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/****************************************************************************
*
* Copyright (C) 2012-2013 PX4 Development Team. All rights reserved.
* Author: Lorenz Meier <lm@inf.ethz.ch>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
* 3. Neither the name PX4 nor the names of its contributors may be
* used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
****************************************************************************/
/**
* @file airspeed.c
* Airspeed estimation
*
* @author Lorenz Meier <lm@inf.ethz.ch>
*
*/
#include "math.h"
float calc_indicated_airspeed(float pressure_front, float pressure_ambient, float temperature)
{
return sqrtf((2.0f*(pressure_front - pressure_ambient)) / air_density_sea_level);
}
/**
* Calculate true airspeed from indicated airspeed.
*
* Note that the true airspeed is NOT the groundspeed, because of the effects of wind
*
* @param speed current indicated airspeed
* @param pressure_ambient pressure at the side of the tube/airplane
* @param temperature air temperature in degrees celcius
* @return true airspeed in m/s
*/
float calc_true_airspeed_from_indicated(float speed, float pressure_ambient, float temperature)
{
return speed * sqrtf(air_density_sea_level / get_air_density(pressure_ambient, temperature));
}
/**
* Directly calculate true airspeed
*
* Note that the true airspeed is NOT the groundspeed, because of the effects of wind
*
* @param pressure_front pressure inside the pitot/prandl tube
* @param pressure_ambient pressure at the side of the tube/airplane
* @param temperature air temperature in degrees celcius
* @return true airspeed in m/s
*/
float calc_true_airspeed(float pressure_front, float pressure_ambient, float temperature)
{
return sqrtf((2.0f*(pressure_front - pressure_ambient)) / get_air_density(pressure_ambient, temperature));
}
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