X-Git-Url: https://git.mxchange.org/?a=blobdiff_plain;f=src%2FCockpit%2Fnavcom.cxx;h=03fae8220bb6208705746fd68b9849b8cba3df97;hb=c0b4531d04215f76f9cf65afbdaed6b7c0b32634;hp=5a87b7461b20cfc2577935e664e86e7a5d2230d5;hpb=51c04e9e4c4d2ecc0f3ee0a6d3559d1e22e247c5;p=flightgear.git

diff --git a/src/Cockpit/navcom.cxx b/src/Cockpit/navcom.cxx
index 5a87b7461..03fae8220 100644
--- a/src/Cockpit/navcom.cxx
+++ b/src/Cockpit/navcom.cxx
@@ -28,13 +28,13 @@
 #include <stdio.h>	// snprintf
 
 #include <simgear/compiler.h>
+#include <simgear/sg_inlines.h>
 #include <simgear/math/sg_random.h>
 #include <simgear/math/vector.hxx>
 
 #include <Aircraft/aircraft.hxx>
 #include <Navaids/ilslist.hxx>
 #include <Navaids/navlist.hxx>
-#include <Time/FGEventMgr.hxx>
 
 #include "navcom.hxx"
 
@@ -59,9 +59,16 @@ FGNavCom::FGNavCom() :
     comm_vol_btn(0.0),
     nav_freq(0.0),
     nav_alt_freq(0.0),
+    nav_heading(0.0),
     nav_radial(0.0),
+    nav_target_radial(0.0),
+    nav_target_radial_true(0.0),
+    nav_target_auto_hdg(0.0),
+    nav_gs_rate_of_climb(0.0),
     nav_vol_btn(0.0),
-    nav_ident_btn(true)
+    nav_ident_btn(true),
+    horiz_vel(0.0),
+    last_x(0.0)
 {
     SGPath path( globals->get_fg_root() );
     SGPath term = path;
@@ -95,109 +102,146 @@ FGNavCom::init ()
     // We assume that index is valid now (it must be set before init()
     // is called.)
     char propname[256];
+    // FIXME: Get rid of snprintf
 
-    sprintf( propname, "/systems/electrical/outputs/navcom[%d]", index );
+    snprintf(propname, 256, "/systems/electrical/outputs/navcom[%d]", index);
     // default to true in case no electrical system defined.
     fgSetDouble( propname, 60.0 );
     bus_power = fgGetNode( propname, true );
 
-    sprintf( propname, "/instrumentation/comm[%d]/servicable", index );
-    com_servicable = fgGetNode( propname, true );
-    com_servicable->setBoolValue( true );
+    snprintf(propname, 256, "/instrumentation/comm[%d]/serviceable", index);
+    com_serviceable = fgGetNode( propname, true );
+    com_serviceable->setBoolValue( true );
 
-    sprintf( propname, "/instrumentation/nav[%d]/servicable", index );
-    nav_servicable = fgGetNode( propname, true );
-    nav_servicable->setBoolValue( true );
+    snprintf(propname, 256, "/instrumentation/nav[%d]/serviceable", index);
+    nav_serviceable = fgGetNode( propname, true );
+    nav_serviceable->setBoolValue( true );
 
-    sprintf( propname, "/instrumentation/vor[%d]/cdi/servicable", index );
-    cdi_servicable = fgGetNode( propname, true );
-    cdi_servicable->setBoolValue( true );
+    snprintf(propname, 256, "/instrumentation/vor[%d]/cdi/serviceable", index);
+    cdi_serviceable = fgGetNode( propname, true );
+    cdi_serviceable->setBoolValue( true );
 
-    sprintf( propname, "/instrumentation/vor[%d]/gs/servicable", index );
-    gs_servicable = fgGetNode( propname, true );
-    gs_servicable->setBoolValue( true );
+    snprintf(propname, 256, "/instrumentation/vor[%d]/gs/serviceable", index);
+    gs_serviceable = fgGetNode( propname, true );
+    gs_serviceable->setBoolValue( true );
 
-    sprintf( propname, "/instrumentation/vor[%d]/to-from/servicable", index );
-    tofrom_servicable = fgGetNode( propname, true );
-    tofrom_servicable->setBoolValue( true );
+    snprintf(propname, 256, "/instrumentation/vor[%d]/to-from/serviceable", index);
+    tofrom_serviceable = fgGetNode( propname, true );
+    tofrom_serviceable->setBoolValue( true );
 }
 
 void
 FGNavCom::bind ()
 {
     char propname[256];
+    // FIXME: Get rid of snprintf
 
 				// User inputs
-    sprintf( propname, "/radios/comm[%d]/inputs/power-btn", index );
+    snprintf(propname, 256, "/radios/comm[%d]/inputs/power-btn", index);
     fgTie( propname, this,
            &FGNavCom::get_power_btn, &FGNavCom::set_power_btn );
     fgSetArchivable( propname );
 
-    sprintf( propname, "/radios/comm[%d]/frequencies/selected-mhz", index );
+    snprintf(propname, 256, "/radios/comm[%d]/frequencies/selected-mhz", index);
     fgTie( propname, this, &FGNavCom::get_comm_freq, &FGNavCom::set_comm_freq );
     fgSetArchivable( propname );
 
-    sprintf( propname, "/radios/comm[%d]/frequencies/standby-mhz", index );
+    snprintf(propname, 256, "/radios/comm[%d]/frequencies/standby-mhz", index);
     fgTie( propname, this,
            &FGNavCom::get_comm_alt_freq, &FGNavCom::set_comm_alt_freq );
     fgSetArchivable( propname );
 
-    sprintf( propname, "/radios/comm[%d]/volume", index );
+    snprintf(propname, 256, "/radios/comm[%d]/volume", index);
     fgTie( propname, this,
            &FGNavCom::get_comm_vol_btn, &FGNavCom::set_comm_vol_btn );
     fgSetArchivable( propname );
 
-    sprintf( propname, "/radios/nav[%d]/frequencies/selected-mhz", index );
+    snprintf(propname, 256, "/radios/nav[%d]/frequencies/selected-mhz", index);
     fgTie( propname, this,
 	  &FGNavCom::get_nav_freq, &FGNavCom::set_nav_freq );
     fgSetArchivable( propname );
 
-    sprintf( propname, "/radios/nav[%d]/frequencies/standby-mhz", index );
+    snprintf(propname, 256, "/radios/nav[%d]/frequencies/standby-mhz", index);
     fgTie( propname , this,
            &FGNavCom::get_nav_alt_freq, &FGNavCom::set_nav_alt_freq);
     fgSetArchivable( propname );
 
-    sprintf( propname, "/radios/nav[%d]/radials/selected-deg", index );
+    snprintf(propname, 256, "/radios/nav[%d]/radials/selected-deg", index);
     fgTie( propname, this,
            &FGNavCom::get_nav_sel_radial, &FGNavCom::set_nav_sel_radial );
     fgSetArchivable( propname );
 
-    sprintf( propname, "/radios/nav[%d]/volume", index );
+    snprintf(propname, 256, "/radios/nav[%d]/volume", index);
     fgTie( propname, this,
            &FGNavCom::get_nav_vol_btn, &FGNavCom::set_nav_vol_btn );
     fgSetArchivable( propname );
 
-    sprintf( propname, "/radios/nav[%d]/ident", index );
+    snprintf(propname, 256, "/radios/nav[%d]/ident", index);
     fgTie( propname, this,
            &FGNavCom::get_nav_ident_btn, &FGNavCom::set_nav_ident_btn );
     fgSetArchivable( propname );
 
 				// Radio outputs
-    sprintf( propname, "/radios/nav[%d]/audio-btn", index );
+    snprintf(propname, 256, "/radios/nav[%d]/audio-btn", index);
     fgTie( propname, this,
            &FGNavCom::get_audio_btn, &FGNavCom::set_audio_btn );
     fgSetArchivable( propname );
 
-    sprintf( propname, "/radios/nav[%d]/radials/actual-deg", index );
+    snprintf(propname, 256, "/radios/nav[%d]/heading-deg", index);
+    fgTie( propname,  this, &FGNavCom::get_nav_heading );
+
+    snprintf(propname, 256, "/radios/nav[%d]/radials/actual-deg", index);
     fgTie( propname,  this, &FGNavCom::get_nav_radial );
 
-    sprintf( propname, "/radios/nav[%d]/to-flag", index );
+    snprintf(propname, 256, "/radios/nav[%d]/radials/target-radial-deg", index);
+    fgTie( propname,  this, &FGNavCom::get_nav_target_radial_true );
+
+    snprintf(propname, 256, "/radios/nav[%d]/radials/target-auto-hdg-deg",
+             index);
+    fgTie( propname,  this, &FGNavCom::get_nav_target_auto_hdg );
+
+    snprintf(propname, 256, "/radios/nav[%d]/to-flag", index);
     fgTie( propname, this, &FGNavCom::get_nav_to_flag );
 
-    sprintf( propname, "/radios/nav[%d]/from-flag", index );
+    snprintf(propname, 256, "/radios/nav[%d]/from-flag", index);
     fgTie( propname, this, &FGNavCom::get_nav_from_flag );
 
-    sprintf( propname, "/radios/nav[%d]/in-range", index );
+    snprintf(propname, 256, "/radios/nav[%d]/in-range", index);
     fgTie( propname, this, &FGNavCom::get_nav_inrange );
 
-    sprintf( propname, "/radios/nav[%d]/heading-needle-deflection", index );
-    fgTie( propname, this, &FGNavCom::get_nav_heading_needle_deflection );
+    snprintf(propname, 256, "/radios/nav[%d]/heading-needle-deflection", index);
+    fgTie( propname, this, &FGNavCom::get_nav_cdi_deflection );
+
+    snprintf(propname, 256, "/radios/nav[%d]/crosstrack-error-m", index);
+    fgTie( propname, this, &FGNavCom::get_nav_cdi_xtrack_error );
 
-    sprintf( propname, "/radios/nav[%d]/has-gs", index );
+    snprintf(propname, 256, "/radios/nav[%d]/has-gs", index);
     fgTie( propname, this, &FGNavCom::get_nav_has_gs );
 
-    sprintf( propname, "/radios/nav[%d]/gs-needle-deflection", index );
-    fgTie( propname, this, &FGNavCom::get_nav_gs_needle_deflection );
+    snprintf(propname, 256, "/radios/nav[%d]/nav-loc", index);
+    fgTie( propname, this, &FGNavCom::get_nav_loc );
+
+    snprintf(propname, 256, "/radios/nav[%d]/gs-rate-of-climb", index);
+    fgTie( propname, this, &FGNavCom::get_nav_gs_rate_of_climb );
+
+    snprintf(propname, 256, "/radios/nav[%d]/gs-needle-deflection", index);
+    fgTie( propname, this, &FGNavCom::get_nav_gs_deflection );
+
+    snprintf(propname, 256, "/radios/nav[%d]/nav-id", index);
+    fgTie( propname, this, &FGNavCom::get_nav_id );
+
+    // put nav_id characters into seperate properties for instrument displays
+    snprintf(propname, 256, "/radios/nav[%d]/nav-id_asc1", index);
+    fgTie( propname, this, &FGNavCom::get_nav_id_c1 );
+
+    snprintf(propname, 256, "/radios/nav[%d]/nav-id_asc2", index);
+    fgTie( propname, this, &FGNavCom::get_nav_id_c2 );
+
+    snprintf(propname, 256, "/radios/nav[%d]/nav-id_asc3", index);
+    fgTie( propname, this, &FGNavCom::get_nav_id_c3 );
+
+    snprintf(propname, 256, "/radios/nav[%d]/nav-id_asc4", index);
+    fgTie( propname, this, &FGNavCom::get_nav_id_c4 );
 
     // end of binding
 }
@@ -207,33 +251,34 @@ void
 FGNavCom::unbind ()
 {
     char propname[256];
+    // FIXME: Get rid of snprintf
 
-    sprintf( propname, "/radios/comm[%d]/inputs/power-btn", index );
+    snprintf(propname, 256, "/radios/comm[%d]/inputs/power-btn", index);
     fgUntie( propname );
-    sprintf( propname, "/radios/comm[%d]/frequencies/selected-mhz", index );
+    snprintf(propname, 256, "/radios/comm[%d]/frequencies/selected-mhz", index);
     fgUntie( propname );
-    sprintf( propname, "/radios/comm[%d]/frequencies/standby-mhz", index );
+    snprintf(propname, 256, "/radios/comm[%d]/frequencies/standby-mhz", index);
     fgUntie( propname );
 
-    sprintf( propname, "/radios/nav[%d]/frequencies/selected-mhz", index );
+    snprintf(propname, 256, "/radios/nav[%d]/frequencies/selected-mhz", index);
     fgUntie( propname );
-    sprintf( propname, "/radios/nav[%d]/frequencies/standby-mhz", index );
+    snprintf(propname, 256, "/radios/nav[%d]/frequencies/standby-mhz", index);
     fgUntie( propname );
-    sprintf( propname, "/radios/nav[%d]/radials/actual-deg", index );
+    snprintf(propname, 256, "/radios/nav[%d]/radials/actual-deg", index);
     fgUntie( propname );
-    sprintf( propname, "/radios/nav[%d]/radials/selected-deg", index );
+    snprintf(propname, 256, "/radios/nav[%d]/radials/selected-deg", index);
     fgUntie( propname );
-    sprintf( propname, "/radios/nav[%d]/ident", index );
+    snprintf(propname, 256, "/radios/nav[%d]/ident", index);
     fgUntie( propname );
-    sprintf( propname, "/radios/nav[%d]/to-flag", index );
+    snprintf(propname, 256, "/radios/nav[%d]/to-flag", index);
     fgUntie( propname );
-    sprintf( propname, "/radios/nav[%d]/from-flag", index );
+    snprintf(propname, 256, "/radios/nav[%d]/from-flag", index);
     fgUntie( propname );
-    sprintf( propname, "/radios/nav[%d]/in-range", index );
+    snprintf(propname, 256, "/radios/nav[%d]/in-range", index);
     fgUntie( propname );
-    sprintf( propname, "/radios/nav[%d]/heading-needle-deflection", index );
+    snprintf(propname, 256, "/radios/nav[%d]/heading-needle-deflection", index);
     fgUntie( propname );
-    sprintf( propname, "/radios/nav[%d]/gs-needle-deflection", index );
+    snprintf(propname, 256, "/radios/nav[%d]/gs-needle-deflection", index);
     fgUntie( propname );
 }
 
@@ -320,7 +365,7 @@ FGNavCom::update(double dt)
     ////////////////////////////////////////////////////////////////////////
 
     if ( nav_valid && power_btn && (bus_power->getDoubleValue() > 1.0)
-         && nav_servicable->getBoolValue() )
+         && nav_serviceable->getBoolValue() )
     {
 	station = Point3D( nav_x, nav_y, nav_z );
 	nav_loc_dist = aircraft.distance3D( station );
@@ -345,7 +390,7 @@ FGNavCom::update(double dt)
                                 lon * SGD_RADIANS_TO_DEGREES, 
                                 nav_gslat, nav_gslon,
                                 &az1, &az2, &s );
-            double r = az1 - nav_radial;
+            double r = az1 - nav_target_radial;
             while ( r >  180.0 ) { r -= 360.0;}
             while ( r < -180.0 ) { r += 360.0;}
             if ( r >= -90.0 && r <= 90.0 ) {
@@ -353,7 +398,7 @@ FGNavCom::update(double dt)
             } else {
                 nav_gs_dist_signed = -nav_gs_dist;
             }
-            /* cout << "Target Radial = " << nav_radial 
+            /* cout << "Target Radial = " << nav_target_radial 
                  << "  Bearing = " << az1
                  << "  dist (signed) = " << nav_gs_dist_signed
                  << endl; */
@@ -367,14 +412,14 @@ FGNavCom::update(double dt)
                             lat * SGD_RADIANS_TO_DEGREES,
                             lon * SGD_RADIANS_TO_DEGREES, 
 			    nav_loclat, nav_loclon,
-			    &az1, &az2, &s );
+			    &nav_heading, &az2, &s );
 	// cout << "az1 = " << az1 << " magvar = " << nav_magvar << endl;
-	nav_heading = az1 - nav_magvar;
+	nav_radial = az2 - nav_twist;
 	// cout << " heading = " << nav_heading
 	//      << " dist = " << nav_dist << endl;
 
 	if ( nav_loc ) {
-	    double offset = nav_heading - nav_radial;
+	    double offset = nav_radial - nav_target_radial;
 	    while ( offset < -180.0 ) { offset += 360.0; }
 	    while ( offset > 180.0 ) { offset -= 360.0; }
 	    // cout << "ils offset = " << offset << endl;
@@ -397,14 +442,100 @@ FGNavCom::update(double dt)
 	}
 
 	if ( !nav_loc ) {
-	    nav_radial = nav_sel_radial;
+	    nav_target_radial = nav_sel_radial;
 	}
+
+        // Calculate some values for the nav/ils hold autopilot
+
+        double cur_radial = get_nav_reciprocal_radial();
+        if ( nav_loc ) {
+            // ILS localizers radials are already "true" in our
+            // database
+        } else {
+            cur_radial += nav_twist;
+        }
+        if ( get_nav_from_flag() ) {
+            cur_radial += 180.0;
+            while ( cur_radial >= 360.0 ) { cur_radial -= 360.0; }
+        }
+        
+        // AUTOPILOT HELPERS
+
+        // determine the target radial in "true" heading
+        nav_target_radial_true = nav_target_radial;
+        if ( nav_loc ) {
+            // ILS localizers radials are already "true" in our
+            // database
+        } else {
+            // VOR radials need to have that vor's offset added in
+            nav_target_radial_true += nav_twist;
+        }
+
+        while ( nav_target_radial_true < 0.0 ) {
+            nav_target_radial_true += 360.0;
+        }
+        while ( nav_target_radial_true > 360.0 ) {
+            nav_target_radial_true -= 360.0;
+        }
+
+        // determine the heading adjustment needed.
+        // over 8km scale by 3.0 
+        //    (3 is chosen because max deflection is 10
+        //    and 30 is clamped angle to radial)
+        // under 8km scale by 10.0
+        //    because the overstated error helps drive it to the radial in a 
+        //    moderate cross wind.
+        double adjustment = 0.0;
+        if (nav_loc_dist > 8000) {
+            adjustment = get_nav_cdi_deflection() * 3.0;
+        } else {
+            adjustment = get_nav_cdi_deflection() * 10.0;
+        }
+        SG_CLAMP_RANGE( adjustment, -30.0, 30.0 );
+        
+        // determine the target heading to fly to intercept the
+        // tgt_radial
+        nav_target_auto_hdg = nav_target_radial_true + adjustment; 
+        while ( nav_target_auto_hdg <   0.0 ) { nav_target_auto_hdg += 360.0; }
+        while ( nav_target_auto_hdg > 360.0 ) { nav_target_auto_hdg -= 360.0; }
+
+        // cross track error
+        // ????
+
+        // Calculate desired rate of climb for intercepting the GS
+        double x = nav_gs_dist;
+        double y = (alt_node->getDoubleValue() - nav_elev)
+            * SG_FEET_TO_METER;
+        double current_angle = atan2( y, x ) * SGD_RADIANS_TO_DEGREES;
+
+        double target_angle = nav_target_gs;
+        double gs_diff = target_angle - current_angle;
+
+        // convert desired vertical path angle into a climb rate
+        double des_angle = current_angle - 10 * gs_diff;
+
+        // estimate horizontal speed towards ILS in meters per minute
+        double dist = last_x - x;
+        last_x = x;
+        if ( dt > 0.0 ) {
+            // avoid nan
+            double new_vel = ( dist / dt );
+ 
+            horiz_vel = 0.75 * horiz_vel + 0.25 * new_vel;
+            // double horiz_vel = cur_fdm_state->get_V_ground_speed()
+            //    * SG_FEET_TO_METER * 60.0;
+            // double horiz_vel = airspeed_node->getFloatValue()
+            //    * SG_FEET_TO_METER * 60.0;
+
+            nav_gs_rate_of_climb = -sin( des_angle * SGD_DEGREES_TO_RADIANS )
+                * horiz_vel * SG_METER_TO_FEET;
+        }
     } else {
 	nav_inrange = false;
 	// cout << "not picking up vor. :-(" << endl;
     }
 
-    if ( nav_valid && nav_inrange && nav_servicable->getBoolValue() ) {
+    if ( nav_valid && nav_inrange && nav_serviceable->getBoolValue() ) {
 	// play station ident via audio system if on + ident,
 	// otherwise turn it off
 	if ( power_btn && (bus_power->getDoubleValue() > 1.0)
@@ -489,13 +620,13 @@ void FGNavCom::search()
 	    nav_gslon = ils->get_gslon();
 	    nav_gslat = ils->get_gslat();
 	    nav_elev = ils->get_gselev();
-	    nav_magvar = 0;
+	    nav_twist = 0;
 	    nav_range = FG_ILS_DEFAULT_RANGE;
 	    nav_effective_range = nav_range;
 	    nav_target_gs = ils->get_gsangle();
-	    nav_radial = ils->get_locheading();
-	    while ( nav_radial <   0.0 ) { nav_radial += 360.0; }
-	    while ( nav_radial > 360.0 ) { nav_radial -= 360.0; }
+	    nav_target_radial = ils->get_locheading();
+	    while ( nav_target_radial <   0.0 ) { nav_target_radial += 360.0; }
+	    while ( nav_target_radial > 360.0 ) { nav_target_radial -= 360.0; }
 	    nav_x = ils->get_x();
 	    nav_y = ils->get_y();
 	    nav_z = ils->get_z();
@@ -505,7 +636,7 @@ void FGNavCom::search()
 
             // derive GS baseline
             double tlon, tlat, taz;
-            geo_direct_wgs_84 ( 0.0, nav_gslat, nav_gslon, nav_radial + 90,  
+            geo_direct_wgs_84 ( 0.0, nav_gslat, nav_gslon, nav_target_radial + 90,  
                                 100.0, &tlat, &tlon, &taz );
             // cout << nav_gslon << "," << nav_gslat << "  "
             //      << tlon << "," << tlat << "  (" << nav_elev << ")" << endl;
@@ -559,12 +690,12 @@ void FGNavCom::search()
 	    nav_has_gs = false;
 	    nav_loclon = nav->get_lon();
 	    nav_loclat = nav->get_lat();
-	    nav_elev = nav->get_elev();
-	    nav_magvar = nav->get_magvar();
+	    nav_elev = nav->get_elev_ft();
+	    nav_twist = nav->get_magvar();
 	    nav_range = nav->get_range();
 	    nav_effective_range = adjustNavRange(nav_elev, elev, nav_range);
 	    nav_target_gs = 0.0;
-	    nav_radial = nav_sel_radial;
+	    nav_target_radial = nav_sel_radial;
 	    nav_x = nav->get_x();
 	    nav_y = nav->get_y();
 	    nav_z = nav->get_z();
@@ -603,7 +734,7 @@ void FGNavCom::search()
     } else {
 	nav_valid = false;
 	nav_id = "";
-	nav_radial = 0;
+	nav_target_radial = 0;
 	nav_trans_ident = "";
 	last_nav_id = "";
 	if ( ! globals->get_soundmgr()->remove( nav_fx_name ) ) {
@@ -617,15 +748,15 @@ void FGNavCom::search()
 
 // return the amount of heading needle deflection, returns a value
 // clamped to the range of ( -10 , 10 )
-double FGNavCom::get_nav_heading_needle_deflection() const {
+double FGNavCom::get_nav_cdi_deflection() const {
     double r;
 
     if ( nav_inrange
-         && nav_servicable->getBoolValue() && cdi_servicable->getBoolValue() )
+         && nav_serviceable->getBoolValue() && cdi_serviceable->getBoolValue() )
     {
-        r = nav_heading - nav_radial;
-	// cout << "Radial = " << nav_radial 
-	//      << "  Bearing = " << nav_heading << endl;
+        r = nav_radial - nav_target_radial;
+	// cout << "Target radial = " << nav_target_radial 
+	//      << "  Actual radial = " << nav_radial << endl;
     
 	while ( r >  180.0 ) { r -= 360.0;}
 	while ( r < -180.0 ) { r += 360.0;}
@@ -633,6 +764,7 @@ double FGNavCom::get_nav_heading_needle_deflection() const {
 	    r = ( r<0.0 ? -r-180.0 : -r+180.0 );
 
 	// According to Robin Peel, the ILS is 4x more sensitive than a vor
+        r = -r;                 // reverse, since radial is outbound
 	if ( nav_loc ) { r *= 4.0; }
 	if ( r < -10.0 ) { r = -10.0; }
 	if ( r >  10.0 ) { r = 10.0; }
@@ -643,12 +775,39 @@ double FGNavCom::get_nav_heading_needle_deflection() const {
     return r;
 }
 
+// return the amount of cross track distance error, returns a meters
+double FGNavCom::get_nav_cdi_xtrack_error() const {
+    double r, m;
+
+    if ( nav_inrange
+         && nav_serviceable->getBoolValue() && cdi_serviceable->getBoolValue() )
+    {
+        r = nav_radial - nav_target_radial;
+	// cout << "Target radial = " << nav_target_radial 
+	//     << "  Actual radial = " << nav_radial
+        //     << "  r = " << r << 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 );
+
+        r = -r;                 // reverse, since radial is outbound
+
+        m = nav_loc_dist * sin(r * SGD_DEGREES_TO_RADIANS);
+
+    } else {
+	m = 0.0;
+    }
+
+    return m;
+}
 
 // return the amount of glide slope needle deflection (.i.e. the
 // number of degrees we are off the glide slope * 5.0
-double FGNavCom::get_nav_gs_needle_deflection() const {
+double FGNavCom::get_nav_gs_deflection() const {
     if ( nav_inrange && nav_has_gs
-         && nav_servicable->getBoolValue() && gs_servicable->getBoolValue() )
+         && nav_serviceable->getBoolValue() && gs_serviceable->getBoolValue() )
     {
 	double x = nav_gs_dist;
 	double y = (fgGetDouble("/position/altitude-ft") - nav_elev)
@@ -669,14 +828,14 @@ bool
 FGNavCom::get_nav_to_flag () const
 {
     if ( nav_inrange
-         && nav_servicable->getBoolValue()
-         && tofrom_servicable->getBoolValue() )
+         && nav_serviceable->getBoolValue()
+         && tofrom_serviceable->getBoolValue() )
     {
-        double offset = fabs(nav_heading - nav_radial);
+        double offset = fabs(nav_radial - nav_target_radial);
         if (nav_loc) {
             return true;
         } else {
-            return (offset <= 90.0 || offset >= 270.0);
+            return !(offset <= 90.0 || offset >= 270.0);
         }
     } else {
         return false;
@@ -691,15 +850,45 @@ bool
 FGNavCom::get_nav_from_flag () const
 {
     if ( nav_inrange
-         && nav_servicable->getBoolValue()
-         && tofrom_servicable->getBoolValue() ) {
-        double offset = fabs(nav_heading - nav_radial);
+         && nav_serviceable->getBoolValue()
+         && tofrom_serviceable->getBoolValue() ) {
+        double offset = fabs(nav_radial - nav_target_radial);
         if (nav_loc) {
             return false;
         } else {
-          return (offset > 90.0 && offset < 270.0);
+          return !(offset > 90.0 && offset < 270.0);
         }
     } else {
         return false;
     }
 }
+
+
+/**
+ * Return the true heading to station
+ */
+double
+FGNavCom::get_nav_heading () const
+{
+    return nav_heading;
+}
+
+
+/**
+ * Return the current radial.
+ */
+double
+FGNavCom::get_nav_radial () const
+{
+    return nav_radial;
+}
+
+double
+FGNavCom::get_nav_reciprocal_radial () const
+{
+    double recip = nav_radial + 180;
+    if ( recip >= 360 ) {
+        recip -= 360;
+    }
+    return recip;
+}