pprz_isa.h

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/*
 * Copyright (C) 2013 Gautier Hattenberger
 *
 * This file is part of paparazzi.
 *
 * paparazzi is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2, or (at your option)
 * any later version.
 *
 * paparazzi is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with paparazzi; see the file COPYING.  If not, see
 * <http://www.gnu.org/licenses/>.
 */

#ifndef PPRZ_ISA_H
#define PPRZ_ISA_H

#ifdef __cplusplus
extern "C" {
#endif

#include "std.h"
#include <math.h>

// Standard Atmosphere constants
#define PPRZ_ISA_SEA_LEVEL_PRESSURE 101325.0

#define PPRZ_ISA_SEA_LEVEL_TEMP 288.15

#define PPRZ_ISA_TEMP_LAPS_RATE 0.0065

#define PPRZ_ISA_GRAVITY 9.80665

#define PPRZ_ISA_GAS_CONSTANT 8.31447

#define PPRZ_ISA_MOLAR_MASS 0.0289644

#define PPRZ_ISA_AIR_GAS_CONSTANT (PPRZ_ISA_GAS_CONSTANT/PPRZ_ISA_MOLAR_MASS)

#define PPRZ_ISA_AIR_DENSITY 1.225

static const float PPRZ_ISA_M_OF_P_CONST = (PPRZ_ISA_AIR_GAS_CONSTANT *PPRZ_ISA_SEA_LEVEL_TEMP / PPRZ_ISA_GRAVITY);

static inline float pprz_isa_altitude_of_pressure(float pressure)
{
  if (pressure > 0.) {
    return (PPRZ_ISA_M_OF_P_CONST * logf(PPRZ_ISA_SEA_LEVEL_PRESSURE / pressure));
  } else {
    return 0.;
  }
}

static inline float pprz_isa_height_of_pressure(float pressure, float ref_p)
{
  if (pressure > 0. && ref_p > 0.) {
    return (PPRZ_ISA_M_OF_P_CONST * logf(ref_p / pressure));
  } else {
    return 0.;
  }
}

static inline float pprz_isa_pressure_of_altitude(float altitude)
{
  return (PPRZ_ISA_SEA_LEVEL_PRESSURE * expf((-1. / PPRZ_ISA_M_OF_P_CONST) * altitude));
}

static inline float pprz_isa_pressure_of_height(float height, float ref_p)
{
  return (ref_p * expf((-1. / PPRZ_ISA_M_OF_P_CONST) * height));
}


static inline float pprz_isa_height_of_pressure_full(float pressure, float ref_p)
{
  if (ref_p > 0.) {
    const float prel = pressure / ref_p;
    const float inv_expo = PPRZ_ISA_GAS_CONSTANT * PPRZ_ISA_TEMP_LAPS_RATE /
                           PPRZ_ISA_GRAVITY / PPRZ_ISA_MOLAR_MASS;
    return (1 - powf(prel, inv_expo)) * PPRZ_ISA_SEA_LEVEL_TEMP / PPRZ_ISA_TEMP_LAPS_RATE;
  } else {
    return 0.;
  }
}

static inline float pprz_isa_ref_pressure_of_height_full(float pressure, float height)
{
  //  Trel = 1 - L*h/T0;
  const float Trel = 1.0 - PPRZ_ISA_TEMP_LAPS_RATE * height / PPRZ_ISA_SEA_LEVEL_TEMP;
  const float expo = PPRZ_ISA_GRAVITY * PPRZ_ISA_MOLAR_MASS / PPRZ_ISA_GAS_CONSTANT /
                     PPRZ_ISA_TEMP_LAPS_RATE;
  return pressure / pow(Trel, expo);
}

#ifdef __cplusplus
} /* extern "C" */
#endif

#endif /* PPRZ_ISA_H */