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/environment/visual_enviro.hxx>
41 #include "environment.hxx"
45 ////////////////////////////////////////////////////////////////////////
47 ////////////////////////////////////////////////////////////////////////
49 // Copied from YASim Atmosphere.cxx, with m converted to ft, degK
50 // converted to degC, Pa converted to inHG, and kg/m^3 converted to
51 // slug/ft^3; they were then converted to deltas from the sea-level
52 // defaults (approx. 15degC, 29.92inHG, and 0.00237slugs/ft^3).
54 // Original comment from YASim:
56 // Copied from McCormick, who got it from "The ARDC Model Atmosphere"
57 // Note that there's an error in the text in the first entry,
58 // McCormick lists 299.16/101325/1.22500, but those don't agree with
59 // R=287. I chose to correct the temperature to 288.20, since 79F is
60 // pretty hot for a "standard" atmosphere.
62 // Elevation (ft), temperature factor (degK), pressure factor (inHG)
63 static double atmosphere_data[][3] = {
64 { 0.00, 1.00, 1.000 },
65 { 2952.76, 0.98, 0.898 },
66 { 5905.51, 0.96, 0.804 },
67 { 8858.27, 0.94, 0.719 },
68 { 11811.02, 0.92, 0.641 },
69 { 14763.78, 0.90, 0.570 },
70 { 17716.54, 0.88, 0.506 },
71 { 20669.29, 0.86, 0.447 },
72 { 23622.05, 0.84, 0.394 },
73 { 26574.80, 0.82, 0.347 },
74 { 29527.56, 0.80, 0.304 },
75 { 32480.31, 0.78, 0.266 },
76 { 35433.07, 0.76, 0.231 },
77 { 38385.83, 0.75, 0.201 },
78 { 41338.58, 0.75, 0.174 },
79 { 44291.34, 0.75, 0.151 },
80 { 47244.09, 0.75, 0.131 },
81 { 50196.85, 0.75, 0.114 },
82 { 53149.61, 0.75, 0.099 },
83 { 56102.36, 0.75, 0.086 },
84 { 59055.12, 0.75, 0.075 },
85 { 62007.87, 0.75, 0.065 },
89 static SGInterpTable * _temperature_degc_table = 0;
90 static SGInterpTable * _pressure_inhg_table = 0;
95 if (_temperature_degc_table != 0)
98 _temperature_degc_table = new SGInterpTable;
99 _pressure_inhg_table = new SGInterpTable;
101 for (int i = 0; atmosphere_data[i][0] != -1; i++) {
102 _temperature_degc_table->addEntry(atmosphere_data[i][0],
103 atmosphere_data[i][1]);
104 _pressure_inhg_table->addEntry(atmosphere_data[i][0],
105 atmosphere_data[i][2]);
111 ////////////////////////////////////////////////////////////////////////
112 // Implementation of FGEnvironment.
113 ////////////////////////////////////////////////////////////////////////
115 FGEnvironment::FGEnvironment()
118 temperature_sea_level_degc(15),
119 temperature_degc(15),
120 dewpoint_sea_level_degc(5), // guess
122 pressure_sea_level_inhg(29.92),
123 pressure_inhg(29.92),
124 turbulence_magnitude_norm(0),
125 turbulence_rate_hz(1),
126 wind_from_heading_deg(0),
128 wind_from_north_fps(0),
129 wind_from_east_fps(0),
130 wind_from_down_fps(0),
131 altitude_half_to_sun_m(1000),
132 altitude_tropo_top_m(10000)
136 _recalc_relative_humidity();
139 FGEnvironment::FGEnvironment (const FGEnvironment &env)
145 FGEnvironment::~FGEnvironment()
150 FGEnvironment::copy (const FGEnvironment &env)
152 elevation_ft = env.elevation_ft;
153 visibility_m = env.visibility_m;
154 temperature_sea_level_degc = env.temperature_sea_level_degc;
155 temperature_degc = env.temperature_degc;
156 dewpoint_sea_level_degc = env.dewpoint_sea_level_degc;
157 dewpoint_degc = env.dewpoint_degc;
158 pressure_sea_level_inhg = env.pressure_sea_level_inhg;
159 wind_from_heading_deg = env.wind_from_heading_deg;
160 wind_speed_kt = env.wind_speed_kt;
161 wind_from_north_fps = env.wind_from_north_fps;
162 wind_from_east_fps = env.wind_from_east_fps;
163 wind_from_down_fps = env.wind_from_down_fps;
164 turbulence_magnitude_norm = env.turbulence_magnitude_norm;
165 turbulence_rate_hz = env.turbulence_rate_hz;
169 maybe_copy_value (FGEnvironment * env, const SGPropertyNode * node,
170 const char * name, void (FGEnvironment::*setter)(double))
172 const SGPropertyNode * child = node->getNode(name);
173 // fragile: depends on not being typed
175 if (child != 0 && child->hasValue() &&
176 child->getStringValue()[0] != '\0') {
177 (env->*setter)(child->getDoubleValue());
185 FGEnvironment::read (const SGPropertyNode * node)
187 maybe_copy_value(this, node, "visibility-m",
188 &FGEnvironment::set_visibility_m);
190 if (!maybe_copy_value(this, node, "temperature-sea-level-degc",
191 &FGEnvironment::set_temperature_sea_level_degc))
192 maybe_copy_value(this, node, "temperature-degc",
193 &FGEnvironment::set_temperature_degc);
195 if (!maybe_copy_value(this, node, "dewpoint-sea-level-degc",
196 &FGEnvironment::set_dewpoint_sea_level_degc))
197 maybe_copy_value(this, node, "dewpoint-degc",
198 &FGEnvironment::set_dewpoint_degc);
200 if (!maybe_copy_value(this, node, "pressure-sea-level-inhg",
201 &FGEnvironment::set_pressure_sea_level_inhg))
202 maybe_copy_value(this, node, "pressure-inhg",
203 &FGEnvironment::set_pressure_inhg);
205 maybe_copy_value(this, node, "wind-from-heading-deg",
206 &FGEnvironment::set_wind_from_heading_deg);
208 maybe_copy_value(this, node, "wind-speed-kt",
209 &FGEnvironment::set_wind_speed_kt);
211 maybe_copy_value(this, node, "elevation-ft",
212 &FGEnvironment::set_elevation_ft);
214 maybe_copy_value(this, node, "turbulence/magnitude-norm",
215 &FGEnvironment::set_turbulence_magnitude_norm);
217 maybe_copy_value(this, node, "turbulence/rate-hz",
218 &FGEnvironment::set_turbulence_rate_hz);
223 FGEnvironment::get_visibility_m () const
229 FGEnvironment::get_temperature_sea_level_degc () const
231 return temperature_sea_level_degc;
235 FGEnvironment::get_temperature_degc () const
237 return temperature_degc;
241 FGEnvironment::get_temperature_degf () const
243 return (temperature_degc * 9.0 / 5.0) + 32.0;
247 FGEnvironment::get_dewpoint_sea_level_degc () const
249 return dewpoint_sea_level_degc;
253 FGEnvironment::get_dewpoint_degc () const
255 return dewpoint_degc;
259 FGEnvironment::get_pressure_sea_level_inhg () const
261 return pressure_sea_level_inhg;
265 FGEnvironment::get_pressure_inhg () const
267 return pressure_inhg;
271 FGEnvironment::get_density_slugft3 () const
273 return density_slugft3;
277 FGEnvironment::get_relative_humidity () const
279 return relative_humidity;
283 FGEnvironment::get_density_tropo_avg_kgm3 () const
285 return density_tropo_avg_kgm3;
289 FGEnvironment::get_altitude_half_to_sun_m () const
291 return altitude_half_to_sun_m;
295 FGEnvironment::get_altitude_tropo_top_m () const
297 return altitude_tropo_top_m;
301 FGEnvironment::get_wind_from_heading_deg () const
303 return wind_from_heading_deg;
307 FGEnvironment::get_wind_speed_kt () const
309 return wind_speed_kt;
313 FGEnvironment::get_wind_from_north_fps () const
315 return wind_from_north_fps;
319 FGEnvironment::get_wind_from_east_fps () const
321 return wind_from_east_fps;
325 FGEnvironment::get_wind_from_down_fps () const
327 return wind_from_down_fps;
331 FGEnvironment::get_turbulence_magnitude_norm () const
333 if( sgEnviro.get_turbulence_enable_state() )
334 if (fgGetBool("/environment/params/real-world-weather-fetch") == true)
335 return sgEnviro.get_cloud_turbulence();
336 return turbulence_magnitude_norm;
340 FGEnvironment::get_turbulence_rate_hz () const
342 return turbulence_rate_hz;
346 FGEnvironment::get_elevation_ft () const
352 FGEnvironment::set_visibility_m (double v)
358 FGEnvironment::set_temperature_sea_level_degc (double t)
360 temperature_sea_level_degc = t;
361 if (dewpoint_sea_level_degc > t)
362 dewpoint_sea_level_degc = t;
363 _recalc_alt_temperature();
368 FGEnvironment::set_temperature_degc (double t)
370 temperature_degc = t;
371 _recalc_sl_temperature();
373 _recalc_relative_humidity();
377 FGEnvironment::set_dewpoint_sea_level_degc (double t)
379 dewpoint_sea_level_degc = t;
380 if (temperature_sea_level_degc < t)
381 temperature_sea_level_degc = t;
382 _recalc_alt_dewpoint();
387 FGEnvironment::set_dewpoint_degc (double t)
390 _recalc_sl_dewpoint();
392 _recalc_relative_humidity();
396 FGEnvironment::set_pressure_sea_level_inhg (double p)
398 pressure_sea_level_inhg = p;
399 _recalc_alt_pressure();
404 FGEnvironment::set_pressure_inhg (double p)
407 _recalc_sl_pressure();
412 FGEnvironment::set_wind_from_heading_deg (double h)
414 wind_from_heading_deg = h;
419 FGEnvironment::set_wind_speed_kt (double s)
426 FGEnvironment::set_wind_from_north_fps (double n)
428 wind_from_north_fps = n;
433 FGEnvironment::set_wind_from_east_fps (double e)
435 wind_from_east_fps = e;
440 FGEnvironment::set_wind_from_down_fps (double d)
442 wind_from_down_fps = d;
447 FGEnvironment::set_turbulence_magnitude_norm (double t)
449 turbulence_magnitude_norm = t;
453 FGEnvironment::set_turbulence_rate_hz (double r)
455 turbulence_rate_hz = r;
459 FGEnvironment::set_elevation_ft (double e)
462 _recalc_alt_temperature();
463 _recalc_alt_dewpoint();
464 _recalc_alt_pressure();
466 _recalc_relative_humidity();
470 FGEnvironment::set_altitude_half_to_sun_m (double alt)
472 altitude_half_to_sun_m = alt;
473 _recalc_density_tropo_avg_kgm3();
477 FGEnvironment::set_altitude_tropo_top_m (double alt)
479 altitude_tropo_top_m = alt;
480 _recalc_density_tropo_avg_kgm3();
485 FGEnvironment::_recalc_hdgspd ()
489 if (wind_from_east_fps == 0) {
490 angle_rad = (wind_from_north_fps >= 0 ? SGD_PI_2 : -SGD_PI_2);
492 angle_rad = atan(wind_from_north_fps/wind_from_east_fps);
494 wind_from_heading_deg = angle_rad * SGD_RADIANS_TO_DEGREES;
495 if (wind_from_east_fps >= 0)
496 wind_from_heading_deg = 90 - wind_from_heading_deg;
498 wind_from_heading_deg = 270 - wind_from_heading_deg;
501 // FIXME: Windspeed can become negative with these formulas.
502 // which can cause problems for animations that rely
503 // on the windspeed property.
505 wind_speed_kt = fabs(wind_from_east_fps
506 * SG_METER_TO_NM * SG_FEET_TO_METER * 3600);
508 wind_speed_kt = (wind_from_north_fps / sin(angle_rad))
509 * SG_METER_TO_NM * SG_FEET_TO_METER * 3600;
511 wind_speed_kt = sqrt(wind_from_north_fps * wind_from_north_fps +
512 wind_from_east_fps * wind_from_east_fps)
513 * SG_METER_TO_NM * SG_FEET_TO_METER * 3600;
518 FGEnvironment::_recalc_ne ()
521 wind_speed_kt * SG_NM_TO_METER * SG_METER_TO_FEET * (1.0/3600);
523 wind_from_north_fps = speed_fps *
524 cos(wind_from_heading_deg * SGD_DEGREES_TO_RADIANS);
525 wind_from_east_fps = speed_fps *
526 sin(wind_from_heading_deg * SGD_DEGREES_TO_RADIANS);
530 FGEnvironment::_recalc_sl_temperature ()
532 // If we're in the stratosphere, leave sea-level temp alone
533 if (elevation_ft < 38000) {
534 temperature_sea_level_degc = (temperature_degc + 273.15)
535 / _temperature_degc_table->interpolate(elevation_ft)
541 FGEnvironment::_recalc_alt_temperature ()
543 if (elevation_ft < 38000) {
544 temperature_degc = (temperature_sea_level_degc + 273.15) *
545 _temperature_degc_table->interpolate(elevation_ft) - 273.15;
547 temperature_degc = -56.49; // Stratosphere is constant
552 FGEnvironment::_recalc_sl_dewpoint ()
555 // FIXME: this will work only for low
557 dewpoint_sea_level_degc = dewpoint_degc + (elevation_ft * .0002);
558 if (dewpoint_sea_level_degc > temperature_sea_level_degc)
559 dewpoint_sea_level_degc = temperature_sea_level_degc;
563 FGEnvironment::_recalc_alt_dewpoint ()
566 // FIXME: this will work only for low
568 dewpoint_degc = dewpoint_sea_level_degc + (elevation_ft * .0002);
569 if (dewpoint_degc > temperature_degc)
570 dewpoint_degc = temperature_degc;
574 FGEnvironment::_recalc_sl_pressure ()
576 pressure_sea_level_inhg =
577 pressure_inhg / _pressure_inhg_table->interpolate(elevation_ft);
581 FGEnvironment::_recalc_alt_pressure ()
584 pressure_sea_level_inhg * _pressure_inhg_table->interpolate(elevation_ft);
588 FGEnvironment::_recalc_density ()
590 double pressure_psf = pressure_inhg * 70.7487;
592 // adjust for humidity
593 // calculations taken from USA Today (oops!) at
594 // http://www.usatoday.com/weather/basics/density-calculations.htm
595 double temperature_degk = temperature_degc + 273.15;
596 double pressure_mb = pressure_inhg * 33.86;
597 double vapor_pressure_mb =
598 6.11 * pow(10.0, 7.5 * dewpoint_degc / (237.7 + dewpoint_degc));
599 double virtual_temperature_degk = temperature_degk / (1 - (vapor_pressure_mb / pressure_mb) * (1.0 - 0.622));
600 double virtual_temperature_degr = virtual_temperature_degk * 1.8;
602 density_slugft3 = pressure_psf / (virtual_temperature_degr * 1718);
603 _recalc_density_tropo_avg_kgm3();
606 // This is used to calculate the average density on the path
607 // of sunlight to the observer for calculating sun-color
609 FGEnvironment::_recalc_density_tropo_avg_kgm3 ()
611 double pressure_mb = pressure_inhg * 33.86;
612 double vaporpressure = 6.11 * pow(10, ((7.5 * dewpoint_degc) / (237.7 + dewpoint_degc)));
614 double virtual_temp = (temperature_degc + 273.15) / (1 - 0.379 * (vaporpressure/pressure_mb));
616 double density_half = (100 * pressure_mb * exp(-altitude_half_to_sun_m / 8000))
617 / (287.05 * virtual_temp);
618 double density_tropo = (100 * pressure_mb * exp((-1 * altitude_tropo_top_m) / 8000))
619 / ( 287.05 * virtual_temp);
621 density_tropo_avg_kgm3 = ((density_slugft3 * 515.379) + density_half + density_tropo) / 3;
625 FGEnvironment::_recalc_relative_humidity ()
627 double vaporpressure = 6.11 * pow(10, ((7.5 * dewpoint_degc) / ( 237.7 + dewpoint_degc)));
628 double sat_vaporpressure = 6.11 * pow(10, ((7.5 * temperature_degc)
629 / ( 237.7 + temperature_degc)) );
630 relative_humidity = 100 * vaporpressure / sat_vaporpressure ;
635 ////////////////////////////////////////////////////////////////////////
637 ////////////////////////////////////////////////////////////////////////
640 do_interp (double a, double b, double fraction)
642 double retval = (a + ((b - a) * fraction));
647 do_interp_deg (double a, double b, double fraction)
651 if (fabs(b-a) > 180) {
657 return fmod(do_interp(a, b, fraction), 360);
661 interpolate (const FGEnvironment * env1, const FGEnvironment * env2,
662 double fraction, FGEnvironment * result)
664 result->set_visibility_m
665 (do_interp(env1->get_visibility_m(),
666 env2->get_visibility_m(),
669 result->set_temperature_sea_level_degc
670 (do_interp(env1->get_temperature_sea_level_degc(),
671 env2->get_temperature_sea_level_degc(),
674 result->set_dewpoint_degc
675 (do_interp(env1->get_dewpoint_sea_level_degc(),
676 env2->get_dewpoint_sea_level_degc(),
679 result->set_pressure_sea_level_inhg
680 (do_interp(env1->get_pressure_sea_level_inhg(),
681 env2->get_pressure_sea_level_inhg(),
684 result->set_wind_from_heading_deg
685 (do_interp_deg(env1->get_wind_from_heading_deg(),
686 env2->get_wind_from_heading_deg(),
689 result->set_wind_speed_kt
690 (do_interp(env1->get_wind_speed_kt(),
691 env2->get_wind_speed_kt(),
694 result->set_elevation_ft
695 (do_interp(env1->get_elevation_ft(),
696 env2->get_elevation_ft(),
699 result->set_turbulence_magnitude_norm
700 (do_interp(env1->get_turbulence_magnitude_norm(),
701 env2->get_turbulence_magnitude_norm(),
704 result->set_turbulence_rate_hz
705 (do_interp(env1->get_turbulence_rate_hz(),
706 env2->get_turbulence_rate_hz(),
710 // end of environment.cxx