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.
36 #include <simgear/constants.h>
37 #include <simgear/debug/logstream.hxx>
38 #include <simgear/math/interpolater.hxx>
39 #include <simgear/props/props.hxx>
40 #include <simgear/environment/visual_enviro.hxx>
42 #include <Main/fg_props.hxx>
44 #include "environment.hxx"
48 ////////////////////////////////////////////////////////////////////////
50 ////////////////////////////////////////////////////////////////////////
52 // Calculated based on the ISA standard day, as found at e.g.
53 // http://www.av8n.com/physics/altimetry.htm
55 // Each line of data has 3 elements:
57 // temperature factor (dimensionless ratio of absolute temp),
58 // pressure factor (dimensionless ratio)
59 static double atmosphere_data[][3] = {
60 { -3000.00, 1.021, 1.1133 },
61 { 0.00, 1.000, 1.0000 },
62 { 2952.76, 0.980, 0.8978 },
63 { 5905.51, 0.959, 0.8042 },
64 { 8858.27, 0.939, 0.7187 },
65 { 11811.02, 0.919, 0.6407 },
66 { 14763.78, 0.898, 0.5697 },
67 { 17716.54, 0.878, 0.5052 },
68 { 20669.29, 0.858, 0.4468 },
69 { 23622.05, 0.838, 0.3940 },
70 { 26574.80, 0.817, 0.3463 },
71 { 29527.56, 0.797, 0.3034 },
72 { 32480.31, 0.777, 0.2649 },
73 { 35433.07, 0.756, 0.2305 },
74 { 38385.83, 0.752, 0.2000 },
75 { 41338.58, 0.752, 0.1736 },
76 { 44291.34, 0.752, 0.1506 },
77 { 47244.09, 0.752, 0.1307 },
78 { 50196.85, 0.752, 0.1134 },
79 { 53149.61, 0.752, 0.0984 },
80 { 56102.36, 0.752, 0.0854 },
81 { 59055.12, 0.752, 0.0741 },
82 { 62007.87, 0.752, 0.0643 },
83 { 65000.00, 0.752, 0.0557 },
84 { 68000.00, 0.754, 0.0482 },
85 { 71000.00, 0.758, 0.0418 },
86 { 74000.00, 0.761, 0.0362 },
87 { 77000.00, 0.764, 0.0314 },
88 { 80000.00, 0.767, 0.0273 },
89 { 83000.00, 0.770, 0.0237 },
90 { 86000.00, 0.773, 0.0206 },
91 { 89000.00, 0.777, 0.0179 },
92 { 92000.00, 0.780, 0.0156 },
93 { 95000.00, 0.783, 0.0135 },
94 { 98000.00, 0.786, 0.0118 },
95 { 101000.00, 0.789, 0.0103 },
99 static SGInterpTable * _temperature_degc_table = 0;
100 static SGInterpTable * _pressure_inhg_table = 0;
105 if (_temperature_degc_table != 0)
108 _temperature_degc_table = new SGInterpTable;
109 _pressure_inhg_table = new SGInterpTable;
111 for (int i = 0; atmosphere_data[i][0] != -1; i++) {
112 _temperature_degc_table->addEntry(atmosphere_data[i][0],
113 atmosphere_data[i][1]);
114 _pressure_inhg_table->addEntry(atmosphere_data[i][0],
115 atmosphere_data[i][2]);
121 ////////////////////////////////////////////////////////////////////////
122 // Implementation of FGEnvironment.
123 ////////////////////////////////////////////////////////////////////////
125 FGEnvironment::FGEnvironment()
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 altitude_half_to_sun_m(1000),
142 altitude_tropo_top_m(10000)
146 _recalc_relative_humidity();
149 FGEnvironment::FGEnvironment (const FGEnvironment &env)
155 FGEnvironment::~FGEnvironment()
160 FGEnvironment::copy (const FGEnvironment &env)
162 elevation_ft = env.elevation_ft;
163 visibility_m = env.visibility_m;
164 temperature_sea_level_degc = env.temperature_sea_level_degc;
165 temperature_degc = env.temperature_degc;
166 dewpoint_sea_level_degc = env.dewpoint_sea_level_degc;
167 dewpoint_degc = env.dewpoint_degc;
168 pressure_sea_level_inhg = env.pressure_sea_level_inhg;
169 wind_from_heading_deg = env.wind_from_heading_deg;
170 wind_speed_kt = env.wind_speed_kt;
171 wind_from_north_fps = env.wind_from_north_fps;
172 wind_from_east_fps = env.wind_from_east_fps;
173 wind_from_down_fps = env.wind_from_down_fps;
174 turbulence_magnitude_norm = env.turbulence_magnitude_norm;
175 turbulence_rate_hz = env.turbulence_rate_hz;
179 maybe_copy_value (FGEnvironment * env, const SGPropertyNode * node,
180 const char * name, void (FGEnvironment::*setter)(double))
182 const SGPropertyNode * child = node->getNode(name);
183 // fragile: depends on not being typed
185 if (child != 0 && child->hasValue() &&
186 child->getStringValue()[0] != '\0') {
187 (env->*setter)(child->getDoubleValue());
195 FGEnvironment::read (const SGPropertyNode * node)
197 maybe_copy_value(this, node, "visibility-m",
198 &FGEnvironment::set_visibility_m);
200 if (!maybe_copy_value(this, node, "temperature-sea-level-degc",
201 &FGEnvironment::set_temperature_sea_level_degc))
202 maybe_copy_value(this, node, "temperature-degc",
203 &FGEnvironment::set_temperature_degc);
205 if (!maybe_copy_value(this, node, "dewpoint-sea-level-degc",
206 &FGEnvironment::set_dewpoint_sea_level_degc))
207 maybe_copy_value(this, node, "dewpoint-degc",
208 &FGEnvironment::set_dewpoint_degc);
210 if (!maybe_copy_value(this, node, "pressure-sea-level-inhg",
211 &FGEnvironment::set_pressure_sea_level_inhg))
212 maybe_copy_value(this, node, "pressure-inhg",
213 &FGEnvironment::set_pressure_inhg);
215 maybe_copy_value(this, node, "wind-from-heading-deg",
216 &FGEnvironment::set_wind_from_heading_deg);
218 maybe_copy_value(this, node, "wind-speed-kt",
219 &FGEnvironment::set_wind_speed_kt);
221 maybe_copy_value(this, node, "elevation-ft",
222 &FGEnvironment::set_elevation_ft);
224 maybe_copy_value(this, node, "turbulence/magnitude-norm",
225 &FGEnvironment::set_turbulence_magnitude_norm);
227 maybe_copy_value(this, node, "turbulence/rate-hz",
228 &FGEnvironment::set_turbulence_rate_hz);
233 FGEnvironment::get_visibility_m () const
239 FGEnvironment::get_temperature_sea_level_degc () const
241 return temperature_sea_level_degc;
245 FGEnvironment::get_temperature_degc () const
247 return temperature_degc;
251 FGEnvironment::get_temperature_degf () const
253 return (temperature_degc * 9.0 / 5.0) + 32.0;
257 FGEnvironment::get_dewpoint_sea_level_degc () const
259 return dewpoint_sea_level_degc;
263 FGEnvironment::get_dewpoint_degc () const
265 return dewpoint_degc;
269 FGEnvironment::get_pressure_sea_level_inhg () const
271 return pressure_sea_level_inhg;
275 FGEnvironment::get_pressure_inhg () const
277 return pressure_inhg;
281 FGEnvironment::get_density_slugft3 () const
283 return density_slugft3;
287 FGEnvironment::get_relative_humidity () const
289 return relative_humidity;
293 FGEnvironment::get_density_tropo_avg_kgm3 () const
295 return density_tropo_avg_kgm3;
299 FGEnvironment::get_altitude_half_to_sun_m () const
301 return altitude_half_to_sun_m;
305 FGEnvironment::get_altitude_tropo_top_m () const
307 return altitude_tropo_top_m;
311 FGEnvironment::get_wind_from_heading_deg () const
313 return wind_from_heading_deg;
317 FGEnvironment::get_wind_speed_kt () const
319 return wind_speed_kt;
323 FGEnvironment::get_wind_from_north_fps () const
325 return wind_from_north_fps;
329 FGEnvironment::get_wind_from_east_fps () const
331 return wind_from_east_fps;
335 FGEnvironment::get_wind_from_down_fps () const
337 return wind_from_down_fps;
341 FGEnvironment::get_turbulence_magnitude_norm () const
343 if( sgEnviro.get_turbulence_enable_state() )
344 if (fgGetBool("/environment/params/real-world-weather-fetch") == true)
345 return sgEnviro.get_cloud_turbulence();
346 return turbulence_magnitude_norm;
350 FGEnvironment::get_turbulence_rate_hz () const
352 return turbulence_rate_hz;
356 FGEnvironment::get_elevation_ft () const
362 FGEnvironment::set_visibility_m (double v)
368 FGEnvironment::set_temperature_sea_level_degc (double t)
370 temperature_sea_level_degc = t;
371 if (dewpoint_sea_level_degc > t)
372 dewpoint_sea_level_degc = t;
373 _recalc_alt_temperature();
378 FGEnvironment::set_temperature_degc (double t)
380 temperature_degc = t;
381 _recalc_sl_temperature();
383 _recalc_relative_humidity();
387 FGEnvironment::set_dewpoint_sea_level_degc (double t)
389 dewpoint_sea_level_degc = t;
390 if (temperature_sea_level_degc < t)
391 temperature_sea_level_degc = t;
392 _recalc_alt_dewpoint();
397 FGEnvironment::set_dewpoint_degc (double t)
400 _recalc_sl_dewpoint();
402 _recalc_relative_humidity();
406 FGEnvironment::set_pressure_sea_level_inhg (double p)
408 pressure_sea_level_inhg = p;
409 _recalc_alt_pressure();
414 FGEnvironment::set_pressure_inhg (double p)
417 _recalc_sl_pressure();
422 FGEnvironment::set_wind_from_heading_deg (double h)
424 wind_from_heading_deg = h;
429 FGEnvironment::set_wind_speed_kt (double s)
436 FGEnvironment::set_wind_from_north_fps (double n)
438 wind_from_north_fps = n;
443 FGEnvironment::set_wind_from_east_fps (double e)
445 wind_from_east_fps = e;
450 FGEnvironment::set_wind_from_down_fps (double d)
452 wind_from_down_fps = d;
457 FGEnvironment::set_turbulence_magnitude_norm (double t)
459 turbulence_magnitude_norm = t;
463 FGEnvironment::set_turbulence_rate_hz (double r)
465 turbulence_rate_hz = r;
469 FGEnvironment::set_elevation_ft (double e)
472 _recalc_alt_temperature();
473 _recalc_alt_dewpoint();
474 _recalc_alt_pressure();
476 _recalc_relative_humidity();
480 FGEnvironment::set_altitude_half_to_sun_m (double alt)
482 altitude_half_to_sun_m = alt;
483 _recalc_density_tropo_avg_kgm3();
487 FGEnvironment::set_altitude_tropo_top_m (double alt)
489 altitude_tropo_top_m = alt;
490 _recalc_density_tropo_avg_kgm3();
495 FGEnvironment::_recalc_hdgspd ()
499 if (wind_from_east_fps == 0) {
500 angle_rad = (wind_from_north_fps >= 0 ? SGD_PI_2 : -SGD_PI_2);
502 angle_rad = atan(wind_from_north_fps/wind_from_east_fps);
504 wind_from_heading_deg = angle_rad * SGD_RADIANS_TO_DEGREES;
505 if (wind_from_east_fps >= 0)
506 wind_from_heading_deg = 90 - wind_from_heading_deg;
508 wind_from_heading_deg = 270 - wind_from_heading_deg;
511 // FIXME: Windspeed can become negative with these formulas.
512 // which can cause problems for animations that rely
513 // on the windspeed property.
515 wind_speed_kt = fabs(wind_from_east_fps
516 * SG_METER_TO_NM * SG_FEET_TO_METER * 3600);
518 wind_speed_kt = (wind_from_north_fps / sin(angle_rad))
519 * SG_METER_TO_NM * SG_FEET_TO_METER * 3600;
521 wind_speed_kt = sqrt(wind_from_north_fps * wind_from_north_fps +
522 wind_from_east_fps * wind_from_east_fps)
523 * SG_METER_TO_NM * SG_FEET_TO_METER * 3600;
528 FGEnvironment::_recalc_ne ()
531 wind_speed_kt * SG_NM_TO_METER * SG_METER_TO_FEET * (1.0/3600);
533 wind_from_north_fps = speed_fps *
534 cos(wind_from_heading_deg * SGD_DEGREES_TO_RADIANS);
535 wind_from_east_fps = speed_fps *
536 sin(wind_from_heading_deg * SGD_DEGREES_TO_RADIANS);
540 FGEnvironment::_recalc_sl_temperature ()
542 // If we're in the stratosphere, leave sea-level temp alone
543 if (elevation_ft < 38000) {
544 temperature_sea_level_degc = (temperature_degc + 273.15)
545 / _temperature_degc_table->interpolate(elevation_ft)
551 FGEnvironment::_recalc_alt_temperature ()
553 if (elevation_ft < 38000) {
554 temperature_degc = (temperature_sea_level_degc + 273.15) *
555 _temperature_degc_table->interpolate(elevation_ft) - 273.15;
557 temperature_degc = -56.49; // Stratosphere is constant
562 FGEnvironment::_recalc_sl_dewpoint ()
565 // FIXME: this will work only for low
567 dewpoint_sea_level_degc = dewpoint_degc + (elevation_ft * .0002);
568 if (dewpoint_sea_level_degc > temperature_sea_level_degc)
569 dewpoint_sea_level_degc = temperature_sea_level_degc;
573 FGEnvironment::_recalc_alt_dewpoint ()
576 // FIXME: this will work only for low
578 dewpoint_degc = dewpoint_sea_level_degc + (elevation_ft * .0002);
579 if (dewpoint_degc > temperature_degc)
580 dewpoint_degc = temperature_degc;
584 FGEnvironment::_recalc_sl_pressure ()
586 pressure_sea_level_inhg =
587 pressure_inhg / _pressure_inhg_table->interpolate(elevation_ft);
591 FGEnvironment::_recalc_alt_pressure ()
594 pressure_sea_level_inhg * _pressure_inhg_table->interpolate(elevation_ft);
598 FGEnvironment::_recalc_density ()
600 double pressure_psf = pressure_inhg * 70.7487;
602 // adjust for humidity
603 // calculations taken from USA Today (oops!) at
604 // http://www.usatoday.com/weather/basics/density-calculations.htm
605 double temperature_degk = temperature_degc + 273.15;
606 double pressure_mb = pressure_inhg * 33.86;
607 double vapor_pressure_mb =
608 6.11 * pow(10.0, 7.5 * dewpoint_degc / (237.7 + dewpoint_degc));
609 double virtual_temperature_degk = temperature_degk / (1 - (vapor_pressure_mb / pressure_mb) * (1.0 - 0.622));
610 double virtual_temperature_degr = virtual_temperature_degk * 1.8;
612 density_slugft3 = pressure_psf / (virtual_temperature_degr * 1718);
613 _recalc_density_tropo_avg_kgm3();
616 // This is used to calculate the average density on the path
617 // of sunlight to the observer for calculating sun-color
619 FGEnvironment::_recalc_density_tropo_avg_kgm3 ()
621 double pressure_mb = pressure_inhg * 33.86;
622 double vaporpressure = 6.11 * pow(10.0, ((7.5 * dewpoint_degc) / (237.7 + dewpoint_degc)));
624 double virtual_temp = (temperature_degc + 273.15) / (1 - 0.379 * (vaporpressure/pressure_mb));
626 double density_half = (100 * pressure_mb * exp(-altitude_half_to_sun_m / 8000))
627 / (287.05 * virtual_temp);
628 double density_tropo = (100 * pressure_mb * exp((-1 * altitude_tropo_top_m) / 8000))
629 / ( 287.05 * virtual_temp);
631 density_tropo_avg_kgm3 = ((density_slugft3 * 515.379) + density_half + density_tropo) / 3;
635 FGEnvironment::_recalc_relative_humidity ()
637 double vaporpressure = 6.11 * pow(10.0, ((7.5 * dewpoint_degc) / ( 237.7 + dewpoint_degc)));
638 double sat_vaporpressure = 6.11 * pow(10.0, ((7.5 * temperature_degc)
639 / ( 237.7 + temperature_degc)) );
640 relative_humidity = 100 * vaporpressure / sat_vaporpressure ;
645 ////////////////////////////////////////////////////////////////////////
647 ////////////////////////////////////////////////////////////////////////
650 do_interp (double a, double b, double fraction)
652 double retval = (a + ((b - a) * fraction));
657 do_interp_deg (double a, double b, double fraction)
661 if (fabs(b-a) > 180) {
667 return fmod(do_interp(a, b, fraction), 360);
671 interpolate (const FGEnvironment * env1, const FGEnvironment * env2,
672 double fraction, FGEnvironment * result)
674 result->set_visibility_m
675 (do_interp(env1->get_visibility_m(),
676 env2->get_visibility_m(),
679 result->set_temperature_sea_level_degc
680 (do_interp(env1->get_temperature_sea_level_degc(),
681 env2->get_temperature_sea_level_degc(),
684 result->set_dewpoint_degc
685 (do_interp(env1->get_dewpoint_sea_level_degc(),
686 env2->get_dewpoint_sea_level_degc(),
689 result->set_pressure_sea_level_inhg
690 (do_interp(env1->get_pressure_sea_level_inhg(),
691 env2->get_pressure_sea_level_inhg(),
694 result->set_wind_from_heading_deg
695 (do_interp_deg(env1->get_wind_from_heading_deg(),
696 env2->get_wind_from_heading_deg(),
699 result->set_wind_speed_kt
700 (do_interp(env1->get_wind_speed_kt(),
701 env2->get_wind_speed_kt(),
704 result->set_elevation_ft
705 (do_interp(env1->get_elevation_ft(),
706 env2->get_elevation_ft(),
709 result->set_turbulence_magnitude_norm
710 (do_interp(env1->get_turbulence_magnitude_norm(),
711 env2->get_turbulence_magnitude_norm(),
714 result->set_turbulence_rate_hz
715 (do_interp(env1->get_turbulence_rate_hz(),
716 env2->get_turbulence_rate_hz(),
720 // end of environment.cxx