bool
LXDevice::PutQNH(const AtmosphericPressure &pres)
{
fixed altitude_offset =
pres.StaticPressureToQNHAltitude(AtmosphericPressure::Standard());
char buffer[100];
sprintf(buffer, "PFLX3,%.2f,,,,,,,,,,,,", (double)altitude_offset / 0.3048);
PortWriteNMEA(port, buffer);
return true;
}
static bool
test_qnh_round2()
{
AtmosphericPressure pres;
pres.FindQNH(fixed(100), fixed(120));
fixed p0 = pres.get_QNH()*100;
fixed h0 = pres.StaticPressureToQNHAltitude(p0);
if (verbose) {
printf("%g %g\n",FIXED_DOUBLE(p0),FIXED_DOUBLE(h0));
}
return fabs(h0)<fixed(1);
}
static bool
test_qnh_round2()
{
AtmosphericPressure sp = AtmosphericPressure::Standard().QNHAltitudeToStaticPressure(fixed(100));
AtmosphericPressure pres =
AtmosphericPressure::FindQNHFromPressure(sp, fixed(120));
fixed h0 = pres.StaticPressureToQNHAltitude(pres);
if (verbose) {
printf("%g %g\n", FIXED_DOUBLE(pres.GetPascal()), FIXED_DOUBLE(h0));
}
return fabs(h0)<fixed(1);
}
static void
ComputePressure(NMEAInfo &basic, const AtmosphericPressure qnh)
{
const bool qnh_available = qnh.IsPlausible();
const bool static_pressure_available = basic.static_pressure_available;
const bool pressure_altitude_available = basic.pressure_altitude_available;
if (!static_pressure_available) {
if (pressure_altitude_available) {
basic.static_pressure =
AtmosphericPressure::PressureAltitudeToStaticPressure(basic.pressure_altitude);
basic.static_pressure_available = basic.pressure_altitude_available;
} else if (basic.baro_altitude_available && qnh_available) {
basic.static_pressure =
qnh.QNHAltitudeToStaticPressure(basic.baro_altitude);
basic.static_pressure_available = basic.baro_altitude_available;
}
}
if (!pressure_altitude_available) {
if (static_pressure_available) {
basic.pressure_altitude =
AtmosphericPressure::StaticPressureToPressureAltitude(basic.static_pressure);
basic.pressure_altitude_available = basic.static_pressure_available;
} else if (basic.baro_altitude_available && qnh_available) {
basic.pressure_altitude =
qnh.QNHAltitudeToPressureAltitude(basic.baro_altitude);
basic.pressure_altitude_available = basic.baro_altitude_available;
}
}
if (qnh_available) {
/* if the current pressure and the QNH is known, then true baro
altitude should be discarded, because the external device which
provided it may have a different QNH setting */
if (static_pressure_available) {
basic.baro_altitude =
qnh.StaticPressureToQNHAltitude(basic.static_pressure);
basic.baro_altitude_available = basic.static_pressure_available;
} else if (pressure_altitude_available) {
basic.baro_altitude =
qnh.PressureAltitudeToQNHAltitude(basic.pressure_altitude);
basic.baro_altitude_available = basic.pressure_altitude_available;
}
} else if (!basic.baro_altitude_available && pressure_altitude_available)
/* no QNH, but let's fill in the best fallback value we can get,
without setting BaroAltitudeAvailable */
basic.baro_altitude = basic.pressure_altitude;
}
bool
LXDevice::PutQNH(const AtmosphericPressure &pres, OperationEnvironment &env)
{
if (!EnableNMEA(env))
return false;
double altitude_offset =
(double)pres.StaticPressureToQNHAltitude(AtmosphericPressure::Standard()) / 0.3048;
char buffer[100];
if (IsV7())
sprintf(buffer, "PLXV0,QNH,W,%.2f", altitude_offset);
else
sprintf(buffer, "PFLX3,%.2f,,,,,,,,,,,,", altitude_offset);
return PortWriteNMEA(port, buffer, env);
}