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  /**
   * @file airspeed.h
   * Airspeed estimation declarations
   *
   * @author Lorenz Meier <lorenz@px4.io>
   *
   */
  
  #ifndef AIRSPEED_H_
  #define AIRSPEED_H_
  
  #include "math.h"
  
  __BEGIN_DECLS
  
  enum AIRSPEED_SENSOR_MODEL {
  	AIRSPEED_SENSOR_MODEL_MEMBRANE = 0,
  	AIRSPEED_SENSOR_MODEL_SDP3X,
  };
  
  enum AIRSPEED_COMPENSATION_MODEL {
  	AIRSPEED_COMPENSATION_MODEL_PITOT = 0,
  	AIRSPEED_COMPENSATION_MODEL_NO_PITOT = 1,
  	AIRSPEED_COMPENSATION_TUBE_PRESSURE_LOSS = 2,
  	AIRSPEED_COMPENSATION_TFSLOT = 3
  };
  
  /**
   * Calculate indicated airspeed (IAS) and correct for friction inside pitot and tube.
   *
   * Note that the indicated airspeed is not the true airspeed because it
   * lacks the air density compensation. Use the calc_true_airspeed functions to get
   * the true airspeed.
   *
   * @param total_pressure pressure inside the pitot/prandtl tube
   * @param static_pressure pressure at the side of the tube/airplane
   * @return indicated airspeed in m/s
   */
  __EXPORT float calc_IAS_corrected(enum AIRSPEED_COMPENSATION_MODEL pmodel,
  				  enum AIRSPEED_SENSOR_MODEL smodel,
  				  float tube_len, float tube_dia_mm, float differential_pressure, float pressure_ambient, float temperature_celsius);
  
  /**
   * Calculate indicated airspeed (IAS).
   *
   * Note that the indicated airspeed is not the true airspeed because it
   * lacks the air density compensation. Use the calc_true_airspeed functions to get
   * the true airspeed.
   *
   * @param total_pressure pressure inside the pitot/prandtl tube
   * @param static_pressure pressure at the side of the tube/airplane
   * @return indicated airspeed in m/s
   */
  __EXPORT float calc_IAS(float differential_pressure);
  
  /**
   * Calculate true airspeed (TAS) from calibrated airspeed (CAS).
   *
   * Note that the true airspeed is NOT the groundspeed, because of the effects of wind.
   *
   * @param speed_equivalent current calibrated airspeed
   * @param pressure_ambient pressure at the side of the tube/airplane
   * @param temperature_celsius air temperature in degrees celcius
   * @return TAS in m/s
   */
  __EXPORT float calc_TAS_from_CAS(float speed_indicated, float pressure_ambient,
  				 float temperature_celsius);
  
  /**
   * Calculate calibrated airspeed (CAS) from indicated airspeed (IAS).
   *
   * @param speed_indicated current indicated airspeed
   * @param scale scale from IAS to CAS (accounting for instrument and pitot position erros)
   * @return CAS in m/s
   */
  __EXPORT float calc_CAS_from_IAS(float speed_indicated, float scale);
  
  
  /**
   * Directly calculate true airspeed (TAS).
   *
   * Here we assume to have no instrument or pitot position error (IAS = CAS).
   * Note that the true airspeed is NOT the groundspeed, because of the effects of wind.
   *
   * @param total_pressure pressure inside the pitot/prandtl tube
   * @param static_pressure pressure at the side of the tube/airplane
   * @param temperature_celsius air temperature in degrees celcius
   * @return true airspeed in m/s
   */
  __EXPORT float calc_TAS(float total_pressure, float static_pressure, float temperature_celsius);
  
  /**
  * Calculates air density.
  *
  * @param static_pressure ambient pressure in millibar
  * @param temperature_celcius air / ambient temperature in celcius
  */
  __EXPORT float get_air_density(float static_pressure, float temperature_celsius);
  
  /**
   * Calculate calibrated airspeed (CAS) from true airspeed (TAS).
   * It is the inverse function to calc_TAS_from_CAS()
   *
   * @param speed_true current true airspeed
   * @param pressure_ambient pressure at the side of the tube/airplane
   * @param temperature_celsius air temperature in degrees celcius
   * @return CAS in m/s
   */
  __EXPORT float calc_CAS_from_TAS(float speed_true, float pressure_ambient,
  				 float temperature_celsius);
  
  __END_DECLS
  
  #endif
  