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 <Main/fg_props.hxx>
42 #include "environment.hxx"
46 ////////////////////////////////////////////////////////////////////////
48 ////////////////////////////////////////////////////////////////////////
50 // Copied from YASim Atmosphere.cxx, with m converted to ft, degK
51 // converted to degC, Pa converted to inHG, and kg/m^3 converted to
52 // slug/ft^3; they were then converted to deltas from the sea-level
53 // defaults (approx. 15degC, 29.92inHG, and 0.00237slugs/ft^3).
55 // Original comment from YASim:
57 // Copied from McCormick, who got it from "The ARDC Model Atmosphere"
58 // Note that there's an error in the text in the first entry,
59 // McCormick lists 299.16/101325/1.22500, but those don't agree with
60 // R=287. I chose to correct the temperature to 288.20, since 79F is
61 // pretty hot for a "standard" atmosphere.
63 // Elevation (ft), temperature factor (degK), pressure factor (inHG)
64 static double atmosphere_data[][3] = {
65 { 0.00, 1.00, 1.000 },
66 { 2952.76, 0.98, 0.898 },
67 { 5905.51, 0.96, 0.804 },
68 { 8858.27, 0.94, 0.719 },
69 { 11811.02, 0.92, 0.641 },
70 { 14763.78, 0.90, 0.570 },
71 { 17716.54, 0.88, 0.506 },
72 { 20669.29, 0.86, 0.447 },
73 { 23622.05, 0.84, 0.394 },
74 { 26574.80, 0.82, 0.347 },
75 { 29527.56, 0.80, 0.304 },
76 { 32480.31, 0.78, 0.266 },
77 { 35433.07, 0.76, 0.231 },
78 { 38385.83, 0.75, 0.201 },
79 { 41338.58, 0.75, 0.174 },
80 { 44291.34, 0.75, 0.151 },
81 { 47244.09, 0.75, 0.131 },
82 { 50196.85, 0.75, 0.114 },
83 { 53149.61, 0.75, 0.099 },
84 { 56102.36, 0.75, 0.086 },
85 { 59055.12, 0.75, 0.075 },
86 { 62007.87, 0.75, 0.065 },
90 static SGInterpTable * _temperature_degc_table = 0;
91 static SGInterpTable * _pressure_inhg_table = 0;
96 if (_temperature_degc_table != 0)
99 _temperature_degc_table = new SGInterpTable;
100 _pressure_inhg_table = new SGInterpTable;
102 for (int i = 0; atmosphere_data[i][0] != -1; i++) {
103 _temperature_degc_table->addEntry(atmosphere_data[i][0],
104 atmosphere_data[i][1]);
105 _pressure_inhg_table->addEntry(atmosphere_data[i][0],
106 atmosphere_data[i][2]);
112 ////////////////////////////////////////////////////////////////////////
113 // Implementation of FGEnvironment.
114 ////////////////////////////////////////////////////////////////////////
116 FGEnvironment::FGEnvironment()
119 temperature_sea_level_degc(15),
120 temperature_degc(15),
121 dewpoint_sea_level_degc(5), // guess
123 pressure_sea_level_inhg(29.92),
124 pressure_inhg(29.92),
125 turbulence_magnitude_norm(0),
126 turbulence_rate_hz(1),
127 wind_from_heading_deg(0),
129 wind_from_north_fps(0),
130 wind_from_east_fps(0),
131 wind_from_down_fps(0),
132 altitude_half_to_sun_m(1000),
133 altitude_tropo_top_m(10000)
137 _recalc_relative_humidity();
140 FGEnvironment::FGEnvironment (const FGEnvironment &env)
146 FGEnvironment::~FGEnvironment()
151 FGEnvironment::copy (const FGEnvironment &env)
153 elevation_ft = env.elevation_ft;
154 visibility_m = env.visibility_m;
155 temperature_sea_level_degc = env.temperature_sea_level_degc;
156 temperature_degc = env.temperature_degc;
157 dewpoint_sea_level_degc = env.dewpoint_sea_level_degc;
158 dewpoint_degc = env.dewpoint_degc;
159 pressure_sea_level_inhg = env.pressure_sea_level_inhg;
160 wind_from_heading_deg = env.wind_from_heading_deg;
161 wind_speed_kt = env.wind_speed_kt;
162 wind_from_north_fps = env.wind_from_north_fps;
163 wind_from_east_fps = env.wind_from_east_fps;
164 wind_from_down_fps = env.wind_from_down_fps;
165 turbulence_magnitude_norm = env.turbulence_magnitude_norm;
166 turbulence_rate_hz = env.turbulence_rate_hz;
170 maybe_copy_value (FGEnvironment * env, const SGPropertyNode * node,
171 const char * name, void (FGEnvironment::*setter)(double))
173 const SGPropertyNode * child = node->getNode(name);
174 // fragile: depends on not being typed
176 if (child != 0 && child->hasValue() &&
177 child->getStringValue()[0] != '\0') {
178 (env->*setter)(child->getDoubleValue());
186 FGEnvironment::read (const SGPropertyNode * node)
188 maybe_copy_value(this, node, "visibility-m",
189 &FGEnvironment::set_visibility_m);
191 if (!maybe_copy_value(this, node, "temperature-sea-level-degc",
192 &FGEnvironment::set_temperature_sea_level_degc))
193 maybe_copy_value(this, node, "temperature-degc",
194 &FGEnvironment::set_temperature_degc);
196 if (!maybe_copy_value(this, node, "dewpoint-sea-level-degc",
197 &FGEnvironment::set_dewpoint_sea_level_degc))
198 maybe_copy_value(this, node, "dewpoint-degc",
199 &FGEnvironment::set_dewpoint_degc);
201 if (!maybe_copy_value(this, node, "pressure-sea-level-inhg",
202 &FGEnvironment::set_pressure_sea_level_inhg))
203 maybe_copy_value(this, node, "pressure-inhg",
204 &FGEnvironment::set_pressure_inhg);
206 maybe_copy_value(this, node, "wind-from-heading-deg",
207 &FGEnvironment::set_wind_from_heading_deg);
209 maybe_copy_value(this, node, "wind-speed-kt",
210 &FGEnvironment::set_wind_speed_kt);
212 maybe_copy_value(this, node, "elevation-ft",
213 &FGEnvironment::set_elevation_ft);
215 maybe_copy_value(this, node, "turbulence/magnitude-norm",
216 &FGEnvironment::set_turbulence_magnitude_norm);
218 maybe_copy_value(this, node, "turbulence/rate-hz",
219 &FGEnvironment::set_turbulence_rate_hz);
224 FGEnvironment::get_visibility_m () const
230 FGEnvironment::get_temperature_sea_level_degc () const
232 return temperature_sea_level_degc;
236 FGEnvironment::get_temperature_degc () const
238 return temperature_degc;
242 FGEnvironment::get_temperature_degf () const
244 return (temperature_degc * 9.0 / 5.0) + 32.0;
248 FGEnvironment::get_dewpoint_sea_level_degc () const
250 return dewpoint_sea_level_degc;
254 FGEnvironment::get_dewpoint_degc () const
256 return dewpoint_degc;
260 FGEnvironment::get_pressure_sea_level_inhg () const
262 return pressure_sea_level_inhg;
266 FGEnvironment::get_pressure_inhg () const
268 return pressure_inhg;
272 FGEnvironment::get_density_slugft3 () const
274 return density_slugft3;
278 FGEnvironment::get_relative_humidity () const
280 return relative_humidity;
284 FGEnvironment::get_density_tropo_avg_kgm3 () const
286 return density_tropo_avg_kgm3;
290 FGEnvironment::get_altitude_half_to_sun_m () const
292 return altitude_half_to_sun_m;
296 FGEnvironment::get_altitude_tropo_top_m () const
298 return altitude_tropo_top_m;
302 FGEnvironment::get_wind_from_heading_deg () const
304 return wind_from_heading_deg;
308 FGEnvironment::get_wind_speed_kt () const
310 return wind_speed_kt;
314 FGEnvironment::get_wind_from_north_fps () const
316 return wind_from_north_fps;
320 FGEnvironment::get_wind_from_east_fps () const
322 return wind_from_east_fps;
326 FGEnvironment::get_wind_from_down_fps () const
328 return wind_from_down_fps;
332 FGEnvironment::get_turbulence_magnitude_norm () const
334 if( sgEnviro.get_turbulence_enable_state() )
335 if (fgGetBool("/environment/params/real-world-weather-fetch") == true)
336 return sgEnviro.get_cloud_turbulence();
337 return turbulence_magnitude_norm;
341 FGEnvironment::get_turbulence_rate_hz () const
343 return turbulence_rate_hz;
347 FGEnvironment::get_elevation_ft () const
353 FGEnvironment::set_visibility_m (double v)
359 FGEnvironment::set_temperature_sea_level_degc (double t)
361 temperature_sea_level_degc = t;
362 if (dewpoint_sea_level_degc > t)
363 dewpoint_sea_level_degc = t;
364 _recalc_alt_temperature();
369 FGEnvironment::set_temperature_degc (double t)
371 temperature_degc = t;
372 _recalc_sl_temperature();
374 _recalc_relative_humidity();
378 FGEnvironment::set_dewpoint_sea_level_degc (double t)
380 dewpoint_sea_level_degc = t;
381 if (temperature_sea_level_degc < t)
382 temperature_sea_level_degc = t;
383 _recalc_alt_dewpoint();
388 FGEnvironment::set_dewpoint_degc (double t)
391 _recalc_sl_dewpoint();
393 _recalc_relative_humidity();
397 FGEnvironment::set_pressure_sea_level_inhg (double p)
399 pressure_sea_level_inhg = p;
400 _recalc_alt_pressure();
405 FGEnvironment::set_pressure_inhg (double p)
408 _recalc_sl_pressure();
413 FGEnvironment::set_wind_from_heading_deg (double h)
415 wind_from_heading_deg = h;
420 FGEnvironment::set_wind_speed_kt (double s)
427 FGEnvironment::set_wind_from_north_fps (double n)
429 wind_from_north_fps = n;
434 FGEnvironment::set_wind_from_east_fps (double e)
436 wind_from_east_fps = e;
441 FGEnvironment::set_wind_from_down_fps (double d)
443 wind_from_down_fps = d;
448 FGEnvironment::set_turbulence_magnitude_norm (double t)
450 turbulence_magnitude_norm = t;
454 FGEnvironment::set_turbulence_rate_hz (double r)
456 turbulence_rate_hz = r;
460 FGEnvironment::set_elevation_ft (double e)
463 _recalc_alt_temperature();
464 _recalc_alt_dewpoint();
465 _recalc_alt_pressure();
467 _recalc_relative_humidity();
471 FGEnvironment::set_altitude_half_to_sun_m (double alt)
473 altitude_half_to_sun_m = alt;
474 _recalc_density_tropo_avg_kgm3();
478 FGEnvironment::set_altitude_tropo_top_m (double alt)
480 altitude_tropo_top_m = alt;
481 _recalc_density_tropo_avg_kgm3();
486 FGEnvironment::_recalc_hdgspd ()
490 if (wind_from_east_fps == 0) {
491 angle_rad = (wind_from_north_fps >= 0 ? SGD_PI_2 : -SGD_PI_2);
493 angle_rad = atan(wind_from_north_fps/wind_from_east_fps);
495 wind_from_heading_deg = angle_rad * SGD_RADIANS_TO_DEGREES;
496 if (wind_from_east_fps >= 0)
497 wind_from_heading_deg = 90 - wind_from_heading_deg;
499 wind_from_heading_deg = 270 - wind_from_heading_deg;
502 // FIXME: Windspeed can become negative with these formulas.
503 // which can cause problems for animations that rely
504 // on the windspeed property.
506 wind_speed_kt = fabs(wind_from_east_fps
507 * SG_METER_TO_NM * SG_FEET_TO_METER * 3600);
509 wind_speed_kt = (wind_from_north_fps / sin(angle_rad))
510 * SG_METER_TO_NM * SG_FEET_TO_METER * 3600;
512 wind_speed_kt = sqrt(wind_from_north_fps * wind_from_north_fps +
513 wind_from_east_fps * wind_from_east_fps)
514 * SG_METER_TO_NM * SG_FEET_TO_METER * 3600;
519 FGEnvironment::_recalc_ne ()
522 wind_speed_kt * SG_NM_TO_METER * SG_METER_TO_FEET * (1.0/3600);
524 wind_from_north_fps = speed_fps *
525 cos(wind_from_heading_deg * SGD_DEGREES_TO_RADIANS);
526 wind_from_east_fps = speed_fps *
527 sin(wind_from_heading_deg * SGD_DEGREES_TO_RADIANS);
531 FGEnvironment::_recalc_sl_temperature ()
533 // If we're in the stratosphere, leave sea-level temp alone
534 if (elevation_ft < 38000) {
535 temperature_sea_level_degc =
536 (temperature_degc + 273.15)
537 /_temperature_degc_table->interpolate(elevation_ft)
543 FGEnvironment::_recalc_alt_temperature ()
545 if (elevation_ft < 38000) {
547 (temperature_sea_level_degc + 273.15) *
548 _temperature_degc_table->interpolate(elevation_ft) - 273.15;
550 temperature_degc = -56.49; // Stratosphere is constant
555 FGEnvironment::_recalc_sl_dewpoint ()
558 // FIXME: this will work only for low
560 dewpoint_sea_level_degc = dewpoint_degc + (elevation_ft * .0002);
561 if (dewpoint_sea_level_degc > temperature_sea_level_degc)
562 dewpoint_sea_level_degc = temperature_sea_level_degc;
566 FGEnvironment::_recalc_alt_dewpoint ()
569 // FIXME: this will work only for low
571 dewpoint_degc = dewpoint_sea_level_degc + (elevation_ft * .0002);
572 if (dewpoint_degc > temperature_degc)
573 dewpoint_degc = temperature_degc;
577 FGEnvironment::_recalc_sl_pressure ()
579 pressure_sea_level_inhg =
580 pressure_inhg / _pressure_inhg_table->interpolate(elevation_ft);
584 FGEnvironment::_recalc_alt_pressure ()
587 pressure_sea_level_inhg * _pressure_inhg_table->interpolate(elevation_ft);
591 FGEnvironment::_recalc_density ()
593 double pressure_psf = pressure_inhg * 70.7487;
595 // adjust for humidity
596 // calculations taken from USA Today (oops!) at
597 // http://www.usatoday.com/weather/basics/density-calculations.htm
598 double temperature_degk = temperature_degc + 273.15;
599 double pressure_mb = pressure_inhg * 33.86;
600 double vapor_pressure_mb =
601 6.11 * pow(10.0, 7.5 * dewpoint_degc / (237.7 + dewpoint_degc));
602 double virtual_temperature_degk = temperature_degk / (1 - (vapor_pressure_mb / pressure_mb) * (1.0 - 0.622));
603 double virtual_temperature_degr = virtual_temperature_degk * 1.8;
605 density_slugft3 = pressure_psf / (virtual_temperature_degr * 1718);
606 _recalc_density_tropo_avg_kgm3();
609 // This is used to calculate the average density on the path
610 // of sunlight to the observer for calculating sun-color
612 FGEnvironment::_recalc_density_tropo_avg_kgm3 ()
614 double pressure_mb = pressure_inhg * 33.86;
615 double vaporpressure = 6.11 * pow ( 10, ((7.5 * dewpoint_degc) /( 237.7 + dewpoint_degc)));
617 double virtual_temp = (temperature_degc + 273.15) / (1 - 0.379 * (vaporpressure/pressure_mb));
619 double density_half = (100* pressure_mb * exp (-altitude_half_to_sun_m / 8000)) / (287.05 * virtual_temp);
620 double density_tropo = (100* pressure_mb * exp ((-1 * altitude_tropo_top_m) / 8000)) /( 287.05 * virtual_temp);
622 density_tropo_avg_kgm3 = ((density_slugft3 * 515.379) + density_half + density_tropo) / 3;
626 FGEnvironment::_recalc_relative_humidity ()
628 double vaporpressure = 6.11 * pow ( 10, ((7.5 * dewpoint_degc) /( 237.7 + dewpoint_degc)));
629 double sat_vaporpressure = 6.11 * pow ( 10, ((7.5 * temperature_degc) /( 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