void
AtmosphericPressure::FindQNH(const fixed alt_raw, const fixed alt_known)
{
// step 1, find static pressure from device assuming it's QNH adjusted
const fixed psraw = QNHAltitudeToStaticPressure(alt_raw);
// step 2, calculate QNH so that reported alt will be known alt
m_QNH = pow(pow(psraw * pa_to_hpa, k1) + k2 * alt_known, inv_k1);
}
/**
* Calculates the current QNH by comparing a raw altitude
* to a known altitude of a certain location
*
* Original comment:
*
* find QNH so that the static pressure gives the specified altitude
* (altitude can come from GPS or known airfield altitude or terrain
* height on ground)
*
* This function assumes the barometric altitude (alt_raw) is
* already adjusted for QNH ---> the function returns the
* QNH value to make the barometric altitude equal to the
* alt_known value.
* @param alt_raw Current altitude
* @param alt_known Altitude of a known location
* @return QNH
*/
double FindQNH(double alt_raw, double alt_known) {
const double k1=0.190263;
const double k2=8.417286e-5;
// step 1, find static pressure from device assuming it's QNH adjusted
double psraw = QNHAltitudeToStaticPressure(alt_raw);
// step 2, calculate QNH so that reported alt will be known alt
return pow(pow(psraw/100.0,k1) + k2*alt_known,1/k1);
// example, QNH=1014, ps=100203
// alt= 100
// alt_known = 120
// qnh= 1016
}
double FindQNH(double alt_raw, double alt_known) {
// find QNH so that the static pressure gives the specified altitude
// (altitude can come from GPS or known airfield altitude or terrain
// height on ground)
// This function assumes the barometric altitude (alt_raw) is
// already adjusted for QNH ---> the function returns the
// QNH value to make the barometric altitude equal to the
// alt_known value.
const double k1=0.190263;
const double k2=8.417286e-5;
// step 1, find static pressure from device assuming it's QNH adjusted
double psraw = QNHAltitudeToStaticPressure(alt_raw);
// step 2, calculate QNH so that reported alt will be known alt
return pow(pow(psraw/100.0,k1) + k2*alt_known,1/k1);
// example, QNH=1014, ps=100203
// alt= 100
// alt_known = 120
// qnh= 1016
}
double AltitudeToQNEAltitude(double alt) {
return StaticPressureToQNEAltitude(QNHAltitudeToStaticPressure(alt));
}
////////////////////////////////////////////////////////////////////////////////////////////////////////
// $PCPROBE,T,Q0,Q1,Q2,Q3,ax,ay,az,temp,rh,batt,delta_press,abs_press,C,
// - "T" after "$PCPROBE" indicates that the string contains data. Data are represented as signed,
// 16-bit hexadecimal integers. The only exception is abs_press which is in signed 24-bits hex
// format.
// - Q0, Q1, Q2, Q3: 3D orientation of the C-Probe in quaternion format. Heading, pitch, and roll can
// be calculated as follows:
// q0 = Q0 * 0.001;
// q1 = Q1 * 0.001;
// q2 = Q2 * 0.001;
// q3 = Q3 * 0.001;
// sin_pitch = -2 * (q0 * q2 - q3 * q1); // if sin_pitch > 1 or sin_pitch < -1, discard the data
// pitch = asin(sin_pitch);
// heading = M_PI + atan2(2*(q1 * q2 + q3 * q0), q3 * q3 - q0 * q0 - q1 * q1 + q2 * q2);
// roll = atan2( 2 * (q0 * q1 + q3 * q2), q3 * q3 + q0 * q0 - q1 * q1 - q2 * q2);
// - ax, ay, az: x, y, z components of the acceleration in units of 0.001 g.
// - temp: temperature in units of 0.1°C.
// - rh: relative humidity in units of 0.1%.
// - batt: battery level from 0 to 100%.
// - delta_press: differential pressure (dynamic - static) in units of 0.1 Pa.
// - abs_press: absolute pressure in units of 1/400 Pa
// - C: is transmitted only if the C-Probe is being charged. In this case, heat produced by the charging
// process is likely to affect the readings of the temperature and humidity sensors.
////////////////////////////////////////////////////////////////////////////////////////////////////////
BOOL CDevCProbe::ParseData( tnmeastring& wiss, NMEA_INFO *pINFO ) {
double q0 = int16toDouble(HexStrToInt(wiss.GetNextString())) * 0.001;
double q1 = int16toDouble(HexStrToInt(wiss.GetNextString())) * 0.001;
double q2 = int16toDouble(HexStrToInt(wiss.GetNextString())) * 0.001;
double q3 = int16toDouble(HexStrToInt(wiss.GetNextString())) * 0.001;
double sin_pitch = -2 * (q0 * q2 - q3 * q1); // if sin_pitch > 1 or sin_pitch < -1, discard the data
if(sin_pitch < 1.0 && sin_pitch > -1.0){
pINFO->MagneticHeadingAvailable=TRUE;
pINFO->MagneticHeading = (PI + atan2(2*(q1 * q2 + q3 * q0), q3 * q3 - q0 * q0 - q1 * q1 + q2 * q2))*RAD_TO_DEG;
pINFO->GyroscopeAvailable=TRUE;
pINFO->Pitch = asin(sin_pitch)*RAD_TO_DEG;
pINFO->Roll = atan2( 2 * (q0 * q1 + q3 * q2), q3 * q3 + q0 * q0 - q1 * q1 - q2 * q2)*RAD_TO_DEG;
}else{
pINFO->MagneticHeadingAvailable=FALSE;
pINFO->GyroscopeAvailable=FALSE;
}
pINFO->AccelerationAvailable=TRUE;
pINFO->AccelX = int16toDouble(HexStrToInt(wiss.GetNextString())) * 0.001;
pINFO->AccelY = int16toDouble(HexStrToInt(wiss.GetNextString())) * 0.001;
pINFO->AccelZ = int16toDouble(HexStrToInt(wiss.GetNextString())) * 0.001;
pINFO->TemperatureAvailable=TRUE;
pINFO->OutsideAirTemperature = int16toDouble(HexStrToInt(wiss.GetNextString())) * 0.1;
pINFO->HumidityAvailable=TRUE;
pINFO->RelativeHumidity = int16toDouble(HexStrToInt(wiss.GetNextString())) * 0.1;
pINFO->ExtBatt1_Voltage = int16toDouble(HexStrToInt(wiss.GetNextString()))+1000;
double delta_press = int16toDouble(HexStrToInt(wiss.GetNextString())) * 1.0/10.0 ;
double abs_press = int24toDouble(HexStrToInt(wiss.GetNextString())) * (1.0/4.0);
LockDeviceData();
m_delta_press = delta_press;
m_abs_press = abs_press;
UnlockDeviceData();
// the highest sea level air pressure ever recorded was 1084 mb (32.01 in.)
// at Siberia associated with an extremely cold air mass.
if(abs_press > 0.0 && abs_press < 115000.0) {
UpdateBaroSource(pINFO, BARO__CPROBE, NULL, StaticPressureToAltitude(abs_press));
}
else {
if(pINFO->BaroAltitudeAvailable) {
abs_press = QNHAltitudeToStaticPressure(pINFO->BaroAltitude);
}
else {
abs_press = QNHAltitudeToStaticPressure(pINFO->Altitude);
}
}
if(delta_press>0.0){
pINFO->AirspeedAvailable = TRUE;
pINFO->IndicatedAirspeed = sqrt(2 * delta_press / 1.225);
pINFO->TrueAirspeed = TrueAirSpeed(delta_press, pINFO->RelativeHumidity, pINFO->OutsideAirTemperature, abs_press>0.0?abs_press:101325.0);
}
if(*(wiss.GetNextString()) == L'C'){
pINFO->ExtBatt1_Voltage *= -1;
}
TriggerVarioUpdate();
return TRUE;
}
////////////////////////////////////////////////////////////////////////////////////////////////////////
// $PCPROBE,T,Q0,Q1,Q2,Q3,ax,ay,az,temp,rh,batt,delta_press,abs_press,C,
// - "T" after "$PCPROBE" indicates that the string contains data. Data are represented as signed,
// 16-bit hexadecimal integers. The only exception is abs_press which is in signed 24-bits hex
// format.
// - Q0, Q1, Q2, Q3: 3D orientation of the C-Probe in quaternion format. Heading, pitch, and roll can
// be calculated as follows:
// q0 = Q0 * 0.001;
// q1 = Q1 * 0.001;
// q2 = Q2 * 0.001;
// q3 = Q3 * 0.001;
// sin_pitch = -2 * (q0 * q2 - q3 * q1); // if sin_pitch > 1 or sin_pitch < -1, discard the data
// pitch = asin(sin_pitch);
// heading = M_PI + atan2(2*(q1 * q2 + q3 * q0), q3 * q3 - q0 * q0 - q1 * q1 + q2 * q2);
// roll = atan2( 2 * (q0 * q1 + q3 * q2), q3 * q3 + q0 * q0 - q1 * q1 - q2 * q2);
// - ax, ay, az: x, y, z components of the acceleration in units of 0.001 g.
// - temp: temperature in units of 0.1°C.
// - rh: relative humidity in units of 0.1%.
// - batt: battery level from 0 to 100%.
// - delta_press: differential pressure (dynamic - static) in units of 0.1 Pa.
// - abs_press: absolute pressure in units of 1/400 Pa
// - C: is transmitted only if the C-Probe is being charged. In this case, heat produced by the charging
// process is likely to affect the readings of the temperature and humidity sensors.
////////////////////////////////////////////////////////////////////////////////////////////////////////
BOOL CDevCProbe::ParseData( wnmeastring& wiss, NMEA_INFO *pINFO ) {
double q0 = int16toDouble(HexStrToInt(wiss.GetNextString())) * 0.001;
double q1 = int16toDouble(HexStrToInt(wiss.GetNextString())) * 0.001;
double q2 = int16toDouble(HexStrToInt(wiss.GetNextString())) * 0.001;
double q3 = int16toDouble(HexStrToInt(wiss.GetNextString())) * 0.001;
double sin_pitch = -2 * (q0 * q2 - q3 * q1); // if sin_pitch > 1 or sin_pitch < -1, discard the data
if(sin_pitch < 1.0 && sin_pitch > -1.0){
pINFO->MagneticCompassAvailable=TRUE;
pINFO->Heading = (PI + atan2(2*(q1 * q2 + q3 * q0), q3 * q3 - q0 * q0 - q1 * q1 + q2 * q2))*RAD_TO_DEG;
pINFO->GyroscopeAvailable=TRUE;
pINFO->Pitch = asin(sin_pitch)*RAD_TO_DEG;
pINFO->Roll = atan2( 2 * (q0 * q1 + q3 * q2), q3 * q3 + q0 * q0 - q1 * q1 - q2 * q2)*RAD_TO_DEG;
}else{
pINFO->MagneticCompassAvailable=FALSE;
pINFO->GyroscopeAvailable=FALSE;
}
pINFO->AccelerationAvailable=TRUE;
pINFO->AccelX = int16toDouble(HexStrToInt(wiss.GetNextString())) * 0.001;
pINFO->AccelY = int16toDouble(HexStrToInt(wiss.GetNextString())) * 0.001;
pINFO->AccelZ = int16toDouble(HexStrToInt(wiss.GetNextString())) * 0.001;
pINFO->Gload = sqrt(pow(pINFO->AccelX,2.0)+pow(pINFO->AccelY,2.0)+pow(pINFO->AccelZ,2.0));
pINFO->TemperatureAvailable=TRUE;
pINFO->OutsideAirTemperature = int16toDouble(HexStrToInt(wiss.GetNextString())) * 0.1;
pINFO->HumidityAvailable=TRUE;
pINFO->RelativeHumidity = int16toDouble(HexStrToInt(wiss.GetNextString())) * 0.1;
pINFO->ExtBatt1_Voltage = int16toDouble(HexStrToInt(wiss.GetNextString()))+1000;
double delta_press = int16toDouble(HexStrToInt(wiss.GetNextString())) / 10.0 ;
double abs_press = int24toDouble(HexStrToInt(wiss.GetNextString())) / 400.0;
if(abs_press > 0.0) {
UpdateBaroSource(pINFO, BARO__CPROBE, NULL, StaticPressureToAltitude(abs_press*100));
}
else {
if(pINFO->BaroAltitudeAvailable) {
abs_press = QNHAltitudeToStaticPressure(pINFO->BaroAltitude);
}
else {
abs_press = QNHAltitudeToStaticPressure(pINFO->Altitude);
}
}
if(delta_press>=0){
pINFO->AirspeedAvailable = TRUE;
pINFO->IndicatedAirspeed = sqrt(2*delta_press);
pINFO->TrueAirspeed = TrueAirSpeed(delta_press, pINFO->RelativeHumidity, pINFO->OutsideAirTemperature, abs_press>0.0?abs_press*100:101325.0);
}
if(*(wiss.GetNextString()) == L'C'){
pINFO->ExtBatt1_Voltage *= -1;
}
LockDeviceData();
m_delta_press = delta_press;
m_abs_press = abs_press;
UnlockDeviceData();
TriggerVarioUpdate();
return TRUE;
}
fixed
AtmosphericPressure::QNHAltitudeToPressureAltitude(const fixed alt) const
{
return StaticPressureToPressureAltitude(QNHAltitudeToStaticPressure(alt));
}
fixed
AtmosphericPressure::QNHAltitudeToPressureAltitude(const fixed alt) const
{
return (pow(fixed_101325, k1) - pow(QNHAltitudeToStaticPressure(alt) * pa_to_hpa, k1)) * inv_k2;
}
