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., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
  20 //
  21 // $Id$
  22
  23
  24 #ifdef HAVE_CONFIG_H
  25 #  include <config.h>
  26 #endif
  27
  28 #include <math.h>
  29
  30 #include <simgear/constants.h>
  31 #include <simgear/debug/logstream.hxx>
  32 #include <simgear/math/interpolater.hxx>
  33 #include <simgear/props/props.hxx>
  34 #include <simgear/environment/visual_enviro.hxx>
  35
  36 #include <Main/fg_props.hxx>
  37
  38 #include "environment.hxx"
  39
  40
  41 \f
  42 ////////////////////////////////////////////////////////////////////////
  43 // Atmosphere model.
  44 ////////////////////////////////////////////////////////////////////////
  45
  46 // Calculated based on the ISA standard day, as found at e.g.
  47 // http://www.av8n.com/physics/altimetry.htm
  48
  49 // Each line of data has 3 elements:
  50 //   Elevation (ft),
  51 //   temperature factor (dimensionless ratio of absolute temp),
  52 //   pressure factor (dimensionless ratio)
  53 static double atmosphere_data[][3] = {
  54  {  -3000.00,   1.021,  1.1133 },
  55  {      0.00,   1.000,  1.0000 },
  56  {   2952.76,   0.980,  0.8978 },
  57  {   5905.51,   0.959,  0.8042 },
  58  {   8858.27,   0.939,  0.7187 },
  59  {  11811.02,   0.919,  0.6407 },
  60  {  14763.78,   0.898,  0.5697 },
  61  {  17716.54,   0.878,  0.5052 },
  62  {  20669.29,   0.858,  0.4468 },
  63  {  23622.05,   0.838,  0.3940 },
  64  {  26574.80,   0.817,  0.3463 },
  65  {  29527.56,   0.797,  0.3034 },
  66  {  32480.31,   0.777,  0.2649 },
  67  {  35433.07,   0.756,  0.2305 },
  68  {  38385.83,   0.752,  0.2000 },
  69  {  41338.58,   0.752,  0.1736 },
  70  {  44291.34,   0.752,  0.1506 },
  71  {  47244.09,   0.752,  0.1307 },
  72  {  50196.85,   0.752,  0.1134 },
  73  {  53149.61,   0.752,  0.0984 },
  74  {  56102.36,   0.752,  0.0854 },
  75  {  59055.12,   0.752,  0.0741 },
  76  {  62007.87,   0.752,  0.0643 },
  77  {  65000.00,   0.752,  0.0557 },
  78  {  68000.00,   0.754,  0.0482 },
  79  {  71000.00,   0.758,  0.0418 },
  80  {  74000.00,   0.761,  0.0362 },
  81  {  77000.00,   0.764,  0.0314 },
  82  {  80000.00,   0.767,  0.0273 },
  83  {  83000.00,   0.770,  0.0237 },
  84  {  86000.00,   0.773,  0.0206 },
  85  {  89000.00,   0.777,  0.0179 },
  86  {  92000.00,   0.780,  0.0156 },
  87  {  95000.00,   0.783,  0.0135 },
  88  {  98000.00,   0.786,  0.0118 },
  89  { 101000.00,   0.789,  0.0103 },
  90  { -1, -1, -1 }
  91 };
  92
  93 static SGInterpTable * _temperature_degc_table = 0;
  94 static SGInterpTable * _pressure_inhg_table = 0;
  95
  96 static void
  97 _setup_tables ()
  98 {
  99   if (_temperature_degc_table != 0)
 100       return;
 101
 102   _temperature_degc_table = new SGInterpTable;
 103   _pressure_inhg_table = new SGInterpTable;
 104
 105   for (int i = 0; atmosphere_data[i][0] != -1; i++) {
 106     _temperature_degc_table->addEntry(atmosphere_data[i][0],
 107                                       atmosphere_data[i][1]);
 108     _pressure_inhg_table->addEntry(atmosphere_data[i][0],
 109                                    atmosphere_data[i][2]);
 110   }
 111 }
 112
 113
 114 \f
 115 ////////////////////////////////////////////////////////////////////////
 116 // Implementation of FGEnvironment.
 117 ////////////////////////////////////////////////////////////////////////
 118
 119 void FGEnvironment::_init()
 120 {
 121     elevation_ft = 0;
 122     visibility_m = 32000;
 123     temperature_sea_level_degc = 15;
 124     temperature_degc = 15;
 125     dewpoint_sea_level_degc = 5; // guess
 126     dewpoint_degc = 5;
 127     pressure_sea_level_inhg = 29.92;
 128     pressure_inhg = 29.92;
 129     turbulence_magnitude_norm = 0;
 130     turbulence_rate_hz = 1;
 131     wind_from_heading_deg = 0;
 132     wind_speed_kt = 0;
 133     wind_from_north_fps = 0;
 134     wind_from_east_fps = 0;
 135     wind_from_down_fps = 0;
 136     altitude_half_to_sun_m = 1000;
 137     altitude_tropo_top_m = 10000;
 138     _setup_tables();
 139     _recalc_density();
 140     _recalc_relative_humidity();
 141
 142 }
 143
 144 FGEnvironment::FGEnvironment()
 145 {
 146     _init();
 147 }
 148
 149 FGEnvironment::FGEnvironment (const FGEnvironment &env)
 150 {
 151     _init();
 152     copy(env);
 153 }
 154
 155 FGEnvironment::~FGEnvironment()
 156 {
 157 }
 158
 159 void
 160 FGEnvironment::copy (const FGEnvironment &env)
 161 {
 162     elevation_ft = env.elevation_ft;
 163     visibility_m = env.visibility_m;
 164     temperature_sea_level_degc = env.temperature_sea_level_degc;
 165     temperature_degc = env.temperature_degc;
 166     dewpoint_sea_level_degc = env.dewpoint_sea_level_degc;
 167     dewpoint_degc = env.dewpoint_degc;
 168     pressure_sea_level_inhg = env.pressure_sea_level_inhg;
 169     wind_from_heading_deg = env.wind_from_heading_deg;
 170     wind_speed_kt = env.wind_speed_kt;
 171     wind_from_north_fps = env.wind_from_north_fps;
 172     wind_from_east_fps = env.wind_from_east_fps;
 173     wind_from_down_fps = env.wind_from_down_fps;
 174     turbulence_magnitude_norm = env.turbulence_magnitude_norm;
 175     turbulence_rate_hz = env.turbulence_rate_hz;
 176 }
 177
 178 static inline bool
 179 maybe_copy_value (FGEnvironment * env, const SGPropertyNode * node,
 180                   const char * name, void (FGEnvironment::*setter)(double))
 181 {
 182     const SGPropertyNode * child = node->getNode(name);
 183                                 // fragile: depends on not being typed
 184                                 // as a number
 185     if (child != 0 && child->hasValue() &&
 186         child->getStringValue()[0] != '\0') {
 187         (env->*setter)(child->getDoubleValue());
 188         return true;
 189     } else {
 190         return false;
 191     }
 192 }
 193
 194 void
 195 FGEnvironment::read (const SGPropertyNode * node)
 196 {
 197     maybe_copy_value(this, node, "visibility-m",
 198                      &FGEnvironment::set_visibility_m);
 199
 200     if (!maybe_copy_value(this, node, "temperature-sea-level-degc",
 201                           &FGEnvironment::set_temperature_sea_level_degc))
 202         maybe_copy_value(this, node, "temperature-degc",
 203                          &FGEnvironment::set_temperature_degc);
 204
 205     if (!maybe_copy_value(this, node, "dewpoint-sea-level-degc",
 206                           &FGEnvironment::set_dewpoint_sea_level_degc))
 207         maybe_copy_value(this, node, "dewpoint-degc",
 208                          &FGEnvironment::set_dewpoint_degc);
 209
 210     if (!maybe_copy_value(this, node, "pressure-sea-level-inhg",
 211                           &FGEnvironment::set_pressure_sea_level_inhg))
 212         maybe_copy_value(this, node, "pressure-inhg",
 213                          &FGEnvironment::set_pressure_inhg);
 214
 215     maybe_copy_value(this, node, "wind-from-heading-deg",
 216                      &FGEnvironment::set_wind_from_heading_deg);
 217
 218     maybe_copy_value(this, node, "wind-speed-kt",
 219                      &FGEnvironment::set_wind_speed_kt);
 220
 221     maybe_copy_value(this, node, "elevation-ft",
 222                      &FGEnvironment::set_elevation_ft);
 223
 224     maybe_copy_value(this, node, "turbulence/magnitude-norm",
 225                      &FGEnvironment::set_turbulence_magnitude_norm);
 226
 227     maybe_copy_value(this, node, "turbulence/rate-hz",
 228                      &FGEnvironment::set_turbulence_rate_hz);
 229 }
 230
 231
 232 double
 233 FGEnvironment::get_visibility_m () const
 234 {
 235   return visibility_m;
 236 }
 237
 238 double
 239 FGEnvironment::get_temperature_sea_level_degc () const
 240 {
 241   return temperature_sea_level_degc;
 242 }
 243
 244 double
 245 FGEnvironment::get_temperature_degc () const
 246 {
 247   return temperature_degc;
 248 }
 249
 250 double
 251 FGEnvironment::get_temperature_degf () const
 252 {
 253   return (temperature_degc * 9.0 / 5.0) + 32.0;
 254 }
 255
 256 double
 257 FGEnvironment::get_dewpoint_sea_level_degc () const
 258 {
 259   return dewpoint_sea_level_degc;
 260 }
 261
 262 double
 263 FGEnvironment::get_dewpoint_degc () const
 264 {
 265   return dewpoint_degc;
 266 }
 267
 268 double
 269 FGEnvironment::get_pressure_sea_level_inhg () const
 270 {
 271   return pressure_sea_level_inhg;
 272 }
 273
 274 double
 275 FGEnvironment::get_pressure_inhg () const
 276 {
 277   return pressure_inhg;
 278 }
 279
 280 double
 281 FGEnvironment::get_density_slugft3 () const
 282 {
 283   return density_slugft3;
 284 }
 285
 286 double
 287 FGEnvironment::get_relative_humidity () const
 288 {
 289   return relative_humidity;
 290 }
 291
 292 double
 293 FGEnvironment::get_density_tropo_avg_kgm3 () const
 294 {
 295   return density_tropo_avg_kgm3;
 296 }
 297
 298 double
 299 FGEnvironment::get_altitude_half_to_sun_m () const
 300 {
 301   return altitude_half_to_sun_m;
 302 }
 303
 304 double
 305 FGEnvironment::get_altitude_tropo_top_m () const
 306 {
 307   return altitude_tropo_top_m;
 308 }
 309
 310 double
 311 FGEnvironment::get_wind_from_heading_deg () const
 312 {
 313   return wind_from_heading_deg;
 314 }
 315
 316 double
 317 FGEnvironment::get_wind_speed_kt () const
 318 {
 319   return wind_speed_kt;
 320 }
 321
 322 double
 323 FGEnvironment::get_wind_from_north_fps () const
 324 {
 325   return wind_from_north_fps;
 326 }
 327
 328 double
 329 FGEnvironment::get_wind_from_east_fps () const
 330 {
 331   return wind_from_east_fps;
 332 }
 333
 334 double
 335 FGEnvironment::get_wind_from_down_fps () const
 336 {
 337   return wind_from_down_fps;
 338 }
 339
 340 double
 341 FGEnvironment::get_turbulence_magnitude_norm () const
 342 {
 343   if( sgEnviro.get_turbulence_enable_state() )
 344     if (fgGetBool("/environment/params/real-world-weather-fetch") == true)
 345       return sgEnviro.get_cloud_turbulence();
 346   return turbulence_magnitude_norm;
 347 }
 348
 349 double
 350 FGEnvironment::get_turbulence_rate_hz () const
 351 {
 352   return turbulence_rate_hz;
 353 }
 354
 355 double
 356 FGEnvironment::get_elevation_ft () const
 357 {
 358   return elevation_ft;
 359 }
 360
 361 void
 362 FGEnvironment::set_visibility_m (double v)
 363 {
 364   visibility_m = v;
 365 }
 366
 367 void
 368 FGEnvironment::set_temperature_sea_level_degc (double t)
 369 {
 370   temperature_sea_level_degc = t;
 371   if (dewpoint_sea_level_degc > t)
 372       dewpoint_sea_level_degc = t;
 373   _recalc_alt_temperature();
 374   _recalc_density();
 375 }
 376
 377 void
 378 FGEnvironment::set_temperature_degc (double t)
 379 {
 380   temperature_degc = t;
 381   _recalc_sl_temperature();
 382   _recalc_density();
 383   _recalc_relative_humidity();
 384 }
 385
 386 void
 387 FGEnvironment::set_dewpoint_sea_level_degc (double t)
 388 {
 389   dewpoint_sea_level_degc = t;
 390   if (temperature_sea_level_degc < t)
 391       temperature_sea_level_degc = t;
 392   _recalc_alt_dewpoint();
 393   _recalc_density();
 394 }
 395
 396 void
 397 FGEnvironment::set_dewpoint_degc (double t)
 398 {
 399   dewpoint_degc = t;
 400   _recalc_sl_dewpoint();
 401   _recalc_density();
 402   _recalc_relative_humidity();
 403 }
 404
 405 void
 406 FGEnvironment::set_pressure_sea_level_inhg (double p)
 407 {
 408   pressure_sea_level_inhg = p;
 409   _recalc_alt_pressure();
 410   _recalc_density();
 411 }
 412
 413 void
 414 FGEnvironment::set_pressure_inhg (double p)
 415 {
 416   pressure_inhg = p;
 417   _recalc_sl_pressure();
 418   _recalc_density();
 419 }
 420
 421 void
 422 FGEnvironment::set_wind_from_heading_deg (double h)
 423 {
 424   wind_from_heading_deg = h;
 425   _recalc_ne();
 426 }
 427
 428 void
 429 FGEnvironment::set_wind_speed_kt (double s)
 430 {
 431   wind_speed_kt = s;
 432   _recalc_ne();
 433 }
 434
 435 void
 436 FGEnvironment::set_wind_from_north_fps (double n)
 437 {
 438   wind_from_north_fps = n;
 439   _recalc_hdgspd();
 440 }
 441
 442 void
 443 FGEnvironment::set_wind_from_east_fps (double e)
 444 {
 445   wind_from_east_fps = e;
 446   _recalc_hdgspd();
 447 }
 448
 449 void
 450 FGEnvironment::set_wind_from_down_fps (double d)
 451 {
 452   wind_from_down_fps = d;
 453   _recalc_hdgspd();
 454 }
 455
 456 void
 457 FGEnvironment::set_turbulence_magnitude_norm (double t)
 458 {
 459   turbulence_magnitude_norm = t;
 460 }
 461
 462 void
 463 FGEnvironment::set_turbulence_rate_hz (double r)
 464 {
 465   turbulence_rate_hz = r;
 466 }
 467
 468 void
 469 FGEnvironment::set_elevation_ft (double e)
 470 {
 471   elevation_ft = e;
 472   _recalc_alt_temperature();
 473   _recalc_alt_dewpoint();
 474   _recalc_alt_pressure();
 475   _recalc_density();
 476   _recalc_relative_humidity();
 477 }
 478
 479 void
 480 FGEnvironment::set_altitude_half_to_sun_m (double alt)
 481 {
 482  altitude_half_to_sun_m = alt;
 483  _recalc_density_tropo_avg_kgm3();
 484 }
 485
 486 void
 487 FGEnvironment::set_altitude_tropo_top_m (double alt)
 488 {
 489  altitude_tropo_top_m = alt;
 490  _recalc_density_tropo_avg_kgm3();
 491 }
 492
 493
 494 void
 495 FGEnvironment::_recalc_hdgspd ()
 496 {
 497   double angle_rad;
 498
 499   if (wind_from_east_fps == 0) {
 500     angle_rad = (wind_from_north_fps >= 0 ? SGD_PI_2 : -SGD_PI_2);
 501   } else {
 502     angle_rad = atan(wind_from_north_fps/wind_from_east_fps);
 503   }
 504   wind_from_heading_deg = angle_rad * SGD_RADIANS_TO_DEGREES;
 505   if (wind_from_east_fps >= 0)
 506     wind_from_heading_deg = 90 - wind_from_heading_deg;
 507   else
 508     wind_from_heading_deg = 270 - wind_from_heading_deg;
 509
 510 #if 0
 511   // FIXME: Windspeed can become negative with these formulas.
 512   //        which can cause problems for animations that rely
 513   //        on the windspeed property.
 514   if (angle_rad == 0)
 515     wind_speed_kt = fabs(wind_from_east_fps
 516                          * SG_METER_TO_NM * SG_FEET_TO_METER * 3600);
 517   else
 518     wind_speed_kt = (wind_from_north_fps / sin(angle_rad))
 519       * SG_METER_TO_NM * SG_FEET_TO_METER * 3600;
 520 #else
 521   wind_speed_kt = sqrt(wind_from_north_fps * wind_from_north_fps +
 522                        wind_from_east_fps * wind_from_east_fps)
 523                   * SG_METER_TO_NM * SG_FEET_TO_METER * 3600;
 524 #endif
 525 }
 526
 527 void
 528 FGEnvironment::_recalc_ne ()
 529 {
 530   double speed_fps =
 531     wind_speed_kt * SG_NM_TO_METER * SG_METER_TO_FEET * (1.0/3600);
 532
 533   wind_from_north_fps = speed_fps *
 534     cos(wind_from_heading_deg * SGD_DEGREES_TO_RADIANS);
 535   wind_from_east_fps = speed_fps *
 536     sin(wind_from_heading_deg * SGD_DEGREES_TO_RADIANS);
 537 }
 538
 539 void
 540 FGEnvironment::_recalc_sl_temperature ()
 541 {
 542   // If we're in the stratosphere, leave sea-level temp alone
 543   if (elevation_ft < 38000) {
 544     temperature_sea_level_degc = (temperature_degc + 273.15)
 545         / _temperature_degc_table->interpolate(elevation_ft)
 546       - 273.15;
 547   }
 548 }
 549
 550 void
 551 FGEnvironment::_recalc_alt_temperature ()
 552 {
 553   if (elevation_ft < 38000) {
 554     temperature_degc = (temperature_sea_level_degc + 273.15) *
 555         _temperature_degc_table->interpolate(elevation_ft) - 273.15;
 556   } else {
 557     temperature_degc = -56.49;  // Stratosphere is constant
 558   }
 559 }
 560
 561 void
 562 FGEnvironment::_recalc_sl_dewpoint ()
 563 {
 564                                 // 0.2degC/1000ft
 565                                 // FIXME: this will work only for low
 566                                 // elevations
 567   dewpoint_sea_level_degc = dewpoint_degc + (elevation_ft * .0002);
 568   if (dewpoint_sea_level_degc > temperature_sea_level_degc)
 569     dewpoint_sea_level_degc = temperature_sea_level_degc;
 570 }
 571
 572 void
 573 FGEnvironment::_recalc_alt_dewpoint ()
 574 {
 575                                 // 0.2degC/1000ft
 576                                 // FIXME: this will work only for low
 577                                 // elevations
 578   dewpoint_degc = dewpoint_sea_level_degc + (elevation_ft * .0002);
 579   if (dewpoint_degc > temperature_degc)
 580     dewpoint_degc = temperature_degc;
 581 }
 582
 583 void
 584 FGEnvironment::_recalc_sl_pressure ()
 585 {
 586   pressure_sea_level_inhg =
 587     pressure_inhg / _pressure_inhg_table->interpolate(elevation_ft);
 588 }
 589
 590 void
 591 FGEnvironment::_recalc_alt_pressure ()
 592 {
 593   pressure_inhg =
 594     pressure_sea_level_inhg * _pressure_inhg_table->interpolate(elevation_ft);
 595 }
 596
 597 void
 598 FGEnvironment::_recalc_density ()
 599 {
 600   double pressure_psf = pressure_inhg * 70.7487;
 601
 602   // adjust for humidity
 603   // calculations taken from USA Today (oops!) at
 604   // http://www.usatoday.com/weather/basics/density-calculations.htm
 605   double temperature_degk = temperature_degc + 273.15;
 606   double pressure_mb = pressure_inhg * 33.86;
 607   double vapor_pressure_mb =
 608     6.11 * pow(10.0, 7.5 * dewpoint_degc / (237.7 + dewpoint_degc));
 609   double virtual_temperature_degk = temperature_degk / (1 - (vapor_pressure_mb / pressure_mb) * (1.0 - 0.622));
 610   double virtual_temperature_degr = virtual_temperature_degk * 1.8;
 611
 612   density_slugft3 = pressure_psf / (virtual_temperature_degr * 1718);
 613   _recalc_density_tropo_avg_kgm3();
 614 }
 615
 616 // This is used to calculate the average density on the path
 617 // of sunlight to the observer for calculating sun-color
 618 void
 619 FGEnvironment::_recalc_density_tropo_avg_kgm3 ()
 620 {
 621   double pressure_mb = pressure_inhg * 33.86;
 622   double vaporpressure = 6.11 * pow(10.0, ((7.5 * dewpoint_degc) / (237.7 + dewpoint_degc)));
 623
 624   double virtual_temp = (temperature_degc + 273.15) / (1 - 0.379 * (vaporpressure/pressure_mb));
 625
 626   double density_half = (100 * pressure_mb * exp(-altitude_half_to_sun_m / 8000))
 627       / (287.05 * virtual_temp);
 628   double density_tropo = (100 * pressure_mb * exp((-1 * altitude_tropo_top_m) / 8000))
 629       / ( 287.05 * virtual_temp);
 630
 631   density_tropo_avg_kgm3 = ((density_slugft3 * 515.379) + density_half + density_tropo) / 3;
 632 }
 633
 634 void
 635 FGEnvironment::_recalc_relative_humidity ()
 636 {
 637   double vaporpressure = 6.11 * pow(10.0, ((7.5 * dewpoint_degc) / ( 237.7 + dewpoint_degc)));
 638   double sat_vaporpressure = 6.11 * pow(10.0, ((7.5 * temperature_degc)
 639       / ( 237.7 + temperature_degc)) );
 640   relative_humidity = 100 * vaporpressure / sat_vaporpressure ;
 641 }
 642
 643
 644
 645 ////////////////////////////////////////////////////////////////////////
 646 // Functions.
 647 ////////////////////////////////////////////////////////////////////////
 648
 649 static inline double
 650 do_interp (double a, double b, double fraction)
 651 {
 652     double retval = (a + ((b - a) * fraction));
 653     return retval;
 654 }
 655
 656 static inline double
 657 do_interp_deg (double a, double b, double fraction)
 658 {
 659     a = fmod(a, 360);
 660     b = fmod(b, 360);
 661     if (fabs(b-a) > 180) {
 662         if (a < b)
 663             a += 360;
 664         else
 665             b += 360;
 666     }
 667     return fmod(do_interp(a, b, fraction), 360);
 668 }
 669
 670 void
 671 interpolate (const FGEnvironment * env1, const FGEnvironment * env2,
 672              double fraction, FGEnvironment * result)
 673 {
 674     result->set_visibility_m
 675         (do_interp(env1->get_visibility_m(),
 676                    env2->get_visibility_m(),
 677                    fraction));
 678
 679     result->set_temperature_sea_level_degc
 680         (do_interp(env1->get_temperature_sea_level_degc(),
 681                    env2->get_temperature_sea_level_degc(),
 682                    fraction));
 683
 684     result->set_dewpoint_degc
 685         (do_interp(env1->get_dewpoint_sea_level_degc(),
 686                    env2->get_dewpoint_sea_level_degc(),
 687                    fraction));
 688
 689     result->set_pressure_sea_level_inhg
 690         (do_interp(env1->get_pressure_sea_level_inhg(),
 691                    env2->get_pressure_sea_level_inhg(),
 692                    fraction));
 693
 694     result->set_wind_from_heading_deg
 695         (do_interp_deg(env1->get_wind_from_heading_deg(),
 696                        env2->get_wind_from_heading_deg(),
 697                        fraction));
 698
 699     result->set_wind_speed_kt
 700         (do_interp(env1->get_wind_speed_kt(),
 701                    env2->get_wind_speed_kt(),
 702                    fraction));
 703
 704     result->set_elevation_ft
 705         (do_interp(env1->get_elevation_ft(),
 706                    env2->get_elevation_ft(),
 707                    fraction));
 708
 709     result->set_turbulence_magnitude_norm
 710         (do_interp(env1->get_turbulence_magnitude_norm(),
 711                    env2->get_turbulence_magnitude_norm(),
 712                    fraction));
 713
 714     result->set_turbulence_rate_hz
 715         (do_interp(env1->get_turbulence_rate_hz(),
 716                    env2->get_turbulence_rate_hz(),
 717                    fraction));
 718 }
 719
 720 // end of environment.cxx