//
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
-// Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
//
-// $Id$
-
#ifdef HAVE_CONFIG_H
# include <config.h>
#endif
-#ifdef HAVE_WINDOWS_H
-# include <windows.h>
-#endif
-
#include <math.h>
-#include <simgear/debug/logstream.hxx>
+#include <boost/tuple/tuple.hpp>
+
+#include <simgear/props/props.hxx>
#include <Main/fg_props.hxx>
+
#include "environment.hxx"
+#include "atmosphere.hxx"
+
+\f
+////////////////////////////////////////////////////////////////////////
+// Atmosphere model.
+////////////////////////////////////////////////////////////////////////
+
+#ifdef USING_TABLES
+
+// Calculated based on the ISA standard day, as found at e.g.
+// http://www.av8n.com/physics/altimetry.htm
+
+// Each line of data has 3 elements:
+// Elevation (ft),
+// temperature factor (dimensionless ratio of absolute temp),
+// pressure factor (dimensionless ratio)
+static double atmosphere_data[][3] = {
+ { -3000.00, 1.021, 1.1133 },
+ { 0.00, 1.000, 1.0000 },
+ { 2952.76, 0.980, 0.8978 },
+ { 5905.51, 0.959, 0.8042 },
+ { 8858.27, 0.939, 0.7187 },
+ { 11811.02, 0.919, 0.6407 },
+ { 14763.78, 0.898, 0.5697 },
+ { 17716.54, 0.878, 0.5052 },
+ { 20669.29, 0.858, 0.4468 },
+ { 23622.05, 0.838, 0.3940 },
+ { 26574.80, 0.817, 0.3463 },
+ { 29527.56, 0.797, 0.3034 },
+ { 32480.31, 0.777, 0.2649 },
+ { 35433.07, 0.756, 0.2305 },
+ { 38385.83, 0.752, 0.2000 },
+ { 41338.58, 0.752, 0.1736 },
+ { 44291.34, 0.752, 0.1506 },
+ { 47244.09, 0.752, 0.1307 },
+ { 50196.85, 0.752, 0.1134 },
+ { 53149.61, 0.752, 0.0984 },
+ { 56102.36, 0.752, 0.0854 },
+ { 59055.12, 0.752, 0.0741 },
+ { 62007.87, 0.752, 0.0643 },
+ { 65000.00, 0.752, 0.0557 },
+ { 68000.00, 0.754, 0.0482 },
+ { 71000.00, 0.758, 0.0418 },
+ { 74000.00, 0.761, 0.0362 },
+ { 77000.00, 0.764, 0.0314 },
+ { 80000.00, 0.767, 0.0273 },
+ { 83000.00, 0.770, 0.0237 },
+ { 86000.00, 0.773, 0.0206 },
+ { 89000.00, 0.777, 0.0179 },
+ { 92000.00, 0.780, 0.0156 },
+ { 95000.00, 0.783, 0.0135 },
+ { 98000.00, 0.786, 0.0118 },
+ { 101000.00, 0.789, 0.0103 },
+ { -1, -1, -1 }
+};
+
+static SGInterpTable * _temperature_degc_table = 0;
+static SGInterpTable * _pressure_inhg_table = 0;
+
+static void
+_setup_tables ()
+{
+ if (_temperature_degc_table != 0)
+ return;
+
+ _temperature_degc_table = new SGInterpTable;
+ _pressure_inhg_table = new SGInterpTable;
+
+ 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]);
+ }
+}
+#endif
+\f
+////////////////////////////////////////////////////////////////////////
+// Implementation of FGEnvironment.
+////////////////////////////////////////////////////////////////////////
+
+void FGEnvironment::_init()
+{
+ 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;
+ turbulence_magnitude_norm = 0;
+ turbulence_rate_hz = 1;
+ wind_from_heading_deg = 0;
+ wind_speed_kt = 0;
+ wind_from_north_fps = 0;
+ wind_from_east_fps = 0;
+ wind_from_down_fps = 0;
+ altitude_half_to_sun_m = 1000;
+ altitude_tropo_top_m = 10000;
+#ifdef USING_TABLES
+ _setup_tables();
+#endif
+ _recalc_density();
+ _recalc_relative_humidity();
+ live_update = true;
+}
FGEnvironment::FGEnvironment()
- : visibility_m(32000),
- wind_from_heading_deg(0),
- wind_speed_kt(0),
- wind_from_north_fps(0),
- wind_from_east_fps(0),
- wind_from_down_fps(0)
{
+ _init();
}
+FGEnvironment::FGEnvironment (const FGEnvironment &env)
+{
+ _init();
+ copy(env);
+}
FGEnvironment::~FGEnvironment()
{
+ Untie();
+}
+
+FGEnvironment & FGEnvironment::operator = ( const FGEnvironment & other )
+{
+ copy( other );
+ return *this;
+}
+
+void
+FGEnvironment::copy (const FGEnvironment &env)
+{
+ elevation_ft = env.elevation_ft;
+ visibility_m = env.visibility_m;
+ temperature_sea_level_degc = env.temperature_sea_level_degc;
+ temperature_degc = env.temperature_degc;
+ dewpoint_sea_level_degc = env.dewpoint_sea_level_degc;
+ dewpoint_degc = env.dewpoint_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_north_fps = env.wind_from_north_fps;
+ wind_from_east_fps = env.wind_from_east_fps;
+ wind_from_down_fps = env.wind_from_down_fps;
+ turbulence_magnitude_norm = env.turbulence_magnitude_norm;
+ turbulence_rate_hz = env.turbulence_rate_hz;
+}
+
+static inline bool
+maybe_copy_value (FGEnvironment * env, const SGPropertyNode * node,
+ const char * name, void (FGEnvironment::*setter)(double))
+{
+ const SGPropertyNode * child = node->getNode(name);
+ // fragile: depends on not being typed
+ // as a number
+ if (child != 0 && child->hasValue() &&
+ child->getStringValue()[0] != '\0') {
+ (env->*setter)(child->getDoubleValue());
+ return true;
+ } else {
+ return false;
+ }
+}
+
+void
+FGEnvironment::read (const SGPropertyNode * node)
+{
+ bool live_update = set_live_update( false );
+ maybe_copy_value(this, node, "visibility-m",
+ &FGEnvironment::set_visibility_m);
+
+ maybe_copy_value(this, node, "elevation-ft",
+ &FGEnvironment::set_elevation_ft);
+
+ if (!maybe_copy_value(this, node, "temperature-sea-level-degc",
+ &FGEnvironment::set_temperature_sea_level_degc)) {
+ if( maybe_copy_value(this, node, "temperature-degc",
+ &FGEnvironment::set_temperature_degc)) {
+ _recalc_sl_temperature();
+ }
+ }
+
+ if (!maybe_copy_value(this, node, "dewpoint-sea-level-degc",
+ &FGEnvironment::set_dewpoint_sea_level_degc)) {
+ if( maybe_copy_value(this, node, "dewpoint-degc",
+ &FGEnvironment::set_dewpoint_degc)) {
+ _recalc_sl_dewpoint();
+ }
+ }
+
+ if (!maybe_copy_value(this, node, "pressure-sea-level-inhg",
+ &FGEnvironment::set_pressure_sea_level_inhg)) {
+ if( maybe_copy_value(this, node, "pressure-inhg",
+ &FGEnvironment::set_pressure_inhg)) {
+ _recalc_sl_pressure();
+ }
+ }
+
+ maybe_copy_value(this, node, "wind-from-heading-deg",
+ &FGEnvironment::set_wind_from_heading_deg);
+
+ maybe_copy_value(this, node, "wind-speed-kt",
+ &FGEnvironment::set_wind_speed_kt);
+
+ maybe_copy_value(this, node, "turbulence/magnitude-norm",
+ &FGEnvironment::set_turbulence_magnitude_norm);
+
+ maybe_copy_value(this, node, "turbulence/rate-hz",
+ &FGEnvironment::set_turbulence_rate_hz);
+
+ // calculate derived properties here to avoid duplicate expensive computations
+ _recalc_ne();
+ _recalc_alt_pt();
+ _recalc_alt_dewpoint();
+ _recalc_density();
+ _recalc_relative_humidity();
+
+ set_live_update(live_update);
+}
+
+void FGEnvironment::Tie( SGPropertyNode_ptr base, bool archivable )
+{
+ _tiedProperties.setRoot( base );
+
+ _tiedProperties.Tie( "visibility-m", this,
+ &FGEnvironment::get_visibility_m,
+ &FGEnvironment::set_visibility_m)
+ ->setAttribute( SGPropertyNode::ARCHIVE, archivable );
+
+ _tiedProperties.Tie("temperature-sea-level-degc", this,
+ &FGEnvironment::get_temperature_sea_level_degc,
+ &FGEnvironment::set_temperature_sea_level_degc)
+ ->setAttribute( SGPropertyNode::ARCHIVE, archivable );
+
+ _tiedProperties.Tie("temperature-degc", this,
+ &FGEnvironment::get_temperature_degc,
+ &FGEnvironment::set_temperature_degc)
+ ->setAttribute( SGPropertyNode::ARCHIVE, archivable );
+
+ _tiedProperties.Tie("temperature-degf", this,
+ &FGEnvironment::get_temperature_degf);
+
+ _tiedProperties.Tie("dewpoint-sea-level-degc", this,
+ &FGEnvironment::get_dewpoint_sea_level_degc,
+ &FGEnvironment::set_dewpoint_sea_level_degc)
+ ->setAttribute( SGPropertyNode::ARCHIVE, archivable );
+
+ _tiedProperties.Tie("dewpoint-degc", this,
+ &FGEnvironment::get_dewpoint_degc,
+ &FGEnvironment::set_dewpoint_degc)
+ ->setAttribute( SGPropertyNode::ARCHIVE, archivable );
+
+ _tiedProperties.Tie("pressure-sea-level-inhg", this,
+ &FGEnvironment::get_pressure_sea_level_inhg,
+ &FGEnvironment::set_pressure_sea_level_inhg)
+ ->setAttribute( SGPropertyNode::ARCHIVE, archivable );
+
+ _tiedProperties.Tie("pressure-inhg", this,
+ &FGEnvironment::get_pressure_inhg,
+ &FGEnvironment::set_pressure_inhg)
+ ->setAttribute( SGPropertyNode::ARCHIVE, archivable );
+
+ _tiedProperties.Tie("density-slugft3", this,
+ &FGEnvironment::get_density_slugft3); // read-only
+
+ _tiedProperties.Tie("relative-humidity", this,
+ &FGEnvironment::get_relative_humidity); //ro
+
+ _tiedProperties.Tie("atmosphere/density-tropo-avg", this,
+ &FGEnvironment::get_density_tropo_avg_kgm3); //ro
+
+ _tiedProperties.Tie("atmosphere/altitude-half-to-sun", this,
+ &FGEnvironment::get_altitude_half_to_sun_m,
+ &FGEnvironment::set_altitude_half_to_sun_m)
+ ->setAttribute( SGPropertyNode::ARCHIVE, archivable );
+
+ _tiedProperties.Tie("atmosphere/altitude-troposphere-top", this,
+ &FGEnvironment::get_altitude_tropo_top_m,
+ &FGEnvironment::set_altitude_tropo_top_m)
+ ->setAttribute( SGPropertyNode::ARCHIVE, archivable );
+
+ _tiedProperties.Tie("wind-from-heading-deg", this,
+ &FGEnvironment::get_wind_from_heading_deg,
+ &FGEnvironment::set_wind_from_heading_deg)
+ ->setAttribute( SGPropertyNode::ARCHIVE, archivable );
+
+ _tiedProperties.Tie("wind-speed-kt", this,
+ &FGEnvironment::get_wind_speed_kt,
+ &FGEnvironment::set_wind_speed_kt)
+ ->setAttribute( SGPropertyNode::ARCHIVE, archivable );
+
+ _tiedProperties.Tie("wind-from-north-fps", this,
+ &FGEnvironment::get_wind_from_north_fps,
+ &FGEnvironment::set_wind_from_north_fps)
+ ->setAttribute( SGPropertyNode::ARCHIVE, archivable );
+
+ _tiedProperties.Tie("wind-from-east-fps", this,
+ &FGEnvironment::get_wind_from_east_fps,
+ &FGEnvironment::set_wind_from_east_fps)
+ ->setAttribute( SGPropertyNode::ARCHIVE, archivable );
+
+ _tiedProperties.Tie("wind-from-down-fps", this,
+ &FGEnvironment::get_wind_from_down_fps,
+ &FGEnvironment::set_wind_from_down_fps)
+ ->setAttribute( SGPropertyNode::ARCHIVE, archivable );
+
+ _tiedProperties.Tie("turbulence/magnitude-norm", this,
+ &FGEnvironment::get_turbulence_magnitude_norm,
+ &FGEnvironment::set_turbulence_magnitude_norm)
+ ->setAttribute( SGPropertyNode::ARCHIVE, archivable );
+
+ _tiedProperties.Tie("turbulence/rate-hz", this,
+ &FGEnvironment::get_turbulence_rate_hz,
+ &FGEnvironment::set_turbulence_rate_hz)
+ ->setAttribute( SGPropertyNode::ARCHIVE, archivable );
+}
+
+void FGEnvironment::Untie()
+{
+ _tiedProperties.Untie();
+}
+
+double
+FGEnvironment::get_visibility_m () const
+{
+ return visibility_m;
+}
+
+double
+FGEnvironment::get_temperature_sea_level_degc () const
+{
+ return temperature_sea_level_degc;
+}
+
+double
+FGEnvironment::get_temperature_degc () const
+{
+ return temperature_degc;
+}
+
+double
+FGEnvironment::get_temperature_degf () const
+{
+ return (temperature_degc * 9.0 / 5.0) + 32.0;
+}
+
+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_sea_level_inhg;
+}
+
+double
+FGEnvironment::get_pressure_inhg () const
+{
+ return pressure_inhg;
+}
+
+double
+FGEnvironment::get_density_slugft3 () const
+{
+ return density_slugft3;
+}
+
+double
+FGEnvironment::get_relative_humidity () const
+{
+ return relative_humidity;
+}
+
+double
+FGEnvironment::get_density_tropo_avg_kgm3 () const
+{
+ return density_tropo_avg_kgm3;
+}
+
+double
+FGEnvironment::get_altitude_half_to_sun_m () const
+{
+ return altitude_half_to_sun_m;
+}
+
+double
+FGEnvironment::get_altitude_tropo_top_m () const
+{
+ return altitude_tropo_top_m;
+}
+
+double
+FGEnvironment::get_wind_from_heading_deg () const
+{
+ return wind_from_heading_deg;
+}
+
+double
+FGEnvironment::get_wind_speed_kt () const
+{
+ return wind_speed_kt;
+}
+
+double
+FGEnvironment::get_wind_from_north_fps () const
+{
+ return wind_from_north_fps;
}
+double
+FGEnvironment::get_wind_from_east_fps () const
+{
+ return wind_from_east_fps;
+}
+
+double
+FGEnvironment::get_wind_from_down_fps () const
+{
+ return wind_from_down_fps;
+}
+
+double
+FGEnvironment::get_turbulence_magnitude_norm () const
+{
+ return turbulence_magnitude_norm;
+}
+
+double
+FGEnvironment::get_turbulence_rate_hz () const
+{
+ return turbulence_rate_hz;
+}
+
+double
+FGEnvironment::get_elevation_ft () const
+{
+ return elevation_ft;
+}
void
FGEnvironment::set_visibility_m (double v)
visibility_m = v;
}
+void
+FGEnvironment::set_temperature_sea_level_degc (double t)
+{
+ temperature_sea_level_degc = t;
+ if (dewpoint_sea_level_degc > t)
+ dewpoint_sea_level_degc = t;
+ if( live_update ) {
+ _recalc_alt_pt();
+ _recalc_density();
+ }
+}
+
+void
+FGEnvironment::set_temperature_degc (double t)
+{
+ temperature_degc = t;
+ if( live_update ) {
+ _recalc_sl_temperature();
+ _recalc_sl_pressure();
+ _recalc_alt_pt();
+ _recalc_density();
+ _recalc_relative_humidity();
+ }
+}
+
+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;
+ if( live_update ) {
+ _recalc_alt_dewpoint();
+ _recalc_density();
+ }
+}
+
+void
+FGEnvironment::set_dewpoint_degc (double t)
+{
+ dewpoint_degc = t;
+ if( live_update ) {
+ _recalc_sl_dewpoint();
+ _recalc_density();
+ _recalc_relative_humidity();
+ }
+}
+
+void
+FGEnvironment::set_pressure_sea_level_inhg (double p)
+{
+ pressure_sea_level_inhg = p;
+ if( live_update ) {
+ _recalc_alt_pt();
+ _recalc_density();
+ }
+}
+
+void
+FGEnvironment::set_pressure_inhg (double p)
+{
+ pressure_inhg = p;
+ if( live_update ) {
+ _recalc_sl_pressure();
+ _recalc_density();
+ }
+}
+
void
FGEnvironment::set_wind_from_heading_deg (double h)
{
wind_from_heading_deg = h;
- _recalc_ne();
+ if( live_update ) {
+ _recalc_ne();
+ }
}
void
FGEnvironment::set_wind_speed_kt (double s)
{
wind_speed_kt = s;
- _recalc_ne();
+ if( live_update ) {
+ _recalc_ne();
+ }
}
void
FGEnvironment::set_wind_from_north_fps (double n)
{
wind_from_north_fps = n;
- _recalc_hdgspd();
+ if( live_update ) {
+ _recalc_hdgspd();
+ }
}
void
FGEnvironment::set_wind_from_east_fps (double e)
{
wind_from_east_fps = e;
- _recalc_hdgspd();
+ if( live_update ) {
+ _recalc_hdgspd();
+ }
}
void
FGEnvironment::set_wind_from_down_fps (double d)
{
wind_from_down_fps = d;
- _recalc_hdgspd();
+ if( live_update ) {
+ _recalc_hdgspd();
+ }
}
void
-FGEnvironment::_recalc_hdgspd ()
+FGEnvironment::set_turbulence_magnitude_norm (double t)
{
- double angle_rad;
+ turbulence_magnitude_norm = t;
+}
- if (wind_from_east_fps == 0) {
- angle_rad = (wind_from_north_fps >= 0 ? SGD_PI/2 : -SGD_PI/2);
- } else {
- angle_rad = atan(wind_from_north_fps/wind_from_east_fps);
+void
+FGEnvironment::set_turbulence_rate_hz (double r)
+{
+ turbulence_rate_hz = r;
+}
+
+void
+FGEnvironment::set_elevation_ft (double e)
+{
+ elevation_ft = e;
+ if( live_update ) {
+ _recalc_alt_pt();
+ _recalc_alt_dewpoint();
+ _recalc_density();
+ _recalc_relative_humidity();
+ }
+}
+
+void
+FGEnvironment::set_altitude_half_to_sun_m (double alt)
+{
+ altitude_half_to_sun_m = alt;
+ if( live_update ) {
+ _recalc_density_tropo_avg_kgm3();
+ }
+}
+
+void
+FGEnvironment::set_altitude_tropo_top_m (double alt)
+{
+ altitude_tropo_top_m = alt;
+ if( live_update ) {
+ _recalc_density_tropo_avg_kgm3();
}
- wind_from_heading_deg = angle_rad * SGD_RADIANS_TO_DEGREES;
- if (wind_from_east_fps >= 0)
- wind_from_heading_deg = 90 - wind_from_heading_deg;
- else
- wind_from_heading_deg = 270 - wind_from_heading_deg;
- if (angle_rad == 0)
- wind_speed_kt = fabs(wind_from_east_fps
- * SG_METER_TO_NM * SG_FEET_TO_METER * 3600);
- else
- wind_speed_kt = (wind_from_north_fps / sin(angle_rad))
- * SG_METER_TO_NM * SG_FEET_TO_METER * 3600;
+}
+
+
+void
+FGEnvironment::_recalc_hdgspd ()
+{
+ wind_from_heading_deg =
+ atan2(wind_from_east_fps, wind_from_north_fps) * SGD_RADIANS_TO_DEGREES;
+
+ if( wind_from_heading_deg < 0 )
+ wind_from_heading_deg += 360.0;
+
+ wind_speed_kt = sqrt(wind_from_north_fps * wind_from_north_fps +
+ wind_from_east_fps * wind_from_east_fps)
+ * SG_METER_TO_NM * SG_FEET_TO_METER * 3600;
}
void
sin(wind_from_heading_deg * SGD_DEGREES_TO_RADIANS);
}
-// end of environment.cxx
+// Intended to help with the interpretation of METAR data,
+// not for random in-flight outside-air temperatures.
+void
+FGEnvironment::_recalc_sl_temperature ()
+{
+
+#if 0
+ {
+ SG_LOG(SG_GENERAL, SG_DEBUG, "recalc_sl_temperature: using "
+ << temperature_degc << " @ " << elevation_ft << " :: " << this);
+ }
+#endif
+
+ if (elevation_ft * atmodel::foot >= ISA_def[1].height) {
+ SG_LOG(SG_GENERAL, SG_ALERT, "recalc_sl_temperature: "
+ << "valid only in troposphere, not " << elevation_ft);
+ return;
+ }
+// Clamp: temperature of the stratosphere, in degrees C:
+ double t_strato = ISA_def[1].temp - atmodel::freezing;
+ if (temperature_degc < t_strato) temperature_sea_level_degc = t_strato;
+ else temperature_sea_level_degc =
+ temperature_degc + elevation_ft * atmodel::foot * ISA_def[0].lapse;
+
+// Alternative implemenation:
+// else temperature_sea_level_inhg = T_layer(0., elevation_ft * foot,
+// pressure_inhg * inHg, temperature_degc + freezing, ISA_def[0].lapse) - freezing;
+}
+
+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_dewpoint ()
+{
+ // 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;
+}
+
+void
+FGEnvironment::_recalc_sl_pressure ()
+{
+ using namespace atmodel;
+#if 0
+ {
+ SG_LOG(SG_GENERAL, SG_ALERT, "recalc_sl_pressure: using "
+ << pressure_inhg << " and "
+ << temperature_degc << " @ " << elevation_ft << " :: " << this);
+ }
+#endif
+ pressure_sea_level_inhg = P_layer(0., elevation_ft * foot,
+ pressure_inhg * inHg, temperature_degc + freezing, ISA_def[0].lapse) / inHg;
+}
+
+// This gets called at frame rate, to account for the aircraft's
+// changing altitude.
+// Called by set_elevation_ft() which is called by FGEnvironmentMgr::update
+
+void
+FGEnvironment::_recalc_alt_pt ()
+{
+ using namespace atmodel;
+#if 0
+ {
+ static int count(0);
+ if (++count % 1000 == 0) {
+ SG_LOG(SG_GENERAL, SG_ALERT,
+ "recalc_alt_pt for: " << elevation_ft
+ << " using " << pressure_sea_level_inhg
+ << " and " << temperature_sea_level_degc
+ << " :: " << this
+ << " # " << count);
+ }
+ }
+#endif
+ double press = pressure_inhg * inHg;
+ double temp = temperature_degc + freezing;
+ boost::tie(press, temp) = PT_vs_hpt(elevation_ft * foot,
+ pressure_sea_level_inhg * inHg, temperature_sea_level_degc + freezing);
+ temperature_degc = temp - freezing;
+ pressure_inhg = press / inHg;
+}
+
+void
+FGEnvironment::_recalc_density ()
+{
+ 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);
+ _recalc_density_tropo_avg_kgm3();
+}
+
+// This is used to calculate the average density on the path
+// of sunlight to the observer for calculating sun-color
+void
+FGEnvironment::_recalc_density_tropo_avg_kgm3 ()
+{
+ double pressure_mb = pressure_inhg * 33.86;
+ double vaporpressure = 6.11 * pow(10.0, ((7.5 * dewpoint_degc) / (237.7 + dewpoint_degc)));
+
+ double virtual_temp = (temperature_degc + 273.15) / (1 - 0.379 * (vaporpressure/pressure_mb));
+
+ double density_half = (100 * pressure_mb * exp(-altitude_half_to_sun_m / 8000))
+ / (287.05 * virtual_temp);
+ double density_tropo = (100 * pressure_mb * exp((-1 * altitude_tropo_top_m) / 8000))
+ / ( 287.05 * virtual_temp);
+
+ density_tropo_avg_kgm3 = ((density_slugft3 * 515.379) + density_half + density_tropo) / 3;
+}
+
+void
+FGEnvironment::_recalc_relative_humidity ()
+{
+/*
+ double vaporpressure = 6.11 * pow(10.0, ((7.5 * dewpoint_degc) / ( 237.7 + dewpoint_degc)));
+ double sat_vaporpressure = 6.11 * pow(10.0, ((7.5 * temperature_degc)
+ / ( 237.7 + temperature_degc)) );
+ relative_humidity = 100 * vaporpressure / sat_vaporpressure ;
+
+ with a little algebra, this gets the same result and spares two multiplications and one pow()
+*/
+ double a = (7.5 * dewpoint_degc) / ( 237.7 + dewpoint_degc);
+ double b = (7.5 * temperature_degc) / ( 237.7 + temperature_degc);
+ relative_humidity = 100 * pow(10.0,a-b);
+}
+
+bool
+FGEnvironment::set_live_update( bool _live_update )
+{
+ bool b = live_update;
+ live_update = _live_update;
+ return b;
+}
+
+
+////////////////////////////////////////////////////////////////////////
+// Functions.
+////////////////////////////////////////////////////////////////////////
+
+static inline double
+do_interp (double a, double b, double fraction)
+{
+ double retval = (a + ((b - a) * fraction));
+ return retval;
+}
+
+static inline double
+do_interp_deg (double a, double b, double fraction)
+{
+ a = fmod(a, 360);
+ b = fmod(b, 360);
+ if (fabs(b-a) > 180) {
+ if (a < b)
+ a += 360;
+ else
+ b += 360;
+ }
+ return fmod(do_interp(a, b, fraction), 360);
+}
+
+FGEnvironment &
+FGEnvironment::interpolate( const FGEnvironment & env2,
+ double fraction, FGEnvironment * result) const
+{
+ // don't calculate each internal property every time we set a single value
+ // we trigger that at the end of the interpolation process
+ bool live_update = result->set_live_update( false );
+
+ result->set_visibility_m
+ (do_interp(get_visibility_m(),
+ env2.get_visibility_m(),
+ fraction));
+
+ result->set_temperature_sea_level_degc
+ (do_interp(get_temperature_sea_level_degc(),
+ env2.get_temperature_sea_level_degc(),
+ fraction));
+
+ result->set_dewpoint_sea_level_degc
+ (do_interp(get_dewpoint_sea_level_degc(),
+ env2.get_dewpoint_sea_level_degc(),
+ fraction));
+
+ result->set_pressure_sea_level_inhg
+ (do_interp(get_pressure_sea_level_inhg(),
+ env2.get_pressure_sea_level_inhg(),
+ fraction));
+
+ result->set_wind_from_heading_deg
+ (do_interp_deg(get_wind_from_heading_deg(),
+ env2.get_wind_from_heading_deg(),
+ fraction));
+
+ result->set_wind_speed_kt
+ (do_interp(get_wind_speed_kt(),
+ env2.get_wind_speed_kt(),
+ fraction));
+
+ result->set_elevation_ft
+ (do_interp(get_elevation_ft(),
+ env2.get_elevation_ft(),
+ fraction));
+
+ result->set_turbulence_magnitude_norm
+ (do_interp(get_turbulence_magnitude_norm(),
+ env2.get_turbulence_magnitude_norm(),
+ fraction));
+
+ result->set_turbulence_rate_hz
+ (do_interp(get_turbulence_rate_hz(),
+ env2.get_turbulence_rate_hz(),
+ fraction));
+
+ // calculate derived properties here to avoid duplicate expensive computations
+ result->_recalc_ne();
+ result->_recalc_alt_pt();
+ result->_recalc_alt_dewpoint();
+ result->_recalc_density();
+ result->_recalc_relative_humidity();
+
+ result->set_live_update(live_update);
+
+ return *result;
+}
+
+// end of environment.cxx
projects / flightgear.git / blobdiff