << "2. Using mean elevation : " << elevationMean << " and " << slope << endl;
+
+
+                    WorldCoordinate( obj_pos, segments[k]->getLatitude(), segments[k]->getLongitude(), elevationMean+ 0.5, -(segments[k]->getHeading()), slope );
+
+                    obj_trans->setMatrix( obj_pos );
+                    //osg::Vec3 center(0, 0, 0)
+
+                    float width = segments[k]->getLength() /2.0;
+                    osg::Vec3 corner(-width, 0, 0.25f);
+                    osg::Vec3 widthVec(2*width + 1, 0, 0);
+                    osg::Vec3 heightVec(0, 1, 0);
+                    osg::Geometry* geometry;
+                    geometry = osg::createTexturedQuadGeometry(corner, widthVec, heightVec);
+                    simgear::EffectGeode* geode = new simgear::EffectGeode;
+                    geode->setName("test");
+                    geode->addDrawable(geometry);
+                    //osg::Node *custom_obj;
+                    SGMaterial *mat;
+                    if (segments[k]->hasBlock(now)) {
+                        mat = matlib->find("UnidirectionalTaperRed");
+                    } else {
+                        mat = matlib->find("UnidirectionalTaperGreen");
+                    }
+                    if (mat)
+                        geode->setEffect(mat->get_effect());
+                    obj_trans->addChild(geode);
+                    // wire as much of the scene graph together as we can
+                    //->addChild( obj_trans );
+                    group->addChild( obj_trans );
+                }
+            }
+            //dx += 0.1;
+        }
+        globals->get_scenery()->get_scene_graph()->addChild(group);
+    }
+}
+
+string FGGroundNetwork::getName() {
+    return string(parent->getId() + "-ground");
+}
+
+void FGGroundNetwork::update(double dt)
+{
+    time_t now = time(NULL) + fgGetLong("/sim/time/warp");
+    for (FGTaxiSegmentVectorIterator tsi = segments.begin(); tsi != segments.end(); tsi++) {
+        (*tsi)->unblock(now);
+    }
+    int priority = 1;
+    //sort(activeTraffic.begin(), activeTraffic.end(), compare_trafficrecords);
+    // Handle traffic that is under ground control first; this way we'll prevent clutter at the gate areas.
+    // Don't allow an aircraft to pushback when a taxiing aircraft is currently using part of the intended route.
+    for   (TrafficVectorIterator i = parent->getDynamics()->getStartupController()->getActiveTraffic().begin();
+            i != parent->getDynamics()->getStartupController()->getActiveTraffic().end(); i++) {
+        i->allowPushBack();
+        i->setPriority(priority++);
+        // in meters per second;
+        double vTaxi = (i->getAircraft()->getPerformance()->vTaxi() * SG_NM_TO_METER) / 3600;
+        if (i->isActive(0)) {
+
+            // Check for all active aircraft whether it's current pos segment is
+            // an opposite of one of the departing aircraft's intentions
+            for (TrafficVectorIterator j = activeTraffic.begin(); j != activeTraffic.end(); j++) {
+                int pos = j->getCurrentPosition();
+                if (pos > 0) {
+                    FGTaxiSegment *seg = segments[pos-1]->opposite();
+                    if (seg) {
+                        int posReverse = seg->getIndex();
+                        for (intVecIterator k = i->getIntentions().begin(); k != i->getIntentions().end(); k++) {
+                            if ((*k) == posReverse) {
+                                i->denyPushBack();
+                                segments[posReverse-1]->block(i->getId(), now, now);
+                            }
+                        }
+                    }
+                }
+            }
+            // if the current aircraft is still allowed to pushback, we can start reserving a route for if by blocking all the entry taxiways.
+            if (i->pushBackAllowed()) {
+                double length = 0;
+                int pos = i->getCurrentPosition();
+                if (pos > 0) {
+                    FGTaxiSegment *seg = segments[pos-1];
+                    FGTaxiNode *node = seg->getEnd();
+                    length = seg->getLength();
+                    for (FGTaxiSegmentVectorIterator tsi = segments.begin(); tsi != segments.end(); tsi++) {
+                        if (((*tsi)->getEnd() == node) && ((*tsi) != seg)) {
+                            (*tsi)->block(i->getId(), now, now);
+                        }
+                    }
+                }
+                for (intVecIterator j = i->getIntentions().begin(); j != i->getIntentions().end(); j++) {
+                    int pos = (*j);
+                    if (pos > 0) {
+                        FGTaxiSegment *seg = segments[pos-1];
+                        FGTaxiNode *node = seg->getEnd();
+                        length += seg->getLength();
+                        time_t blockTime = now + (length / vTaxi);
+                        for (FGTaxiSegmentVectorIterator tsi = segments.begin(); tsi != segments.end(); tsi++) {
+                            if (((*tsi)->getEnd() == node) && ((*tsi) != seg)) {
+                                (*tsi)->block(i->getId(), blockTime-30, now);
+                            }
+                        }
+                    }
+                }
+            }
+        }
+    }
+    for   (TrafficVectorIterator i = activeTraffic.begin(); i != activeTraffic.end(); i++) {
+        double length = 0;
+        double vTaxi = (i->getAircraft()->getPerformance()->vTaxi() * SG_NM_TO_METER) / 3600;
+        i->setPriority(priority++);
+        int pos = i->getCurrentPosition();
+        if (pos > 0) {
+            length = segments[pos-1]->getLength();
+            if (segments[pos-1]->hasBlock(now)) {
+                //SG_LOG(SG_GENERAL, SG_ALERT, "Taxiway incursion for AI aircraft" << i->getAircraft()->getCallSign());
+            }
+
+        }
+        intVecIterator ivi;
+        for (ivi = i->getIntentions().begin(); ivi != i->getIntentions().end(); ivi++) {
+            int segIndex = (*ivi);
+            if (segIndex > 0) {
+                if (segments[segIndex-1]->hasBlock(now))
+                    break;
+            }
+        }
+        //after this, ivi points just behind the last valid unblocked taxi segment.
+        for (intVecIterator j = i->getIntentions().begin(); j != ivi; j++) {
+            int pos = (*j);
+            if (pos > 0) {
+                FGTaxiSegment *seg = segments[pos-1];
+                FGTaxiNode *node = seg->getEnd();
+                length += seg->getLength();
+                for (FGTaxiSegmentVectorIterator tsi = segments.begin(); tsi != segments.end(); tsi++) {
+                    if (((*tsi)->getEnd() == node) && ((*tsi) != seg)) {
+                        time_t blockTime = now + (length / vTaxi);
+                        (*tsi)->block(i->getId(), blockTime - 30, now);
+                    }
+                }
+            }
+        }
+    }
+}
+