X-Git-Url: https://git.mxchange.org/?a=blobdiff_plain;f=src%2FCockpit%2Fradiostack.cxx;h=9b93cc8bc296bbfe95a274629f3803a090076823;hb=29275ce1ecf9c4ea302aacca8c5ae5d4d3319a17;hp=94a68383a8b57c563dbdf05c06efd71e90f41aaf;hpb=56ad909452f9bd88767dee5762c3887773b64159;p=flightgear.git

diff --git a/src/Cockpit/radiostack.cxx b/src/Cockpit/radiostack.cxx
index 94a68383a..9b93cc8bc 100644
--- a/src/Cockpit/radiostack.cxx
+++ b/src/Cockpit/radiostack.cxx
@@ -21,76 +21,581 @@
 // $Id$
 
 
+#include <Aircraft/aircraft.hxx>
+#include <Main/bfi.hxx>
 #include <Navaids/ilslist.hxx>
 #include <Navaids/navlist.hxx>
+#include <Time/event.hxx>
 
 #include "radiostack.hxx"
 
+/**
+ * Boy, this is ugly!  Make the VOR range vary by altitude difference.
+ */
+static inline double
+kludgeRange (double stationElev, double aircraftElev, double nominalRange)
+{
+				// Assume that the nominal range (usually
+				// 50nm) applies at a 5,000 ft difference.
+				// Just a wild guess!
+  double factor = ((aircraftElev*METER_TO_FEET) - stationElev) / 1000.0;
+  double range = fabs(nominalRange * factor);
+
+				// Clamp the range to keep it sane; for
+				// now, never less than 25% or more than
+				// 500% of nominal range.
+  if (range < nominalRange/4.0) {
+    range = nominalRange/4.0;
+  } else if (range > nominalRange*5.0) {
+    range = nominalRange*5.0;
+  }
+
+  return range;
+}
+
+
+FGRadioStack *current_radiostack;
+
+
+// periodic radio station search wrapper
+static void fgRadioSearch( void ) {
+    current_radiostack->search();
+}
 
 // Constructor
 FGRadioStack::FGRadioStack() {
+    nav1_radial = 0.0;
+    nav1_dme_dist = 0.0;
+    nav2_radial = 0.0;
+    nav2_dme_dist = 0.0;
     need_update = true;
+    longitudeVal = fgGetValue("/position/longitude");
+    latitudeVal = fgGetValue("/position/latitude");
+    altitudeVal = fgGetValue("/position/altitude");
 }
 
 
 // Destructor
-FGRadioStack::~FGRadioStack() {
+FGRadioStack::~FGRadioStack() 
+{
+    unbind();			// FIXME: should be called externally
+}
+
+
+void
+FGRadioStack::init ()
+{
+    search();
+    update();
+
+    // Search radio database once per second
+    global_events.Register( "fgRadioSearch()", fgRadioSearch,
+			    fgEVENT::FG_EVENT_READY, 1000);
 }
 
+void
+FGRadioStack::bind ()
+{
+				// User inputs
+    fgTie("/radios/nav1/frequencies/selected", this,
+	  &FGRadioStack::get_nav1_freq, &FGRadioStack::set_nav1_freq);
+    fgTie("/radios/nav1/frequencies/standby", this,
+	  &FGRadioStack::get_nav1_alt_freq, &FGRadioStack::set_nav1_alt_freq);
+    fgTie("/radios/nav1/radials/selected", this,
+	  &FGRadioStack::get_nav1_sel_radial,
+	  &FGRadioStack::set_nav1_sel_radial);
+
+				// Radio outputs
+    fgTie("/radios/nav1/radials/actual", this, &FGRadioStack::get_nav1_radial);
+    fgTie("/radios/nav1/to-flag", this, &FGRadioStack::get_nav1_to_flag);
+    fgTie("/radios/nav1/from-flag", this, &FGRadioStack::get_nav1_from_flag);
+    fgTie("/radios/nav1/in-range", this, &FGRadioStack::get_nav1_inrange);
+    fgTie("/radios/nav1/dme/distance", this, &FGRadioStack::get_nav1_dme_dist);
+    fgTie("/radios/nav1/dme/in-range", this,
+	  &FGRadioStack::get_nav1_dme_inrange);
+    fgTie("/radios/nav1/heading-needle-deflection", this,
+	  &FGRadioStack::get_nav1_heading_needle_deflection);
+    fgTie("/radios/nav1/gs-needle-deflection", this,
+	  &FGRadioStack::get_nav1_gs_needle_deflection);
+
+				// User inputs
+    fgTie("/radios/nav2/frequencies/selected", this,
+	  &FGRadioStack::get_nav2_freq, &FGRadioStack::set_nav2_freq);
+    fgTie("/radios/nav2/frequencies/standby", this,
+	  &FGRadioStack::get_nav2_alt_freq, &FGRadioStack::set_nav2_alt_freq);
+    fgTie("/radios/nav2/radials/selected", this,
+	  &FGRadioStack::get_nav2_sel_radial,
+	  &FGRadioStack::set_nav2_sel_radial);
+
+				// Radio outputs
+    fgTie("/radios/nav2/radials/actual", this, &FGRadioStack::get_nav2_radial);
+    fgTie("/radios/nav2/to-flag", this, &FGRadioStack::get_nav2_to_flag);
+    fgTie("/radios/nav2/from-flag", this, &FGRadioStack::get_nav2_from_flag);
+    fgTie("/radios/nav2/in-range", this, &FGRadioStack::get_nav2_inrange);
+    fgTie("/radios/nav2/dme/distance", this, &FGRadioStack::get_nav2_dme_dist);
+    fgTie("/radios/nav2/dme/in-range", this,
+	  &FGRadioStack::get_nav2_dme_inrange);
+    fgTie("/radios/nav2/heading-needle-deflection", this,
+	  &FGRadioStack::get_nav2_heading_needle_deflection);
+    fgTie("/radios/nav2/gs-needle-deflection", this,
+	  &FGRadioStack::get_nav2_gs_needle_deflection);
+
+				// User inputs
+    fgTie("/radios/adf/frequencies/selected", this,
+	  &FGRadioStack::get_adf_freq, &FGRadioStack::set_adf_freq);
+    fgTie("/radios/adf/frequencies/standby", this,
+	  &FGRadioStack::get_adf_alt_freq, &FGRadioStack::set_adf_alt_freq);
+    fgTie("/radios/adf/rotation", this,
+	  &FGRadioStack::get_adf_rotation, &FGRadioStack::set_adf_rotation);
+}
+
+void
+FGRadioStack::unbind ()
+{
+    fgUntie("/radios/nav1/frequencies/selected");
+    fgUntie("/radios/nav1/frequencies/standby");
+    fgUntie("/radios/nav1/radials/actual");
+    fgUntie("/radios/nav1/radials/selected");
+    fgUntie("/radios/nav1/to-flag");
+    fgUntie("/radios/nav1/from-flag");
+    fgUntie("/radios/nav1/in-range");
+    fgUntie("/radios/nav1/dme/distance");
+    fgUntie("/radios/nav1/dme/in-range");
+    fgUntie("/radios/nav1/heading-needle-deflection");
+    fgUntie("/radios/nav1/gs-needle-deflection");
+
+    fgUntie("/radios/nav2/frequencies/selected");
+    fgUntie("/radios/nav2/frequencies/standby");
+    fgUntie("/radios/nav2/radials/actual");
+    fgUntie("/radios/nav2/radials/selected");
+    fgUntie("/radios/nav2/to-flag");
+    fgUntie("/radios/nav2/from-flag");
+    fgUntie("/radios/nav2/in-range");
+    fgUntie("/radios/nav2/dme/distance");
+    fgUntie("/radios/nav2/dme/in-range");
+    fgUntie("/radios/nav2/heading-needle-deflection");
+    fgUntie("/radios/nav2/gs-needle-deflection");
+
+    fgUntie("/radios/adf/frequencies/selected");
+    fgUntie("/radios/adf/frequencies/standby");
+    fgUntie("/radios/adf/rotation");
+}
+
+// Search the database for the current frequencies given current location
+void 
+FGRadioStack::update() 
+{
+    double lon = longitudeVal->getDoubleValue() * DEG_TO_RAD;
+    double lat = latitudeVal->getDoubleValue() * DEG_TO_RAD;
+    double elev = altitudeVal->getDoubleValue() * FEET_TO_METER;
 
-// Update nav/adf radios based on current postition
-void FGRadioStack::update( double lon, double lat, double elev ) {
     need_update = false;
 
-    FGNav n;
+    Point3D aircraft = sgGeodToCart( Point3D( lon, lat, elev ) );
+    Point3D station;
+    double az1, az2, s;
 
-    // nav1
-    if ( current_navlist->query( lon, lat, elev, nav1_freq,
-				 &n, &nav1_heading, &nav1_dist) ) {
-	nav1_inrange = true;
-	nav1_lon = n.get_lon();
-	nav1_lat = n.get_lat();
-	nav1_elev = n.get_elev();
-	cout << "Found a vor station in range" << endl;
-	cout << " id = " << n.get_ident() << endl;
-	cout << " heading = " << nav1_heading
-	     << " dist = " << nav1_dist << endl;
+    if ( nav1_valid ) {
+	station = Point3D( nav1_x, nav1_y, nav1_z );
+	nav1_loc_dist = aircraft.distance3D( station );
+
+	if ( nav1_has_dme ) {
+	    // staightline distance
+	    station = Point3D( nav1_dme_x, nav1_dme_y, nav1_dme_z );
+	    nav1_dme_dist = aircraft.distance3D( station );
+	} else {
+	    nav1_dme_dist = 0.0;
+	}
+
+	if ( nav1_has_gs ) {
+	    station = Point3D( nav1_gs_x, nav1_gs_y, nav1_gs_z );
+	    nav1_gs_dist = aircraft.distance3D( station );
+	} else {
+	    nav1_gs_dist = 0.0;
+	}
+	
+	if ( nav1_loc_dist < nav1_effective_range * NM_TO_METER ) {
+	    nav1_inrange = true;
+	    
+	    // wgs84 heading
+	    geo_inverse_wgs_84( elev, lat * RAD_TO_DEG, lon * RAD_TO_DEG, 
+				nav1_loclat, nav1_loclon,
+				&az1, &az2, &s );
+	    // cout << "az1 = " << az1 << " magvar = " << nav1_magvar << endl;
+	    nav1_heading = az1 - nav1_magvar;
+	    // Alex: nav1_heading = - (az1 - FGBFI::getMagVar() / RAD_TO_DEG);
+
+	    // cout << " heading = " << nav1_heading
+	    //      << " dist = " << nav1_dist << endl;
+	} else {
+	    nav1_inrange = false;
+	}
+
+	if ( nav1_loc ) {
+	} else {
+	    nav1_radial = nav1_sel_radial;
+	}
     } else {
 	nav1_inrange = false;
-	cout << "not picking up vor. :-(" << endl;
+	nav1_dme_dist = 0.0;
+	// cout << "not picking up vor. :-(" << endl;
     }
 
-    // nav1
-    if ( current_navlist->query( lon, lat, elev, nav2_freq,
-				 &n, &nav2_heading, &nav2_dist) ) {
-	nav2_inrange = true;
-	nav2_lon = n.get_lon();
-	nav2_lat = n.get_lat();
-	nav2_elev = n.get_elev();
-	cout << "Found a vor station in range" << endl;
-	cout << " id = " << n.get_ident() << endl;
-	cout << " heading = " << nav2_heading
-	     << " dist = " << nav2_dist << endl;
+    if ( nav2_valid ) {
+	station = Point3D( nav2_x, nav2_y, nav2_z );
+	nav2_loc_dist = aircraft.distance3D( station );
+
+	if ( nav2_has_dme ) {
+	    // staightline distance
+	    station = Point3D( nav2_dme_x, nav2_dme_y, nav2_dme_z );
+	    nav2_dme_dist = aircraft.distance3D( station );
+	} else {
+	    nav2_dme_dist = 0.0;
+	}
+
+	if ( nav2_has_gs ) {
+	    station = Point3D( nav2_gs_x, nav2_gs_y, nav2_gs_z );
+	    nav2_gs_dist = aircraft.distance3D( station );
+	} else {
+	    nav2_gs_dist = 0.0;
+	}
+
+	if ( nav2_loc_dist < nav2_effective_range * NM_TO_METER ) {
+	    nav2_inrange = true;
+
+	    // wgs84 heading
+	    geo_inverse_wgs_84( elev, lat * RAD_TO_DEG, lon * RAD_TO_DEG, 
+				nav2_loclat, nav2_loclon,
+				&az1, &az2, &s );
+	    nav2_heading = az1 - nav2_magvar;
+	    // Alex: nav2_heading = - (az1 - FGBFI::getMagVar() / RAD_TO_DEG);
+
+	    // cout << " heading = " << nav2_heading
+	    //      << " dist = " << nav2_dist << endl;
+	} else {
+	    nav2_inrange = false;
+	}
+
+	if ( !nav2_loc ) {
+	    nav2_radial = nav2_sel_radial;
+	}
     } else {
 	nav2_inrange = false;
-	cout << "not picking up vor. :-(" << endl;
+	// cout << "not picking up vor. :-(" << endl;
     }
 
     // adf
-    double junk;
-    if ( current_navlist->query( lon, lat, elev, adf_freq,
-				 &n, &adf_heading, &junk) ) {
-	adf_inrange = true;
-	adf_lon = n.get_lon();
-	adf_lat = n.get_lat();
-	adf_elev = n.get_elev();
-	cout << "Found an adf station in range" << endl;
-	cout << " id = " << n.get_ident() << endl;
-	cout << " heading = " << adf_heading
-	     << " dist = " << junk << endl;
+    if ( adf_valid ) {
+	// staightline distance
+	station = Point3D( adf_x, adf_y, adf_z );
+	adf_dist = aircraft.distance3D( station );
+
+	if ( adf_dist < adf_effective_range * NM_TO_METER ) {
+	    adf_inrange = true;
+
+	    // wgs84 heading
+	    geo_inverse_wgs_84( elev, lat * RAD_TO_DEG, lon * RAD_TO_DEG, 
+				adf_lat, adf_lon,
+				&az1, &az2, &s );
+	    adf_heading = az1;
+
+	    // cout << " heading = " << nav2_heading
+	    //      << " dist = " << nav2_dist << endl;
+	} else {
+	    adf_inrange = false;
+	}
     } else {
 	adf_inrange = false;
-	cout << "not picking up adf. :-(" << endl;
     }
 }
 
+
+// Update current nav/adf radio stations based on current postition
+void FGRadioStack::search () 
+{
+    double lon = longitudeVal->getDoubleValue() * DEG_TO_RAD;
+    double lat = latitudeVal->getDoubleValue() * DEG_TO_RAD;
+    double elev = altitudeVal->getDoubleValue() * FEET_TO_METER;
+
+    // nav1
+    FGILS ils;
+    FGNav nav;
+
+    if ( current_ilslist->query( lon, lat, elev, nav1_freq, &ils ) ) {
+	nav1_valid = true;
+	nav1_loc = true;
+	nav1_has_dme = ils.get_has_dme();
+	nav1_has_gs = ils.get_has_gs();
+
+	nav1_loclon = ils.get_loclon();
+	nav1_loclat = ils.get_loclat();
+	nav1_gslon = ils.get_gslon();
+	nav1_gslat = ils.get_gslat();
+	nav1_dmelon = ils.get_dmelon();
+	nav1_dmelat = ils.get_dmelat();
+	nav1_elev = ils.get_gselev();
+	nav1_magvar = 0;
+	nav1_effective_range = FG_ILS_DEFAULT_RANGE;
+	nav1_target_gs = ils.get_gsangle();
+	nav1_radial = ils.get_locheading();
+	while ( nav1_radial <   0.0 ) { nav1_radial += 360.0; }
+	while ( nav1_radial > 360.0 ) { nav1_radial -= 360.0; }
+	nav1_x = ils.get_x();
+	nav1_y = ils.get_y();
+	nav1_z = ils.get_z();
+	nav1_gs_x = ils.get_gs_x();
+	nav1_gs_y = ils.get_gs_y();
+	nav1_gs_z = ils.get_gs_z();
+	nav1_dme_x = ils.get_dme_x();
+	nav1_dme_y = ils.get_dme_y();
+	nav1_dme_z = ils.get_dme_z();
+	// cout << "Found an ils station in range" << endl;
+	// cout << " id = " << ils.get_locident() << endl;
+    } else if ( current_navlist->query( lon, lat, elev, nav1_freq, &nav ) ) {
+	nav1_valid = true;
+	nav1_loc = false;
+	nav1_has_dme = nav.get_has_dme();
+	nav1_has_gs = false;
+	nav1_loclon = nav.get_lon();
+	nav1_loclat = nav.get_lat();
+	nav1_elev = nav.get_elev();
+	nav1_magvar = nav.get_magvar();
+	nav1_effective_range = kludgeRange(nav1_elev, elev, nav.get_range());
+	nav1_target_gs = 0.0;
+	nav1_radial = nav1_sel_radial;
+	nav1_x = nav1_dme_x = nav.get_x();
+	nav1_y = nav1_dme_y = nav.get_y();
+	nav1_z = nav1_dme_z = nav.get_z();
+	// cout << "Found a vor station in range" << endl;
+	// cout << " id = " << nav.get_ident() << endl;
+    } else {
+	nav1_valid = false;
+	nav1_radial = 0;
+	nav1_dme_dist = 0;
+	// cout << "not picking up vor1. :-(" << endl;
+    }
+
+    if ( current_ilslist->query( lon, lat, elev, nav2_freq, &ils ) ) {
+	nav2_valid = true;
+	nav2_loc = true;
+	nav2_has_dme = ils.get_has_dme();
+	nav2_has_gs = ils.get_has_gs();
+
+	nav2_loclon = ils.get_loclon();
+	nav2_loclat = ils.get_loclat();
+	nav2_elev = ils.get_gselev();
+	nav2_magvar = 0;
+	nav2_effective_range = FG_ILS_DEFAULT_RANGE;
+	nav2_target_gs = ils.get_gsangle();
+	nav2_radial = ils.get_locheading();
+	while ( nav2_radial <   0.0 ) { nav2_radial += 360.0; }
+	while ( nav2_radial > 360.0 ) { nav2_radial -= 360.0; }
+	nav2_x = ils.get_x();
+	nav2_y = ils.get_y();
+	nav2_z = ils.get_z();
+	nav2_gs_x = ils.get_gs_x();
+	nav2_gs_y = ils.get_gs_y();
+	nav2_gs_z = ils.get_gs_z();
+	nav2_dme_x = ils.get_dme_x();
+	nav2_dme_y = ils.get_dme_y();
+	nav2_dme_z = ils.get_dme_z();
+	// cout << "Found an ils station in range" << endl;
+	// cout << " id = " << ils.get_locident() << endl;
+    } else if ( current_navlist->query( lon, lat, elev, nav2_freq, &nav ) ) {
+	nav2_valid = true;
+	nav2_loc = false;
+	nav2_has_dme = nav.get_has_dme();
+	nav2_has_dme = false;
+	nav2_loclon = nav.get_lon();
+	nav2_loclat = nav.get_lat();
+	nav2_elev = nav.get_elev();
+	nav2_magvar = nav.get_magvar();
+	nav2_effective_range = kludgeRange(nav2_elev, elev, nav.get_range());
+	nav2_target_gs = 0.0;
+	nav2_radial = nav2_sel_radial;
+	nav2_x = nav2_dme_x = nav.get_x();
+	nav2_y = nav2_dme_y = nav.get_y();
+	nav2_z = nav2_dme_z = nav.get_z();
+	// cout << "Found a vor station in range" << endl;
+	// cout << " id = " << nav.get_ident() << endl;
+    } else {
+	nav2_valid = false;
+	nav2_radial = 0;
+	nav2_dme_dist = 0;
+	// cout << "not picking up vor2. :-(" << endl;
+    }
+
+    // adf
+    if ( current_navlist->query( lon, lat, elev, adf_freq, &nav ) ) {
+	adf_valid = true;
+
+	adf_lon = nav.get_lon();
+	adf_lat = nav.get_lat();
+	adf_elev = nav.get_elev();
+	adf_effective_range = kludgeRange(adf_elev, elev, nav.get_range());
+	adf_x = nav.get_x();
+	adf_y = nav.get_y();
+	adf_z = nav.get_z();
+	// cout << "Found an adf station in range" << endl;
+	// cout << " id = " << nav.get_ident() << endl;
+    } else {
+	adf_valid = false;
+	// cout << "not picking up adf. :-(" << endl;
+    }
+}
+
+
+// return the amount of heading needle deflection, returns a value
+// clamped to the range of ( -10 , 10 )
+double FGRadioStack::get_nav1_heading_needle_deflection() const {
+    double r;
+
+    if ( nav1_inrange ) {
+        r = nav1_heading - nav1_radial;
+	// cout << "Radial = " << nav1_radial 
+	//      << "  Bearing = " << nav1_heading << endl;
+    
+	while ( r >  180.0 ) { r -= 360.0;}
+	while ( r < -180.0 ) { r += 360.0;}
+	if ( fabs(r) > 90.0 ) {
+	    r = ( r<0.0 ? -r-180.0 : -r+180.0 );
+	    if ( nav1_loc ) {
+		r = -r;
+	    }
+	}
+
+	// According to Robin Peel, the ILS is 4x more sensitive than a vor
+	if ( nav1_loc ) { r *= 4.0; }
+	if ( r < -10.0 ) { r = -10.0; }
+	if ( r >  10.0 ) { r = 10.0; }
+    } else {
+	r = 0.0;
+    }
+
+    return r;
+}
+
+// return the amount of heading needle deflection, returns a value
+// clamped to the range of ( -10 , 10 )
+double FGRadioStack::get_nav2_heading_needle_deflection() const {
+    double r;
+
+    if ( nav2_inrange ) {
+        r = nav2_heading - nav2_radial;
+	// cout << "Radial = " << nav2_radial 
+	//      << "  Bearing = " << nav2_heading << endl;
+    
+	while (r> 180.0) r-=360.0;
+	while (r<-180.0) r+=360.0;
+	if ( fabs(r) > 90.0 )
+	    r = ( r<0.0 ? -r-180.0 : -r+180.0 );
+	// According to Robin Peel, the ILS is 4x more sensitive than a vor
+	if ( nav2_loc ) r *= 4.0;
+	if ( r < -10.0 ) r = -10.0;
+	if ( r > 10.0 ) r = 10.0;
+    } else {
+	r = 0.0;
+    }
+
+    return r;
+}
+
+// return the amount of glide slope needle deflection (.i.e. the
+// number of degrees we are off the glide slope * 5.0
+double FGRadioStack::get_nav1_gs_needle_deflection() const {
+    if ( nav1_inrange && nav1_has_gs ) {
+	double x = nav1_gs_dist;
+	double y = (FGBFI::getAltitude() - nav1_elev) * FEET_TO_METER;
+	double angle = atan2( y, x ) * RAD_TO_DEG;
+	return (nav1_target_gs - angle) * 5.0;
+    } else {
+	return 0.0;
+    }
+}
+
+
+// return the amount of glide slope needle deflection (.i.e. the
+// number of degrees we are off the glide slope * 5.0
+double FGRadioStack::get_nav2_gs_needle_deflection() const {
+    if ( nav2_inrange && nav2_has_gs ) {
+	double x = nav2_gs_dist;
+	double y = (FGBFI::getAltitude() - nav2_elev) * FEET_TO_METER;
+	double angle = atan2( y, x ) * RAD_TO_DEG;
+	return (nav2_target_gs - angle) * 5.0;
+    } else {
+	return 0.0;
+    }
+}
+
+
+/**
+ * Return true if the NAV1 TO flag should be active.
+ */
+bool 
+FGRadioStack::get_nav1_to_flag () const
+{
+  if (nav1_inrange) {
+    double offset = fabs(nav1_heading - nav1_radial);
+    if (nav1_loc)
+      return true;
+    else
+      return (offset <= 90.0 || offset >= 270.0);
+  } else {
+    return false;
+  }
+}
+
+
+/**
+ * Return true if the NAV1 FROM flag should be active.
+ */
+bool
+FGRadioStack::get_nav1_from_flag () const
+{
+  if (nav1_inrange) {
+    double offset = fabs(nav1_heading - nav1_radial);
+    if (nav1_loc)
+      return false;
+    else
+      return (offset > 90.0 && offset < 270.0);
+  } else {
+    return false;
+  }
+}
+
+
+/**
+ * Return true if the NAV2 TO flag should be active.
+ */
+bool 
+FGRadioStack::get_nav2_to_flag () const
+{
+  if (nav2_inrange) {
+    double offset = fabs(nav2_heading - nav2_radial);
+    if (nav2_loc)
+      return true;
+    else
+      return (offset <= 90.0 || offset >= 270.0);
+  } else {
+    return false;
+  }
+}
+
+
+/**
+ * Return true if the NAV2 FROM flag should be active.
+ */
+bool
+FGRadioStack::get_nav2_from_flag () const
+{
+  if (nav2_inrange) {
+    double offset = fabs(nav2_heading - nav2_radial);
+    if (nav2_loc)
+      return false;
+    else
+      return (offset > 90.0 && offset < 270.0);
+  } else {
+    return false;
+  }
+}
+