1 // simulates ridge lift
3 // Written by Patrice Poly
4 // Copyright (C) 2009 Patrice Poly - p.polypa@gmail.com
7 // Entirely based on the paper :
8 // http://carrier.csi.cam.ac.uk/forsterlewis/soaring/sim/fsx/dev/sim_probe/sim_probe_paper.html
9 // by Ian Forster-Lewis, University of Cambridge, 26th December 2007
12 // This program is free software; you can redistribute it and/or
13 // modify it under the terms of the GNU General Public License as
14 // published by the Free Software Foundation; either version 2 of the
15 // License, or (at your option) any later version.
17 // This program is distributed in the hope that it will be useful, but
18 // WITHOUT ANY WARRANTY; without even the implied warranty of
19 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
20 // General Public License for more details.
22 // You should have received a copy of the GNU General Public License
23 // along with this program; if not, write to the Free Software
24 // Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
33 #include <Main/fg_props.hxx>
34 #include <Main/globals.hxx>
35 #include <Main/util.hxx>
36 #include <Scenery/scenery.hxx>
39 #include <simgear/sg_inlines.h>
43 #include "ridge_lift.hxx"
45 static const double BOUNDARY1_m = 40.0;
47 const double FGRidgeLift::dist_probe_m[] = { // in meters
56 FGRidgeLift::FGRidgeLift ()
60 for( int i = 0; i < 5; i++ )
61 probe_elev_m[i] = probe_lat_deg[i] = probe_lon_deg[i] = 0.0;
63 for( int i = 0; i < 4; i++ )
68 FGRidgeLift::~FGRidgeLift()
73 void FGRidgeLift::init(void)
75 _enabled_node = fgGetNode( "/environment/ridge-lift/enabled", false );
77 _ridge_lift_fps_node = fgGetNode("/environment/ridge-lift-fps", true);
78 _surface_wind_from_deg_node =
79 fgGetNode("/environment/config/boundary/entry[0]/wind-from-heading-deg"
81 _surface_wind_speed_node =
82 fgGetNode("/environment/config/boundary/entry[0]/wind-speed-kt"
84 _user_longitude_node = fgGetNode("/position/longitude-deg", true);
85 _user_latitude_node = fgGetNode("/position/latitude-deg", true);
86 _user_altitude_agl_ft_node = fgGetNode("/position/altitude-agl-ft", true);
87 _ground_elev_node = fgGetNode("/position/ground-elev-ft", true );
90 void FGRidgeLift::bind() {
93 _tiedProperties.setRoot( fgGetNode("/environment/ridge-lift",true));
94 for( int i = 0; i < 5; i++ ) {
95 _tiedProperties.Tie( "probe-elev-m", i, this, i, &FGRidgeLift::get_probe_elev_m );
96 _tiedProperties.Tie( "probe-lat-deg", i, this, i, &FGRidgeLift::get_probe_lat_deg );
97 _tiedProperties.Tie( "probe-lon-deg", i, this, i, &FGRidgeLift::get_probe_lon_deg );
100 for( int i = 0; i < 4; i++ ) {
101 _tiedProperties.Tie( "slope", i, this, i, &FGRidgeLift::get_slope );
105 void FGRidgeLift::unbind() {
106 _tiedProperties.Untie();
109 void FGRidgeLift::update(double dt) {
111 if( dt <= SGLimitsd::min() ) // paused, do nothing but keep current lift
114 if( _enabled_node && false == _enabled_node->getBoolValue() ) {
115 // do nothing if lift has been zeroed
116 if( strength != 0.0 ) {
117 if( strength > 0.1 ) {
118 // slowly fade out strong lifts
119 strength = fgGetLowPass( strength, 0, dt );
123 _ridge_lift_fps_node->setDoubleValue( strength );
131 // probe0 is current position
132 probe_lat_deg[0] = _user_latitude_node->getDoubleValue();
133 probe_lon_deg[0] = _user_longitude_node->getDoubleValue();
134 probe_elev_m[0] = _ground_elev_node->getDoubleValue() * SG_FEET_TO_METER;
136 // position is geodetic, need geocentric for advanceRadM
137 SGGeod myGeodPos = SGGeod::fromDegM( probe_lon_deg[0], probe_lat_deg[0], 20000.0 );
138 SGGeoc myGeocPos = SGGeoc::fromGeod( myGeodPos );
139 double ground_wind_from_rad = _surface_wind_from_deg_node->getDoubleValue() * SG_DEGREES_TO_RADIANS;
141 // compute the remaining probes
142 for (unsigned i = 1; i < sizeof(probe_elev_m)/sizeof(probe_elev_m[0]); i++) {
143 SGGeoc probe = myGeocPos.advanceRadM( ground_wind_from_rad, dist_probe_m[i] );
144 // convert to geodetic position for ground level computation
145 SGGeod probeGeod = SGGeod::fromGeoc( probe );
146 probe_lat_deg[i] = probeGeod.getLatitudeDeg();
147 probe_lon_deg[i] = probeGeod.getLongitudeDeg();
148 if (!globals->get_scenery()->get_elevation_m( probeGeod, probe_elev_m[i], NULL )) {
149 // no ground found? use elevation of previous probe :-(
150 probe_elev_m[i] = probe_elev_m[i-1];
155 double adj_slope[sizeof(slope)];
156 slope[0] = (probe_elev_m[0] - probe_elev_m[1]) / dist_probe_m[1];
157 slope[1] = (probe_elev_m[1] - probe_elev_m[2]) / dist_probe_m[2];
158 slope[2] = (probe_elev_m[2] - probe_elev_m[3]) / dist_probe_m[3];
159 slope[3] = (probe_elev_m[4] - probe_elev_m[0]) / -dist_probe_m[4];
161 for (unsigned i = 0; i < sizeof(slope)/sizeof(slope[0]); i++)
162 adj_slope[i] = sin(atan(5.0 * pow ( (fabs(slope[i])),1.7) ) ) *SG_SIGN<double>(slope[i]);
167 if ( adj_slope [2] < 0.0 ) {
173 if ( ( adj_slope [0] >= 0.0 ) && ( adj_slope [3] < 0.0 ) ) {
178 lift_factor = adj_slope[0]+adj_slope[1]+adj_slope[2]+adj_slope[3];
184 //user altitude above ground
185 double user_altitude_agl_m = _user_altitude_agl_ft_node->getDoubleValue() * SG_FEET_TO_METER;
188 double boundary2_m = 130.0; // in the lift
189 if (lift_factor < 0.0) { // in the sink
190 double highest_probe_temp= std::max ( probe_elev_m[1], probe_elev_m[2] );
191 double highest_probe_downwind_m= std::max ( highest_probe_temp, probe_elev_m[3] );
192 boundary2_m = highest_probe_downwind_m - probe_elev_m[0];
196 if ( user_altitude_agl_m < BOUNDARY1_m ) {
197 agl_factor = 0.5+0.5*user_altitude_agl_m /BOUNDARY1_m ;
198 } else if ( user_altitude_agl_m < boundary2_m ) {
201 agl_factor = exp(-(2 + probe_elev_m[0] / 2000) *
202 (user_altitude_agl_m - boundary2_m) / std::max(probe_elev_m[0],200.0));
205 double ground_wind_speed_mps = _surface_wind_speed_node->getDoubleValue() * SG_NM_TO_METER / 3600;
206 double lift_mps = lift_factor* ground_wind_speed_mps * agl_factor;
208 //the updraft, finally, in ft per second
209 strength = fgGetLowPass( strength, lift_mps * SG_METER_TO_FEET, dt );
210 _ridge_lift_fps_node->setDoubleValue( strength );