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.
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>
40 #include "environment.hxx"
44 ////////////////////////////////////////////////////////////////////////
46 ////////////////////////////////////////////////////////////////////////
48 // Calculated based on the ISA standard day, as found at e.g.
49 // http://www.av8n.com/physics/altimetry.htm
51 // Each line of data has 3 elements:
53 // temperature factor (dimensionless ratio of absolute temp),
54 // pressure factor (dimensionless ratio)
55 static double atmosphere_data[][3] = {
56 { -3000.00, 1.021, 1.1133 },
57 { 0.00, 1.000, 1.0000 },
58 { 2952.76, 0.980, 0.8978 },
59 { 5905.51, 0.959, 0.8042 },
60 { 8858.27, 0.939, 0.7187 },
61 { 11811.02, 0.919, 0.6407 },
62 { 14763.78, 0.898, 0.5697 },
63 { 17716.54, 0.878, 0.5052 },
64 { 20669.29, 0.858, 0.4468 },
65 { 23622.05, 0.838, 0.3940 },
66 { 26574.80, 0.817, 0.3463 },
67 { 29527.56, 0.797, 0.3034 },
68 { 32480.31, 0.777, 0.2649 },
69 { 35433.07, 0.756, 0.2305 },
70 { 38385.83, 0.752, 0.2000 },
71 { 41338.58, 0.752, 0.1736 },
72 { 44291.34, 0.752, 0.1506 },
73 { 47244.09, 0.752, 0.1307 },
74 { 50196.85, 0.752, 0.1134 },
75 { 53149.61, 0.752, 0.0984 },
76 { 56102.36, 0.752, 0.0854 },
77 { 59055.12, 0.752, 0.0741 },
78 { 62007.87, 0.752, 0.0643 },
79 { 65000.00, 0.752, 0.0557 },
80 { 68000.00, 0.754, 0.0482 },
81 { 71000.00, 0.758, 0.0418 },
82 { 74000.00, 0.761, 0.0362 },
83 { 77000.00, 0.764, 0.0314 },
84 { 80000.00, 0.767, 0.0273 },
85 { 83000.00, 0.770, 0.0237 },
86 { 86000.00, 0.773, 0.0206 },
87 { 89000.00, 0.777, 0.0179 },
88 { 92000.00, 0.780, 0.0156 },
89 { 95000.00, 0.783, 0.0135 },
90 { 98000.00, 0.786, 0.0118 },
91 { 101000.00, 0.789, 0.0103 },
95 static SGInterpTable * _temperature_degc_table = 0;
96 static SGInterpTable * _pressure_inhg_table = 0;
101 if (_temperature_degc_table != 0)
104 _temperature_degc_table = new SGInterpTable;
105 _pressure_inhg_table = new SGInterpTable;
107 for (int i = 0; atmosphere_data[i][0] != -1; i++) {
108 _temperature_degc_table->addEntry(atmosphere_data[i][0],
109 atmosphere_data[i][1]);
110 _pressure_inhg_table->addEntry(atmosphere_data[i][0],
111 atmosphere_data[i][2]);
117 ////////////////////////////////////////////////////////////////////////
118 // Implementation of FGEnvironment.
119 ////////////////////////////////////////////////////////////////////////
121 void FGEnvironment::_init()
124 visibility_m = 32000;
125 temperature_sea_level_degc = 15;
126 temperature_degc = 15;
127 dewpoint_sea_level_degc = 5; // guess
129 pressure_sea_level_inhg = 29.92;
130 pressure_inhg = 29.92;
131 turbulence_magnitude_norm = 0;
132 turbulence_rate_hz = 1;
133 wind_from_heading_deg = 0;
135 wind_from_north_fps = 0;
136 wind_from_east_fps = 0;
137 wind_from_down_fps = 0;
138 altitude_half_to_sun_m = 1000;
139 altitude_tropo_top_m = 10000;
142 _recalc_relative_humidity();
146 FGEnvironment::FGEnvironment()
151 FGEnvironment::FGEnvironment (const FGEnvironment &env)
157 FGEnvironment::~FGEnvironment()
162 FGEnvironment::copy (const FGEnvironment &env)
164 elevation_ft = env.elevation_ft;
165 visibility_m = env.visibility_m;
166 temperature_sea_level_degc = env.temperature_sea_level_degc;
167 temperature_degc = env.temperature_degc;
168 dewpoint_sea_level_degc = env.dewpoint_sea_level_degc;
169 dewpoint_degc = env.dewpoint_degc;
170 pressure_sea_level_inhg = env.pressure_sea_level_inhg;
171 wind_from_heading_deg = env.wind_from_heading_deg;
172 wind_speed_kt = env.wind_speed_kt;
173 wind_from_north_fps = env.wind_from_north_fps;
174 wind_from_east_fps = env.wind_from_east_fps;
175 wind_from_down_fps = env.wind_from_down_fps;
176 turbulence_magnitude_norm = env.turbulence_magnitude_norm;
177 turbulence_rate_hz = env.turbulence_rate_hz;
181 maybe_copy_value (FGEnvironment * env, const SGPropertyNode * node,
182 const char * name, void (FGEnvironment::*setter)(double))
184 const SGPropertyNode * child = node->getNode(name);
185 // fragile: depends on not being typed
187 if (child != 0 && child->hasValue() &&
188 child->getStringValue()[0] != '\0') {
189 (env->*setter)(child->getDoubleValue());
197 FGEnvironment::read (const SGPropertyNode * node)
199 maybe_copy_value(this, node, "visibility-m",
200 &FGEnvironment::set_visibility_m);
202 if (!maybe_copy_value(this, node, "temperature-sea-level-degc",
203 &FGEnvironment::set_temperature_sea_level_degc))
204 maybe_copy_value(this, node, "temperature-degc",
205 &FGEnvironment::set_temperature_degc);
207 if (!maybe_copy_value(this, node, "dewpoint-sea-level-degc",
208 &FGEnvironment::set_dewpoint_sea_level_degc))
209 maybe_copy_value(this, node, "dewpoint-degc",
210 &FGEnvironment::set_dewpoint_degc);
212 if (!maybe_copy_value(this, node, "pressure-sea-level-inhg",
213 &FGEnvironment::set_pressure_sea_level_inhg))
214 maybe_copy_value(this, node, "pressure-inhg",
215 &FGEnvironment::set_pressure_inhg);
217 maybe_copy_value(this, node, "wind-from-heading-deg",
218 &FGEnvironment::set_wind_from_heading_deg);
220 maybe_copy_value(this, node, "wind-speed-kt",
221 &FGEnvironment::set_wind_speed_kt);
223 maybe_copy_value(this, node, "elevation-ft",
224 &FGEnvironment::set_elevation_ft);
226 maybe_copy_value(this, node, "turbulence/magnitude-norm",
227 &FGEnvironment::set_turbulence_magnitude_norm);
229 maybe_copy_value(this, node, "turbulence/rate-hz",
230 &FGEnvironment::set_turbulence_rate_hz);
235 FGEnvironment::get_visibility_m () const
241 FGEnvironment::get_temperature_sea_level_degc () const
243 return temperature_sea_level_degc;
247 FGEnvironment::get_temperature_degc () const
249 return temperature_degc;
253 FGEnvironment::get_temperature_degf () const
255 return (temperature_degc * 9.0 / 5.0) + 32.0;
259 FGEnvironment::get_dewpoint_sea_level_degc () const
261 return dewpoint_sea_level_degc;
265 FGEnvironment::get_dewpoint_degc () const
267 return dewpoint_degc;
271 FGEnvironment::get_pressure_sea_level_inhg () const
273 return pressure_sea_level_inhg;
277 FGEnvironment::get_pressure_inhg () const
279 return pressure_inhg;
283 FGEnvironment::get_density_slugft3 () const
285 return density_slugft3;
289 FGEnvironment::get_relative_humidity () const
291 return relative_humidity;
295 FGEnvironment::get_density_tropo_avg_kgm3 () const
297 return density_tropo_avg_kgm3;
301 FGEnvironment::get_altitude_half_to_sun_m () const
303 return altitude_half_to_sun_m;
307 FGEnvironment::get_altitude_tropo_top_m () const
309 return altitude_tropo_top_m;
313 FGEnvironment::get_wind_from_heading_deg () const
315 return wind_from_heading_deg;
319 FGEnvironment::get_wind_speed_kt () const
321 return wind_speed_kt;
325 FGEnvironment::get_wind_from_north_fps () const
327 return wind_from_north_fps;
331 FGEnvironment::get_wind_from_east_fps () const
333 return wind_from_east_fps;
337 FGEnvironment::get_wind_from_down_fps () const
339 return wind_from_down_fps;
343 FGEnvironment::get_turbulence_magnitude_norm () const
345 if( sgEnviro.get_turbulence_enable_state() )
346 if (fgGetBool("/environment/params/real-world-weather-fetch") == true)
347 return sgEnviro.get_cloud_turbulence();
348 return turbulence_magnitude_norm;
352 FGEnvironment::get_turbulence_rate_hz () const
354 return turbulence_rate_hz;
358 FGEnvironment::get_elevation_ft () const
364 FGEnvironment::set_visibility_m (double v)
370 FGEnvironment::set_temperature_sea_level_degc (double t)
372 temperature_sea_level_degc = t;
373 if (dewpoint_sea_level_degc > t)
374 dewpoint_sea_level_degc = t;
375 _recalc_alt_temperature();
380 FGEnvironment::set_temperature_degc (double t)
382 temperature_degc = t;
383 _recalc_sl_temperature();
385 _recalc_relative_humidity();
389 FGEnvironment::set_dewpoint_sea_level_degc (double t)
391 dewpoint_sea_level_degc = t;
392 if (temperature_sea_level_degc < t)
393 temperature_sea_level_degc = t;
394 _recalc_alt_dewpoint();
399 FGEnvironment::set_dewpoint_degc (double t)
402 _recalc_sl_dewpoint();
404 _recalc_relative_humidity();
408 FGEnvironment::set_pressure_sea_level_inhg (double p)
410 pressure_sea_level_inhg = p;
411 _recalc_alt_pressure();
416 FGEnvironment::set_pressure_inhg (double p)
419 _recalc_sl_pressure();
424 FGEnvironment::set_wind_from_heading_deg (double h)
426 wind_from_heading_deg = h;
431 FGEnvironment::set_wind_speed_kt (double s)
438 FGEnvironment::set_wind_from_north_fps (double n)
440 wind_from_north_fps = n;
445 FGEnvironment::set_wind_from_east_fps (double e)
447 wind_from_east_fps = e;
452 FGEnvironment::set_wind_from_down_fps (double d)
454 wind_from_down_fps = d;
459 FGEnvironment::set_turbulence_magnitude_norm (double t)
461 turbulence_magnitude_norm = t;
465 FGEnvironment::set_turbulence_rate_hz (double r)
467 turbulence_rate_hz = r;
471 FGEnvironment::set_elevation_ft (double e)
474 _recalc_alt_temperature();
475 _recalc_alt_dewpoint();
476 _recalc_alt_pressure();
478 _recalc_relative_humidity();
482 FGEnvironment::set_altitude_half_to_sun_m (double alt)
484 altitude_half_to_sun_m = alt;
485 _recalc_density_tropo_avg_kgm3();
489 FGEnvironment::set_altitude_tropo_top_m (double alt)
491 altitude_tropo_top_m = alt;
492 _recalc_density_tropo_avg_kgm3();
497 FGEnvironment::_recalc_hdgspd ()
501 if (wind_from_east_fps == 0) {
502 angle_rad = (wind_from_north_fps >= 0 ? SGD_PI_2 : -SGD_PI_2);
504 angle_rad = atan(wind_from_north_fps/wind_from_east_fps);
506 wind_from_heading_deg = angle_rad * SGD_RADIANS_TO_DEGREES;
507 if (wind_from_east_fps >= 0)
508 wind_from_heading_deg = 90 - wind_from_heading_deg;
510 wind_from_heading_deg = 270 - wind_from_heading_deg;
513 // FIXME: Windspeed can become negative with these formulas.
514 // which can cause problems for animations that rely
515 // on the windspeed property.
517 wind_speed_kt = fabs(wind_from_east_fps
518 * SG_METER_TO_NM * SG_FEET_TO_METER * 3600);
520 wind_speed_kt = (wind_from_north_fps / sin(angle_rad))
521 * SG_METER_TO_NM * SG_FEET_TO_METER * 3600;
523 wind_speed_kt = sqrt(wind_from_north_fps * wind_from_north_fps +
524 wind_from_east_fps * wind_from_east_fps)
525 * SG_METER_TO_NM * SG_FEET_TO_METER * 3600;
530 FGEnvironment::_recalc_ne ()
533 wind_speed_kt * SG_NM_TO_METER * SG_METER_TO_FEET * (1.0/3600);
535 wind_from_north_fps = speed_fps *
536 cos(wind_from_heading_deg * SGD_DEGREES_TO_RADIANS);
537 wind_from_east_fps = speed_fps *
538 sin(wind_from_heading_deg * SGD_DEGREES_TO_RADIANS);
542 FGEnvironment::_recalc_sl_temperature ()
544 // If we're in the stratosphere, leave sea-level temp alone
545 if (elevation_ft < 38000) {
546 temperature_sea_level_degc = (temperature_degc + 273.15)
547 / _temperature_degc_table->interpolate(elevation_ft)
553 FGEnvironment::_recalc_alt_temperature ()
555 if (elevation_ft < 38000) {
556 temperature_degc = (temperature_sea_level_degc + 273.15) *
557 _temperature_degc_table->interpolate(elevation_ft) - 273.15;
559 temperature_degc = -56.49; // Stratosphere is constant
564 FGEnvironment::_recalc_sl_dewpoint ()
567 // FIXME: this will work only for low
569 dewpoint_sea_level_degc = dewpoint_degc + (elevation_ft * .0002);
570 if (dewpoint_sea_level_degc > temperature_sea_level_degc)
571 dewpoint_sea_level_degc = temperature_sea_level_degc;
575 FGEnvironment::_recalc_alt_dewpoint ()
578 // FIXME: this will work only for low
580 dewpoint_degc = dewpoint_sea_level_degc + (elevation_ft * .0002);
581 if (dewpoint_degc > temperature_degc)
582 dewpoint_degc = temperature_degc;
586 FGEnvironment::_recalc_sl_pressure ()
588 pressure_sea_level_inhg =
589 pressure_inhg / _pressure_inhg_table->interpolate(elevation_ft);
593 FGEnvironment::_recalc_alt_pressure ()
596 pressure_sea_level_inhg * _pressure_inhg_table->interpolate(elevation_ft);
600 FGEnvironment::_recalc_density ()
602 double pressure_psf = pressure_inhg * 70.7487;
604 // adjust for humidity
605 // calculations taken from USA Today (oops!) at
606 // http://www.usatoday.com/weather/basics/density-calculations.htm
607 double temperature_degk = temperature_degc + 273.15;
608 double pressure_mb = pressure_inhg * 33.86;
609 double vapor_pressure_mb =
610 6.11 * pow(10.0, 7.5 * dewpoint_degc / (237.7 + dewpoint_degc));
611 double virtual_temperature_degk = temperature_degk / (1 - (vapor_pressure_mb / pressure_mb) * (1.0 - 0.622));
612 double virtual_temperature_degr = virtual_temperature_degk * 1.8;
614 density_slugft3 = pressure_psf / (virtual_temperature_degr * 1718);
615 _recalc_density_tropo_avg_kgm3();
618 // This is used to calculate the average density on the path
619 // of sunlight to the observer for calculating sun-color
621 FGEnvironment::_recalc_density_tropo_avg_kgm3 ()
623 double pressure_mb = pressure_inhg * 33.86;
624 double vaporpressure = 6.11 * pow(10.0, ((7.5 * dewpoint_degc) / (237.7 + dewpoint_degc)));
626 double virtual_temp = (temperature_degc + 273.15) / (1 - 0.379 * (vaporpressure/pressure_mb));
628 double density_half = (100 * pressure_mb * exp(-altitude_half_to_sun_m / 8000))
629 / (287.05 * virtual_temp);
630 double density_tropo = (100 * pressure_mb * exp((-1 * altitude_tropo_top_m) / 8000))
631 / ( 287.05 * virtual_temp);
633 density_tropo_avg_kgm3 = ((density_slugft3 * 515.379) + density_half + density_tropo) / 3;
637 FGEnvironment::_recalc_relative_humidity ()
639 double vaporpressure = 6.11 * pow(10.0, ((7.5 * dewpoint_degc) / ( 237.7 + dewpoint_degc)));
640 double sat_vaporpressure = 6.11 * pow(10.0, ((7.5 * temperature_degc)
641 / ( 237.7 + temperature_degc)) );
642 relative_humidity = 100 * vaporpressure / sat_vaporpressure ;
647 ////////////////////////////////////////////////////////////////////////
649 ////////////////////////////////////////////////////////////////////////
652 do_interp (double a, double b, double fraction)
654 double retval = (a + ((b - a) * fraction));
659 do_interp_deg (double a, double b, double fraction)
663 if (fabs(b-a) > 180) {
669 return fmod(do_interp(a, b, fraction), 360);
673 interpolate (const FGEnvironment * env1, const FGEnvironment * env2,
674 double fraction, FGEnvironment * result)
676 result->set_visibility_m
677 (do_interp(env1->get_visibility_m(),
678 env2->get_visibility_m(),
681 result->set_temperature_sea_level_degc
682 (do_interp(env1->get_temperature_sea_level_degc(),
683 env2->get_temperature_sea_level_degc(),
686 result->set_dewpoint_degc
687 (do_interp(env1->get_dewpoint_sea_level_degc(),
688 env2->get_dewpoint_sea_level_degc(),
691 result->set_pressure_sea_level_inhg
692 (do_interp(env1->get_pressure_sea_level_inhg(),
693 env2->get_pressure_sea_level_inhg(),
696 result->set_wind_from_heading_deg
697 (do_interp_deg(env1->get_wind_from_heading_deg(),
698 env2->get_wind_from_heading_deg(),
701 result->set_wind_speed_kt
702 (do_interp(env1->get_wind_speed_kt(),
703 env2->get_wind_speed_kt(),
706 result->set_elevation_ft
707 (do_interp(env1->get_elevation_ft(),
708 env2->get_elevation_ft(),
711 result->set_turbulence_magnitude_norm
712 (do_interp(env1->get_turbulence_magnitude_norm(),
713 env2->get_turbulence_magnitude_norm(),
716 result->set_turbulence_rate_hz
717 (do_interp(env1->get_turbulence_rate_hz(),
718 env2->get_turbulence_rate_hz(),
722 // end of environment.cxx