src/Environment/environment.cxx

   1 // environment.cxx -- routines to model the natural environment
   2 //
   3 // Written by David Megginson, started February 2002.
   4 //
   5 // Copyright (C) 2002  David Megginson - david@megginson.com
   6 //
   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.
  11 //
  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.
  16 //
  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., 675 Mass Ave, Cambridge, MA 02139, USA.
  20 //
  21 // $Id$
  22
  23
  24 #ifdef HAVE_CONFIG_H
  25 #  include <config.h>
  26 #endif
  27
  28 #ifdef HAVE_WINDOWS_H
  29 #  include <windows.h>
  30 #endif
  31
  32 #include <math.h>
  33
  34 #include <plib/sg.h>
  35
  36 #include <simgear/constants.h>
  37 #include <simgear/debug/logstream.hxx>
  38 #include <simgear/math/interpolater.hxx>
  39
  40 #include <Main/fg_props.hxx>
  41 #include "environment.hxx"
  42
  43
  44 FGEnvironment::FGEnvironment()
  45   : _temperature_degc_table(new SGInterpTable),
  46     _pressure_inhg_table(new SGInterpTable),
  47     _density_slugft3_table(new SGInterpTable),
  48     visibility_m(32000),
  49     temperature_sea_level_degc(20),
  50     pressure_sea_level_inhg(29.92),
  51     density_sea_level_slugft3(0.00237),
  52     wind_from_heading_deg(0),
  53     wind_speed_kt(0),
  54     wind_from_north_fps(0),
  55     wind_from_east_fps(0),
  56     wind_from_down_fps(0)
  57 {
  58   _setup_tables();
  59 }
  60
  61 FGEnvironment::FGEnvironment (const FGEnvironment &env)
  62   : _temperature_degc_table(new SGInterpTable),
  63     _pressure_inhg_table(new SGInterpTable),
  64     _density_slugft3_table(new SGInterpTable),
  65     elevation_ft(env.elevation_ft),
  66     visibility_m(env.visibility_m),
  67     temperature_sea_level_degc(env.temperature_sea_level_degc),
  68     pressure_sea_level_inhg(env.pressure_sea_level_inhg),
  69     density_sea_level_slugft3(env.density_sea_level_slugft3),
  70     wind_from_heading_deg(env.wind_from_heading_deg),
  71     wind_speed_kt(env.wind_speed_kt),
  72     wind_from_north_fps(env.wind_from_north_fps),
  73     wind_from_east_fps(env.wind_from_east_fps),
  74     wind_from_down_fps(env.wind_from_down_fps)
  75 {
  76   _setup_tables();
  77 }
  78
  79 FGEnvironment::~FGEnvironment()
  80 {
  81   delete _temperature_degc_table;
  82   delete _pressure_inhg_table;
  83   delete _density_slugft3_table;
  84 }
  85
  86
  87 double
  88 FGEnvironment::get_visibility_m () const
  89 {
  90   return visibility_m;
  91 }
  92
  93 double
  94 FGEnvironment::get_temperature_sea_level_degc () const
  95 {
  96   return temperature_sea_level_degc;
  97 }
  98
  99 double
 100 FGEnvironment::get_temperature_degc () const
 101 {
 102   return temperature_degc;
 103 }
 104
 105 double
 106 FGEnvironment::get_pressure_sea_level_inhg () const
 107 {
 108   return pressure_sea_level_inhg;
 109 }
 110
 111 double
 112 FGEnvironment::get_pressure_inhg () const
 113 {
 114   return pressure_inhg;
 115 }
 116
 117 double
 118 FGEnvironment::get_density_sea_level_slugft3 () const
 119 {
 120   return density_sea_level_slugft3;
 121 }
 122
 123 double
 124 FGEnvironment::get_density_slugft3 () const
 125 {
 126   return density_slugft3;
 127 }
 128
 129 double
 130 FGEnvironment::get_wind_from_heading_deg () const
 131 {
 132   return wind_from_heading_deg;
 133 }
 134
 135 double
 136 FGEnvironment::get_wind_speed_kt () const
 137 {
 138   return wind_speed_kt;
 139 }
 140
 141 double
 142 FGEnvironment::get_wind_from_north_fps () const
 143 {
 144   return wind_from_north_fps;
 145 }
 146
 147 double
 148 FGEnvironment::get_wind_from_east_fps () const
 149 {
 150   return wind_from_east_fps;
 151 }
 152
 153 double
 154 FGEnvironment::get_wind_from_down_fps () const
 155 {
 156   return wind_from_down_fps;
 157 }
 158
 159 double
 160 FGEnvironment::get_elevation_ft () const
 161 {
 162   return elevation_ft;
 163 }
 164
 165 void
 166 FGEnvironment::set_visibility_m (double v)
 167 {
 168   visibility_m = v;
 169 }
 170
 171 void
 172 FGEnvironment::set_temperature_sea_level_degc (double t)
 173 {
 174   temperature_sea_level_degc = t;
 175   _recalc_alt_temperature();
 176 }
 177
 178 void
 179 FGEnvironment::set_temperature_degc (double t)
 180 {
 181   temperature_degc = t;
 182   _recalc_sl_temperature();
 183 }
 184
 185 void
 186 FGEnvironment::set_pressure_sea_level_inhg (double p)
 187 {
 188   pressure_sea_level_inhg = p;
 189   _recalc_alt_pressure();
 190 }
 191
 192 void
 193 FGEnvironment::set_pressure_inhg (double p)
 194 {
 195   pressure_inhg = p;
 196   _recalc_sl_pressure();
 197 }
 198
 199 void
 200 FGEnvironment::set_density_sea_level_slugft3 (double d)
 201 {
 202   density_sea_level_slugft3 = d;
 203   _recalc_alt_density();
 204 }
 205
 206 void
 207 FGEnvironment::set_density_slugft3 (double d)
 208 {
 209   density_slugft3 = d;
 210   _recalc_sl_density();
 211 }
 212
 213 void
 214 FGEnvironment::set_wind_from_heading_deg (double h)
 215 {
 216   wind_from_heading_deg = h;
 217   _recalc_ne();
 218 }
 219
 220 void
 221 FGEnvironment::set_wind_speed_kt (double s)
 222 {
 223   wind_speed_kt = s;
 224   _recalc_ne();
 225 }
 226
 227 void
 228 FGEnvironment::set_wind_from_north_fps (double n)
 229 {
 230   wind_from_north_fps = n;
 231   _recalc_hdgspd();
 232 }
 233
 234 void
 235 FGEnvironment::set_wind_from_east_fps (double e)
 236 {
 237   wind_from_east_fps = e;
 238   _recalc_hdgspd();
 239 }
 240
 241 void
 242 FGEnvironment::set_wind_from_down_fps (double d)
 243 {
 244   wind_from_down_fps = d;
 245   _recalc_hdgspd();
 246 }
 247
 248 void
 249 FGEnvironment::set_elevation_ft (double e)
 250 {
 251   elevation_ft = e;
 252   _recalc_alt_temperature();
 253   _recalc_alt_pressure();
 254   _recalc_alt_density();
 255 }
 256
 257 // Atmosphere model.
 258
 259 // Copied from YASim Atmosphere.cxx, with m converted to ft, degK
 260 // converted to degC, Pa converted to inHG, and kg/m^3 converted to
 261 // slug/ft^3; they were then converted to deltas from the sea-level
 262 // defaults (approx. 15degC, 29.92inHG, and 0.00237slugs/ft^3).
 263
 264 // Original comment from YASim:
 265
 266 // Copied from McCormick, who got it from "The ARDC Model Atmosphere"
 267 // Note that there's an error in the text in the first entry,
 268 // McCormick lists 299.16/101325/1.22500, but those don't agree with
 269 // R=287.  I chose to correct the temperature to 288.20, since 79F is
 270 // pretty hot for a "standard" atmosphere.
 271
 272 // Elevation (ft), temperature factor (degK), pressure factor (inHG),
 273 // density factor (slug/ft^3)
 274 static double atmosphere_data[][4] = {
 275   0.00, 1.00, 1.000, 1.000000,
 276   2952.76, 0.98, 0.898, 0.916408,
 277   5905.51, 0.96, 0.804, 0.838286,
 278   8858.27, 0.94, 0.719, 0.765429,
 279   11811.02, 0.92, 0.641, 0.697510,
 280   14763.78, 0.90, 0.570, 0.634318,
 281   17716.54, 0.88, 0.506, 0.575616,
 282   20669.29, 0.86, 0.447, 0.521184,
 283   23622.05, 0.84, 0.394, 0.470784,
 284   26574.80, 0.82, 0.347, 0.424220,
 285   29527.56, 0.80, 0.304, 0.381273,
 286   32480.31, 0.78, 0.266, 0.341747,
 287   35433.07, 0.76, 0.231, 0.305445,
 288   38385.83, 0.75, 0.201, 0.266931,
 289   41338.58, 0.75, 0.174, 0.231739,
 290   44291.34, 0.75, 0.151, 0.201192,
 291   47244.09, 0.75, 0.131, 0.174686,
 292   50196.85, 0.75, 0.114, 0.151673,
 293   53149.61, 0.75, 0.099, 0.131698,
 294   56102.36, 0.75, 0.086, 0.114359,
 295   59055.12, 0.75, 0.075, 0.099306,
 296   62007.87, 0.75, 0.065, 0.086237,
 297   -1, -1, -1, -1
 298 };
 299
 300 void
 301 FGEnvironment::_setup_tables ()
 302 {
 303   for (int i = 0; atmosphere_data[i][0] != -1; i++) {
 304     _temperature_degc_table->addEntry(atmosphere_data[i][0],
 305                                       atmosphere_data[i][1]);
 306     _pressure_inhg_table->addEntry(atmosphere_data[i][0],
 307                                    atmosphere_data[i][2]);
 308     _density_slugft3_table->addEntry(atmosphere_data[i][0],
 309                                      atmosphere_data[i][3]);
 310   }
 311 }
 312
 313 void
 314 FGEnvironment::_recalc_hdgspd ()
 315 {
 316   double angle_rad;
 317
 318   if (wind_from_east_fps == 0) {
 319     angle_rad = (wind_from_north_fps >= 0 ? SGD_PI/2 : -SGD_PI/2);
 320   } else {
 321     angle_rad = atan(wind_from_north_fps/wind_from_east_fps);
 322   }
 323   wind_from_heading_deg = angle_rad * SGD_RADIANS_TO_DEGREES;
 324   if (wind_from_east_fps >= 0)
 325     wind_from_heading_deg = 90 - wind_from_heading_deg;
 326   else
 327     wind_from_heading_deg = 270 - wind_from_heading_deg;
 328   if (angle_rad == 0)
 329     wind_speed_kt = fabs(wind_from_east_fps
 330                          * SG_METER_TO_NM * SG_FEET_TO_METER * 3600);
 331   else
 332     wind_speed_kt = (wind_from_north_fps / sin(angle_rad))
 333       * SG_METER_TO_NM * SG_FEET_TO_METER * 3600;
 334 }
 335
 336 void
 337 FGEnvironment::_recalc_ne ()
 338 {
 339   double speed_fps =
 340     wind_speed_kt * SG_NM_TO_METER * SG_METER_TO_FEET * (1.0/3600);
 341
 342   wind_from_north_fps = speed_fps *
 343     cos(wind_from_heading_deg * SGD_DEGREES_TO_RADIANS);
 344   wind_from_east_fps = speed_fps *
 345     sin(wind_from_heading_deg * SGD_DEGREES_TO_RADIANS);
 346 }
 347
 348 void
 349 FGEnvironment::_recalc_sl_temperature ()
 350 {
 351   // If we're in the stratosphere, leave sea-level temp alone
 352   if (elevation_ft < 38000) {
 353     temperature_sea_level_degc =
 354       (temperature_degc + 273.15)
 355       /_temperature_degc_table->interpolate(elevation_ft)
 356       - 273.15;
 357   }
 358 }
 359
 360 void
 361 FGEnvironment::_recalc_alt_temperature ()
 362 {
 363   if (elevation_ft < 38000) {
 364     temperature_degc =
 365       (temperature_sea_level_degc + 273.15) *
 366       _temperature_degc_table->interpolate(elevation_ft) - 273.15;
 367   } else {
 368     temperature_degc = -56.49;  // Stratosphere is constant
 369   }
 370 }
 371
 372 void
 373 FGEnvironment::_recalc_sl_pressure ()
 374 {
 375   pressure_sea_level_inhg =
 376     pressure_inhg / _pressure_inhg_table->interpolate(elevation_ft);
 377 }
 378
 379 void
 380 FGEnvironment::_recalc_alt_pressure ()
 381 {
 382   pressure_inhg =
 383     pressure_sea_level_inhg * _pressure_inhg_table->interpolate(elevation_ft);
 384 }
 385
 386 void
 387 FGEnvironment::_recalc_sl_density ()
 388 {
 389   density_sea_level_slugft3 =
 390     density_slugft3 / _density_slugft3_table->interpolate(elevation_ft);
 391 }
 392
 393 void
 394 FGEnvironment::_recalc_alt_density ()
 395 {
 396   density_slugft3 =
 397     density_sea_level_slugft3 *
 398     _density_slugft3_table->interpolate(elevation_ft);
 399 }
 400
 401 // end of environment.cxx