Added simple GPS support (no waypoints yet).

src/Instrumentation/Makefile.am

@@ -2,6 +2,7 @@ noinst_LIBRARIES = libInstrumentation.a
 
 libInstrumentation_a_SOURCES = instrument_mgr.cxx instrument_mgr.hxx \
                                dme.cxx dme.hxx \
+                               gps.cxx gps.hxx \
                                gyro.cxx gyro.hxx \
                                airspeed_indicator.cxx airspeed_indicator.hxx \
                                attitude_indicator.cxx attitude_indicator.hxx \

src/Instrumentation/gps.cxx

@@ -0,0 +1,106 @@
+// gps.cxx - distance-measuring equipment.
+// Written by David Megginson, started 2003.
+//
+// This file is in the Public Domain and comes with no warranty.
+
+#include <simgear/compiler.h>
+#include <simgear/math/sg_geodesy.hxx>
+
+#include <Main/fg_props.hxx>
+
+#include "gps.hxx"
+
+
+GPS::GPS ()
+    : _last_valid(false),
+      _last_longitude_deg(0),
+      _last_latitude_deg(0),
+      _last_altitude_m(0)
+{
+}
+
+GPS::~GPS ()
+{
+}
+
+void
+GPS::init ()
+{
+    _longitude_node = fgGetNode("/position/longitude-deg", true);
+    _latitude_node = fgGetNode("/position/latitude-deg", true);
+    _altitude_node = fgGetNode("/position/altitude-ft", true);
+    _magvar_node = fgGetNode("/environment/magnetic-variation-deg", true);
+    _serviceable_node = fgGetNode("/instrumentation/gps/serviceable", true);
+    _electrical_node = fgGetNode("/systems/electrical/outputs/gps", true);
+
+    _raim_node = fgGetNode("/instrumentation/gps/raim", true);
+    _indicated_longitude_node =
+        fgGetNode("/instrumentation/gps/indicated-longitude-deg", true);
+    _indicated_latitude_node =
+        fgGetNode("/instrumentation/gps/indicated-latitude-deg", true);
+    _indicated_altitude_node =
+        fgGetNode("/instrumentation/gps/indicated-altitude-ft", true);
+    _true_track_node =
+        fgGetNode("/instrumentation/gps/indicated-track-true-deg", true);
+    _magnetic_track_node =
+        fgGetNode("/instrumentation/gps/indicated-track-magnetic-deg", true);
+    _speed_node =
+        fgGetNode("/instrumentation/gps/indicated-ground-speed-kt", true);
+}
+
+void
+GPS::update (double delta_time_sec)
+{
+                                // If it's off, don't bother.
+    if (!_serviceable_node->getBoolValue() ||
+        !_electrical_node->getBoolValue()) {
+        _last_valid = false;
+        _last_longitude_deg = 0;
+        _last_latitude_deg = 0;
+        _last_altitude_m = 0;
+        _raim_node->setDoubleValue(false);
+        _indicated_longitude_node->setDoubleValue(0);
+        _indicated_latitude_node->setDoubleValue(0);
+        _indicated_altitude_node->setDoubleValue(0);
+        _true_track_node->setDoubleValue(0);
+        _magnetic_track_node->setDoubleValue(0);
+        _speed_node->setDoubleValue(0);
+        return;
+    }
+
+                                // Get the aircraft position
+    double longitude_deg = _longitude_node->getDoubleValue();
+    double latitude_deg = _latitude_node->getDoubleValue();
+    double altitude_m = _altitude_node->getDoubleValue() * SG_FEET_TO_METER;
+    double magvar_deg = _magvar_node->getDoubleValue();
+
+    _raim_node->setBoolValue(true);
+    _indicated_longitude_node->setDoubleValue(longitude_deg);
+    _indicated_latitude_node->setDoubleValue(latitude_deg);
+    _indicated_altitude_node->setDoubleValue(altitude_m * SG_METER_TO_FEET);
+
+    if (_last_valid) {
+        double track1_deg, track2_deg, distance_m;
+        geo_inverse_wgs_84(altitude_m,
+                           _last_latitude_deg, _last_longitude_deg,
+                           latitude_deg, longitude_deg,
+                           &track1_deg, &track2_deg, &distance_m);
+        double distance_nm = distance_m * SG_METER_TO_NM;
+        double speed_kt = ((distance_m * SG_METER_TO_NM) *
+                           ((1 / delta_time_sec) * 3600.0));
+        _true_track_node->setDoubleValue(track1_deg);
+        _magnetic_track_node->setDoubleValue(track1_deg - magvar_deg);
+        _speed_node->setDoubleValue(speed_kt);
+    } else {
+        _true_track_node->setDoubleValue(0);
+        _magnetic_track_node->setDoubleValue(0);
+        _speed_node->setDoubleValue(0);
+    }
+
+    _last_valid = true;
+    _last_longitude_deg = longitude_deg;
+    _last_latitude_deg = latitude_deg;
+    _last_altitude_m = altitude_m;
+}
+
+// end of gps.cxx

src/Instrumentation/gps.hxx

@@ -0,0 +1,78 @@
+// gps.hxx - distance-measuring equipment.
+// Written by David Megginson, started 2003.
+//
+// This file is in the Public Domain and comes with no warranty.
+
+
+#ifndef __INSTRUMENTS_GPS_HXX
+#define __INSTRUMENTS_GPS_HXX 1
+
+#ifndef __cplusplus
+# error This library requires C++
+#endif
+
+#include <simgear/misc/props.hxx>
+#include <Main/fgfs.hxx>
+
+
+/**
+ * Model a GPS radio.
+ *
+ * Input properties:
+ *
+ * /position/longitude-deg
+ * /position/latitude-deg
+ * /position/altitude-ft
+ * /environment/magnetic-variation-deg
+ * /systems/electrical/outputs/gps
+ * /instrumentation/gps/serviceable
+ *
+ * Output properties:
+ *
+ * /instrumentation/gps/indicated-longitude-deg
+ * /instrumentation/gps/indicated-latitude-deg
+ * /instrumentation/gps/indicated-altitude-ft
+ * /instrumentation/gps/indicated-track-true-deg
+ * /instrumentation/gps/indicated-track-magnetic-deg
+ * /instrumentation/gps/indicated-ground-speed-kt
+ */
+class GPS : public FGSubsystem
+{
+
+public:
+
+    GPS ();
+    virtual ~GPS ();
+
+    virtual void init ();
+    virtual void update (double delta_time_sec);
+
+private:
+
+    void search (double frequency, double longitude_rad,
+                 double latitude_rad, double altitude_m);
+
+    SGPropertyNode_ptr _longitude_node;
+    SGPropertyNode_ptr _latitude_node;
+    SGPropertyNode_ptr _altitude_node;
+    SGPropertyNode_ptr _magvar_node;
+    SGPropertyNode_ptr _serviceable_node;
+    SGPropertyNode_ptr _electrical_node;
+
+    SGPropertyNode_ptr _raim_node;
+    SGPropertyNode_ptr _indicated_longitude_node;
+    SGPropertyNode_ptr _indicated_latitude_node;
+    SGPropertyNode_ptr _indicated_altitude_node;
+    SGPropertyNode_ptr _true_track_node;
+    SGPropertyNode_ptr _magnetic_track_node;
+    SGPropertyNode_ptr _speed_node;
+
+    bool _last_valid;
+    double _last_longitude_deg;
+    double _last_latitude_deg;
+    double _last_altitude_m;
+
+};
+
+
+#endif // __INSTRUMENTS_GPS_HXX

src/Instrumentation/instrument_mgr.cxx

@@ -13,7 +13,9 @@
 #include "heading_indicator.hxx"
 #include "vertical_speed_indicator.hxx"
 #include "mag_compass.hxx"
+
 #include "dme.hxx"
+#include "gps.hxx"
 
 
 FGInstrumentMgr::FGInstrumentMgr ()
@@ -27,6 +29,7 @@ FGInstrumentMgr::FGInstrumentMgr ()
     set_subsystem("vsi", new VerticalSpeedIndicator);
     set_subsystem("compass", new MagCompass);
     set_subsystem("dme", new DME, 1.0);
+    set_subsystem("gps", new GPS, 0.45);
 }
 
 FGInstrumentMgr::~FGInstrumentMgr ()