1 // environment.cxx -- routines to model the natural environment
3 // Written by David Megginson, started February 2002.
5 // Copyright (C) 2002 David Megginson - david@megginson.com
7 // This program is free software; you can redistribute it and/or
8 // modify it under the terms of the GNU General Public License as
9 // published by the Free Software Foundation; either version 2 of the
10 // License, or (at your option) any later version.
12 // This program is distributed in the hope that it will be useful, but
13 // WITHOUT ANY WARRANTY; without even the implied warranty of
14 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 // General Public License for more details.
17 // You should have received a copy of the GNU General Public License
18 // along with this program; if not, write to the Free Software
19 // Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
30 #include <boost/tuple/tuple.hpp>
32 #include <simgear/constants.h>
33 #include <simgear/debug/logstream.hxx>
34 #include <simgear/math/interpolater.hxx>
35 #include <simgear/props/props.hxx>
36 #include <simgear/environment/visual_enviro.hxx>
38 #include <Main/fg_props.hxx>
41 #include "environment.hxx"
42 #include "atmosphere.hxx"
45 ////////////////////////////////////////////////////////////////////////
47 ////////////////////////////////////////////////////////////////////////
51 // Calculated based on the ISA standard day, as found at e.g.
52 // http://www.av8n.com/physics/altimetry.htm
54 // Each line of data has 3 elements:
56 // temperature factor (dimensionless ratio of absolute temp),
57 // pressure factor (dimensionless ratio)
58 static double atmosphere_data[][3] = {
59 { -3000.00, 1.021, 1.1133 },
60 { 0.00, 1.000, 1.0000 },
61 { 2952.76, 0.980, 0.8978 },
62 { 5905.51, 0.959, 0.8042 },
63 { 8858.27, 0.939, 0.7187 },
64 { 11811.02, 0.919, 0.6407 },
65 { 14763.78, 0.898, 0.5697 },
66 { 17716.54, 0.878, 0.5052 },
67 { 20669.29, 0.858, 0.4468 },
68 { 23622.05, 0.838, 0.3940 },
69 { 26574.80, 0.817, 0.3463 },
70 { 29527.56, 0.797, 0.3034 },
71 { 32480.31, 0.777, 0.2649 },
72 { 35433.07, 0.756, 0.2305 },
73 { 38385.83, 0.752, 0.2000 },
74 { 41338.58, 0.752, 0.1736 },
75 { 44291.34, 0.752, 0.1506 },
76 { 47244.09, 0.752, 0.1307 },
77 { 50196.85, 0.752, 0.1134 },
78 { 53149.61, 0.752, 0.0984 },
79 { 56102.36, 0.752, 0.0854 },
80 { 59055.12, 0.752, 0.0741 },
81 { 62007.87, 0.752, 0.0643 },
82 { 65000.00, 0.752, 0.0557 },
83 { 68000.00, 0.754, 0.0482 },
84 { 71000.00, 0.758, 0.0418 },
85 { 74000.00, 0.761, 0.0362 },
86 { 77000.00, 0.764, 0.0314 },
87 { 80000.00, 0.767, 0.0273 },
88 { 83000.00, 0.770, 0.0237 },
89 { 86000.00, 0.773, 0.0206 },
90 { 89000.00, 0.777, 0.0179 },
91 { 92000.00, 0.780, 0.0156 },
92 { 95000.00, 0.783, 0.0135 },
93 { 98000.00, 0.786, 0.0118 },
94 { 101000.00, 0.789, 0.0103 },
98 static SGInterpTable * _temperature_degc_table = 0;
99 static SGInterpTable * _pressure_inhg_table = 0;
104 if (_temperature_degc_table != 0)
107 _temperature_degc_table = new SGInterpTable;
108 _pressure_inhg_table = new SGInterpTable;
110 for (int i = 0; atmosphere_data[i][0] != -1; i++) {
111 _temperature_degc_table->addEntry(atmosphere_data[i][0],
112 atmosphere_data[i][1]);
113 _pressure_inhg_table->addEntry(atmosphere_data[i][0],
114 atmosphere_data[i][2]);
120 ////////////////////////////////////////////////////////////////////////
121 // Implementation of FGEnvironment.
122 ////////////////////////////////////////////////////////////////////////
124 void FGEnvironment::_init()
127 visibility_m = 32000;
128 temperature_sea_level_degc = 15;
129 temperature_degc = 15;
130 dewpoint_sea_level_degc = 5; // guess
132 pressure_sea_level_inhg = 29.92;
133 pressure_inhg = 29.92;
134 turbulence_magnitude_norm = 0;
135 turbulence_rate_hz = 1;
136 wind_from_heading_deg = 0;
138 wind_from_north_fps = 0;
139 wind_from_east_fps = 0;
140 wind_from_down_fps = 0;
141 thermal_lift_fps = 0;
143 local_weather_lift_fps=0;
144 altitude_half_to_sun_m = 1000;
145 altitude_tropo_top_m = 10000;
150 _recalc_relative_humidity();
154 FGEnvironment::FGEnvironment()
159 FGEnvironment::FGEnvironment (const FGEnvironment &env)
165 FGEnvironment::~FGEnvironment()
170 FGEnvironment::copy (const FGEnvironment &env)
172 elevation_ft = env.elevation_ft;
173 visibility_m = env.visibility_m;
174 temperature_sea_level_degc = env.temperature_sea_level_degc;
175 temperature_degc = env.temperature_degc;
176 dewpoint_sea_level_degc = env.dewpoint_sea_level_degc;
177 dewpoint_degc = env.dewpoint_degc;
178 pressure_sea_level_inhg = env.pressure_sea_level_inhg;
179 wind_from_heading_deg = env.wind_from_heading_deg;
180 wind_speed_kt = env.wind_speed_kt;
181 wind_from_north_fps = env.wind_from_north_fps;
182 wind_from_east_fps = env.wind_from_east_fps;
183 wind_from_down_fps = env.wind_from_down_fps;
184 thermal_lift_fps = env.thermal_lift_fps;
185 ridge_lift_fps= env.ridge_lift_fps;
186 local_weather_lift_fps = env.local_weather_lift_fps;
187 turbulence_magnitude_norm = env.turbulence_magnitude_norm;
188 turbulence_rate_hz = env.turbulence_rate_hz;
192 maybe_copy_value (FGEnvironment * env, const SGPropertyNode * node,
193 const char * name, void (FGEnvironment::*setter)(double))
195 const SGPropertyNode * child = node->getNode(name);
196 // fragile: depends on not being typed
198 if (child != 0 && child->hasValue() &&
199 child->getStringValue()[0] != '\0') {
200 (env->*setter)(child->getDoubleValue());
208 FGEnvironment::read (const SGPropertyNode * node)
210 bool live_update = set_live_update( false );
211 maybe_copy_value(this, node, "visibility-m",
212 &FGEnvironment::set_visibility_m);
214 if (!maybe_copy_value(this, node, "temperature-sea-level-degc",
215 &FGEnvironment::set_temperature_sea_level_degc))
216 maybe_copy_value(this, node, "temperature-degc",
217 &FGEnvironment::set_temperature_degc);
219 if (!maybe_copy_value(this, node, "dewpoint-sea-level-degc",
220 &FGEnvironment::set_dewpoint_sea_level_degc))
221 maybe_copy_value(this, node, "dewpoint-degc",
222 &FGEnvironment::set_dewpoint_degc);
224 if (!maybe_copy_value(this, node, "pressure-sea-level-inhg",
225 &FGEnvironment::set_pressure_sea_level_inhg))
226 maybe_copy_value(this, node, "pressure-inhg",
227 &FGEnvironment::set_pressure_inhg);
229 maybe_copy_value(this, node, "wind-from-heading-deg",
230 &FGEnvironment::set_wind_from_heading_deg);
232 maybe_copy_value(this, node, "wind-speed-kt",
233 &FGEnvironment::set_wind_speed_kt);
235 maybe_copy_value(this, node, "elevation-ft",
236 &FGEnvironment::set_elevation_ft);
238 maybe_copy_value(this, node, "turbulence/magnitude-norm",
239 &FGEnvironment::set_turbulence_magnitude_norm);
241 maybe_copy_value(this, node, "turbulence/rate-hz",
242 &FGEnvironment::set_turbulence_rate_hz);
244 // calculate derived properties here to avoid duplicate expensive computations
247 _recalc_alt_dewpoint();
249 _recalc_relative_humidity();
251 set_live_update(live_update);
256 FGEnvironment::get_visibility_m () const
262 FGEnvironment::get_temperature_sea_level_degc () const
264 return temperature_sea_level_degc;
268 FGEnvironment::get_temperature_degc () const
270 return temperature_degc;
274 FGEnvironment::get_temperature_degf () const
276 return (temperature_degc * 9.0 / 5.0) + 32.0;
280 FGEnvironment::get_dewpoint_sea_level_degc () const
282 return dewpoint_sea_level_degc;
286 FGEnvironment::get_dewpoint_degc () const
288 return dewpoint_degc;
292 FGEnvironment::get_pressure_sea_level_inhg () const
294 return pressure_sea_level_inhg;
298 FGEnvironment::get_pressure_inhg () const
300 return pressure_inhg;
304 FGEnvironment::get_density_slugft3 () const
306 return density_slugft3;
310 FGEnvironment::get_relative_humidity () const
312 return relative_humidity;
316 FGEnvironment::get_density_tropo_avg_kgm3 () const
318 return density_tropo_avg_kgm3;
322 FGEnvironment::get_altitude_half_to_sun_m () const
324 return altitude_half_to_sun_m;
328 FGEnvironment::get_altitude_tropo_top_m () const
330 return altitude_tropo_top_m;
334 FGEnvironment::get_wind_from_heading_deg () const
336 return wind_from_heading_deg;
340 FGEnvironment::get_wind_speed_kt () const
342 return wind_speed_kt;
346 FGEnvironment::get_wind_from_north_fps () const
348 return wind_from_north_fps;
352 FGEnvironment::get_wind_from_east_fps () const
354 return wind_from_east_fps;
358 FGEnvironment::get_wind_from_down_fps () const
360 return wind_from_down_fps;
364 FGEnvironment::get_thermal_lift_fps () const
366 return thermal_lift_fps;
370 FGEnvironment::get_ridge_lift_fps () const
372 return ridge_lift_fps;
376 FGEnvironment::get_local_weather_lift_fps () const
378 return local_weather_lift_fps;
382 FGEnvironment::get_turbulence_magnitude_norm () const
384 if( sgEnviro.get_turbulence_enable_state() )
385 if (fgGetBool("/environment/params/real-world-weather-fetch") == true)
386 return sgEnviro.get_cloud_turbulence();
387 return turbulence_magnitude_norm;
391 FGEnvironment::get_turbulence_rate_hz () const
393 return turbulence_rate_hz;
397 FGEnvironment::get_elevation_ft () const
403 FGEnvironment::set_visibility_m (double v)
409 FGEnvironment::set_temperature_sea_level_degc (double t)
411 temperature_sea_level_degc = t;
412 if (dewpoint_sea_level_degc > t)
413 dewpoint_sea_level_degc = t;
421 FGEnvironment::set_temperature_degc (double t)
423 temperature_degc = t;
425 _recalc_sl_temperature();
426 _recalc_sl_pressure();
429 _recalc_relative_humidity();
434 FGEnvironment::set_dewpoint_sea_level_degc (double t)
436 dewpoint_sea_level_degc = t;
437 if (temperature_sea_level_degc < t)
438 temperature_sea_level_degc = t;
440 _recalc_alt_dewpoint();
446 FGEnvironment::set_dewpoint_degc (double t)
450 _recalc_sl_dewpoint();
452 _recalc_relative_humidity();
457 FGEnvironment::set_pressure_sea_level_inhg (double p)
459 pressure_sea_level_inhg = p;
467 FGEnvironment::set_pressure_inhg (double p)
471 _recalc_sl_pressure();
477 FGEnvironment::set_wind_from_heading_deg (double h)
479 wind_from_heading_deg = h;
486 FGEnvironment::set_wind_speed_kt (double s)
495 FGEnvironment::set_wind_from_north_fps (double n)
497 wind_from_north_fps = n;
504 FGEnvironment::set_wind_from_east_fps (double e)
506 wind_from_east_fps = e;
513 FGEnvironment::set_wind_from_down_fps (double d)
515 wind_from_down_fps = d;
522 FGEnvironment::set_thermal_lift_fps (double th)
524 thermal_lift_fps = th;
531 FGEnvironment::set_ridge_lift_fps (double ri)
540 FGEnvironment::set_local_weather_lift_fps (double lwl)
542 local_weather_lift_fps = lwl;
549 FGEnvironment::set_turbulence_magnitude_norm (double t)
551 turbulence_magnitude_norm = t;
555 FGEnvironment::set_turbulence_rate_hz (double r)
557 turbulence_rate_hz = r;
561 FGEnvironment::set_elevation_ft (double e)
566 _recalc_alt_dewpoint();
568 _recalc_relative_humidity();
573 FGEnvironment::set_altitude_half_to_sun_m (double alt)
575 altitude_half_to_sun_m = alt;
577 _recalc_density_tropo_avg_kgm3();
582 FGEnvironment::set_altitude_tropo_top_m (double alt)
584 altitude_tropo_top_m = alt;
586 _recalc_density_tropo_avg_kgm3();
592 FGEnvironment::_recalc_hdgspd ()
596 if (wind_from_east_fps == 0) {
597 angle_rad = (wind_from_north_fps >= 0 ? SGD_PI_2 : -SGD_PI_2);
599 angle_rad = atan(wind_from_north_fps/wind_from_east_fps);
601 wind_from_heading_deg = angle_rad * SGD_RADIANS_TO_DEGREES;
602 if (wind_from_east_fps >= 0)
603 wind_from_heading_deg = 90 - wind_from_heading_deg;
605 wind_from_heading_deg = 270 - wind_from_heading_deg;
608 // FIXME: Windspeed can become negative with these formulas.
609 // which can cause problems for animations that rely
610 // on the windspeed property.
612 wind_speed_kt = fabs(wind_from_east_fps
613 * SG_METER_TO_NM * SG_FEET_TO_METER * 3600);
615 wind_speed_kt = (wind_from_north_fps / sin(angle_rad))
616 * SG_METER_TO_NM * SG_FEET_TO_METER * 3600;
618 wind_speed_kt = sqrt(wind_from_north_fps * wind_from_north_fps +
619 wind_from_east_fps * wind_from_east_fps)
620 * SG_METER_TO_NM * SG_FEET_TO_METER * 3600;
625 FGEnvironment::_recalc_ne ()
628 wind_speed_kt * SG_NM_TO_METER * SG_METER_TO_FEET * (1.0/3600);
630 wind_from_north_fps = speed_fps *
631 cos(wind_from_heading_deg * SGD_DEGREES_TO_RADIANS);
632 wind_from_east_fps = speed_fps *
633 sin(wind_from_heading_deg * SGD_DEGREES_TO_RADIANS);
637 FGEnvironment::_recalc_updraft ()
639 wind_from_down_fps = thermal_lift_fps + ridge_lift_fps + local_weather_lift_fps ;
642 // Intended to help with the interpretation of METAR data,
643 // not for random in-flight outside-air temperatures.
645 FGEnvironment::_recalc_sl_temperature ()
650 SG_LOG(SG_GENERAL, SG_DEBUG, "recalc_sl_temperature: using "
651 << temperature_degc << " @ " << elevation_ft << " :: " << this);
655 if (elevation_ft >= ISA_def[1].height) {
656 SG_LOG(SG_GENERAL, SG_ALERT, "recalc_sl_temperature: "
657 << "valid only in troposphere, not " << elevation_ft);
661 // Clamp: temperature of the stratosphere, in degrees C:
662 double t_strato = ISA_def[1].temp - atmodel::freezing;
663 if (temperature_degc < t_strato) temperature_sea_level_degc = t_strato;
664 else temperature_sea_level_degc =
665 temperature_degc + elevation_ft * atmodel::foot * ISA_def[0].lapse;
667 // Alternative implemenation:
668 // else temperature_sea_level_inhg = T_layer(0., elevation_ft * foot,
669 // pressure_inhg * inHg, temperature_degc + freezing, ISA_def[0].lapse) - freezing;
673 FGEnvironment::_recalc_sl_dewpoint ()
676 // FIXME: this will work only for low
678 dewpoint_sea_level_degc = dewpoint_degc + (elevation_ft * .0002);
679 if (dewpoint_sea_level_degc > temperature_sea_level_degc)
680 dewpoint_sea_level_degc = temperature_sea_level_degc;
684 FGEnvironment::_recalc_alt_dewpoint ()
687 // FIXME: this will work only for low
689 dewpoint_degc = dewpoint_sea_level_degc + (elevation_ft * .0002);
690 if (dewpoint_degc > temperature_degc)
691 dewpoint_degc = temperature_degc;
695 FGEnvironment::_recalc_sl_pressure ()
697 using namespace atmodel;
700 SG_LOG(SG_GENERAL, SG_ALERT, "recalc_sl_pressure: using "
701 << pressure_inhg << " and "
702 << temperature_degc << " @ " << elevation_ft << " :: " << this);
705 pressure_sea_level_inhg = P_layer(0., elevation_ft * foot,
706 pressure_inhg * inHg, temperature_degc + freezing, ISA_def[0].lapse) / inHg;
709 // This gets called at frame rate, to account for the aircraft's
710 // changing altitude.
711 // Called by set_elevation_ft() which is called by FGEnvironmentMgr::update
714 FGEnvironment::_recalc_alt_pt ()
716 using namespace atmodel;
720 if (++count % 1000 == 0) {
721 SG_LOG(SG_GENERAL, SG_ALERT,
722 "recalc_alt_pt for: " << elevation_ft
723 << " using " << pressure_sea_level_inhg
724 << " and " << temperature_sea_level_degc
731 boost::tie(press, temp) = PT_vs_hpt(elevation_ft * foot,
732 pressure_sea_level_inhg * inHg, temperature_sea_level_degc + freezing);
733 temperature_degc = temp - freezing;
734 pressure_inhg = press / inHg;
738 FGEnvironment::_recalc_density ()
740 double pressure_psf = pressure_inhg * 70.7487;
742 // adjust for humidity
743 // calculations taken from USA Today (oops!) at
744 // http://www.usatoday.com/weather/basics/density-calculations.htm
745 double temperature_degk = temperature_degc + 273.15;
746 double pressure_mb = pressure_inhg * 33.86;
747 double vapor_pressure_mb =
748 6.11 * pow(10.0, 7.5 * dewpoint_degc / (237.7 + dewpoint_degc));
749 double virtual_temperature_degk = temperature_degk / (1 - (vapor_pressure_mb / pressure_mb) * (1.0 - 0.622));
750 double virtual_temperature_degr = virtual_temperature_degk * 1.8;
752 density_slugft3 = pressure_psf / (virtual_temperature_degr * 1718);
753 _recalc_density_tropo_avg_kgm3();
756 // This is used to calculate the average density on the path
757 // of sunlight to the observer for calculating sun-color
759 FGEnvironment::_recalc_density_tropo_avg_kgm3 ()
761 double pressure_mb = pressure_inhg * 33.86;
762 double vaporpressure = 6.11 * pow(10.0, ((7.5 * dewpoint_degc) / (237.7 + dewpoint_degc)));
764 double virtual_temp = (temperature_degc + 273.15) / (1 - 0.379 * (vaporpressure/pressure_mb));
766 double density_half = (100 * pressure_mb * exp(-altitude_half_to_sun_m / 8000))
767 / (287.05 * virtual_temp);
768 double density_tropo = (100 * pressure_mb * exp((-1 * altitude_tropo_top_m) / 8000))
769 / ( 287.05 * virtual_temp);
771 density_tropo_avg_kgm3 = ((density_slugft3 * 515.379) + density_half + density_tropo) / 3;
775 FGEnvironment::_recalc_relative_humidity ()
778 double vaporpressure = 6.11 * pow(10.0, ((7.5 * dewpoint_degc) / ( 237.7 + dewpoint_degc)));
779 double sat_vaporpressure = 6.11 * pow(10.0, ((7.5 * temperature_degc)
780 / ( 237.7 + temperature_degc)) );
781 relative_humidity = 100 * vaporpressure / sat_vaporpressure ;
783 with a little algebra, this gets the same result and spares two multiplications and one pow()
785 double a = (7.5 * dewpoint_degc) / ( 237.7 + dewpoint_degc);
786 double b = (7.5 * temperature_degc) / ( 237.7 + temperature_degc);
787 relative_humidity = 100 * pow(10.0,a-b);
791 FGEnvironment::set_live_update( bool _live_update )
793 bool b = live_update;
794 live_update = _live_update;
799 ////////////////////////////////////////////////////////////////////////
801 ////////////////////////////////////////////////////////////////////////
804 do_interp (double a, double b, double fraction)
806 double retval = (a + ((b - a) * fraction));
811 do_interp_deg (double a, double b, double fraction)
815 if (fabs(b-a) > 180) {
821 return fmod(do_interp(a, b, fraction), 360);
825 interpolate (const FGEnvironment * env1, const FGEnvironment * env2,
826 double fraction, FGEnvironment * result)
828 // don't calculate each internal property every time we set a single value
829 // we trigger that at the end of the interpolation process
830 bool live_update = result->set_live_update( false );
832 result->set_visibility_m
833 (do_interp(env1->get_visibility_m(),
834 env2->get_visibility_m(),
837 result->set_temperature_sea_level_degc
838 (do_interp(env1->get_temperature_sea_level_degc(),
839 env2->get_temperature_sea_level_degc(),
842 result->set_dewpoint_sea_level_degc
843 (do_interp(env1->get_dewpoint_sea_level_degc(),
844 env2->get_dewpoint_sea_level_degc(),
847 result->set_pressure_sea_level_inhg
848 (do_interp(env1->get_pressure_sea_level_inhg(),
849 env2->get_pressure_sea_level_inhg(),
852 result->set_wind_from_heading_deg
853 (do_interp_deg(env1->get_wind_from_heading_deg(),
854 env2->get_wind_from_heading_deg(),
857 result->set_wind_speed_kt
858 (do_interp(env1->get_wind_speed_kt(),
859 env2->get_wind_speed_kt(),
862 result->set_elevation_ft
863 (do_interp(env1->get_elevation_ft(),
864 env2->get_elevation_ft(),
867 result->set_turbulence_magnitude_norm
868 (do_interp(env1->get_turbulence_magnitude_norm(),
869 env2->get_turbulence_magnitude_norm(),
872 result->set_turbulence_rate_hz
873 (do_interp(env1->get_turbulence_rate_hz(),
874 env2->get_turbulence_rate_hz(),
877 // calculate derived properties here to avoid duplicate expensive computations
878 result->_recalc_ne();
879 result->_recalc_alt_pt();
880 result->_recalc_alt_dewpoint();
881 result->_recalc_density();
882 result->_recalc_relative_humidity();
884 result->set_live_update(live_update);
887 // end of environment.cxx