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
  39 #include <Main/fg_props.hxx>
  40 #include "environment.hxx"
  41
  42
  43 FGEnvironment::FGEnvironment()
  44   : visibility_m(32000),
  45     temperature_sea_level_degc(20),
  46     pressure_sea_level_inhg(28),
  47     wind_from_heading_deg(0),
  48     wind_speed_kt(0),
  49     wind_from_north_fps(0),
  50     wind_from_east_fps(0),
  51     wind_from_down_fps(0)
  52 {
  53 }
  54
  55 FGEnvironment::FGEnvironment (const FGEnvironment &env)
  56   : elevation_ft(env.elevation_ft),
  57     visibility_m(env.visibility_m),
  58     temperature_sea_level_degc(env.temperature_sea_level_degc),
  59     pressure_sea_level_inhg(env.pressure_sea_level_inhg),
  60     wind_from_heading_deg(env.wind_from_heading_deg),
  61     wind_speed_kt(env.wind_speed_kt),
  62     wind_from_north_fps(env.wind_from_north_fps),
  63     wind_from_east_fps(env.wind_from_east_fps),
  64     wind_from_down_fps(env.wind_from_down_fps)
  65 {
  66 }
  67
  68 FGEnvironment::~FGEnvironment()
  69 {
  70 }
  71
  72
  73 double
  74 FGEnvironment::get_visibility_m () const
  75 {
  76   return visibility_m;
  77 }
  78
  79 double
  80 FGEnvironment::get_temperature_sea_level_degc () const
  81 {
  82   return temperature_sea_level_degc;
  83 }
  84
  85 double
  86 FGEnvironment::get_temperature_degc () const
  87 {
  88   return temperature_degc;
  89 }
  90
  91 double
  92 FGEnvironment::get_pressure_sea_level_inhg () const
  93 {
  94   return pressure_sea_level_inhg;
  95 }
  96
  97 double
  98 FGEnvironment::get_pressure_inhg () const
  99 {
 100   return pressure_inhg;
 101 }
 102
 103 double
 104 FGEnvironment::get_wind_from_heading_deg () const
 105 {
 106   return wind_from_heading_deg;
 107 }
 108
 109 double
 110 FGEnvironment::get_wind_speed_kt () const
 111 {
 112   return wind_speed_kt;
 113 }
 114
 115 double
 116 FGEnvironment::get_wind_from_north_fps () const
 117 {
 118   return wind_from_north_fps;
 119 }
 120
 121 double
 122 FGEnvironment::get_wind_from_east_fps () const
 123 {
 124   return wind_from_east_fps;
 125 }
 126
 127 double
 128 FGEnvironment::get_wind_from_down_fps () const
 129 {
 130   return wind_from_down_fps;
 131 }
 132
 133 double
 134 FGEnvironment::get_elevation_ft () const
 135 {
 136   return elevation_ft;
 137 }
 138
 139
 140
 141 void
 142 FGEnvironment::set_visibility_m (double v)
 143 {
 144   visibility_m = v;
 145 }
 146
 147 void
 148 FGEnvironment::set_temperature_sea_level_degc (double t)
 149 {
 150   temperature_sea_level_degc = t;
 151   _recalc_alt_temp();
 152 }
 153
 154 void
 155 FGEnvironment::set_temperature_degc (double t)
 156 {
 157   temperature_degc = t;
 158   _recalc_sl_temp();
 159 }
 160
 161 void
 162 FGEnvironment::set_pressure_sea_level_inhg (double p)
 163 {
 164   pressure_sea_level_inhg = p;
 165   _recalc_alt_press();
 166 }
 167
 168 void
 169 FGEnvironment::set_pressure_inhg (double p)
 170 {
 171   pressure_inhg = p;
 172   _recalc_sl_press();
 173 }
 174
 175 void
 176 FGEnvironment::set_wind_from_heading_deg (double h)
 177 {
 178   wind_from_heading_deg = h;
 179   _recalc_ne();
 180 }
 181
 182 void
 183 FGEnvironment::set_wind_speed_kt (double s)
 184 {
 185   wind_speed_kt = s;
 186   _recalc_ne();
 187 }
 188
 189 void
 190 FGEnvironment::set_wind_from_north_fps (double n)
 191 {
 192   wind_from_north_fps = n;
 193   _recalc_hdgspd();
 194 }
 195
 196 void
 197 FGEnvironment::set_wind_from_east_fps (double e)
 198 {
 199   wind_from_east_fps = e;
 200   _recalc_hdgspd();
 201 }
 202
 203 void
 204 FGEnvironment::set_wind_from_down_fps (double d)
 205 {
 206   wind_from_down_fps = d;
 207   _recalc_hdgspd();
 208 }
 209
 210 void
 211 FGEnvironment::set_elevation_ft (double e)
 212 {
 213   elevation_ft = e;
 214   _recalc_alt_temp();
 215   _recalc_alt_press();
 216 }
 217
 218 void
 219 FGEnvironment::_recalc_hdgspd ()
 220 {
 221   double angle_rad;
 222
 223   if (wind_from_east_fps == 0) {
 224     angle_rad = (wind_from_north_fps >= 0 ? SGD_PI/2 : -SGD_PI/2);
 225   } else {
 226     angle_rad = atan(wind_from_north_fps/wind_from_east_fps);
 227   }
 228   wind_from_heading_deg = angle_rad * SGD_RADIANS_TO_DEGREES;
 229   if (wind_from_east_fps >= 0)
 230     wind_from_heading_deg = 90 - wind_from_heading_deg;
 231   else
 232     wind_from_heading_deg = 270 - wind_from_heading_deg;
 233   if (angle_rad == 0)
 234     wind_speed_kt = fabs(wind_from_east_fps
 235                          * SG_METER_TO_NM * SG_FEET_TO_METER * 3600);
 236   else
 237     wind_speed_kt = (wind_from_north_fps / sin(angle_rad))
 238       * SG_METER_TO_NM * SG_FEET_TO_METER * 3600;
 239 }
 240
 241 void
 242 FGEnvironment::_recalc_ne ()
 243 {
 244   double speed_fps =
 245     wind_speed_kt * SG_NM_TO_METER * SG_METER_TO_FEET * (1.0/3600);
 246
 247   wind_from_north_fps = speed_fps *
 248     cos(wind_from_heading_deg * SGD_DEGREES_TO_RADIANS);
 249   wind_from_east_fps = speed_fps *
 250     sin(wind_from_heading_deg * SGD_DEGREES_TO_RADIANS);
 251 }
 252
 253 void
 254 FGEnvironment::_recalc_sl_temp ()
 255 {
 256   // Earth atmosphere model from
 257   // http://www.grc.nasa.gov/WWW/K-12/airplane/atmos.html
 258
 259   // Stratospheric temperatures are not really reversible, so use 15degC.
 260
 261   if (elevation_ft < 36152)     // Troposphere
 262     temperature_sea_level_degc =
 263       temperature_degc + (.00649 * SG_FEET_TO_METER * elevation_ft);
 264   // If we're in the stratosphere, leave sea-level temp alone
 265 }
 266
 267 void
 268 FGEnvironment::_recalc_alt_temp ()
 269 {
 270   // Earth atmosphere model from
 271   // http://www.grc.nasa.gov/WWW/K-12/airplane/atmos.html
 272
 273   if (elevation_ft < 36152)     // Troposphere
 274     temperature_degc =
 275       temperature_sea_level_degc - (.00649 * SG_FEET_TO_METER * elevation_ft);
 276   else if (elevation_ft < 82345) // Lower Stratosphere
 277     temperature_degc = -56.46;
 278   else
 279     temperature_degc = -131.21 + (.00299 * SG_FEET_TO_METER * elevation_ft);
 280 }
 281
 282 void
 283 FGEnvironment::_recalc_sl_press ()
 284 {
 285   // FIXME: calculate properly
 286   pressure_sea_level_inhg = pressure_inhg;
 287 }
 288
 289 void
 290 FGEnvironment::_recalc_alt_press ()
 291 {
 292   // FIXME: calculate properly
 293   pressure_inhg = pressure_sea_level_inhg;
 294 }
 295
 296 // end of environment.cxx
 297