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), delta temperature (degC), delta pressure (inHG),
 273 // delta density (slug/ft^3)
 274 static double atmosphere_data[][4] = {
 275   0, 0.00, 0.000, 0.000000,
 276   2952, -5.89, -3.058, -0.000198,
 277   5905, -11.74, -5.856, -0.000384,
 278   8858, -17.58, -8.413, -0.000556,
 279   11811, -23.43, -10.745, -0.000717,
 280   14763, -29.27, -12.867, -0.000867,
 281   17716, -35.11, -14.794, -0.001006,
 282   20669, -40.95, -16.541, -0.001136,
 283   23622, -46.79, -18.120, -0.001255,
 284   26574, -52.62, -19.544, -0.001366,
 285   29527, -58.46, -20.826, -0.001467,
 286   32480, -64.29, -21.976, -0.001561,
 287   35433, -70.12, -23.005, -0.001647,
 288   38385, -71.54, -23.916, -0.001739,
 289   41338, -71.54, -24.708, -0.001822,
 290   44291, -71.54, -25.395, -0.001894,
 291   47244, -71.54, -25.991, -0.001957,
 292   50196, -71.54, -26.509, -0.002012,
 293   53149, -71.54, -26.959, -0.002059,
 294   56102, -71.54, -27.349, -0.002100,
 295   59055, -71.54, -27.687, -0.002136,
 296   62007, -71.54, -27.981, -0.002167,
 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 (elevation_ft < 38000) {
 352     temperature_sea_level_degc =
 353       temperature_degc - _temperature_degc_table->interpolate(elevation_ft);
 354   }
 355   // If we're in the stratosphere, leave sea-level temp alone
 356 }
 357
 358 void
 359 FGEnvironment::_recalc_alt_temperature ()
 360 {
 361   temperature_degc =
 362     temperature_sea_level_degc +
 363     _temperature_degc_table->interpolate(elevation_ft);
 364 }
 365
 366 void
 367 FGEnvironment::_recalc_sl_pressure ()
 368 {
 369   pressure_sea_level_inhg =
 370     pressure_inhg - _pressure_inhg_table->interpolate(elevation_ft);
 371 }
 372
 373 void
 374 FGEnvironment::_recalc_alt_pressure ()
 375 {
 376   pressure_inhg =
 377     pressure_sea_level_inhg + _pressure_inhg_table->interpolate(elevation_ft);
 378 }
 379
 380 void
 381 FGEnvironment::_recalc_sl_density ()
 382 {
 383   density_sea_level_slugft3 =
 384     density_slugft3 - _density_slugft3_table->interpolate(elevation_ft);
 385 }
 386
 387 void
 388 FGEnvironment::_recalc_alt_density ()
 389 {
 390   density_slugft3 =
 391     density_sea_level_slugft3 +
 392     _density_slugft3_table->interpolate(elevation_ft);
 393 }
 394
 395 // end of environment.cxx