X-Git-Url: https://git.mxchange.org/?a=blobdiff_plain;f=src%2FNavaids%2Fnavrecord.cxx;h=041c12f1a663fc84aef85f6b021682eedb01c089;hb=6989f4fb355bf39001aadeb6bee187d5a337b58a;hp=6bb71a54c9d2e40e3506b4e17e451b910e80fd94;hpb=21122fa03ebfb676eacf9c705fb4b2a31416eb78;p=flightgear.git

diff --git a/src/Navaids/navrecord.cxx b/src/Navaids/navrecord.cxx
index 6bb71a54c..041c12f1a 100644
--- a/src/Navaids/navrecord.cxx
+++ b/src/Navaids/navrecord.cxx
@@ -91,6 +91,9 @@ void FGNavRecord::initAirportRelation()
   }
   
   mRunway = getRunwayFromName(_name);  
+  if (!mRunway) {
+    return;
+  }
   
   if (type() != GS) {
     readAirportSceneryData();
@@ -178,6 +181,38 @@ void FGNavRecord::alignLocaliserWithRunway(double aThreshold)
   }
 }
 
+double FGNavRecord::localizerWidth() const
+{
+  if (!mRunway) {
+    return 6.0;
+  }
+  
+  SGVec3d thresholdCart(SGVec3d::fromGeod(mRunway->threshold()));
+  double axisLength = dist(cart(), thresholdCart);
+  double landingLength = dist(thresholdCart, SGVec3d::fromGeod(mRunway->end()));
+  
+// Reference: http://dcaa.slv.dk:8000/icaodocs/
+// ICAO standard width at threshold is 210 m = 689 feet = approx 700 feet.
+// ICAO 3.1.1 half course = DDM = 0.0775
+// ICAO 3.1.3.7.1 Sensitivity 0.00145 DDM/m at threshold
+//  implies peg-to-peg of 214 m ... we will stick with 210.
+// ICAO 3.1.3.7.1 "Course sector angle shall not exceed 6 degrees."
+              
+// Very short runway:  less than 1200 m (4000 ft) landing length:
+  if (landingLength < 1200.0) {
+// ICAO fudges localizer sensitivity for very short runways.
+// This produces a non-monotonic sensitivity-versus length relation.
+    axisLength += 1050.0;
+  }
+
+// Example: very short: San Diego   KMYF (Montgomery Field) ILS RWY 28R
+// Example: short:      Tom's River KMJX (Robert J. Miller) ILS RWY 6
+// Example: very long:  Denver      KDEN (Denver)           ILS RWY 16R
+  double raw_width = 210.0 / axisLength * SGD_RADIANS_TO_DEGREES;
+  return raw_width < 6.0? raw_width : 6.0;
+
+}
+
 FGTACANRecord::FGTACANRecord(void) :
     channel(""),
     freq(0)