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>
34 #include <simgear/constants.h>
35 #include <simgear/debug/logstream.hxx>
36 #include <simgear/math/interpolater.hxx>
37 #include <simgear/props/props.hxx>
38 #include <simgear/environment/visual_enviro.hxx>
40 #include <Main/fg_props.hxx>
43 #include "environment.hxx"
44 #include "atmosphere.hxx"
47 ////////////////////////////////////////////////////////////////////////
49 ////////////////////////////////////////////////////////////////////////
53 // Calculated based on the ISA standard day, as found at e.g.
54 // http://www.av8n.com/physics/altimetry.htm
56 // Each line of data has 3 elements:
58 // temperature factor (dimensionless ratio of absolute temp),
59 // pressure factor (dimensionless ratio)
60 static double atmosphere_data[][3] = {
61 { -3000.00, 1.021, 1.1133 },
62 { 0.00, 1.000, 1.0000 },
63 { 2952.76, 0.980, 0.8978 },
64 { 5905.51, 0.959, 0.8042 },
65 { 8858.27, 0.939, 0.7187 },
66 { 11811.02, 0.919, 0.6407 },
67 { 14763.78, 0.898, 0.5697 },
68 { 17716.54, 0.878, 0.5052 },
69 { 20669.29, 0.858, 0.4468 },
70 { 23622.05, 0.838, 0.3940 },
71 { 26574.80, 0.817, 0.3463 },
72 { 29527.56, 0.797, 0.3034 },
73 { 32480.31, 0.777, 0.2649 },
74 { 35433.07, 0.756, 0.2305 },
75 { 38385.83, 0.752, 0.2000 },
76 { 41338.58, 0.752, 0.1736 },
77 { 44291.34, 0.752, 0.1506 },
78 { 47244.09, 0.752, 0.1307 },
79 { 50196.85, 0.752, 0.1134 },
80 { 53149.61, 0.752, 0.0984 },
81 { 56102.36, 0.752, 0.0854 },
82 { 59055.12, 0.752, 0.0741 },
83 { 62007.87, 0.752, 0.0643 },
84 { 65000.00, 0.752, 0.0557 },
85 { 68000.00, 0.754, 0.0482 },
86 { 71000.00, 0.758, 0.0418 },
87 { 74000.00, 0.761, 0.0362 },
88 { 77000.00, 0.764, 0.0314 },
89 { 80000.00, 0.767, 0.0273 },
90 { 83000.00, 0.770, 0.0237 },
91 { 86000.00, 0.773, 0.0206 },
92 { 89000.00, 0.777, 0.0179 },
93 { 92000.00, 0.780, 0.0156 },
94 { 95000.00, 0.783, 0.0135 },
95 { 98000.00, 0.786, 0.0118 },
96 { 101000.00, 0.789, 0.0103 },
100 static SGInterpTable * _temperature_degc_table = 0;
101 static SGInterpTable * _pressure_inhg_table = 0;
106 if (_temperature_degc_table != 0)
109 _temperature_degc_table = new SGInterpTable;
110 _pressure_inhg_table = new SGInterpTable;
112 for (int i = 0; atmosphere_data[i][0] != -1; i++) {
113 _temperature_degc_table->addEntry(atmosphere_data[i][0],
114 atmosphere_data[i][1]);
115 _pressure_inhg_table->addEntry(atmosphere_data[i][0],
116 atmosphere_data[i][2]);
122 ////////////////////////////////////////////////////////////////////////
123 // Implementation of FGEnvironment.
124 ////////////////////////////////////////////////////////////////////////
126 void FGEnvironment::_init()
129 visibility_m = 32000;
130 temperature_sea_level_degc = 15;
131 temperature_degc = 15;
132 dewpoint_sea_level_degc = 5; // guess
134 pressure_sea_level_inhg = 29.92;
135 pressure_inhg = 29.92;
136 turbulence_magnitude_norm = 0;
137 turbulence_rate_hz = 1;
138 wind_from_heading_deg = 0;
140 wind_from_north_fps = 0;
141 wind_from_east_fps = 0;
142 wind_from_down_fps = 0;
143 altitude_half_to_sun_m = 1000;
144 altitude_tropo_top_m = 10000;
149 _recalc_relative_humidity();
153 FGEnvironment::FGEnvironment()
158 FGEnvironment::FGEnvironment (const FGEnvironment &env)
164 FGEnvironment::~FGEnvironment()
169 FGEnvironment::copy (const FGEnvironment &env)
171 elevation_ft = env.elevation_ft;
172 visibility_m = env.visibility_m;
173 temperature_sea_level_degc = env.temperature_sea_level_degc;
174 temperature_degc = env.temperature_degc;
175 dewpoint_sea_level_degc = env.dewpoint_sea_level_degc;
176 dewpoint_degc = env.dewpoint_degc;
177 pressure_sea_level_inhg = env.pressure_sea_level_inhg;
178 wind_from_heading_deg = env.wind_from_heading_deg;
179 wind_speed_kt = env.wind_speed_kt;
180 wind_from_north_fps = env.wind_from_north_fps;
181 wind_from_east_fps = env.wind_from_east_fps;
182 wind_from_down_fps = env.wind_from_down_fps;
183 turbulence_magnitude_norm = env.turbulence_magnitude_norm;
184 turbulence_rate_hz = env.turbulence_rate_hz;
188 maybe_copy_value (FGEnvironment * env, const SGPropertyNode * node,
189 const char * name, void (FGEnvironment::*setter)(double))
191 const SGPropertyNode * child = node->getNode(name);
192 // fragile: depends on not being typed
194 if (child != 0 && child->hasValue() &&
195 child->getStringValue()[0] != '\0') {
196 (env->*setter)(child->getDoubleValue());
204 FGEnvironment::read (const SGPropertyNode * node)
206 maybe_copy_value(this, node, "visibility-m",
207 &FGEnvironment::set_visibility_m);
209 if (!maybe_copy_value(this, node, "temperature-sea-level-degc",
210 &FGEnvironment::set_temperature_sea_level_degc))
211 maybe_copy_value(this, node, "temperature-degc",
212 &FGEnvironment::set_temperature_degc);
214 if (!maybe_copy_value(this, node, "dewpoint-sea-level-degc",
215 &FGEnvironment::set_dewpoint_sea_level_degc))
216 maybe_copy_value(this, node, "dewpoint-degc",
217 &FGEnvironment::set_dewpoint_degc);
219 if (!maybe_copy_value(this, node, "pressure-sea-level-inhg",
220 &FGEnvironment::set_pressure_sea_level_inhg))
221 maybe_copy_value(this, node, "pressure-inhg",
222 &FGEnvironment::set_pressure_inhg);
224 maybe_copy_value(this, node, "wind-from-heading-deg",
225 &FGEnvironment::set_wind_from_heading_deg);
227 maybe_copy_value(this, node, "wind-speed-kt",
228 &FGEnvironment::set_wind_speed_kt);
230 maybe_copy_value(this, node, "elevation-ft",
231 &FGEnvironment::set_elevation_ft);
233 maybe_copy_value(this, node, "turbulence/magnitude-norm",
234 &FGEnvironment::set_turbulence_magnitude_norm);
236 maybe_copy_value(this, node, "turbulence/rate-hz",
237 &FGEnvironment::set_turbulence_rate_hz);
242 FGEnvironment::get_visibility_m () const
248 FGEnvironment::get_temperature_sea_level_degc () const
250 return temperature_sea_level_degc;
254 FGEnvironment::get_temperature_degc () const
256 return temperature_degc;
260 FGEnvironment::get_temperature_degf () const
262 return (temperature_degc * 9.0 / 5.0) + 32.0;
266 FGEnvironment::get_dewpoint_sea_level_degc () const
268 return dewpoint_sea_level_degc;
272 FGEnvironment::get_dewpoint_degc () const
274 return dewpoint_degc;
278 FGEnvironment::get_pressure_sea_level_inhg () const
280 return pressure_sea_level_inhg;
284 FGEnvironment::get_pressure_inhg () const
286 return pressure_inhg;
290 FGEnvironment::get_density_slugft3 () const
292 return density_slugft3;
296 FGEnvironment::get_relative_humidity () const
298 return relative_humidity;
302 FGEnvironment::get_density_tropo_avg_kgm3 () const
304 return density_tropo_avg_kgm3;
308 FGEnvironment::get_altitude_half_to_sun_m () const
310 return altitude_half_to_sun_m;
314 FGEnvironment::get_altitude_tropo_top_m () const
316 return altitude_tropo_top_m;
320 FGEnvironment::get_wind_from_heading_deg () const
322 return wind_from_heading_deg;
326 FGEnvironment::get_wind_speed_kt () const
328 return wind_speed_kt;
332 FGEnvironment::get_wind_from_north_fps () const
334 return wind_from_north_fps;
338 FGEnvironment::get_wind_from_east_fps () const
340 return wind_from_east_fps;
344 FGEnvironment::get_wind_from_down_fps () const
346 return wind_from_down_fps;
350 FGEnvironment::get_turbulence_magnitude_norm () const
352 if( sgEnviro.get_turbulence_enable_state() )
353 if (fgGetBool("/environment/params/real-world-weather-fetch") == true)
354 return sgEnviro.get_cloud_turbulence();
355 return turbulence_magnitude_norm;
359 FGEnvironment::get_turbulence_rate_hz () const
361 return turbulence_rate_hz;
365 FGEnvironment::get_elevation_ft () const
371 FGEnvironment::set_visibility_m (double v)
377 FGEnvironment::set_temperature_sea_level_degc (double t)
379 temperature_sea_level_degc = t;
380 if (dewpoint_sea_level_degc > t)
381 dewpoint_sea_level_degc = t;
387 FGEnvironment::set_temperature_degc (double t)
389 temperature_degc = t;
390 _recalc_sl_temperature();
391 _recalc_sl_pressure();
394 _recalc_relative_humidity();
398 FGEnvironment::set_dewpoint_sea_level_degc (double t)
400 dewpoint_sea_level_degc = t;
401 if (temperature_sea_level_degc < t)
402 temperature_sea_level_degc = t;
403 _recalc_alt_dewpoint();
408 FGEnvironment::set_dewpoint_degc (double t)
411 _recalc_sl_dewpoint();
413 _recalc_relative_humidity();
417 FGEnvironment::set_pressure_sea_level_inhg (double p)
419 pressure_sea_level_inhg = p;
425 FGEnvironment::set_pressure_inhg (double p)
428 _recalc_sl_pressure();
433 FGEnvironment::set_wind_from_heading_deg (double h)
435 wind_from_heading_deg = h;
440 FGEnvironment::set_wind_speed_kt (double s)
447 FGEnvironment::set_wind_from_north_fps (double n)
449 wind_from_north_fps = n;
454 FGEnvironment::set_wind_from_east_fps (double e)
456 wind_from_east_fps = e;
461 FGEnvironment::set_wind_from_down_fps (double d)
463 wind_from_down_fps = d;
468 FGEnvironment::set_turbulence_magnitude_norm (double t)
470 turbulence_magnitude_norm = t;
474 FGEnvironment::set_turbulence_rate_hz (double r)
476 turbulence_rate_hz = r;
480 FGEnvironment::set_elevation_ft (double e)
483 _recalc_alt_dewpoint();
486 _recalc_relative_humidity();
490 FGEnvironment::set_altitude_half_to_sun_m (double alt)
492 altitude_half_to_sun_m = alt;
493 _recalc_density_tropo_avg_kgm3();
497 FGEnvironment::set_altitude_tropo_top_m (double alt)
499 altitude_tropo_top_m = alt;
500 _recalc_density_tropo_avg_kgm3();
505 FGEnvironment::_recalc_hdgspd ()
509 if (wind_from_east_fps == 0) {
510 angle_rad = (wind_from_north_fps >= 0 ? SGD_PI_2 : -SGD_PI_2);
512 angle_rad = atan(wind_from_north_fps/wind_from_east_fps);
514 wind_from_heading_deg = angle_rad * SGD_RADIANS_TO_DEGREES;
515 if (wind_from_east_fps >= 0)
516 wind_from_heading_deg = 90 - wind_from_heading_deg;
518 wind_from_heading_deg = 270 - wind_from_heading_deg;
521 // FIXME: Windspeed can become negative with these formulas.
522 // which can cause problems for animations that rely
523 // on the windspeed property.
525 wind_speed_kt = fabs(wind_from_east_fps
526 * SG_METER_TO_NM * SG_FEET_TO_METER * 3600);
528 wind_speed_kt = (wind_from_north_fps / sin(angle_rad))
529 * SG_METER_TO_NM * SG_FEET_TO_METER * 3600;
531 wind_speed_kt = sqrt(wind_from_north_fps * wind_from_north_fps +
532 wind_from_east_fps * wind_from_east_fps)
533 * SG_METER_TO_NM * SG_FEET_TO_METER * 3600;
538 FGEnvironment::_recalc_ne ()
541 wind_speed_kt * SG_NM_TO_METER * SG_METER_TO_FEET * (1.0/3600);
543 wind_from_north_fps = speed_fps *
544 cos(wind_from_heading_deg * SGD_DEGREES_TO_RADIANS);
545 wind_from_east_fps = speed_fps *
546 sin(wind_from_heading_deg * SGD_DEGREES_TO_RADIANS);
549 // Intended to help with the interpretation of METAR data,
550 // not for random in-flight outside-air temperatures.
552 FGEnvironment::_recalc_sl_temperature ()
557 SG_LOG(SG_GENERAL, SG_DEBUG, "recalc_sl_temperature: using "
558 << temperature_degc << " @ " << elevation_ft << " :: " << this);
562 if (elevation_ft >= ISA_def[1].height) {
563 SG_LOG(SG_GENERAL, SG_ALERT, "recalc_sl_temperature: "
564 << "valid only in troposphere, not " << elevation_ft);
568 // Clamp: temperature of the stratosphere, in degrees C:
569 double t_strato = ISA_def[1].temp - atmodel::freezing;
570 if (temperature_degc < t_strato) temperature_sea_level_degc = t_strato;
571 else temperature_sea_level_degc =
572 temperature_degc - elevation_ft * ISA_def[0].lapse;
574 // Alternative implemenation:
575 // else temperature_sea_level_inhg = T_layer(0., elevation_ft * foot,
576 // pressure_inhg * inHg, temperature_degc + freezing, ISA_def[0].lapse) - freezing;
580 FGEnvironment::_recalc_sl_dewpoint ()
583 // FIXME: this will work only for low
585 dewpoint_sea_level_degc = dewpoint_degc + (elevation_ft * .0002);
586 if (dewpoint_sea_level_degc > temperature_sea_level_degc)
587 dewpoint_sea_level_degc = temperature_sea_level_degc;
591 FGEnvironment::_recalc_alt_dewpoint ()
594 // FIXME: this will work only for low
596 dewpoint_degc = dewpoint_sea_level_degc + (elevation_ft * .0002);
597 if (dewpoint_degc > temperature_degc)
598 dewpoint_degc = temperature_degc;
602 FGEnvironment::_recalc_sl_pressure ()
604 using namespace atmodel;
607 SG_LOG(SG_GENERAL, SG_ALERT, "recalc_sl_pressure: using "
608 << pressure_inhg << " and "
609 << temperature_degc << " @ " << elevation_ft << " :: " << this);
612 pressure_sea_level_inhg = P_layer(0., elevation_ft * foot,
613 pressure_inhg * inHg, temperature_degc + freezing, ISA_def[0].lapse) / inHg;
616 // This gets called at frame rate, to account for the aircraft's
617 // changing altitude.
618 // Called by set_elevation_ft() which is called by FGEnvironmentMgr::update
621 FGEnvironment::_recalc_alt_pt ()
623 using namespace atmodel;
627 if (++count % 1000 == 0) {
628 SG_LOG(SG_GENERAL, SG_ALERT,
629 "recalc_alt_pt for: " << elevation_ft
630 << " using " << pressure_sea_level_inhg
631 << " and " << temperature_sea_level_degc
634 ///////////////////////////////////raise(SIGUSR1);
639 boost::tie(press, temp) = PT_vs_hpt(elevation_ft * foot,
640 pressure_sea_level_inhg * inHg, temperature_sea_level_degc + freezing);
641 temperature_degc = temp - freezing;
642 pressure_inhg = press / inHg;
646 FGEnvironment::_recalc_density ()
648 double pressure_psf = pressure_inhg * 70.7487;
650 // adjust for humidity
651 // calculations taken from USA Today (oops!) at
652 // http://www.usatoday.com/weather/basics/density-calculations.htm
653 double temperature_degk = temperature_degc + 273.15;
654 double pressure_mb = pressure_inhg * 33.86;
655 double vapor_pressure_mb =
656 6.11 * pow(10.0, 7.5 * dewpoint_degc / (237.7 + dewpoint_degc));
657 double virtual_temperature_degk = temperature_degk / (1 - (vapor_pressure_mb / pressure_mb) * (1.0 - 0.622));
658 double virtual_temperature_degr = virtual_temperature_degk * 1.8;
660 density_slugft3 = pressure_psf / (virtual_temperature_degr * 1718);
661 _recalc_density_tropo_avg_kgm3();
664 // This is used to calculate the average density on the path
665 // of sunlight to the observer for calculating sun-color
667 FGEnvironment::_recalc_density_tropo_avg_kgm3 ()
669 double pressure_mb = pressure_inhg * 33.86;
670 double vaporpressure = 6.11 * pow(10.0, ((7.5 * dewpoint_degc) / (237.7 + dewpoint_degc)));
672 double virtual_temp = (temperature_degc + 273.15) / (1 - 0.379 * (vaporpressure/pressure_mb));
674 double density_half = (100 * pressure_mb * exp(-altitude_half_to_sun_m / 8000))
675 / (287.05 * virtual_temp);
676 double density_tropo = (100 * pressure_mb * exp((-1 * altitude_tropo_top_m) / 8000))
677 / ( 287.05 * virtual_temp);
679 density_tropo_avg_kgm3 = ((density_slugft3 * 515.379) + density_half + density_tropo) / 3;
683 FGEnvironment::_recalc_relative_humidity ()
685 double vaporpressure = 6.11 * pow(10.0, ((7.5 * dewpoint_degc) / ( 237.7 + dewpoint_degc)));
686 double sat_vaporpressure = 6.11 * pow(10.0, ((7.5 * temperature_degc)
687 / ( 237.7 + temperature_degc)) );
688 relative_humidity = 100 * vaporpressure / sat_vaporpressure ;
693 ////////////////////////////////////////////////////////////////////////
695 ////////////////////////////////////////////////////////////////////////
698 do_interp (double a, double b, double fraction)
700 double retval = (a + ((b - a) * fraction));
705 do_interp_deg (double a, double b, double fraction)
709 if (fabs(b-a) > 180) {
715 return fmod(do_interp(a, b, fraction), 360);
719 interpolate (const FGEnvironment * env1, const FGEnvironment * env2,
720 double fraction, FGEnvironment * result)
722 result->set_visibility_m
723 (do_interp(env1->get_visibility_m(),
724 env2->get_visibility_m(),
727 result->set_temperature_sea_level_degc
728 (do_interp(env1->get_temperature_sea_level_degc(),
729 env2->get_temperature_sea_level_degc(),
732 result->set_dewpoint_degc
733 (do_interp(env1->get_dewpoint_sea_level_degc(),
734 env2->get_dewpoint_sea_level_degc(),
737 result->set_pressure_sea_level_inhg
738 (do_interp(env1->get_pressure_sea_level_inhg(),
739 env2->get_pressure_sea_level_inhg(),
742 result->set_wind_from_heading_deg
743 (do_interp_deg(env1->get_wind_from_heading_deg(),
744 env2->get_wind_from_heading_deg(),
747 result->set_wind_speed_kt
748 (do_interp(env1->get_wind_speed_kt(),
749 env2->get_wind_speed_kt(),
752 result->set_elevation_ft
753 (do_interp(env1->get_elevation_ft(),
754 env2->get_elevation_ft(),
757 result->set_turbulence_magnitude_norm
758 (do_interp(env1->get_turbulence_magnitude_norm(),
759 env2->get_turbulence_magnitude_norm(),
762 result->set_turbulence_rate_hz
763 (do_interp(env1->get_turbulence_rate_hz(),
764 env2->get_turbulence_rate_hz(),
768 // end of environment.cxx