Working on ironing out issues with VOR navigation. It think we are "as

good as we can get" until we find a data source with actual VOR magnetic
offsets.  We can use VOR offsets from some fixed date, but not all VOR's
were installed on the same day so no matter what date we pick we will be off on most of them.

src/Autopilot/newauto.cxx

@@ -375,10 +375,11 @@ int FGAutopilot::run() {
 		// localizers radials are "true"
 		tgt_radial = current_radiostack->get_nav1_radial();
 	    } else {
-		tgt_radial = current_radiostack->get_nav1_radial() 
+		tgt_radial = current_radiostack->get_nav1_radial() +
-		    + FGBFI::getMagVar();
+		    current_radiostack->get_nav1_magvar(); 
 	    }
-	    cur_radial = current_radiostack->get_nav1_heading();
+	    cur_radial = current_radiostack->get_nav1_heading() +
+		    current_radiostack->get_nav1_magvar();
 	    // cout << "target rad (true) = " << tgt_radial 
 	    //      << "  current rad (true) = " << cur_radial
 	    //      << endl;
@@ -394,6 +395,7 @@ int FGAutopilot::run() {
 	    TargetHeading = cur_radial - diff;
 	    while ( TargetHeading <   0.0 ) { TargetHeading += 360.0; }
 	    while ( TargetHeading > 360.0 ) { TargetHeading -= 360.0; }
+	    MakeTargetHeadingStr( TargetHeading );
 	    // cout << "target course (true) = " << TargetHeading << endl;
 	} else if ( heading_mode == FG_HEADING_WAYPOINT ) {
 	    // update target heading to waypoint

src/Cockpit/radiostack.cxx

@@ -209,7 +209,7 @@ FGRadioStack::update()
 	    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;
+	    // cout << "az1 = " << az1 << " magvar = " << nav1_magvar << endl;
 	    nav1_heading = az1 - nav1_magvar;
 	    // Alex: nav1_heading = - (az1 - FGBFI::getMagVar() / RAD_TO_DEG);
 

src/Cockpit/radiostack.hxx

@@ -202,6 +202,7 @@ public:
     inline double get_nav1_heading() const { return nav1_heading; }
     inline double get_nav1_radial() const { return nav1_radial; }
     inline double get_nav1_target_gs() const { return nav1_target_gs; }
+    inline double get_nav1_magvar() const { return nav1_magvar; }
 
     inline bool get_nav2_inrange() const { return nav2_inrange; }
     bool get_nav2_to_flag () const;
@@ -225,6 +226,7 @@ public:
     inline double get_nav2_heading() const { return nav2_heading; }
     inline double get_nav2_radial() const { return nav2_radial; }
     inline double get_nav2_target_gs() const { return nav2_target_gs; }
+    inline double get_nav2_magvar() const { return nav2_magvar; }
 
     inline bool get_adf_inrange() const { return adf_inrange; }
     inline double get_adf_lon() const { return adf_lon; }

src/Cockpit/steam.cxx

@@ -130,9 +130,6 @@ void FGSteam::update ( int timesteps )
 	_UpdatesPending += timesteps;
 }
 
-#undef DF1
-#undef DF2
-
 
 /* tc should be (elapsed_time_between_updates / desired_smoothing_time) */
 void FGSteam::set_lowpass ( double *outthe, double inthe, double tc )
@@ -169,11 +166,10 @@ void FGSteam::set_lowpass ( double *outthe, double inthe, double tc )
 double pressInHgToAltFt(double p_inhg)
 {
     // Ref. Aviation Formulary, Ed Williams, www.best.com/~williams/avform.htm
-    const double P_0 = 29.92126;  // Std. MSL pressure, inHg. (=10135.25 mb)
+    const double P_0 = 29.92126;  // Std. MSL pressure, inHg. (=1013.25 mb)
     const double p_Tr = 0.2233609 * P_0;  // Pressure at tropopause, same units.
     const double h_Tr = 36089.24;  // Alt of tropopause, ft. (=11.0 km)
 
-    // return (P_0 - p_inhg) * 1000.0;  // ### crude approx. for low alt's
     if (p_inhg > p_Tr)  // 0.0 to 11.0 km
 	return (1.0 - pow((p_inhg / P_0), 1.0 / 5.2558797)) / 6.8755856e-6;
     return h_Tr + log10(p_inhg / p_Tr) / -4.806346e-5;  // 11.0 to 20.0 km
@@ -181,6 +177,21 @@ double pressInHgToAltFt(double p_inhg)
 }
 
 
+// Convert altitude to air pressure by ICAO Standard Atmosphere
+double altFtToPressInHg(double alt_ft)
+{
+    // Ref. Aviation Formulary, Ed Williams, www.best.com/~williams/avform.htm
+    const double P_0 = 29.92126;  // Std. MSL pressure, inHg. (=1013.25 mb)
+    const double p_Tr = 0.2233609 * P_0;  // Pressure at tropopause, same units.
+    const double h_Tr = 36089.24;  // Alt of tropopause, ft. (=11.0 km)
+
+    if (alt_ft < h_Tr)  // 0.0 to 11.0 km
+	return P_0 * pow(1.0 - 6.8755856e-6 * alt_ft, 5.2558797);
+    return p_Tr * exp(-4.806346e-5 * (alt_ft - h_Tr));  // 11.0 to 20.0 km
+    // We could put more code for higher altitudes here.
+}
+
+
 
 ////////////////////////////////////////////////////////////////////////
 // Here the fun really begins
@@ -322,13 +333,7 @@ void FGSteam::_CatchUp()
 	We filter the actual value by one second to
 	account for the line impedance of the plumbing.
 	*/
-	double static_inhg = 29.92; 
+	double static_inhg = altFtToPressInHg(FGBFI::getAltitude());
-	i = (int) FGBFI::getAltitude();
-	while ( i > 9000 )
-	{	static_inhg *= 0.707;
-		i -= 9000;
-	}
-	static_inhg *= ( 1.0 - 0.293 * i / 9000.0 );
 	set_lowpass ( & the_STATIC_inhg, static_inhg, dt ); 
 
 	/*
@@ -429,9 +434,9 @@ double FGSteam::get_HackVOR1_deg () {
     if ( current_radiostack->get_nav1_inrange() ) {
         r = current_radiostack->get_nav1_heading()
 	    - current_radiostack->get_nav1_radial();
-	cout << "Radial = " << current_radiostack->get_nav1_radial() 
+	// cout << "Radial = " << current_radiostack->get_nav1_radial() 
-	     << "  Bearing = " << current_radiostack->get_nav1_heading()
+	//      << "  Bearing = " << current_radiostack->get_nav1_heading()
-	     << endl;
+	//      << endl;
     
 	if (r> 180.0) r-=360.0; else
 	    if (r<-180.0) r+=360.0;

src/Navaids/Makefile.am

@@ -8,6 +8,9 @@ libNavaids_a_SOURCES = \
 	nav.hxx navlist.hxx navlist.cxx
 
 testnavs_SOURCES = testnavs.cxx
-testnavs_LDADD = libNavaids.a -lsgmath -lsgmisc -lsgdebug -lsgmagvar -lz
+testnavs_LDADD = \
+	libNavaids.a \
+	-lsgtiming -lsgmath -lsgmisc -lsgdebug -lsgmagvar \
+	-lz
 
 INCLUDES += -I$(top_srcdir) -I$(top_srcdir)/src

src/Navaids/nav.hxx

@@ -30,6 +30,7 @@
 #include <simgear/math/sg_geodesy.hxx>
 #include <simgear/misc/fgstream.hxx>
 #include <simgear/magvar/magvar.hxx>
+#include <simgear/timing/sg_time.hxx>
 
 #ifdef FG_HAVE_STD_INCLUDES
 #  include <istream>
@@ -95,7 +96,16 @@ operator >> ( istream& in, FGNav& n )
     double f;
     char c /* , magvar_dir */ ;
     string magvar_s;
-    
+
+    static SGTime time_params;
+    static bool first_time = true;
+    static double julian_date = 0;
+    if ( first_time ) {
+	time_params.update( 0.0, 0.0, 0 );
+	julian_date = time_params.getJD();
+	first_time = false;
+    }
+
     in >> n.type >> n.lat >> n.lon >> n.elev >> f >> n.range 
        >> c >> n.ident >> magvar_s;
 
@@ -110,9 +120,12 @@ operator >> ( istream& in, FGNav& n )
     // cout << "Calculating magvar for navaid " << n.ident << endl;
     if (magvar_s == "XXX") {
 	// default to mag var as of 1990-01-01 (Julian 2447892.5)
-	n.magvar = -sgGetMagVar(n.lon * DEG_TO_RAD, n.lat * DEG_TO_RAD,
+	// cout << "lat = " << n.lat << " lon = " << n.lon << " elev = " 
+	//      << n.elev << " JD = " 
+	//      << julian_date << endl;
+	n.magvar = sgGetMagVar(n.lon * DEG_TO_RAD, n.lat * DEG_TO_RAD,
 				n.elev * FEET_TO_METER,
-				2447892.5) * RAD_TO_DEG;
+				julian_date) * RAD_TO_DEG;
 	// cout << "Default variation at " << n.lon << ',' << n.lat
 	// 	<< " is " << var << endl;
 #if 0
@@ -134,7 +147,7 @@ operator >> ( istream& in, FGNav& n )
 	    n.magvar = 0 - n.magvar;
 	// cout << "Explicit magvar of " << n.magvar << endl;
     }
-    cout << n.ident << " " << n.magvar << endl;
+    // cout << n.ident << " " << n.magvar << endl;
 
     // generate cartesian coordinates
     Point3D geod( n.lon * DEG_TO_RAD, n.lat * DEG_TO_RAD, n.elev );

src/Navaids/navlist.cxx

@@ -45,9 +45,6 @@ FGNavList::~FGNavList( void ) {
 bool FGNavList::init( FGPath path ) {
     FGNav n;
 
-    SGTime time_params;
-    time_params.update( 0.0, 0.0, 0 );
-
     navaids.erase( navaids.begin(), navaids.end() );
 
     fg_gzifstream in( path.str() );