atmosphere.h

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/***********************************************************************/
#ifndef APPLICATION_ATMOSPHERE_H_
#define APPLICATION_ATMOSPHERE_H_
 
#include "embedded_math.h"
#include <air_density_observer.h>
#include <pt2.h>
 
#define RECIP_STD_DENSITY_TIMES_2 1.632f
 
#define GAS_CONST_DRY_AIR   287.058f
#define GAS_CONST_WATER_VAPOR   461.523f
#define ONE_MINUS_RATIO_GAS_CONSTANTS 0.378f
#define CELSIUS_TO_KELVIN_OFFSET 273.15f
 
class atmosphere_t
{
public:
  atmosphere_t( float p_abs)
  :
    have_ambient_air_data(false),
    pressure ( p_abs),
    temperature(20.0f),
    humidity( 0.0f),
    density_correction(1.0f),
    density_correction_averager(0.001f),
    QFF(101325)
  {
    density_correction_averager.settle(1.0f);
  }
  void update_density_correction( void)
  {
    density_correction_averager.respond(density_correction);
  }
  void initialize( float altitude)
  {
    density_QFF_calculator.initialize(altitude);
  }
  void set_pressure( float p_abs)
  {
    pressure = p_abs;
  }
  float get_pressure( void) const
  {
    return pressure;
  }
  float get_density( void) const
  {
    return  (1.0496346613e-5f * pressure + 0.1671546011f) * density_correction_averager.get_output();
  }
  float get_negative_altitude( void) const
  {
    float tmp = 8.104381531e-4f * pressure;
    return - tmp * tmp  + 0.20867299170f * pressure - 14421.43945f;
  }
  float get_TAS_from_dynamic_pressure( float dynamic_pressure) const
  {
    return SQRT( 2 * dynamic_pressure / get_density());
  }
  float get_IAS_from_dynamic_pressure( float dynamic_pressure) const
  {
    return SQRT( dynamic_pressure * RECIP_STD_DENSITY_TIMES_2);
  }
  void set_ambient_air_data( float temperature, float humidity)
  {
    this->temperature = temperature;
    this->humidity = humidity;
    have_ambient_air_data = true;
  }
  void disregard_ambient_air_data( void)
  {
    have_ambient_air_data = false;
  }
 
  float get_QFF () const
  {
    return QFF;
  }
 
  void feed_QFF_density_metering( float pressure, float MSL_altitude)
    {
    air_data_result result = density_QFF_calculator.feed_metering( pressure, MSL_altitude);
      if( result.valid)
    {
      QFF = result.QFF;
      density_correction = result.density_correction;
    }
    }
 
private:
  float calculateGasConstantHumAir(
      float humidity, float pressure, float temperature);
  float calculateAirDensity(
      float humidity, float pressure, float temperature);
  float calculateSaturationVaporPressure(float temp);
  bool have_ambient_air_data;
  float pressure;
  float temperature;
  float humidity;
  float density_correction;
  pt2<float,float> density_correction_averager;
  float QFF;
  air_density_observer density_QFF_calculator;
};
 
#endif /* APPLICATION_ATMOSPHERE_H_ */