flightgear/src/AIModel/AIFlightPlan.cxx

// FGAIFlightPlan - class for loading and storing  AI flight plans
// Written by David Culp, started May 2004
// - davidculp2@comcast.net
//
// This program is free software; you can redistribute it and/or
// modify it under the terms of the GNU General Public License as
// published by the Free Software Foundation; either version 2 of the
// License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful, but
// WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.


#include "AIFlightPlan.hxx"
#include <simgear/misc/sg_path.hxx>
#include <simgear/debug/logstream.hxx>
#include <simgear/route/waypoint.hxx>
#include <simgear/structure/exception.hxx>
#include <simgear/constants.h>
#ifdef __BORLANDC__
#  define exception c_exception
#endif
#include <simgear/props/props.hxx>
#include <Main/globals.hxx>
#include <Main/fg_props.hxx>


FGAIFlightPlan::FGAIFlightPlan(string filename)
{
  int i;
  SGPath path( globals->get_fg_root() );
  path.append( ("/Data/AI/FlightPlans/" + filename).c_str() );
  SGPropertyNode root;

  try {
      readProperties(path.str(), &root);
  } catch (const sg_exception &e) {
      SG_LOG(SG_GENERAL, SG_ALERT,
       "Error reading AI flight plan: ");
       cout << path.str() << endl;
      return;
  }

  SGPropertyNode * node = root.getNode("flightplan");
  for (i = 0; i < node->nChildren(); i++) { 
     //cout << "Reading waypoint " << i << endl;        
     waypoint* wpt = new waypoint;
     SGPropertyNode * wpt_node = node->getChild(i);
     wpt->name      = wpt_node->getStringValue("name", "END");
     wpt->latitude  = wpt_node->getDoubleValue("lat", 0);
     wpt->longitude = wpt_node->getDoubleValue("lon", 0);
     wpt->altitude  = wpt_node->getDoubleValue("alt", 0);
     wpt->speed     = wpt_node->getDoubleValue("ktas", 0);
     wpt->crossat   = wpt_node->getDoubleValue("crossat", -10000);
     wpt->gear_down = wpt_node->getBoolValue("gear-down", false);
     wpt->flaps_down= wpt_node->getBoolValue("flaps-down", false);
     wpt->on_ground = wpt_node->getBoolValue("on-ground", false);

     if (wpt->name == "END") wpt->finished = true;
     else wpt->finished = false;

     waypoints.push_back( wpt );
   }

  wpt_iterator = waypoints.begin();
  //cout << waypoints.size() << " waypoints read." << endl;
}


// This is a modified version of the constructor,
// Which not only reads the waypoints from a 
// Flight plan file, but also adds the current
// Position computed by the traffic manager, as well
// as setting speeds and altitude computed by the
// traffic manager. 
FGAIFlightPlan::FGAIFlightPlan(string filename, 
			       double lat, 
			       double lon,
			       double alt,
			       double speed,
			       double course)
{
  int i;
  bool useInitialWayPoint = true;
  SGPath path( globals->get_fg_root() );
  path.append( ("/Data/AI/FlightPlans/" + filename).c_str() );
  SGPropertyNode root;

  try {
      readProperties(path.str(), &root);
  } catch (const sg_exception &e) {
      SG_LOG(SG_GENERAL, SG_ALERT,
       "Error reading AI flight plan: ");
       cout << path.str() << endl;
      return;
  }

  SGPropertyNode * node = root.getNode("flightplan");
  // First waypoint is current position of the aircraft as
  // dictated by the traffic manager. 
  waypoint* init_waypoint   = new waypoint;
  init_waypoint->name       = string("initial position");
  init_waypoint->latitude   = lat;
  init_waypoint->longitude  = lon;
  init_waypoint->altitude   = alt;
  init_waypoint->speed      = speed;
  init_waypoint->crossat    = - 10000;
  init_waypoint->gear_down  = false;
  init_waypoint->flaps_down = false;
  waypoints.push_back( init_waypoint );
  for (i = 0; i < node->nChildren(); i++) { 
     //cout << "Reading waypoint " << i << endl;
     waypoint* wpt = new waypoint;
     SGPropertyNode * wpt_node = node->getChild(i);
     wpt->name      = wpt_node->getStringValue("name", "END");
     wpt->latitude  = wpt_node->getDoubleValue("lat", 0);
     wpt->longitude = wpt_node->getDoubleValue("lon", 0);
     wpt->altitude  = wpt_node->getDoubleValue("alt", 0);
     wpt->speed     = wpt_node->getDoubleValue("ktas", 0);
     //wpt->speed     = speed;
     wpt->crossat   = wpt_node->getDoubleValue("crossat", -10000);
     wpt->gear_down = wpt_node->getBoolValue("gear-down", false);
     wpt->flaps_down= wpt_node->getBoolValue("flaps-down", false);

     if (wpt->name == "END") wpt->finished = true;
     else wpt->finished = false;
     // discard this waypoint if it's bearing differs more than
     // 90 degrees from the course we should fly according to the
     // Traffic manager. Those are considered "behind" us.
     SGWayPoint first(init_waypoint->longitude, 
		      init_waypoint->latitude, 
		      init_waypoint->altitude);
     SGWayPoint curr (wpt->longitude, 
		      wpt->latitude, 
		      wpt->altitude);
     double crse, crsDiff;
     double dist;
     first.CourseAndDistance(curr, &crse, &dist);

     dist *= SG_METER_TO_NM;

     // We're only interested in the absolute value of crsDiff
     // wich should fall in the 0-180 deg range.
     crsDiff = fabs(crse-course);
     if (crsDiff > 180)
       crsDiff -= 180;
     // These are the threee conditions that we consder including
     // in our flight plan:
     // 1) current waypoint is less then 100 miles away OR
     // 2) curren waypoint is ahead of us, at any distance
     bool useWpt = false;
     if ((dist > 100.0) && (crsDiff > 90.0) && (wpt->name != string ("EOF")))
       {
	 //useWpt = false;
	 // Once we start including waypoints, we have to continue, even though
	 // one of the following way point would suffice. 
	 // so once is the useWpt flag is set to true, we cannot reset it to false.
	 // cerr << "Discarding waypoint: " << wpt->name 
	 //    << ": Course difference = " << crsDiff << endl;
       }
     else
       useWpt = true;
     
     if (useWpt)
       {
	 if ((dist > 100.0) && (useInitialWayPoint))
	   {
	     waypoints.push_back(init_waypoint);
	     //cerr << "Using waypoint : " << init_waypoint->name <<  endl;
	   }
	 waypoints.push_back( wpt );
	 //cerr << "Using waypoint : " << wpt->name 
	 //    << ": course diff : " << crsDiff 
	 //      << "distance      : " << dist << endl;
	 useInitialWayPoint = false;
       }
     else 
       delete wpt;
  }
  
  wpt_iterator = waypoints.begin();
  //cout << waypoints.size() << " waypoints read." << endl;
}




FGAIFlightPlan::~FGAIFlightPlan()
{
  waypoints.clear();
}


FGAIFlightPlan::waypoint*
FGAIFlightPlan::getPreviousWaypoint( void )
{
  if (wpt_iterator == waypoints.begin()) {
    return 0;
  } else {
    wpt_vector_iterator prev = wpt_iterator;
    return *(--prev);
  }
}

FGAIFlightPlan::waypoint*
FGAIFlightPlan::getCurrentWaypoint( void )
{
  return *wpt_iterator;
}

FGAIFlightPlan::waypoint*
FGAIFlightPlan::getNextWaypoint( void )
{
  if (wpt_iterator == waypoints.end()) {
    return 0;
  } else {
    wpt_vector_iterator next = wpt_iterator;
    return *(++next);
  }
}

void FGAIFlightPlan::IncrementWaypoint( void )
{
  wpt_iterator++;
}

// gives distance in feet from a position to a waypoint
double FGAIFlightPlan::getDistanceToGo(double lat, double lon, waypoint* wp){
   // get size of a degree at the present latitude
   // this won't work over large distances
   double ft_per_deg_lat = 366468.96 - 3717.12 * cos(lat / SG_RADIANS_TO_DEGREES);
   double ft_per_deg_lon = 365228.16 * cos(lat / SG_RADIANS_TO_DEGREES);
   double lat_diff_ft = fabs(wp->latitude - lat) * ft_per_deg_lat;
   double lon_diff_ft = fabs(wp->longitude - lon) * ft_per_deg_lon;
   return sqrt((lat_diff_ft * lat_diff_ft) + (lon_diff_ft * lon_diff_ft));
}

// sets distance in feet from a lead point to the current waypoint
void FGAIFlightPlan::setLeadDistance(double speed, double bearing, 
                                     waypoint* current, waypoint* next){
  double turn_radius = 0.1911 * speed * speed; // an estimate for 25 degrees bank
  double inbound = bearing;
  double outbound = getBearing(current, next);
  double diff = fabs(inbound - outbound);
  if (diff > 180.0) diff = 360.0 - diff;
  lead_distance = turn_radius * sin(diff * SG_DEGREES_TO_RADIANS); 
}

void FGAIFlightPlan::setLeadDistance(double distance_ft){
  lead_distance = distance_ft;
}


double FGAIFlightPlan::getBearing(waypoint* first, waypoint* second){
  return getBearing(first->latitude, first->longitude, second);
}


double FGAIFlightPlan::getBearing(double lat, double lon, waypoint* wp){
  double course, distance;
 //  double latd = lat;
//   double lond = lon;
//   double latt = wp->latitude;
//   double lont = wp->longitude;
//   double ft_per_deg_lat = 366468.96 - 3717.12 * cos(lat/SG_RADIANS_TO_DEGREES);
//   double ft_per_deg_lon = 365228.16 * cos(lat/SG_RADIANS_TO_DEGREES);

//   if (lond < 0.0) {
//     lond+=360.0;
//     lont+=360;
//   }
//   if (lont < 0.0) {
//     lond+=360.0;
//     lont+=360.0;
//   }
//   latd+=90.0;
//   latt+=90.0;

//   double lat_diff = (latt - latd) * ft_per_deg_lat;
//   double lon_diff = (lont - lond) * ft_per_deg_lon;
//   double angle = atan(fabs(lat_diff / lon_diff)) * SG_RADIANS_TO_DEGREES;

//   bool southerly = true;
//   if (latt > latd) southerly = false;
//   bool easterly = false;
//   if (lont > lond) easterly = true;
//   if (southerly && easterly) return 90.0 + angle;
//   if (!southerly && easterly) return 90.0 - angle;
//   if (southerly && !easterly) return 270.0 - angle;
//   if (!southerly && !easterly) return 270.0 + angle; 
  SGWayPoint sgWp(wp->longitude,wp->latitude, wp->altitude, SGWayPoint::WGS84, string("temp"));
  sgWp.CourseAndDistance(lon, lat, wp->altitude, &course, &distance);
  return course;
  // Omit a compiler warning.
 
}