// altimeter.cxx - an altimeter tied to the static port.
// Written by David Megginson, started 2002.
+// Modified by John Denker in 2007 to use a two layer atmosphere
+// model in src/Environment/atmosphere.?xx
//
// This file is in the Public Domain and comes with no warranty.
+// Example invocation, in the instrumentation.xml file:
+// <altimeter>
+// <name>encoder</name>
+// <number>0</number>
+// <static-pressure>/systems/static/pressure-inhg</static-pressure>
+// <quantum>10</quantum>
+// <tau>0</tau>
+// </altimeter>
+// Note non-default name, quantum, and tau values.
+
+#ifdef HAVE_CONFIG_H
+# include <config.h>
+#endif
+
#include <simgear/math/interpolater.hxx>
+#include <simgear/math/SGMath.hxx>
-#include "altimeter.hxx"
#include <Main/fg_props.hxx>
+#include <Main/util.hxx>
+#include <Environment/atmosphere.hxx>
+#include "altimeter.hxx"
-// Altitude based on pressure difference from sea level.
-// pressure difference inHG, altitude ft
-static double altitude_data[][2] = {
- -8.41, -8858.27,
- 0.00, 0.00,
- 3.05, 2952.76,
- 5.86, 5905.51,
- 8.41, 8858.27,
- 10.74, 11811.02,
- 12.87, 14763.78,
- 14.78, 17716.54,
- 16.55, 20669.29,
- 18.13, 23622.05,
- 19.62, 26574.80,
- 20.82, 29527.56,
- 21.96, 32480.31,
- 23.01, 35433.07,
- 23.91, 38385.83,
- 24.71, 41338.58,
- 25.40, 44291.34,
- 26.00, 47244.09,
- 26.51, 50196.85,
- 26.96, 53149.61,
- 27.35, 56102.36,
- 27.68, 59055.12,
- 27.98, 62007.87,
- 29.62, 100000.00 // just to fill it in
- -1, -1,
-};
-
-
-Altimeter::Altimeter ()
- : _altitude_table(new SGInterpTable)
-{
+const double hPa2inHg = 29.92 / 1013.25;
- for (int i = 0; altitude_data[i][0] != -1; i++)
- _altitude_table->addEntry(altitude_data[i][0], altitude_data[i][1]);
+Altimeter::Altimeter ( SGPropertyNode *node, double quantum )
+ : _rootNode(
+ fgGetNode("/instrumentation",true)->
+ getChild( node->getStringValue("name", "altimeter"),
+ node->getIntValue("number", 0),
+ true)),
+ _static_pressure(node->getStringValue("static-pressure", "/systems/static/pressure-inhg")),
+ _tau(node->getDoubleValue("tau", 0.1)),
+ _quantum(node->getDoubleValue("quantum", quantum)),
+ _settingInHg(29.921260)
+{
+ _tiedProperties.setRoot( _rootNode );
}
Altimeter::~Altimeter ()
+{}
+
+double
+Altimeter::getSettingInHg() const
{
- delete _altitude_table;
+ return _settingInHg;
}
+void
+Altimeter::setSettingInHg( double value )
+{
+ _settingInHg = value;
+}
+
+double
+Altimeter::getSettingHPa() const
+{
+ return _settingInHg / hPa2inHg;
+}
+
+void
+Altimeter::setSettingHPa( double value )
+{
+ _settingInHg = value * hPa2inHg;
+}
+
+
void
Altimeter::init ()
{
- _serviceable_node =
- fgGetNode("/instrumentation/altimeter/serviceable", true);
- _setting_node =
- fgGetNode("/instrumentation/altimeter/setting-inhg", true);
- _pressure_node =
- fgGetNode("/systems/static/pressure-inhg", true);
- _altitude_node =
- fgGetNode("/instrumentation/altimeter/indicated-altitude-ft", true);
+ raw_PA = 0.0;
+ _kollsman = 0.0;
+ _pressure_node = fgGetNode(_static_pressure.c_str(), true);
+ _serviceable_node = _rootNode->getChild("serviceable", 0, true);
+ _press_alt_node = _rootNode->getChild("pressure-alt-ft", 0, true);
+ _mode_c_node = _rootNode->getChild("mode-c-alt-ft", 0, true);
+ _altitude_node = _rootNode->getChild("indicated-altitude-ft", 0, true);
}
void
-Altimeter::bind ()
+Altimeter::bind()
{
+ _tiedProperties.Tie("setting-inhg", this, &Altimeter::getSettingInHg, &Altimeter::setSettingInHg );
+ _tiedProperties.Tie("setting-hpa", this, &Altimeter::getSettingHPa, &Altimeter::setSettingHPa );
}
void
-Altimeter::unbind ()
+Altimeter::unbind()
{
+ _tiedProperties.Untie();
}
void
Altimeter::update (double dt)
{
if (_serviceable_node->getBoolValue()) {
+ double trat = _tau > 0 ? dt/_tau : 100;
double pressure = _pressure_node->getDoubleValue();
- double setting = _setting_node->getDoubleValue();
- _altitude_node
- ->setDoubleValue(_altitude_table->interpolate(setting-pressure));
+ double press_alt = _press_alt_node->getDoubleValue();
+ // The mechanism settles slowly toward new pressure altitude:
+ raw_PA = fgGetLowPass(raw_PA, _altimeter.press_alt_ft(pressure), trat);
+ _mode_c_node->setDoubleValue(100 * SGMiscd::round(raw_PA/100));
+ _kollsman = fgGetLowPass(_kollsman, _altimeter.kollsman_ft(_settingInHg), trat);
+ if (_quantum)
+ press_alt = _quantum * SGMiscd::round(raw_PA/_quantum);
+ else
+ press_alt = raw_PA;
+ _press_alt_node->setDoubleValue(press_alt);
+ _altitude_node->setDoubleValue(press_alt - _kollsman);
}
}