#include <simgear/constants.h>
#include <simgear/debug/logstream.hxx>
+#include <simgear/math/interpolater.hxx>
#include <Main/fg_props.hxx>
#include "environment.hxx"
FGEnvironment::FGEnvironment()
- : visibility_m(32000),
- temperature_sea_level_degc(20),
- pressure_sea_level_inhg(28),
+ : _temperature_degc_table(new SGInterpTable),
+ _pressure_inhg_table(new SGInterpTable),
+ elevation_ft(0),
+ visibility_m(32000),
+ temperature_sea_level_degc(15),
+ temperature_degc(15),
+ dewpoint_sea_level_degc(5), // guess
+ dewpoint_degc(5),
+ pressure_sea_level_inhg(29.92),
+ pressure_inhg(29.92),
wind_from_heading_deg(0),
wind_speed_kt(0),
wind_from_north_fps(0),
wind_from_east_fps(0),
wind_from_down_fps(0)
{
+ _setup_tables();
}
FGEnvironment::FGEnvironment (const FGEnvironment &env)
- : elevation_ft(env.elevation_ft),
+ : _temperature_degc_table(new SGInterpTable),
+ _pressure_inhg_table(new SGInterpTable),
+ elevation_ft(env.elevation_ft),
visibility_m(env.visibility_m),
temperature_sea_level_degc(env.temperature_sea_level_degc),
+ dewpoint_sea_level_degc(env.dewpoint_sea_level_degc),
pressure_sea_level_inhg(env.pressure_sea_level_inhg),
wind_from_heading_deg(env.wind_from_heading_deg),
wind_speed_kt(env.wind_speed_kt),
wind_from_east_fps(env.wind_from_east_fps),
wind_from_down_fps(env.wind_from_down_fps)
{
+ _setup_tables();
}
FGEnvironment::~FGEnvironment()
{
+ delete _temperature_degc_table;
+ delete _pressure_inhg_table;
}
return temperature_degc;
}
+double
+FGEnvironment::get_dewpoint_sea_level_degc () const
+{
+ return dewpoint_sea_level_degc;
+}
+
+double
+FGEnvironment::get_dewpoint_degc () const
+{
+ return dewpoint_degc;
+}
+
double
FGEnvironment::get_pressure_sea_level_inhg () const
{
return pressure_inhg;
}
+double
+FGEnvironment::get_density_slugft3 () const
+{
+ return density_slugft3;
+}
+
double
FGEnvironment::get_wind_from_heading_deg () const
{
return elevation_ft;
}
-
-
void
FGEnvironment::set_visibility_m (double v)
{
FGEnvironment::set_temperature_sea_level_degc (double t)
{
temperature_sea_level_degc = t;
- _recalc_alt_temp();
+ if (dewpoint_sea_level_degc > t)
+ dewpoint_sea_level_degc = t;
+ _recalc_alt_temperature();
+ _recalc_density();
}
void
FGEnvironment::set_temperature_degc (double t)
{
temperature_degc = t;
- _recalc_sl_temp();
+ _recalc_sl_temperature();
+ _recalc_density();
+}
+
+void
+FGEnvironment::set_dewpoint_sea_level_degc (double t)
+{
+ dewpoint_sea_level_degc = t;
+ if (temperature_sea_level_degc < t)
+ temperature_sea_level_degc = t;
+ _recalc_alt_dewpoint();
+ _recalc_density();
+}
+
+void
+FGEnvironment::set_dewpoint_degc (double t)
+{
+ dewpoint_degc = t;
+ _recalc_sl_dewpoint();
+ _recalc_density();
}
void
FGEnvironment::set_pressure_sea_level_inhg (double p)
{
pressure_sea_level_inhg = p;
- _recalc_alt_press();
+ _recalc_alt_pressure();
+ _recalc_density();
}
void
FGEnvironment::set_pressure_inhg (double p)
{
pressure_inhg = p;
- _recalc_sl_press();
+ _recalc_sl_pressure();
+ _recalc_density();
}
void
FGEnvironment::set_elevation_ft (double e)
{
elevation_ft = e;
- _recalc_alt_temp();
- _recalc_alt_press();
+ _recalc_alt_temperature();
+ _recalc_alt_dewpoint();
+ _recalc_alt_pressure();
+ _recalc_density();
+}
+
+// Atmosphere model.
+
+// Copied from YASim Atmosphere.cxx, with m converted to ft, degK
+// converted to degC, Pa converted to inHG, and kg/m^3 converted to
+// slug/ft^3; they were then converted to deltas from the sea-level
+// defaults (approx. 15degC, 29.92inHG, and 0.00237slugs/ft^3).
+
+// Original comment from YASim:
+
+// Copied from McCormick, who got it from "The ARDC Model Atmosphere"
+// Note that there's an error in the text in the first entry,
+// McCormick lists 299.16/101325/1.22500, but those don't agree with
+// R=287. I chose to correct the temperature to 288.20, since 79F is
+// pretty hot for a "standard" atmosphere.
+
+// Elevation (ft), temperature factor (degK), pressure factor (inHG)
+static double atmosphere_data[][3] = {
+ { 0.00, 1.00, 1.000 },
+ { 2952.76, 0.98, 0.898 },
+ { 5905.51, 0.96, 0.804 },
+ { 8858.27, 0.94, 0.719 },
+ { 11811.02, 0.92, 0.641 },
+ { 14763.78, 0.90, 0.570 },
+ { 17716.54, 0.88, 0.506 },
+ { 20669.29, 0.86, 0.447 },
+ { 23622.05, 0.84, 0.394 },
+ { 26574.80, 0.82, 0.347 },
+ { 29527.56, 0.80, 0.304 },
+ { 32480.31, 0.78, 0.266 },
+ { 35433.07, 0.76, 0.231 },
+ { 38385.83, 0.75, 0.201 },
+ { 41338.58, 0.75, 0.174 },
+ { 44291.34, 0.75, 0.151 },
+ { 47244.09, 0.75, 0.131 },
+ { 50196.85, 0.75, 0.114 },
+ { 53149.61, 0.75, 0.099 },
+ { 56102.36, 0.75, 0.086 },
+ { 59055.12, 0.75, 0.075 },
+ { 62007.87, 0.75, 0.065 },
+ { -1, -1, -1 }
+};
+
+void
+FGEnvironment::_setup_tables ()
+{
+ for (int i = 0; atmosphere_data[i][0] != -1; i++) {
+ _temperature_degc_table->addEntry(atmosphere_data[i][0],
+ atmosphere_data[i][1]);
+ _pressure_inhg_table->addEntry(atmosphere_data[i][0],
+ atmosphere_data[i][2]);
+ }
}
void
}
void
-FGEnvironment::_recalc_sl_temp ()
+FGEnvironment::_recalc_sl_temperature ()
{
- // Earth atmosphere model from
- // http://www.grc.nasa.gov/WWW/K-12/airplane/atmos.html
+ // If we're in the stratosphere, leave sea-level temp alone
+ if (elevation_ft < 38000) {
+ temperature_sea_level_degc =
+ (temperature_degc + 273.15)
+ /_temperature_degc_table->interpolate(elevation_ft)
+ - 273.15;
+ }
+}
- // Stratospheric temperatures are not really reversible, so use 15degC.
+void
+FGEnvironment::_recalc_alt_temperature ()
+{
+ if (elevation_ft < 38000) {
+ temperature_degc =
+ (temperature_sea_level_degc + 273.15) *
+ _temperature_degc_table->interpolate(elevation_ft) - 273.15;
+ } else {
+ temperature_degc = -56.49; // Stratosphere is constant
+ }
+}
- if (elevation_ft < 36152) // Troposphere
- temperature_sea_level_degc =
- temperature_degc + (.00649 * SG_FEET_TO_METER * elevation_ft);
- // If we're in the stratosphere, leave sea-level temp alone
+void
+FGEnvironment::_recalc_sl_dewpoint ()
+{
+ // 0.2degC/1000ft
+ // FIXME: this will work only for low
+ // elevations
+ dewpoint_sea_level_degc = dewpoint_degc + (elevation_ft * .0002);
+ if (dewpoint_sea_level_degc > temperature_sea_level_degc)
+ dewpoint_sea_level_degc = temperature_sea_level_degc;
}
void
-FGEnvironment::_recalc_alt_temp ()
+FGEnvironment::_recalc_alt_dewpoint ()
{
- // Earth atmosphere model from
- // http://www.grc.nasa.gov/WWW/K-12/airplane/atmos.html
+ // 0.2degC/1000ft
+ // FIXME: this will work only for low
+ // elevations
+ dewpoint_degc = dewpoint_sea_level_degc + (elevation_ft * .0002);
+ if (dewpoint_degc > temperature_degc)
+ dewpoint_degc = temperature_degc;
+}
- if (elevation_ft < 36152) // Troposphere
- temperature_degc =
- temperature_sea_level_degc - (.00649 * SG_FEET_TO_METER * elevation_ft);
- else if (elevation_ft < 82345) // Lower Stratosphere
- temperature_degc = -56.46;
- else
- temperature_degc = -131.21 + (.00299 * SG_FEET_TO_METER * elevation_ft);
+void
+FGEnvironment::_recalc_sl_pressure ()
+{
+ pressure_sea_level_inhg =
+ pressure_inhg / _pressure_inhg_table->interpolate(elevation_ft);
}
void
-FGEnvironment::_recalc_sl_press ()
+FGEnvironment::_recalc_alt_pressure ()
{
- // FIXME: calculate properly
- pressure_sea_level_inhg = pressure_inhg;
+ pressure_inhg =
+ pressure_sea_level_inhg * _pressure_inhg_table->interpolate(elevation_ft);
}
void
-FGEnvironment::_recalc_alt_press ()
+FGEnvironment::_recalc_density ()
{
- // FIXME: calculate properly
- pressure_inhg = pressure_sea_level_inhg;
+ double pressure_psf = pressure_inhg * 70.7487;
+
+ // adjust for humidity
+ // calculations taken from USA Today (oops!) at
+ // http://www.usatoday.com/weather/basics/density-calculations.htm
+ double temperature_degk = temperature_degc + 273.15;
+ double pressure_mb = pressure_inhg * 33.86;
+ double vapor_pressure_mb =
+ 6.11 * pow(10.0, 7.5 * dewpoint_degc / (237.7 + dewpoint_degc));
+ double virtual_temperature_degk = temperature_degk / (1 - (vapor_pressure_mb / pressure_mb) * (1.0 - 0.622));
+ double virtual_temperature_degr = virtual_temperature_degk * 1.8;
+
+ density_slugft3 = pressure_psf / (virtual_temperature_degr * 1718);
}
// end of environment.cxx
-
projects / flightgear.git / blobdiff