SG_ namespace.

[flightgear.git] / src / Navaids / mkrbeacons.cxx

diff --git a/src/Navaids/mkrbeacons.cxx b/src/Navaids/mkrbeacons.cxx
index a3e8d33ed5f7bc947fdfb266649f5628989d5a88..a843d3f48ba58e6755b263c62944a3abc74a4e44 100644 (file)
--- a/src/Navaids/mkrbeacons.cxx
+++ b/src/Navaids/mkrbeacons.cxx
@@ -36,7 +36,7 @@ FGBeacon::FGBeacon( double _lon, double _lat, double _elev,
     elev = _elev;
     type = _type;
 
-    Point3D pos = sgGeodToCart(Point3D(lon * DEG_TO_RAD, lat * DEG_TO_RAD, 0));
+    Point3D pos = sgGeodToCart(Point3D(lon * SGD_DEGREES_TO_RADIANS, lat * SGD_DEGREES_TO_RADIANS, 0));
     // cout << "pos = " << pos << endl;
     x = pos.x();
     y = pos.y();
@@ -82,7 +82,7 @@ bool FGMarkerBeacons::add( double lon, double lat, double elev,
 
     int lonidx = (int)lon;
     diff = lon - (double)lonidx;
-    if ( (lon < 0.0) && (fabs(diff) > FG_EPSILON) ) {
+    if ( (lon < 0.0) && (fabs(diff) > SG_EPSILON) ) {
        lonidx -= 1;
     }
     double lonfrac = lon - (double)lonidx;
@@ -90,7 +90,7 @@ bool FGMarkerBeacons::add( double lon, double lat, double elev,
 
     int latidx = (int)lat;
     diff = lat - (double)latidx;
-    if ( (lat < 0.0) && (fabs(diff) > FG_EPSILON) ) {
+    if ( (lat < 0.0) && (fabs(diff) > SG_EPSILON) ) {
        latidx -= 1;
     }
     double latfrac = lat - (double)latidx;
@@ -139,14 +139,14 @@ FGBeacon::fgMkrBeacType FGMarkerBeacons::query( double lon, double lat,
 
     int lonidx = (int)lon;
     diff = lon - (double)lonidx;
-    if ( (lon < 0.0) && (fabs(diff) > FG_EPSILON) ) {
+    if ( (lon < 0.0) && (fabs(diff) > SG_EPSILON) ) {
        lonidx -= 1;
     }
     lonidx += 180;
 
     int latidx = (int)lat;
     diff = lat - (double)latidx;
-    if ( (lat < 0.0) && (fabs(diff) > FG_EPSILON) ) {
+    if ( (lat < 0.0) && (fabs(diff) > SG_EPSILON) ) {
        latidx -= 1;
     }
     latidx += 90;
@@ -160,7 +160,7 @@ FGBeacon::fgMkrBeacType FGMarkerBeacons::query( double lon, double lat,
     beacon_list_iterator current = beacons.begin();
     beacon_list_iterator last = beacons.end();
 
-    Point3D aircraft = sgGeodToCart(Point3D(lon*DEG_TO_RAD, lat*DEG_TO_RAD, 0));
+    Point3D aircraft = sgGeodToCart(Point3D(lon*SGD_DEGREES_TO_RADIANS, lat*SGD_DEGREES_TO_RADIANS, 0));
 
     double min_dist = 999999999.0;
 
@@ -172,10 +172,10 @@ FGBeacon::fgMkrBeacType FGMarkerBeacons::query( double lon, double lat,
        // cout << "    aircraft = " << aircraft << " station = " << station 
        //      << endl;
 
-       double d = aircraft.distance3Dsquared( station );
+       double d = aircraft.distance3Dsquared( station ); // meters^2
        // cout << "  distance = " << d << " (" 
-       //      << FG_ILS_DEFAULT_RANGE * NM_TO_METER 
-       //         * FG_ILS_DEFAULT_RANGE * NM_TO_METER
+       //      << FG_ILS_DEFAULT_RANGE * SG_NM_TO_METER 
+       //         * FG_ILS_DEFAULT_RANGE * SG_NM_TO_METER
        //      << ")" << endl;
 
        // cout << "  range = " << sqrt(d) << endl;
@@ -184,23 +184,34 @@ FGBeacon::fgMkrBeacType FGMarkerBeacons::query( double lon, double lat,
            min_dist = d;
        }
 
-       // cout << "elev = " << elev * METER_TO_FEET
+       // cout << "elev = " << elev * SG_METER_TO_FEET
        //      << " current->get_elev() = " << current->get_elev() << endl;
-       double delev = elev * METER_TO_FEET - current->get_elev();
-       double maxrange = 4200 * delev / 1000;
+       double delev = elev * SG_METER_TO_FEET - current->get_elev();
+
+       // max range is the area under r = 2.4 * alt or r^2 = 4000^2 - alt^2
+       // whichever is smaller.  The intersection point is 1538 ...
+       double maxrange2;       // feet^2
+       if ( delev < 1538.0 ) {
+           maxrange2 = 2.4 * 2.4 * delev * delev;
+       } else if ( delev < 4000.0 ) {
+           maxrange2 = 4000 * 4000 - delev * delev;
+       } else {
+           maxrange2 = 0.0;
+       }
+       maxrange2 *= SG_FEET_TO_METER * SG_FEET_TO_METER; // convert to meter^2
        // cout << "delev = " << delev << " maxrange = " << maxrange << endl;
 
        // match up to twice the published range so we can model
        // reduced signal strength
-       if ( d < maxrange * maxrange ) {
-           // cout << "lon = " << lon << " lat = " << lat
-           //      << "  closest beacon = " << sqrt( min_dist ) << endl;
+       if ( d < maxrange2 ) {
+           cout << "lon = " << lon << " lat = " << lat
+                << "  closest beacon = " << sqrt( min_dist ) << endl;
            return current->get_type();
        }
     }
 
-    // cout << "lon = " << lon << " lat = " << lat
-    //      << "  closest beacon = " << sqrt( min_dist ) << endl;
+    cout << "lon = " << lon << " lat = " << lat
+         << "  closest beacon = " << sqrt( min_dist ) << endl;
 
     return FGBeacon::NOBEACON;
 }