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Merge branch 'timoore/atmos'

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This commit is contained in:
Tim Moore 2009-11-06 23:38:37 +01:00
commit 71d042b371
3 changed files with 56 additions and 8 deletions
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15
src/Environment/atmosphere.cxx
View file

@ -260,6 +260,21 @@ double FGAtmo::QNH(const double field_elev, const double field_press) {
return rslt;
}
// Invert the QNH calculation to get the field pressure from a metar
// report.
// field pressure _in pascals_
// ... caller gets to convert to inHg or millibars
// Field elevation in m
// Altimeter setting (QNH) in pascals
// Valid for fields within the troposphere only.
double FGAtmo::fieldPressure(const double field_elev, const double qnh)
{
using namespace atmodel;
static const double nn = ISA::lam0 * Rgas / g / mm;
const double pratio = pow(qnh / ISA::P0, nn);
return ISA::P0 * pow(pratio - field_elev * ISA::lam0 / ISA::T0, 1.0 / nn);
}
void FGAltimeter::dump_stack1(const double Tref) {
using namespace atmodel;
const int bs(200);

9
src/Environment/atmosphere.hxx
View file

@ -110,6 +110,15 @@ public:
// Field pressure in pascals
// Valid for fields within the troposphere only.
double QNH(const double field_elev, const double field_press);
/**
* Invert the QNH calculation to get the field pressure from a metar
* report. Valid for fields within the troposphere only.
* @param field_elev field elevation in m
* @param qnh altimeter setting in pascals
* @return field pressure _in pascals_. Caller gets to convert to inHg
* or millibars
*/
static double fieldPressure(const double field_elev, const double qnh);
};

40
src/Environment/environment_ctrl.cxx
View file

@ -34,6 +34,7 @@
#include <Main/fg_props.hxx>
#include <Main/util.hxx>
#include "atmosphere.hxx"
#include "fgmetar.hxx"
#include "environment_ctrl.hxx"
@ -433,6 +434,25 @@ static inline double convert_to_180( double d )
return d > 180.0 ? d - 360.0 : d;
}
// Return the sea level pressure for a metar observation, in inHg.
// This is different from QNH because it accounts for the current
// temperature at the observation point.
// metarPressure in inHg
// fieldHt in ft
// fieldTemp in C
static double reducePressureSl(double metarPressure, double fieldHt,
double fieldTemp)
{
double elev = fieldHt * SG_FEET_TO_METER;
double fieldPressure
= FGAtmo::fieldPressure(elev, metarPressure * atmodel::inHg);
double slPressure = P_layer(0, elev, fieldPressure,
fieldTemp + atmodel::freezing,
atmodel::ISA::lam0);
return slPressure / atmodel::inHg;
}
void
FGMetarCtrl::update(double dt)
{
@ -444,6 +464,7 @@ FGMetarCtrl::update(double dt)
bool reinit_required = false;
bool layer_rebuild_required = false;
double station_elevation_ft = station_elevation_n->getDoubleValue();
if (first_update) {
double dir = base_wind_dir_n->getDoubleValue()+magnetic_variation_n->getDoubleValue();
@ -455,7 +476,10 @@ FGMetarCtrl::update(double dt)
fgDefaultWeatherValue("visibility-m", metarvis);
double metarpressure = pressure_n->getDoubleValue();
fgDefaultWeatherValue("pressure-sea-level-inhg", metarpressure);
fgDefaultWeatherValue("pressure-sea-level-inhg",
reducePressureSl(metarpressure,
station_elevation_ft,
temperature_n->getDoubleValue()));
// We haven't already loaded a METAR, so apply it immediately.
vector<SGPropertyNode_ptr> layers = clouds_n->getChildren("layer");
@ -597,8 +621,11 @@ FGMetarCtrl::update(double dt)
double pressure = boundary_sea_level_pressure_n->getDoubleValue();
double metarpressure = pressure_n->getDoubleValue();
if( pressure != metarpressure ) {
pressure = interpolate_val( pressure, metarpressure, MaxPressureChangeInHgSec );
double newpressure = reducePressureSl(metarpressure,
station_elevation_ft,
temperature_n->getDoubleValue());
if( pressure != newpressure ) {
pressure = interpolate_val( pressure, newpressure, MaxPressureChangeInHgSec );
fgDefaultWeatherValue("pressure-sea-level-inhg", pressure);
reinit_required = true;
}
@ -666,11 +693,8 @@ FGMetarCtrl::update(double dt)
}
}
}
{
double station_elevation_ft = station_elevation_n->getDoubleValue();
set_temp_at_altitude(temperature_n->getDoubleValue(), station_elevation_ft);
set_dewpoint_at_altitude(dewpoint_n->getDoubleValue(), station_elevation_ft);
}
set_temp_at_altitude(temperature_n->getDoubleValue(), station_elevation_ft);
set_dewpoint_at_altitude(dewpoint_n->getDoubleValue(), station_elevation_ft);
//TODO: check if temperature/dewpoint have changed. This requires reinit.
// Force an update of the 3D clouds