716 lines
18 KiB
C++
716 lines
18 KiB
C++
// environment.cxx -- routines to model the natural environment
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//
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// Written by David Megginson, started February 2002.
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//
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// Copyright (C) 2002 David Megginson - david@megginson.com
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//
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// This program is free software; you can redistribute it and/or
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// modify it under the terms of the GNU General Public License as
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// published by the Free Software Foundation; either version 2 of the
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// License, or (at your option) any later version.
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//
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// This program is distributed in the hope that it will be useful, but
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// WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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// General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with this program; if not, write to the Free Software
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// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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//
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// $Id$
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#ifdef HAVE_CONFIG_H
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# include <config.h>
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#endif
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#include <math.h>
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#include <plib/sg.h>
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#include <simgear/constants.h>
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#include <simgear/debug/logstream.hxx>
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#include <simgear/math/interpolater.hxx>
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#include <simgear/props/props.hxx>
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#include <simgear/environment/visual_enviro.hxx>
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#include <Main/fg_props.hxx>
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#include "environment.hxx"
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////////////////////////////////////////////////////////////////////////
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// Atmosphere model.
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////////////////////////////////////////////////////////////////////////
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// Calculated based on the ISA standard day, as found at e.g.
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// http://www.av8n.com/physics/altimetry.htm
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// Each line of data has 3 elements:
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// Elevation (ft),
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// temperature factor (dimensionless ratio of absolute temp),
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// pressure factor (dimensionless ratio)
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static double atmosphere_data[][3] = {
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{ -3000.00, 1.021, 1.1133 },
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{ 0.00, 1.000, 1.0000 },
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{ 2952.76, 0.980, 0.8978 },
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{ 5905.51, 0.959, 0.8042 },
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{ 8858.27, 0.939, 0.7187 },
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{ 11811.02, 0.919, 0.6407 },
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{ 14763.78, 0.898, 0.5697 },
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{ 17716.54, 0.878, 0.5052 },
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{ 20669.29, 0.858, 0.4468 },
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{ 23622.05, 0.838, 0.3940 },
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{ 26574.80, 0.817, 0.3463 },
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{ 29527.56, 0.797, 0.3034 },
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{ 32480.31, 0.777, 0.2649 },
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{ 35433.07, 0.756, 0.2305 },
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{ 38385.83, 0.752, 0.2000 },
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{ 41338.58, 0.752, 0.1736 },
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{ 44291.34, 0.752, 0.1506 },
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{ 47244.09, 0.752, 0.1307 },
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{ 50196.85, 0.752, 0.1134 },
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{ 53149.61, 0.752, 0.0984 },
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{ 56102.36, 0.752, 0.0854 },
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{ 59055.12, 0.752, 0.0741 },
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{ 62007.87, 0.752, 0.0643 },
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{ 65000.00, 0.752, 0.0557 },
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{ 68000.00, 0.754, 0.0482 },
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{ 71000.00, 0.758, 0.0418 },
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{ 74000.00, 0.761, 0.0362 },
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{ 77000.00, 0.764, 0.0314 },
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{ 80000.00, 0.767, 0.0273 },
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{ 83000.00, 0.770, 0.0237 },
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{ 86000.00, 0.773, 0.0206 },
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{ 89000.00, 0.777, 0.0179 },
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{ 92000.00, 0.780, 0.0156 },
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{ 95000.00, 0.783, 0.0135 },
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{ 98000.00, 0.786, 0.0118 },
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{ 101000.00, 0.789, 0.0103 },
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{ -1, -1, -1 }
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};
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static SGInterpTable * _temperature_degc_table = 0;
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static SGInterpTable * _pressure_inhg_table = 0;
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static void
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_setup_tables ()
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{
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if (_temperature_degc_table != 0)
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return;
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_temperature_degc_table = new SGInterpTable;
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_pressure_inhg_table = new SGInterpTable;
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for (int i = 0; atmosphere_data[i][0] != -1; i++) {
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_temperature_degc_table->addEntry(atmosphere_data[i][0],
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atmosphere_data[i][1]);
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_pressure_inhg_table->addEntry(atmosphere_data[i][0],
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atmosphere_data[i][2]);
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}
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}
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////////////////////////////////////////////////////////////////////////
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// Implementation of FGEnvironment.
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////////////////////////////////////////////////////////////////////////
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FGEnvironment::FGEnvironment()
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: elevation_ft(0),
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visibility_m(32000),
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temperature_sea_level_degc(15),
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temperature_degc(15),
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dewpoint_sea_level_degc(5), // guess
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dewpoint_degc(5),
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pressure_sea_level_inhg(29.92),
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pressure_inhg(29.92),
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turbulence_magnitude_norm(0),
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turbulence_rate_hz(1),
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wind_from_heading_deg(0),
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wind_speed_kt(0),
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wind_from_north_fps(0),
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wind_from_east_fps(0),
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wind_from_down_fps(0),
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altitude_half_to_sun_m(1000),
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altitude_tropo_top_m(10000)
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{
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_setup_tables();
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_recalc_density();
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_recalc_relative_humidity();
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}
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FGEnvironment::FGEnvironment (const FGEnvironment &env)
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{
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FGEnvironment();
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copy(env);
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}
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FGEnvironment::~FGEnvironment()
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{
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}
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void
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FGEnvironment::copy (const FGEnvironment &env)
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{
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elevation_ft = env.elevation_ft;
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visibility_m = env.visibility_m;
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temperature_sea_level_degc = env.temperature_sea_level_degc;
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temperature_degc = env.temperature_degc;
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dewpoint_sea_level_degc = env.dewpoint_sea_level_degc;
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dewpoint_degc = env.dewpoint_degc;
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pressure_sea_level_inhg = env.pressure_sea_level_inhg;
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wind_from_heading_deg = env.wind_from_heading_deg;
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wind_speed_kt = env.wind_speed_kt;
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wind_from_north_fps = env.wind_from_north_fps;
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wind_from_east_fps = env.wind_from_east_fps;
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wind_from_down_fps = env.wind_from_down_fps;
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turbulence_magnitude_norm = env.turbulence_magnitude_norm;
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turbulence_rate_hz = env.turbulence_rate_hz;
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}
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static inline bool
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maybe_copy_value (FGEnvironment * env, const SGPropertyNode * node,
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const char * name, void (FGEnvironment::*setter)(double))
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{
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const SGPropertyNode * child = node->getNode(name);
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// fragile: depends on not being typed
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// as a number
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if (child != 0 && child->hasValue() &&
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child->getStringValue()[0] != '\0') {
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(env->*setter)(child->getDoubleValue());
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return true;
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} else {
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return false;
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}
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}
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void
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FGEnvironment::read (const SGPropertyNode * node)
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{
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maybe_copy_value(this, node, "visibility-m",
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&FGEnvironment::set_visibility_m);
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if (!maybe_copy_value(this, node, "temperature-sea-level-degc",
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&FGEnvironment::set_temperature_sea_level_degc))
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maybe_copy_value(this, node, "temperature-degc",
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&FGEnvironment::set_temperature_degc);
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if (!maybe_copy_value(this, node, "dewpoint-sea-level-degc",
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&FGEnvironment::set_dewpoint_sea_level_degc))
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maybe_copy_value(this, node, "dewpoint-degc",
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&FGEnvironment::set_dewpoint_degc);
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if (!maybe_copy_value(this, node, "pressure-sea-level-inhg",
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&FGEnvironment::set_pressure_sea_level_inhg))
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maybe_copy_value(this, node, "pressure-inhg",
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&FGEnvironment::set_pressure_inhg);
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maybe_copy_value(this, node, "wind-from-heading-deg",
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&FGEnvironment::set_wind_from_heading_deg);
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maybe_copy_value(this, node, "wind-speed-kt",
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&FGEnvironment::set_wind_speed_kt);
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maybe_copy_value(this, node, "elevation-ft",
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&FGEnvironment::set_elevation_ft);
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maybe_copy_value(this, node, "turbulence/magnitude-norm",
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&FGEnvironment::set_turbulence_magnitude_norm);
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maybe_copy_value(this, node, "turbulence/rate-hz",
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&FGEnvironment::set_turbulence_rate_hz);
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}
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double
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FGEnvironment::get_visibility_m () const
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{
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return visibility_m;
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}
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double
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FGEnvironment::get_temperature_sea_level_degc () const
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{
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return temperature_sea_level_degc;
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}
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double
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FGEnvironment::get_temperature_degc () const
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{
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return temperature_degc;
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}
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double
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FGEnvironment::get_temperature_degf () const
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{
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return (temperature_degc * 9.0 / 5.0) + 32.0;
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}
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double
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FGEnvironment::get_dewpoint_sea_level_degc () const
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{
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return dewpoint_sea_level_degc;
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}
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double
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FGEnvironment::get_dewpoint_degc () const
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{
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return dewpoint_degc;
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}
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double
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FGEnvironment::get_pressure_sea_level_inhg () const
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{
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return pressure_sea_level_inhg;
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}
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double
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FGEnvironment::get_pressure_inhg () const
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{
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return pressure_inhg;
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}
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double
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FGEnvironment::get_density_slugft3 () const
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{
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return density_slugft3;
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}
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double
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FGEnvironment::get_relative_humidity () const
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{
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return relative_humidity;
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}
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double
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FGEnvironment::get_density_tropo_avg_kgm3 () const
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{
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return density_tropo_avg_kgm3;
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}
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double
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FGEnvironment::get_altitude_half_to_sun_m () const
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{
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return altitude_half_to_sun_m;
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}
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double
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FGEnvironment::get_altitude_tropo_top_m () const
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{
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return altitude_tropo_top_m;
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}
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double
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FGEnvironment::get_wind_from_heading_deg () const
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{
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return wind_from_heading_deg;
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}
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double
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FGEnvironment::get_wind_speed_kt () const
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{
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return wind_speed_kt;
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}
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double
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FGEnvironment::get_wind_from_north_fps () const
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{
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return wind_from_north_fps;
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}
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double
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FGEnvironment::get_wind_from_east_fps () const
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{
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return wind_from_east_fps;
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}
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double
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FGEnvironment::get_wind_from_down_fps () const
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{
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return wind_from_down_fps;
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}
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double
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FGEnvironment::get_turbulence_magnitude_norm () const
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{
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if( sgEnviro.get_turbulence_enable_state() )
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if (fgGetBool("/environment/params/real-world-weather-fetch") == true)
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return sgEnviro.get_cloud_turbulence();
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return turbulence_magnitude_norm;
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}
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double
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FGEnvironment::get_turbulence_rate_hz () const
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{
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return turbulence_rate_hz;
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}
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double
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FGEnvironment::get_elevation_ft () const
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{
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return elevation_ft;
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}
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void
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FGEnvironment::set_visibility_m (double v)
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{
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visibility_m = v;
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}
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void
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FGEnvironment::set_temperature_sea_level_degc (double t)
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{
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temperature_sea_level_degc = t;
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if (dewpoint_sea_level_degc > t)
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dewpoint_sea_level_degc = t;
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_recalc_alt_temperature();
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_recalc_density();
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}
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void
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FGEnvironment::set_temperature_degc (double t)
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{
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temperature_degc = t;
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_recalc_sl_temperature();
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_recalc_density();
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_recalc_relative_humidity();
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}
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void
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FGEnvironment::set_dewpoint_sea_level_degc (double t)
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{
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dewpoint_sea_level_degc = t;
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if (temperature_sea_level_degc < t)
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temperature_sea_level_degc = t;
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_recalc_alt_dewpoint();
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_recalc_density();
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}
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void
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FGEnvironment::set_dewpoint_degc (double t)
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{
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dewpoint_degc = t;
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_recalc_sl_dewpoint();
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_recalc_density();
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_recalc_relative_humidity();
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}
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void
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FGEnvironment::set_pressure_sea_level_inhg (double p)
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{
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pressure_sea_level_inhg = p;
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_recalc_alt_pressure();
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_recalc_density();
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}
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void
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FGEnvironment::set_pressure_inhg (double p)
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{
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pressure_inhg = p;
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_recalc_sl_pressure();
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_recalc_density();
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}
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void
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FGEnvironment::set_wind_from_heading_deg (double h)
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{
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wind_from_heading_deg = h;
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_recalc_ne();
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}
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void
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FGEnvironment::set_wind_speed_kt (double s)
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{
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wind_speed_kt = s;
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_recalc_ne();
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}
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void
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FGEnvironment::set_wind_from_north_fps (double n)
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{
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wind_from_north_fps = n;
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_recalc_hdgspd();
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}
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void
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FGEnvironment::set_wind_from_east_fps (double e)
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{
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wind_from_east_fps = e;
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_recalc_hdgspd();
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}
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void
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FGEnvironment::set_wind_from_down_fps (double d)
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{
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wind_from_down_fps = d;
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_recalc_hdgspd();
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}
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void
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FGEnvironment::set_turbulence_magnitude_norm (double t)
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{
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turbulence_magnitude_norm = t;
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}
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void
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FGEnvironment::set_turbulence_rate_hz (double r)
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{
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turbulence_rate_hz = r;
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}
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void
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FGEnvironment::set_elevation_ft (double e)
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{
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elevation_ft = e;
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_recalc_alt_temperature();
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_recalc_alt_dewpoint();
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_recalc_alt_pressure();
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_recalc_density();
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_recalc_relative_humidity();
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}
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void
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FGEnvironment::set_altitude_half_to_sun_m (double alt)
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{
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altitude_half_to_sun_m = alt;
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_recalc_density_tropo_avg_kgm3();
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}
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void
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FGEnvironment::set_altitude_tropo_top_m (double alt)
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{
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altitude_tropo_top_m = alt;
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_recalc_density_tropo_avg_kgm3();
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}
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void
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FGEnvironment::_recalc_hdgspd ()
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{
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double angle_rad;
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if (wind_from_east_fps == 0) {
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angle_rad = (wind_from_north_fps >= 0 ? SGD_PI_2 : -SGD_PI_2);
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} else {
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angle_rad = atan(wind_from_north_fps/wind_from_east_fps);
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}
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wind_from_heading_deg = angle_rad * SGD_RADIANS_TO_DEGREES;
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if (wind_from_east_fps >= 0)
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wind_from_heading_deg = 90 - wind_from_heading_deg;
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else
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wind_from_heading_deg = 270 - wind_from_heading_deg;
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#if 0
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// FIXME: Windspeed can become negative with these formulas.
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// which can cause problems for animations that rely
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// on the windspeed property.
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if (angle_rad == 0)
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wind_speed_kt = fabs(wind_from_east_fps
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* SG_METER_TO_NM * SG_FEET_TO_METER * 3600);
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else
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wind_speed_kt = (wind_from_north_fps / sin(angle_rad))
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* SG_METER_TO_NM * SG_FEET_TO_METER * 3600;
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#else
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wind_speed_kt = sqrt(wind_from_north_fps * wind_from_north_fps +
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wind_from_east_fps * wind_from_east_fps)
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* SG_METER_TO_NM * SG_FEET_TO_METER * 3600;
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#endif
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}
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void
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FGEnvironment::_recalc_ne ()
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{
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double speed_fps =
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wind_speed_kt * SG_NM_TO_METER * SG_METER_TO_FEET * (1.0/3600);
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wind_from_north_fps = speed_fps *
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cos(wind_from_heading_deg * SGD_DEGREES_TO_RADIANS);
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wind_from_east_fps = speed_fps *
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sin(wind_from_heading_deg * SGD_DEGREES_TO_RADIANS);
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}
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void
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FGEnvironment::_recalc_sl_temperature ()
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{
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// 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;
|
||
}
|
||
}
|
||
|
||
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
|
||
}
|
||
}
|
||
|
||
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 ()
|
||
{
|
||
pressure_sea_level_inhg =
|
||
pressure_inhg / _pressure_inhg_table->interpolate(elevation_ft);
|
||
}
|
||
|
||
void
|
||
FGEnvironment::_recalc_alt_pressure ()
|
||
{
|
||
pressure_inhg =
|
||
pressure_sea_level_inhg * _pressure_inhg_table->interpolate(elevation_ft);
|
||
}
|
||
|
||
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 ;
|
||
}
|
||
|
||
|
||
|
||
////////////////////////////////////////////////////////////////////////
|
||
// 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);
|
||
}
|
||
|
||
void
|
||
interpolate (const FGEnvironment * env1, const FGEnvironment * env2,
|
||
double fraction, FGEnvironment * result)
|
||
{
|
||
result->set_visibility_m
|
||
(do_interp(env1->get_visibility_m(),
|
||
env2->get_visibility_m(),
|
||
fraction));
|
||
|
||
result->set_temperature_sea_level_degc
|
||
(do_interp(env1->get_temperature_sea_level_degc(),
|
||
env2->get_temperature_sea_level_degc(),
|
||
fraction));
|
||
|
||
result->set_dewpoint_degc
|
||
(do_interp(env1->get_dewpoint_sea_level_degc(),
|
||
env2->get_dewpoint_sea_level_degc(),
|
||
fraction));
|
||
|
||
result->set_pressure_sea_level_inhg
|
||
(do_interp(env1->get_pressure_sea_level_inhg(),
|
||
env2->get_pressure_sea_level_inhg(),
|
||
fraction));
|
||
|
||
result->set_wind_from_heading_deg
|
||
(do_interp_deg(env1->get_wind_from_heading_deg(),
|
||
env2->get_wind_from_heading_deg(),
|
||
fraction));
|
||
|
||
result->set_wind_speed_kt
|
||
(do_interp(env1->get_wind_speed_kt(),
|
||
env2->get_wind_speed_kt(),
|
||
fraction));
|
||
|
||
result->set_elevation_ft
|
||
(do_interp(env1->get_elevation_ft(),
|
||
env2->get_elevation_ft(),
|
||
fraction));
|
||
|
||
result->set_turbulence_magnitude_norm
|
||
(do_interp(env1->get_turbulence_magnitude_norm(),
|
||
env2->get_turbulence_magnitude_norm(),
|
||
fraction));
|
||
|
||
result->set_turbulence_rate_hz
|
||
(do_interp(env1->get_turbulence_rate_hz(),
|
||
env2->get_turbulence_rate_hz(),
|
||
fraction));
|
||
}
|
||
|
||
// end of environment.cxx
|