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Roman Bapst
81 lines
3.2 KiB
C++
81 lines
3.2 KiB
C++
/****************************************************************************
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*
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* Copyright (C) 2023 PX4 Development Team. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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* 3. Neither the name PX4 nor the names of its contributors may be
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* used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*
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****************************************************************************/
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/**
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* @file atmosphere.cpp
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*
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*/
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#include <geo/geo.h>
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#include "atmosphere.h"
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namespace atmosphere
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{
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static constexpr float kTempRefKelvin = 15.f - CONSTANTS_ABSOLUTE_NULL_CELSIUS; // temperature at base height in Kelvin
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static constexpr float kTempGradient = -6.5f / 1000.f; // temperature gradient in degrees per meter
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static constexpr float kPressRefSeaLevelPa = 101325.f; // pressure at sea level in Pa
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float getDensityFromPressureAndTemp(const float pressure_pa, const float temperature_celsius)
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{
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return (pressure_pa / (CONSTANTS_AIR_GAS_CONST * (temperature_celsius - CONSTANTS_ABSOLUTE_NULL_CELSIUS)));
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}
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float getPressureFromAltitude(const float altitude_m)
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{
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return kPressRefSeaLevelPa * powf((altitude_m * kTempGradient + kTempRefKelvin) / kTempRefKelvin,
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-CONSTANTS_ONE_G / (kTempGradient * CONSTANTS_AIR_GAS_CONST));
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}
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float getAltitudeFromPressure(float pressure_pa, float pressure_sealevel_pa)
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{
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// calculate altitude using the hypsometric equation
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const float pressure_ratio = pressure_pa / pressure_sealevel_pa;
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/*
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* Solve:
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*
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* / -(aR / g) \
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* | (p / p1) . T1 | - T1
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* \ /
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* h = ------------------------------- + h1
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* a
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*/
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return (((powf(pressure_ratio, (-(kTempGradient * CONSTANTS_AIR_GAS_CONST) / CONSTANTS_ONE_G))) * kTempRefKelvin) -
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kTempRefKelvin) / kTempGradient;
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}
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float getStandardTemperatureAtAltitude(float altitude_m)
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{
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return 15.0f + kTempGradient * altitude_m;
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}
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} |