/**
* Attempt to compute airspeed when it is not yet available from:
* 1) dynamic pressure and air density derived from some altitude.
* 2) pitot pressure and static pressure.
* 3) ground speed and wind.
*/
static void
ComputeAirspeed(NMEAInfo &basic, const DerivedInfo &calculated)
{
if (basic.airspeed_available && basic.airspeed_real)
/* got it already */
return;
const auto any_altitude = basic.GetAnyAltitude();
if (!basic.airspeed_available && any_altitude.first) {
fixed dyn; bool available = false;
if (basic.dyn_pressure_available) {
dyn = basic.dyn_pressure.GetHectoPascal();
available = true;
} else if (basic.pitot_pressure_available && basic.static_pressure_available) {
dyn = basic.pitot_pressure.GetHectoPascal() - basic.static_pressure.GetHectoPascal();
available = true;
}
if (available) {
basic.indicated_airspeed = sqrt(fixed(163.2653061) * dyn);
basic.true_airspeed = basic.indicated_airspeed *
AirDensityRatio(any_altitude.second);
basic.airspeed_available.Update(basic.clock);
basic.airspeed_real = true; // Anyway not less real then any other method.
return;
}
}
if (!basic.ground_speed_available || !calculated.wind_available ||
!calculated.flight.flying) {
/* impossible to calculate */
basic.airspeed_available.Clear();
return;
}
fixed TrueAirspeedEstimated = fixed(0);
const SpeedVector wind = calculated.wind;
if (positive(basic.ground_speed) || wind.IsNonZero()) {
fixed x0 = basic.track.fastsine() * basic.ground_speed;
fixed y0 = basic.track.fastcosine() * basic.ground_speed;
x0 += wind.bearing.fastsine() * wind.norm;
y0 += wind.bearing.fastcosine() * wind.norm;
TrueAirspeedEstimated = SmallHypot(x0, y0);
}
basic.true_airspeed = TrueAirspeedEstimated;
basic.indicated_airspeed = TrueAirspeedEstimated;
if (any_altitude.first)
basic.indicated_airspeed /= AirDensityRatio(any_altitude.second);
basic.airspeed_available.Update(basic.clock);
basic.airspeed_real = false;
}
void
GlideComputerAirData::Heading(const NMEAInfo &basic, DerivedInfo &calculated)
{
const SpeedVector wind = calculated.wind;
if (calculated.wind_available &&
(positive(basic.ground_speed) || wind.IsNonZero()) &&
calculated.flight.flying) {
fixed x0 = basic.track.fastsine() * basic.ground_speed;
fixed y0 = basic.track.fastcosine() * basic.ground_speed;
x0 += wind.bearing.fastsine() * wind.norm;
y0 += wind.bearing.fastcosine() * wind.norm;
calculated.heading = Angle::Radians(atan2(x0, y0)).AsBearing();
} else {
calculated.heading = basic.track;
}
}
/*
!w,<1>,<2>,<3>,<4>,<5>,<6>,<7>,<8>,<9>,<10>,<11>,<12>,<13>*hh<CR><LF>
<1> Vector wind direction in degrees
<2> Vector wind speed in 10ths of meters per second
<3> Vector wind age in seconds
<4> Component wind in 10ths of Meters per second + 500 (500 = 0, 495 = 0.5 m/s tailwind)
<5> True altitude in Meters + 1000
<6> Instrument QNH setting
<7> True airspeed in 100ths of Meters per second
<8> Variometer reading in 10ths of knots + 200
<9> Averager reading in 10ths of knots + 200
<10> Relative variometer reading in 10ths of knots + 200
<11> Instrument MacCready setting in 10ths of knots
<12> Instrument Ballast setting in percent of capacity
<13> Instrument Bug setting
*hh Checksum, XOR of all bytes
*/
static bool
cai_w(NMEAInputLine &line, NMEAInfo &info)
{
SpeedVector wind;
if (ReadSpeedVector(line, wind))
info.ProvideExternalWind(wind.Reciprocal());
line.skip(2);
fixed value;
if (line.read_checked(value))
info.ProvideBaroAltitudeTrue(value - fixed(1000));
if (line.read_checked(value))
info.settings.ProvideQNH(value, info.clock);
if (line.read_checked(value))
info.ProvideTrueAirspeed(value / 100);
if (line.read_checked(value))
info.ProvideTotalEnergyVario(Units::ToSysUnit((value - fixed(200)) / 10,
unKnots));
line.skip(2);
int i;
if (line.read_checked(i))
info.settings.ProvideMacCready(Units::ToSysUnit(fixed(i) / 10, unKnots),
info.clock);
if (line.read_checked(i))
info.settings.ProvideBallastFraction(fixed(i) / 100, info.clock);
if (line.read_checked(i))
info.settings.ProvideBugs(fixed(i) / 100, info.clock);
return true;
}
void
GlideState::CalcSpeedups(const SpeedVector _wind)
{
if (_wind.IsNonZero()) {
wind = _wind;
effective_wind_angle = wind.bearing.Reciprocal() - vector.bearing;
wind_speed_squared = sqr(wind.norm);
head_wind = -wind.norm * effective_wind_angle.cos();
} else {
wind = SpeedVector::Zero();
effective_wind_angle = Angle::Zero();
head_wind = fixed(0);
wind_speed_squared = fixed(0);
}
}
fixed
GlidePolar::GetLDOverGround(Angle track, SpeedVector wind) const
{
if (wind.IsZero())
return bestLD;
const fixed c_theta = (wind.bearing.Reciprocal() - track).cos();
/* convert the wind speed into some sort of "virtual L/D" to put it
in relation to the polar's best L/D */
const fixed wind_ld = wind.norm / GetSBestLD();
Quadratic q(- Double(wind_ld * c_theta),
sqr(wind_ld) - sqr(bestLD));
if (q.Check())
return std::max(fixed(0), q.SolutionMax());
return fixed(0);
}
static void
DrawThermalSources(Canvas &canvas, const MaskedIcon &icon,
const WindowProjection &projection,
const T &sources,
const double aircraft_altitude,
const SpeedVector &wind)
{
for (const auto &source : sources) {
// find height difference
if (aircraft_altitude < source.ground_height)
continue;
// draw thermal at location it would be at the glider's height
GeoPoint location = wind.IsNonZero()
? source.CalculateAdjustedLocation(aircraft_altitude, wind)
: source.location;
// draw if it is in the field of view
PixelPoint pt;
if (projection.GeoToScreenIfVisible(location, pt))
icon.Draw(canvas, pt);
}
}
