Implementation of ridge lift from Patrice Poly based on an algorithm of Ian Forster-Lewis

src/AIModel/AIManager.cxx

@@ -65,7 +65,7 @@ FGAIManager::init() {
     if (!enabled)
         return;
 
-    wind_from_down_node = fgGetNode("/environment/wind-from-down-fps", true);
+    thermal_lift_node = fgGetNode("/environment/thermal-lift-fps", true);
     wind_from_east_node  = fgGetNode("/environment/wind-from-east-fps",true);
     wind_from_north_node = fgGetNode("/environment/wind-from-north-fps",true);
 
@@ -172,7 +172,7 @@ FGAIManager::update(double dt) {
         }
     }
 
-    wind_from_down_node->setDoubleValue( strength ); // for thermals
+    thermal_lift_node->setDoubleValue( strength );  // for thermals
 }
 
 void
@@ -258,6 +258,8 @@ FGAIManager::processThermal( FGAIThermal* thermal ) {
 
 }
 
+
+
 void
 FGAIManager::processScenario( const string &filename ) {
 
@@ -397,7 +399,7 @@ FGAIManager::calcCollision(double alt, double lat, double lon, double fuse_range
         tgt_ht[type] += fuse_range;
 
         if (fabs(tgt_alt - alt) > tgt_ht[type] || type == FGAIBase::otBallistic
-                || type == FGAIBase::otStorm || type == FGAIBase::otThermal) {
+                || type == FGAIBase::otStorm || type == FGAIBase::otThermal ) {
             SG_LOG(SG_GENERAL, SG_DEBUG, "AIManager: skipping "
                 << fabs(tgt_alt - alt)
                 << " "

src/AIModel/AIManager.hxx

@@ -100,7 +100,7 @@ private:
     double calcRange(double lat, double lon, double lat2, double lon2)const;
 
     SGPropertyNode_ptr root;
-    SGPropertyNode_ptr wind_from_down_node;
+    SGPropertyNode_ptr thermal_lift_node;
     SGPropertyNode_ptr user_latitude_node;
     SGPropertyNode_ptr user_longitude_node;
     SGPropertyNode_ptr user_altitude_node;

src/AIModel/AIThermal.cxx

@@ -1,8 +1,10 @@
 // FGAIThermal - FGAIBase-derived class creates an AI thermal
 //
-// Written by David Culp, started Feb 2004.
+// Original by Written by David Culp
 //
-// Copyright (C) 2004  David P. Culp - davidculp2@comcast.net
+// An attempt to refine the thermal shape and behaviour by WooT 2009
+//
+// Copyright (C) 2009 Patrice Poly ( WooT )
 //
 // This program is free software; you can redistribute it and/or
 // modify it under the terms of the GNU General Public License as
@@ -37,6 +39,10 @@ FGAIThermal::FGAIThermal() : FGAIBase(otThermal) {
    max_strength = 6.0;
    diameter = 0.5;
    strength = factor = 0.0;
+   cycle_timer = 60*(rand()%31); // some random in the birth time
+   ground_elev_ft = 0.0;
+   dt_count=0.9;
+   alt=0.0;
 }
 
 FGAIThermal::~FGAIThermal() {
@@ -56,14 +62,47 @@ void FGAIThermal::readFromScenario(SGPropertyNode* scFileNode) {
 bool FGAIThermal::init(bool search_in_AI_path) {
    factor = 8.0 * max_strength / (diameter * diameter * diameter);
    setAltitude( height );
+   _surface_wind_from_deg_node =
+   	    fgGetNode("/environment/config/boundary/entry[0]/wind-from-heading-deg", true);
+   _surface_wind_speed_node =
+            fgGetNode("/environment/config/boundary/entry[0]/wind-speed-kt", true);
+   _aloft_wind_from_deg_node =
+   	    fgGetNode("/environment/config/aloft/entry[2]/wind-from-heading-deg", true);
+   _aloft_wind_speed_node =
+            fgGetNode("/environment/config/aloft/entry[2]/wind-speed-kt", true);
+    do_agl_calc = 1;
    return FGAIBase::init(search_in_AI_path);
 }
 
 void FGAIThermal::bind() {
+	props->tie("position/altitude-agl-ft", // for debug and tweak
+                SGRawValuePointer<double>(&altitude_agl_ft));
+	props->tie("alt-rel", // for debug and tweak
+                SGRawValuePointer<double>(&alt_rel));
+	props->tie("time", // for debug and tweak
+                SGRawValuePointer<double>(&time));
+	props->tie("xx", // for debug and tweak
+                SGRawValuePointer<double>(&xx));
+	props->tie("is-forming", // for debug abd tweak
+                SGRawValuePointer<bool>(&is_forming));
+	props->tie("is-formed", // for debug abd tweak
+                SGRawValuePointer<bool>(&is_formed));
+	props->tie("is-dying", // for debug abd tweak
+                SGRawValuePointer<bool>(&is_dying));
+	props->tie("is-dead", // for debug abd tweak
+                SGRawValuePointer<bool>(&is_dead));
     FGAIBase::bind();
 }
 
 void FGAIThermal::unbind() {
+	props->untie("position/altitude-agl-ft");
+	props->untie("alt-rel");
+	props->untie("time");	
+	props->untie("is-forming");
+	props->untie("is-formed");
+	props->untie("is-dying");
+	props->untie("is-dead");
+	props->untie("xx");
     FGAIBase::unbind();
 }
 
@@ -75,41 +114,301 @@ void FGAIThermal::update(double dt) {
 }
 
 
-void FGAIThermal::Run(double dt) {
 
-   //###########################//
+//the formula to get the available portion of VUpMax depending on altitude
-   // do calculations for range //
+//returns a double between 0 and 1
-   //###########################//
+double FGAIThermal::get_strength_fac(double alt_frac) {
 
-   // copy values from the AIManager
+double PI = 4.0 * atan(1.0);
-   double user_latitude  = manager->get_user_latitude();
+double fac;
-   double user_longitude = manager->get_user_longitude();
+if ( alt_frac <=0.0 ) { // do submarines get thermals ?
-   double user_altitude  = manager->get_user_altitude();
+	fac = 0.0;
-
+	return fac;
-   // calculate range to target in feet and nautical miles
-   double lat_range = fabs(pos.getLatitudeDeg() - user_latitude) * ft_per_deg_lat;
-   double lon_range = fabs(pos.getLongitudeDeg() - user_longitude) * ft_per_deg_lon;
-   double range_ft = sqrt(lat_range*lat_range + lon_range*lon_range);
-   range = range_ft / 6076.11549;
-
-   // Calculate speed of rising air if within range. 
-   // Air vertical speed is maximum at center of thermal,
-   // and decreases to zero at the edge (as distance cubed).
-   if (range < (diameter * 0.5)) {
-     strength = max_strength - ( range * range * range * factor );
-   } else {
-     strength = 0.0;
 	}
-
+else if ( ( alt_frac>0.0 ) && (alt_frac<=0.1) ) { // ground layer
-   // Stop lift at the top of the thermal (smoothly)
+	fac = ( 0.1*( pow( (10.0*alt_frac),10.0) ) );
-   if (user_altitude > (height + 100.0)) {
+	return fac;
-     strength = 0.0;
 	}
-   else if (user_altitude < height) {
+else if ( ( alt_frac>0.1 ) && (alt_frac<=1.0) ) {   // main body of the thermal
-     // do nothing
+	fac = 0.4175 - 0.5825* ( cos ( PI*  (1.0-sqrt(alt_frac) ) +PI) ) ;
+	return fac;
 	}
-   else {
+else if ( ( alt_frac >1.0 ) && (alt_frac < 1.1 ) ) {  //above the ceiling, but not above the cloud
-     strength -= (strength * (user_altitude - height) * 0.01);
+	fac = (0.5 * ( 1.0 + cos ( PI*( (-2.0*alt_frac)*5.0 ) ) ) );
+	return fac;
+	}
+else if ( alt_frac >= 1.1 ) {  //above the cloud
+	fac = 0.0;
+	return fac;
 	}
 }
 
+
+void FGAIThermal::Run(double dt) {
+
+// *****************************************
+// the thermal characteristics and variables
+// *****************************************
+
+cycle_timer += dt ;
+
+// time
+
+// the time needed for the thermal to be completely formed
+double tmin1 = 5.0 ;
+// the time when the thermal begins to die
+double tmin2 = 20.0 ;
+// the time when the thermal is completely dead
+double tmin3 = 25.0;
+double alive_cycle_time = tmin3*60.0;
+//the time of the complete cycle, including a period of inactivity
+double tmin4 = 30.0;
+// some times expressed in a fraction of tmin3;
+double t1 = tmin1/tmin3 ;
+double t2 = tmin2/tmin3 ;
+double t3 = 1.0 ;
+double t4 = tmin4/tmin3;
+// the time elapsed since the thermal was born, in a 0-1 fraction of tmin3
+
+time = cycle_timer/alive_cycle_time;
+//comment above and
+//uncomment below to freeze the time cycle
+ time=0.5;
+
+if ( time >= t4) { 
+	cycle_timer = 60*(rand()%31);
+	}
+
+
+//the position of the thermal 'top'
+double thermal_foot_lat = (pos.getLatitudeDeg());
+double thermal_foot_lon = (pos.getLongitudeDeg());
+
+//the max updraft one can expect in this thermal
+double MaxUpdraft=max_strength;
+//the max sink one can expect in this thermal, this is a negative number
+double MinUpdraft=-max_strength*0.25;
+//the fraction of MaxUpdraft one can expect at our height and time
+double maxstrengthavail;
+//max updraft at the user altitude and time
+double v_up_max;
+//min updraft at the user altitude and time, this is a negative number
+double v_up_min;
+double wind_speed;
+
+
+//max radius of the the thermal, including the sink area
+double Rmax = diameter/2.0;
+// 'shaping' of the thermal, the higher, the more conical the thermal- between 0 and 1
+double shaping=0.8;
+//the radius of the thermal at our altitude in FT, including sink
+double Rsink;
+//the relative radius of the thermal where we have updraft, between 0 an 1
+double r_up_frac=0.9;
+//radius of the thermal where we have updraft, in FT
+double Rup;
+//how far are we from the thermal center at our altitude in FEET
+double dist_center;
+
+//the position of the center of the thermal slice at our altitude
+double slice_center_lon;
+double slice_center_lat;
+
+
+
+// **************************************
+// various variables relative to the user
+// **************************************
+
+double user_latitude  = manager->get_user_latitude();
+double user_longitude = manager->get_user_longitude();
+double user_altitude  = manager->get_user_altitude(); // MSL
+
+//we need to know the thermal foot AGL altitude
+
+
+//we could do this only once, as thermal don't move
+//but then agl info is lost on user reset
+//so we only do this every 10 seconds to save cpu
+dt_count += dt;
+if (dt_count >= 10.0 ) {
+	//double alt;
+	if (globals->get_scenery()->get_elevation_m(SGGeod::fromGeodM(pos, 20000), alt, 0)){	
+	ground_elev_ft =  alt * SG_METER_TO_FEET;
+	do_agl_calc = 0;
+	altitude_agl_ft = height - ground_elev_ft ;
+	dt_count = 0.0;
+	}
+}
+
+//user altitude relative to the thermal height, seen AGL from the thermal foot
+if ( user_altitude < 1.0 ) { user_altitude = 1.0 ;}; // an ugly way to avoid NaNs for users at alt 0
+double user_altitude_agl= ( user_altitude - ground_elev_ft ) ;
+alt_rel = user_altitude_agl / altitude_agl_ft;
+
+
+
+//the updraft user feels !
+double Vup;
+
+// *********************
+// environment variables
+// *********************
+
+// the  windspeed at the user alt in KT
+double windspeed;
+
+// the  wind heading at the user alt
+double wind_heading;
+double wind_heading_deg;
+double wind_heading_rad;
+
+// the "ambient" sink outside thermals
+double global_sink = -1.0;
+
+// **************
+// some constants
+// **************
+
+double PI = 4.0 * atan(1.0);
+
+
+// ******************
+// thermal main cycle
+// ******************
+
+//we get the max strenght proportion we can expect at the time and altitude, formuled between 0 and 1
+//double xx;
+if (time <= t1) {
+	xx= ( time / t1 );
+	maxstrengthavail = xx* get_strength_fac ( alt_rel / xx );
+
+	is_forming=1;is_formed=0;is_dying=0;is_dead=0;
+
+	}
+else if ( (time > t1) && (time <= t2) ) {
+	maxstrengthavail = get_strength_fac ( (alt_rel) );
+
+	is_forming=0;is_formed=1;is_dying=0;is_dead=0;
+
+	}
+else if ( (time > t2) && (time <= t3) ) {
+	xx= ( ( time - t2) / (1.0 - t2) ) ;
+	maxstrengthavail = get_strength_fac ( alt_rel - xx );
+
+	is_forming=0;is_formed=0;is_dying=1;is_dead=0;
+
+	}
+else {
+	maxstrengthavail = 0.0;
+	is_forming=0;is_formed=0;is_dying=0;is_dead=1;
+
+	}
+
+//we get the diameter of the thermal slice at the user altitude
+//the thermal has a slight conic shape
+
+if ( (alt_rel >= 0.0) && (alt_rel < 1.0 ) ) {
+	Rsink = ( shaping*Rmax ) + ( (  (1.0-shaping)*Rmax*alt_rel ) / altitude_agl_ft );  // in the main thermal body
+	}
+else if ( (alt_rel >=1.0) && (alt_rel < 1.1) ) {
+	Rsink = (Rmax/2.0) * ( 1.0+ cos ( (10.0*PI*alt_rel)-(2.0*PI) ) ); // above the ceiling
+	}
+else {
+	Rsink = 0.0; // above the cloud
+	}
+
+//we get the portion of the diameter that produces lift
+Rup = r_up_frac * Rsink ;
+
+//we now determine v_up_max and VupMin depending on our altitude
+
+v_up_max = maxstrengthavail * MaxUpdraft;
+v_up_min = maxstrengthavail * MinUpdraft;
+
+// Now we know, for current t and alt, v_up_max, VupMin, Rup, Rsink.
+
+// We still need to know how far we are from the thermal center
+
+// To determine the thermal inclinaison in the wind, we use a ugly approximation,
+// in which we say the thermal bends 20° (0.34906 rad ) for 10 kts wind.
+// We move the thermal foot upwind, to keep the cloud model over the "center" at ceiling level.
+// the displacement distance of the center of the thermal slice, at user altitude,
+// and relative to a hipothetical vertical thermal,  would be:
+
+// get surface and 9000 ft wind
+
+double ground_wind_from_deg = _surface_wind_from_deg_node->getDoubleValue();
+double ground_wind_speed_kts  = _surface_wind_speed_node->getDoubleValue();
+double aloft_wind_from_deg = _aloft_wind_from_deg_node->getDoubleValue();
+double aloft_wind_speed_kts  = _aloft_wind_speed_node->getDoubleValue();
+
+double ground_wind_from_rad = (PI/2.0) - PI*( ground_wind_from_deg/180.0);
+double aloft_wind_from_rad = (PI/2.0) - PI*( aloft_wind_from_deg/180.0);
+
+wind_heading_rad= PI+ 0.5*( ground_wind_from_rad + aloft_wind_from_rad );
+
+wind_speed = ground_wind_speed_kts + user_altitude * ( (aloft_wind_speed_kts -ground_wind_speed_kts ) /	9000.0 );
+
+double dt_center_alt = -(tan (0.034906*wind_speed)) * ( altitude_agl_ft-user_altitude_agl );
+
+// now, lets find how far we are from this shifted slice
+
+double dt_slice_lon_FT = ( dt_center_alt * cos ( wind_heading_rad ));
+double dt_slice_lat_FT = ( dt_center_alt * sin ( wind_heading_rad ));
+
+double dt_slice_lon = dt_slice_lon_FT / ft_per_deg_lon;
+double dt_slice_lat = dt_slice_lat_FT / ft_per_deg_lat;
+
+slice_center_lon = thermal_foot_lon + dt_slice_lon;
+slice_center_lat = thermal_foot_lat + dt_slice_lat;
+
+double dist_center_lon = fabs(slice_center_lon - user_longitude)* ft_per_deg_lon;
+double dist_center_lat = fabs(slice_center_lat - user_latitude)* ft_per_deg_lat;
+
+double dist_center_FT = sqrt ( dist_center_lon*dist_center_lon + dist_center_lat*dist_center_lat ); // feet
+
+dist_center = dist_center_FT/ 6076.11549; //nautic miles
+
+
+// Now we can calculate Vup
+
+if ( max_strength >=0.0 ) { // this is a thermal
+
+	if ( ( dist_center >= 0.0 ) && ( dist_center < Rup ) ) {  //user is in the updraft area
+		Vup = v_up_max * cos ( dist_center* PI/(2.0*Rup) );
+		}
+	else if ( ( dist_center > Rup ) && ( dist_center <= ((Rup+Rsink)/2.0) ) ) { //user in the 1st half of the sink area
+		Vup = v_up_min * cos (( dist_center - ( Rup+Rsink)/2.0 ) * PI / ( 2.0* (  ( Rup+Rsink)/2.0 -Rup )));
+		}
+	else if ( ( dist_center > ((Rup+Rsink)/2.0) ) && dist_center <= Rsink ) {   // user in the 2nd half of the sink area
+		Vup = ( global_sink + v_up_min )/2.0 + ( global_sink - v_up_min )/2.0 *cos ( (dist_center-Rsink) *PI/ ( (Rsink-Rup )/2.0) );
+		}
+	else {  // outside the thermal
+		Vup = global_sink;
+		} 
+	}
+
+else { // this is a sink, we don't want updraft on the sides, nor do we want to feel sink near or above ceiling and ground
+	if ( alt_rel <=1.1 ) {
+		double fac =  ( 1.0 - ( 1.0 - 1.815*alt_rel)*( 1.0 - 1.815*alt_rel) );
+		Vup = fac * (global_sink + ( ( v_up_max - global_sink )/2.0 ) * ( 1.0+cos ( dist_center* PI / Rmax ) )) ;
+		}
+	else { Vup = global_sink; }
+}
+
+//correct for no global sink above clouds and outside thermals
+if ( ( (alt_rel > 1.0) && (alt_rel <1.1)) && ( dist_center > Rsink ) ) {
+	Vup = global_sink * ( 11.0 -10.0 * alt_rel );
+	}
+if ( alt_rel >= 1.1 ) { 
+	Vup = 0.0;
+	}
+
+strength = Vup;
+range = dist_center;
+
+}
+
+
+

src/AIModel/AIThermal.hxx

@@ -1,8 +1,10 @@
-// FGAIThermal - AIBase derived class creates an AI thunderstorm
+// FGAIThermal - FGAIBase-derived class creates an AI thermal
 //
-// Written by David Culp, started Feb 2004.
+// Original by Written by David Culp
 //
-// Copyright (C) 2004  David P. Culp - davidculp2@comcast.net
+// An attempt to refine the thermal shape and behaviour by WooT 2009
+//
+// Copyright (C) 2009 Patrice Poly ( WooT )
 //
 // This program is free software; you can redistribute it and/or
 // modify it under the terms of the GNU General Public License as
@@ -45,19 +47,51 @@ public:
 	inline void setMaxStrength( double s ) { max_strength = s; };
         inline void setDiameter( double d ) { diameter = d; };
         inline void setHeight( double h ) { height = h; };
+        inline void setMaxUpdraft( double lift ) { v_up_max = lift; };
+	inline void setMinUpdraft( double sink ) { v_up_min = sink; };
+	inline void setR_up_frac( double r ) { r_up_frac = r; };
+	
 	inline double getStrength() const { return strength; };
         inline double getDiameter() const { return diameter; };
         inline double getHeight() const { return height; };
+        inline double getV_up_max() const { return v_up_max; };
+	inline double getV_up_min() const { return v_up_min; };
+	inline double getR_up_frac() const { return r_up_frac; };
 
         virtual const char* getTypeString(void) const { return "thermal"; }
+	void getGroundElev(double dt);
+	
+
 private:
 
 	void Run(double dt);
+	double get_strength_fac(double alt_frac);
 	double max_strength;
         double strength;
         double diameter;
         double height;
         double factor;
+	double alt_rel;
+	double alt;
+	double v_up_max;
+	double v_up_min;
+        double r_up_frac;
+	double cycle_timer;
+	double dt_count;
+	double time;
+	double xx;
+	double ground_elev_ft; // ground level in ft
+	double altitude_agl_ft; // altitude above ground in feet
+	bool do_agl_calc;
+	bool is_forming;
+	bool is_formed;
+	bool is_dying;
+	bool is_dead;
+	SGPropertyNode_ptr _surface_wind_from_deg_node;
+	SGPropertyNode_ptr _surface_wind_speed_node;
+	SGPropertyNode_ptr _aloft_wind_from_deg_node;
+	SGPropertyNode_ptr _aloft_wind_speed_node;
+
 };
 
 

src/Environment/Makefile.am

@@ -10,6 +10,7 @@ libEnvironment_a_SOURCES = \
 	environment_ctrl.cxx environment_ctrl.hxx \
 	fgmetar.cxx fgmetar.hxx fgclouds.cxx fgclouds.hxx \
 	atmosphere.cxx atmosphere.hxx \
-	precipitation_mgr.cxx precipitation_mgr.hxx
+	precipitation_mgr.cxx precipitation_mgr.hxx \
+	ridge_lift.cxx ridge_lift.hxx
 
 INCLUDES = -I$(top_srcdir) -I$(top_srcdir)/src

src/Environment/environment.cxx

@@ -133,6 +133,8 @@ void FGEnvironment::_init()
     wind_from_north_fps = 0;
     wind_from_east_fps = 0;
     wind_from_down_fps = 0;
+    thermal_lift_fps = 0;
+    ridge_lift_fps= 0;
     altitude_half_to_sun_m = 1000;
     altitude_tropo_top_m = 10000;
     _setup_tables();
@@ -171,6 +173,8 @@ FGEnvironment::copy (const FGEnvironment &env)
     wind_from_north_fps = env.wind_from_north_fps;
     wind_from_east_fps = env.wind_from_east_fps;
     wind_from_down_fps = env.wind_from_down_fps;
+    thermal_lift_fps = env.thermal_lift_fps;
+    ridge_lift_fps= env.ridge_lift_fps;
     turbulence_magnitude_norm = env.turbulence_magnitude_norm;
     turbulence_rate_hz = env.turbulence_rate_hz;
 }
@@ -337,6 +341,18 @@ FGEnvironment::get_wind_from_down_fps () const
   return wind_from_down_fps;
 }
 
+double
+FGEnvironment::get_thermal_lift_fps () const
+{
+  return thermal_lift_fps;
+}
+
+double
+FGEnvironment::get_ridge_lift_fps () const
+{
+  return ridge_lift_fps;
+}
+
 double
 FGEnvironment::get_turbulence_magnitude_norm () const
 {
@@ -453,6 +469,20 @@ FGEnvironment::set_wind_from_down_fps (double d)
   _recalc_hdgspd();
 }
 
+void
+FGEnvironment::set_thermal_lift_fps (double th)
+{
+  thermal_lift_fps = th;
+  _recalc_updraft();
+}
+
+void
+FGEnvironment::set_ridge_lift_fps (double ri)
+{
+  ridge_lift_fps = ri;
+  _recalc_updraft();
+}
+
 void
 FGEnvironment::set_turbulence_magnitude_norm (double t)
 {
@@ -536,6 +566,12 @@ FGEnvironment::_recalc_ne ()
     sin(wind_from_heading_deg * SGD_DEGREES_TO_RADIANS);
 }
 
+void
+FGEnvironment::_recalc_updraft ()
+{
+  wind_from_down_fps = thermal_lift_fps + ridge_lift_fps ;
+}
+
 void
 FGEnvironment::_recalc_sl_temperature ()
 {

src/Environment/environment.hxx

@@ -70,6 +70,8 @@ public:
   virtual double get_wind_from_north_fps () const;
   virtual double get_wind_from_east_fps () const;
   virtual double get_wind_from_down_fps () const;
+  virtual double get_thermal_lift_fps () const;
+  virtual double get_ridge_lift_fps () const;  
 
   virtual double get_turbulence_magnitude_norm () const;
   virtual double get_turbulence_rate_hz () const;
@@ -88,6 +90,8 @@ public:
   virtual void set_wind_from_north_fps (double n);
   virtual void set_wind_from_east_fps (double e);
   virtual void set_wind_from_down_fps (double d);
+  virtual void set_thermal_lift_fps (double th);
+  virtual void set_ridge_lift_fps (double ri);
 
   virtual void set_turbulence_magnitude_norm (double t);
   virtual void set_turbulence_rate_hz (double t);
@@ -101,6 +105,7 @@ private:
   void _init();
   void _recalc_hdgspd ();
   void _recalc_ne ();
+  void _recalc_updraft ();
 
   void _recalc_sl_temperature ();
   void _recalc_alt_temperature ();
@@ -139,6 +144,8 @@ private:
   double wind_from_north_fps;
   double wind_from_east_fps;
   double wind_from_down_fps;
+  double thermal_lift_fps;
+  double ridge_lift_fps;
 
 };
 

src/Environment/environment_mgr.cxx

@@ -145,6 +145,16 @@ FGEnvironmentMgr::bind ()
 	&FGEnvironment::get_wind_from_down_fps,
 	&FGEnvironment::set_wind_from_down_fps);
   fgSetArchivable("/environment/wind-from-down-fps");
+
+  fgTie("/environment/thermal-lift-fps", _environment,
+	&FGEnvironment::get_thermal_lift_fps,
+	&FGEnvironment::set_thermal_lift_fps);
+  fgSetArchivable("/environment/thermal-lift-fps");
+  fgTie("/environment/ridge-lift-fps", _environment,
+	&FGEnvironment::get_ridge_lift_fps,
+	&FGEnvironment::set_ridge_lift_fps);
+  fgSetArchivable("/environment/ridge-lift-fps");
+
   fgTie("/environment/turbulence/magnitude-norm", _environment,
         &FGEnvironment::get_turbulence_magnitude_norm,
         &FGEnvironment::set_turbulence_magnitude_norm);
@@ -227,6 +237,10 @@ FGEnvironmentMgr::unbind ()
   fgUntie("/environment/wind-from-north-fps");
   fgUntie("/environment/wind-from-east-fps");
   fgUntie("/environment/wind-from-down-fps");
+
+  fgUntie("/environment/thermal-lift-fps");
+  fgUntie("/environment/ridge-lift-fps");
+
   fgUntie("/environment/atmosphere/altitude-half-to-sun");
   fgUntie("/environment/atmosphere/altitude-troposphere-top");
   for (int i = 0; i < MAX_CLOUD_LAYERS; i++) {

src/Environment/ridge_lift.cxx

@@ -0,0 +1,317 @@
+// simulates ridge lift
+//
+// Written by Patrice Poly
+// Copyright (C) 2009 Patrice Poly - p.polypa@gmail.com
+//
+//
+// Entirely based  on the paper : 
+// http://carrier.csi.cam.ac.uk/forsterlewis/soaring/sim/fsx/dev/sim_probe/sim_probe_paper.html
+// by Ian Forster-Lewis, University of Cambridge, 26th December 2007
+//
+//
+// 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., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+//
+//
+
+
+#ifdef HAVE_CONFIG_H
+#  include <config.h>
+#endif
+
+#include <Main/fg_props.hxx>
+#include <Main/globals.hxx>
+#include <Scenery/scenery.hxx>
+#include <string>
+#include <math.h>
+
+using std::string;
+
+#include "ridge_lift.hxx"
+
+//constructor
+FGRidgeLift::FGRidgeLift ()
+{	
+	dist_probe_m[0] = 0.0; // in meters
+	dist_probe_m[1] = 250.0;
+	dist_probe_m[2] = 750.0;
+	dist_probe_m[3] = 2000.0;
+	dist_probe_m[4] = -100.0;
+
+	BOUNDARY1_m = 40.0; // in meters
+	BOUNDARY2_m = 130.0; 
+
+	PI = 4.0*atan(1.0); // pi
+	deg2rad = (PI/180.0);
+	rad2deg = (180.0/PI);
+	strength = 0.0;
+	timer = 0.0;
+	scanned = false;
+
+	earth_rad_ft=20899773.07;
+}
+
+//destructor
+FGRidgeLift::~FGRidgeLift()
+{
+
+}
+
+void FGRidgeLift::init(void)
+{
+	_ridge_lift_fps_node =
+			fgGetNode("/environment/ridge-lift-fps"
+			, true);
+	_surface_wind_from_deg_node =
+			fgGetNode("/environment/config/boundary/entry[0]/wind-from-heading-deg"
+			, true);
+	_surface_wind_speed_node =
+			fgGetNode("/environment/config/boundary/entry[0]/wind-speed-kt"
+			, true);
+	_earth_radius_node =
+			fgGetNode("/position/sea-level-radius-ft"
+			, true);
+	_user_longitude_node =
+			fgGetNode("/position/longitude-deg"
+			, true);
+	_user_latitude_node =
+			fgGetNode("/position/latitude-deg"
+			, true);
+	_user_altitude_ft_node =
+			fgGetNode("/position/altitude-ft"
+			, true);
+	_user_altitude_agl_ft_node =
+			fgGetNode("/position/altitude-agl-ft"
+			, true);
+}
+
+void FGRidgeLift::bind() {
+
+	fgTie("/environment/ridge-lift/probe-elev-m[0]", this,
+		&FGRidgeLift::get_probe_elev_m_0); // read-only
+	fgTie("/environment/ridge-lift/probe-elev-m[1]", this,
+		&FGRidgeLift::get_probe_elev_m_1); // read-only
+	fgTie("/environment/ridge-lift/probe-elev-m[2]", this,
+		&FGRidgeLift::get_probe_elev_m_2); // read-only
+	fgTie("/environment/ridge-lift/probe-elev-m[3]", this,
+		&FGRidgeLift::get_probe_elev_m_3); // read-only
+	fgTie("/environment/ridge-lift/probe-elev-m[4]", this,
+		&FGRidgeLift::get_probe_elev_m_4); // read-only
+
+	fgTie("/environment/ridge-lift/probe-lat-deg[0]", this,
+		&FGRidgeLift::get_probe_lat_0); // read-only
+	fgTie("/environment/ridge-lift/probe-lat-deg[1]", this,
+		&FGRidgeLift::get_probe_lat_1); // read-only
+	fgTie("/environment/ridge-lift/probe-lat-deg[2]", this,
+		&FGRidgeLift::get_probe_lat_2); // read-only
+	fgTie("/environment/ridge-lift/probe-lat-deg[3]", this,
+		&FGRidgeLift::get_probe_lat_3); // read-only
+	fgTie("/environment/ridge-lift/probe-lat-deg[4]", this,
+		&FGRidgeLift::get_probe_lat_4); // read-only
+
+	fgTie("/environment/ridge-lift/probe-lon-deg[0]", this,
+		&FGRidgeLift::get_probe_lon_0); // read-only
+	fgTie("/environment/ridge-lift/probe-lon-deg[1]", this,
+		&FGRidgeLift::get_probe_lon_1); // read-only
+	fgTie("/environment/ridge-lift/probe-lon-deg[2]", this,
+		&FGRidgeLift::get_probe_lon_2); // read-only
+	fgTie("/environment/ridge-lift/probe-lon-deg[3]", this,
+		&FGRidgeLift::get_probe_lon_3); // read-only
+	fgTie("/environment/ridge-lift/probe-lon-deg[4]", this,
+		&FGRidgeLift::get_probe_lon_4); // read-only
+
+	fgTie("/environment/ridge-lift/slope[0]", this,
+		&FGRidgeLift::get_slope_0); // read-only
+	fgTie("/environment/ridge-lift/slope[1]", this,
+		&FGRidgeLift::get_slope_1); // read-only
+	fgTie("/environment/ridge-lift/slope[2]", this,
+		&FGRidgeLift::get_slope_2); // read-only
+	fgTie("/environment/ridge-lift/slope[3]", this,
+		&FGRidgeLift::get_slope_3); // read-only
+	
+}
+
+void FGRidgeLift::unbind() {
+
+	fgUntie("/environment/ridge-lift/probe-elev-m[0]");
+	fgUntie("/environment/ridge-lift/probe-elev-m[1]");
+	fgUntie("/environment/ridge-lift/probe-elev-m[2]");
+	fgUntie("/environment/ridge-lift/probe-elev-m[3]");
+	fgUntie("/environment/ridge-lift/probe-elev-m[4]");
+
+	fgUntie("/environment/ridge-lift/probe-lat-deg[0]");
+	fgUntie("/environment/ridge-lift/probe-lat-deg[1]");
+	fgUntie("/environment/ridge-lift/probe-lat-deg[2]");
+	fgUntie("/environment/ridge-lift/probe-lat-deg[3]");
+	fgUntie("/environment/ridge-lift/probe-lat-deg[4]");
+
+	fgUntie("/environment/ridge-lift/probe-lon-deg[0]");
+	fgUntie("/environment/ridge-lift/probe-lon-deg[1]");
+	fgUntie("/environment/ridge-lift/probe-lon-deg[2]");
+	fgUntie("/environment/ridge-lift/probe-lon-deg[3]");
+	fgUntie("/environment/ridge-lift/probe-lon-deg[4]");
+
+	fgUntie("/environment/ridge-lift/slope[0]");
+	fgUntie("/environment/ridge-lift/slope[1]");
+	fgUntie("/environment/ridge-lift/slope[2]");
+	fgUntie("/environment/ridge-lift/slope[3]");
+	
+}
+
+void FGRidgeLift::update(double dt) {
+	Run(dt);
+}
+
+double FGRidgeLift::sign(double x) {
+    if (x == 0.0)
+        return x;
+    else
+        return x/fabs(x);
+}
+
+void FGRidgeLift::Run(double dt) {
+
+	// copy values 
+
+	user_latitude_deg  = _user_latitude_node->getDoubleValue();
+	user_longitude_deg = _user_longitude_node->getDoubleValue();
+	//user_altitude_ft  = _user_altitude_ft_node->getDoubleValue();
+	
+	if ( ( _earth_radius_node->getDoubleValue() ) > 1.0 ) {
+	earth_rad_ft =_earth_radius_node->getDoubleValue(); }
+	else {	earth_rad_ft=20899773.07; }
+
+	//earth_rad_m = earth_rad_ft * 0.3048 ;
+	earth_rad_m = earth_rad_ft * SG_FEET_TO_METER ;
+	
+	//get the windspeed at ground level
+
+	double ground_wind_from_deg = _surface_wind_from_deg_node->getDoubleValue();
+	double ground_wind_speed_kts  = _surface_wind_speed_node->getDoubleValue();
+	//double ground_wind_speed_mps = ground_wind_speed_kts / SG_METER_TO_FEET;
+	double ground_wind_speed_mps = ground_wind_speed_kts / 3.2808399;
+
+	double ground_wind_from_rad = (user_longitude_deg < 0.0)  ? 
+		PI*( ground_wind_from_deg/180.0) +PI : PI*( ground_wind_from_deg/180.0);
+
+	// Placing the probes
+	
+	for (int i = 0; i <= 4; i++)
+	{
+			probe_lat_rad[i] = asin(sin(deg2rad*user_latitude_deg)*cos(dist_probe_m[i]/earth_rad_m)
+				+cos(deg2rad*user_latitude_deg)*sin(dist_probe_m[i]/earth_rad_m)*cos(ground_wind_from_rad));
+		if (probe_lat_rad[i] == 0.0) {
+			probe_lon_rad[i] = (deg2rad*user_latitude_deg);      // probe on a pole	
+		}
+		else {
+			probe_lon_rad[i] = fmod((deg2rad*user_longitude_deg+asin(sin(ground_wind_from_rad)
+						*sin(dist_probe_m[i]/earth_rad_m)/cos(probe_lon_rad[i]))+PI)
+					,(2.0*PI))-PI;
+		}
+		probe_lat_deg[i]= rad2deg*probe_lat_rad[i];
+		probe_lon_deg[i]= rad2deg*probe_lon_rad[i];
+	}
+	
+	// ground elevations
+	// every second
+	
+	timer += dt;
+	if (timer >= 1.0 ) {
+		scanned = true;
+		for (int i = 0; i <= 4; i++)
+		{
+			if (globals->get_scenery()->get_elevation_m(SGGeod::fromGeodM(
+			    SGGeod::fromRad(probe_lon_rad[i],probe_lat_rad[i]), 20000), alt, 0));
+			{
+			probe_elev_m[i] =  alt;
+			}
+		}
+		timer = 0.0;
+		
+	}
+	
+	// slopes
+	
+	double adj_slope[5];
+	
+	slope[0] = (probe_elev_m[0] - probe_elev_m[1]) / dist_probe_m[1];
+	slope[1] = (probe_elev_m[1] - probe_elev_m[2]) / dist_probe_m[2];
+	slope[2] = (probe_elev_m[2] - probe_elev_m[3]) / dist_probe_m[3];
+	slope[3] = (probe_elev_m[4] - probe_elev_m[0]) / -dist_probe_m[4];
+	
+	for (int i = 0; i <= 4; i++)
+	{	
+		adj_slope[i] = sin(atan(5.0 * pow ( (abs(slope[i])),1.7) ) ) *sign(slope[i]);
+	}
+	
+	//adjustment
+	
+	adj_slope[0] = 0.2 * adj_slope[0];
+	adj_slope[1] = 0.2 * adj_slope[1];
+	if ( adj_slope [2] < 0.0 )
+	{
+		adj_slope[2] = 0.5 * adj_slope[2];
+	}
+	else 
+	{
+		adj_slope[2] = 0.0 ;
+	}
+	
+	if ( ( adj_slope [0] >= 0.0 ) && ( adj_slope [3] < 0.0 ) )
+	{
+		adj_slope[3] = 0.0;
+	}
+	else 
+	{
+		adj_slope[3] = 0.2 * adj_slope[3];
+	}
+	
+	double lift_factor = adj_slope[0]+adj_slope[1]+adj_slope[2]+adj_slope[3];
+	
+	//user altitude above ground
+	
+	user_altitude_agl_ft = _user_altitude_agl_ft_node->getDoubleValue();
+	user_altitude_agl_m = ( user_altitude_agl_ft / SG_METER_TO_FEET );
+	
+	//boundaries
+	double agl_factor;
+	
+	if ( user_altitude_agl_m < BOUNDARY1_m )
+	{
+		agl_factor = 0.5+0.5*user_altitude_agl_m /BOUNDARY1_m ;
+	}
+	else if ( user_altitude_agl_m < BOUNDARY2_m )
+	{
+		agl_factor = 1.0;
+	}
+	else
+	{
+		agl_factor =  exp(-(2 + 2 * probe_elev_m[0] / 4000) * 
+				(user_altitude_agl_m - BOUNDARY2_m) / max(probe_elev_m[0],200.0));
+	}
+	
+	double lift_mps = lift_factor* ground_wind_speed_mps * agl_factor;
+	
+	//the updraft, finally, in ft per second
+	strength = lift_mps * SG_METER_TO_FEET ;
+	
+	_ridge_lift_fps_node->setDoubleValue( strength );
+	
+}
+
+
+
+
+
+

src/Environment/ridge_lift.hxx

@@ -0,0 +1,125 @@
+// simulates ridge lift
+//
+// Written by Patrice Poly
+// Copyright (C) 2009 Patrice Poly - p.polypa@gmail.com
+//
+//
+// Entirely based  on the paper : 
+// http://carrier.csi.cam.ac.uk/forsterlewis/soaring/sim/fsx/dev/sim_probe/sim_probe_paper.html
+// by Ian Forster-Lewis, University of Cambridge, 26th December 2007
+//
+//
+// 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., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+//
+
+
+#ifndef _FG_RidgeLift_HXX
+#define _FG_RidgeLift_HXX
+
+#ifdef HAVE_CONFIG
+#  include <config.h>
+#endif
+
+
+#include <string>
+using std::string;
+
+
+class FGRidgeLift : public SGSubsystem {
+public:
+
+	FGRidgeLift();
+	~FGRidgeLift();		
+	
+	virtual void bind();
+	virtual void unbind();
+	virtual void update(double dt);
+	virtual void init();
+
+	inline double getStrength() const { return strength; };
+
+ 	inline double get_probe_elev_m_0() const { return probe_elev_m[0]; };
+ 	inline double get_probe_elev_m_1() const { return probe_elev_m[1]; };
+ 	inline double get_probe_elev_m_2() const { return probe_elev_m[2]; };
+ 	inline double get_probe_elev_m_3() const { return probe_elev_m[3]; };
+ 	inline double get_probe_elev_m_4() const { return probe_elev_m[4]; };
+
+ 	inline double get_probe_lat_0() const { return probe_lat_deg[0]; };
+ 	inline double get_probe_lat_1() const { return probe_lat_deg[1]; };
+ 	inline double get_probe_lat_2() const { return probe_lat_deg[2]; };
+ 	inline double get_probe_lat_3() const { return probe_lat_deg[3]; };
+ 	inline double get_probe_lat_4() const { return probe_lat_deg[4]; };
+
+	inline double get_probe_lon_0() const { return probe_lon_deg[0]; };
+ 	inline double get_probe_lon_1() const { return probe_lon_deg[1]; };
+ 	inline double get_probe_lon_2() const { return probe_lon_deg[2]; };
+ 	inline double get_probe_lon_3() const { return probe_lon_deg[3]; };
+ 	inline double get_probe_lon_4() const { return probe_lon_deg[4]; };
+
+ 	inline double get_slope_0() const { return slope[0]; };
+ 	inline double get_slope_1() const { return slope[1]; };
+ 	inline double get_slope_2() const { return slope[2]; };
+ 	inline double get_slope_3() const { return slope[3]; };
+
+private:
+	//void init();
+	void Run(double dt);
+
+	double dist_probe_m[5];
+	double BOUNDARY1_m;
+	double BOUNDARY2_m;
+	double PI; // pi
+	double deg2rad;
+	double rad2deg;
+
+	bool scanned;
+
+	double strength;
+	double timer;
+
+	double probe_lat_rad[5];
+	double probe_lon_rad[5];
+
+	double probe_lat_deg[5];
+	double probe_lon_deg[5];
+
+	double alt;	
+	double probe_elev_m[5];
+
+	double slope[4];
+	double earth_rad_ft;
+	double earth_rad_m;
+	double user_latitude_deg;
+	double user_longitude_deg;
+	//double user_altitude;
+	double user_altitude_agl_ft;
+	double user_altitude_agl_m;
+
+	double sign(double x);
+
+	SGPropertyNode_ptr _ridge_lift_fps_node;
+
+	SGPropertyNode_ptr _surface_wind_from_deg_node;
+	SGPropertyNode_ptr _surface_wind_speed_node;
+
+	SGPropertyNode_ptr _user_altitude_ft_node;
+	SGPropertyNode_ptr _user_altitude_agl_ft_node;
+	SGPropertyNode_ptr _earth_radius_node;
+	SGPropertyNode_ptr _user_longitude_node;
+	SGPropertyNode_ptr _user_latitude_node;
+
+};
+
+#endif  // _FG_RidgeLift_HXX

src/Main/fg_init.cxx

@@ -115,6 +115,7 @@
 #include <MultiPlayer/multiplaymgr.hxx>
 
 #include <Environment/environment_mgr.hxx>
+#include <Environment/ridge_lift.hxx>
 
 #include "fg_init.hxx"
 #include "fg_io.hxx"
@@ -1508,6 +1509,13 @@ bool fgInitSubsystems() {
     // Initialize the weather modeling subsystem
     globals->add_subsystem("environment", new FGEnvironmentMgr);
 
+    ////////////////////////////////////////////////////////////////////
+    // Initialize the ridge lift simulation.
+    ////////////////////////////////////////////////////////////////////
+
+    // Initialize the ridgelift subsystem
+    globals->add_subsystem("ridgelift", new FGRidgeLift);
+
 
     ////////////////////////////////////////////////////////////////////
     // Initialize the aircraft systems and instrumentation (before the