New version of basic DME support. This can coexist with the old one

for a little while, since it uses different properties.  There are
some improvements, especially with searching and range.  It also has
its own serviceable and in-range properties, independent of any
coupled VOR.

diff --git a/src/Instrumentation/Makefile.am b/src/Instrumentation/Makefile.am
index 84c86e83e4809259a9652653cc96cdbe26f996af..796b44d568572cdd3b1487bd9c5f087f7d42c5b2 100644 (file)
--- a/src/Instrumentation/Makefile.am
+++ b/src/Instrumentation/Makefile.am
@@ -1,6 +1,7 @@
 noinst_LIBRARIES = libInstrumentation.a
 
 libInstrumentation_a_SOURCES = instrument_mgr.cxx instrument_mgr.hxx \
+                               dme.cxx dme.hxx \
                                gyro.cxx gyro.hxx \
                                airspeed_indicator.cxx airspeed_indicator.hxx \
                                attitude_indicator.cxx attitude_indicator.hxx \

diff --git a/src/Instrumentation/dme.cxx b/src/Instrumentation/dme.cxx
new file mode 100644 (file)
index 0000000..afc3f1e
--- /dev/null
+++ b/src/Instrumentation/dme.cxx
@@ -0,0 +1,183 @@
+// dme.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 <simgear/math/sg_random.h>
+
+#include <Main/fg_props.hxx>
+#include <Navaids/ilslist.hxx>
+#include <Navaids/navlist.hxx>
+
+#include "dme.hxx"
+
+
+/**
+ * Adjust the range.
+ *
+ * Start by calculating the radar horizon based on the elevation
+ * difference, then clamp to the maximum, then add a fudge for
+ * borderline reception.
+ */
+static double
+adjust_range (double transmitter_elevation_ft, double aircraft_altitude_ft,
+              double max_range_nm)
+{
+    double delta_elevation_ft =
+        fabs(aircraft_altitude_ft - transmitter_elevation_ft);
+    double range_nm = 1.23 * sqrt(delta_elevation_ft);
+    if (range_nm > max_range_nm)
+        range_nm = max_range_nm;
+    double rand = sg_random();
+    return range_nm + (range_nm * rand * rand);
+}
+
+
+DME::DME ()
+    : _last_distance_nm(0),
+      _last_frequency_mhz(-1),
+      _time_before_search_sec(0),
+      _transmitter_valid(false),
+      _transmitter_elevation_ft(0),
+      _transmitter_range_nm(0)
+{
+}
+
+DME::~DME ()
+{
+}
+
+void
+DME::init ()
+{
+    _longitude_node = fgGetNode("/position/longitude-deg", true);
+    _latitude_node = fgGetNode("/position/latitude-deg", true);
+    _altitude_node = fgGetNode("/position/altitude-deg", true);
+    _serviceable_node = fgGetNode("/instrumentation/dme/serviceable", true);
+    _electrical_node = fgGetNode("/systems/electrical/outputs/dme", true);
+    _source_node = fgGetNode("/instrumentation/dme/frequencies/source", true);
+    _frequency_node =
+        fgGetNode("/instrumentation/dme/frequencies/selected-mhz", true);
+
+    _in_range_node = fgGetNode("/instrumentation/dme/in-range", true);
+    _distance_node =
+        fgGetNode("/instrumentation/dme/indicated-distance-nm", true);
+    _speed_node =
+        fgGetNode("/instrumentation/dme/indicated-ground-speed-kt", true);
+    _time_node =
+        fgGetNode("/instrumentation/dme/indicated-time-min", true);
+}
+
+void
+DME::update (double delta_time_sec)
+{
+                                // Figure out the source
+    const char * source = _source_node->getStringValue();
+    if (source[0] == '\0') {
+        source = "/instrumentation/dme/frequencies/selected-mhz";
+        _source_node->setStringValue(source);
+    }
+
+                                // Get the frequency
+    double frequency_mhz = fgGetDouble(source, 108.0);
+    if (frequency_mhz != _last_frequency_mhz) {
+        _time_before_search_sec = 0;
+        _last_frequency_mhz = frequency_mhz;
+    }
+
+                                // Get the aircraft position
+    double longitude_rad =
+        _longitude_node->getDoubleValue() * SGD_DEGREES_TO_RADIANS;
+    double latitude_rad =
+        _latitude_node->getDoubleValue() * SGD_DEGREES_TO_RADIANS;
+    double altitude_m =
+        _altitude_node->getDoubleValue() * SGD_DEGREES_TO_RADIANS;
+
+                                // On timeout, scan again
+    _time_before_search_sec -= delta_time_sec;
+    if (_time_before_search_sec < 0)
+        search(frequency_mhz, longitude_rad,
+               latitude_rad, altitude_m);
+
+                                // If it's off, don't bother.
+    if (!_serviceable_node->getBoolValue() ||
+        !_electrical_node->getBoolValue() ||
+        !_transmitter_valid) {
+        _last_distance_nm = 0;
+        _in_range_node->setBoolValue(false);
+        _distance_node->setDoubleValue(0);
+        _speed_node->setDoubleValue(0);
+        _time_node->setDoubleValue(0);
+        return;
+    }
+
+                                // Calculate the distance to the transmitter
+    Point3D location =
+        sgGeodToCart(Point3D(longitude_rad, latitude_rad, altitude_m));
+    double distance_nm = _transmitter.distance3D(location) * SG_METER_TO_NM;
+    double range_nm = adjust_range(_transmitter_elevation_ft,
+                                   altitude_m * SG_METER_TO_FEET,
+                                   _transmitter_range_nm);
+    if (distance_nm <= range_nm) {
+        double speed_kt = (fabs(distance_nm - _last_distance_nm) *
+                           ((1 / delta_time_sec) * 3600.0));
+        _last_distance_nm = distance_nm;
+
+        _in_range_node->setBoolValue(true);
+        _distance_node->setDoubleValue(distance_nm);
+        _speed_node->setDoubleValue(speed_kt);
+        _time_node->setDoubleValue(distance_nm/speed_kt*60.0);
+        
+    } else {
+        _last_distance_nm = 0;
+        _in_range_node->setBoolValue(false);
+        _distance_node->setDoubleValue(0);
+        _speed_node->setDoubleValue(0);
+        _time_node->setDoubleValue(0);
+    }
+}
+
+void
+DME::search (double frequency_mhz, double longitude_rad,
+             double latitude_rad, double altitude_m)
+{
+                                // reset search time
+    _time_before_search_sec = 1.0;
+
+                                // try the ILS list first
+    FGILS * ils = current_ilslist->findByFreq(frequency_mhz,
+                                              longitude_rad,
+                                              latitude_rad,
+                                              altitude_m);
+    if (ils != 0 && ils->get_has_dme()) {
+        _transmitter_valid = true;
+        _transmitter = Point3D(ils->get_dme_x(),
+                               ils->get_dme_y(),
+                               ils->get_dme_z());
+        _transmitter_elevation_ft = ils->get_gselev() * SG_METER_TO_FEET;
+        _transmitter_range_nm = 50; // arbitrary
+        return;
+    }
+
+                                // try the VORs next
+    FGNav * nav = current_navlist->findByFreq(frequency_mhz,
+                                              longitude_rad,
+                                              latitude_rad,
+                                              altitude_m);
+    if (nav != 0)
+    if (nav != 0 && nav->get_has_dme()) {
+        _transmitter_valid = true;
+        _transmitter = Point3D(nav->get_x(),
+                               nav->get_y(),
+                               nav->get_z());
+        _transmitter_elevation_ft = nav->get_elev() * SG_METER_TO_FEET;
+        _transmitter_range_nm = nav->get_range(); // fixme
+        return;
+    }
+
+    _transmitter_valid = false;
+}
+
+// end of dme.cxx

diff --git a/src/Instrumentation/dme.hxx b/src/Instrumentation/dme.hxx
new file mode 100644 (file)
index 0000000..266c5f6
--- /dev/null
+++ b/src/Instrumentation/dme.hxx
@@ -0,0 +1,80 @@
+// dme.hxx - distance-measuring equipment.
+// Written by David Megginson, started 2003.
+//
+// This file is in the Public Domain and comes with no warranty.
+
+
+#ifndef __INSTRUMENTS_DME_HXX
+#define __INSTRUMENTS_DME_HXX 1
+
+#ifndef __cplusplus
+# error This library requires C++
+#endif
+
+#include <simgear/math/point3d.hxx>
+#include <simgear/misc/props.hxx>
+#include <Main/fgfs.hxx>
+
+
+/**
+ * Model a DME radio.
+ *
+ * Input properties:
+ *
+ * /position/longitude-deg
+ * /position/latitude-deg
+ * /position/altitude-ft
+ * /systems/electrical/outputs/dme
+ * /instrumentation/dme/serviceable
+ * /instrumentation/dme/frequencies/source
+ * /instrumentation/dme/frequencies/selected-mhz
+ *
+ * Output properties:
+ *
+ * /instrumentation/dme/in-range
+ * /instrumentation/dme/indicated-distance-nm
+ * /instrumentation/dme/indicated-ground-speed-kt
+ * /instrumentation/dme/indicated-time-kt
+ */
+class DME : public FGSubsystem
+{
+
+public:
+
+    DME ();
+    virtual ~DME ();
+
+    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 _serviceable_node;
+    SGPropertyNode_ptr _electrical_node;
+    SGPropertyNode_ptr _source_node;
+    SGPropertyNode_ptr _frequency_node;
+
+    SGPropertyNode_ptr _in_range_node;
+    SGPropertyNode_ptr _distance_node;
+    SGPropertyNode_ptr _speed_node;
+    SGPropertyNode_ptr _time_node;
+
+    double _last_distance_nm;
+    double _last_frequency_mhz;
+    double _time_before_search_sec;
+
+    bool _transmitter_valid;
+    Point3D _transmitter;
+    double _transmitter_elevation_ft;
+    double _transmitter_range_nm;
+
+};
+
+
+#endif // __INSTRUMENTS_DME_HXX

diff --git a/src/Instrumentation/instrument_mgr.cxx b/src/Instrumentation/instrument_mgr.cxx
index 07541da5a0b549bceccae9d236f273e3ddf698e9..228548ec8fcf4c6e0bbbf5279e6b3031f2e0e906 100644 (file)
--- a/src/Instrumentation/instrument_mgr.cxx
+++ b/src/Instrumentation/instrument_mgr.cxx
@@ -13,6 +13,7 @@
 #include "heading_indicator.hxx"
 #include "vertical_speed_indicator.hxx"
 #include "mag_compass.hxx"
+#include "dme.hxx"
 
 
 FGInstrumentMgr::FGInstrumentMgr ()
@@ -25,6 +26,7 @@ FGInstrumentMgr::FGInstrumentMgr ()
     set_subsystem("hi", new HeadingIndicator);
     set_subsystem("vsi", new VerticalSpeedIndicator);
     set_subsystem("compass", new MagCompass);
+    set_subsystem("dme", new DME, 1.0);
 }
 
 FGInstrumentMgr::~FGInstrumentMgr ()