From dbda2fb95d6e18a3e25d07a6c4114e0c32442c73 Mon Sep 17 00:00:00 2001
From: James Turner <zakalawe@mac.com>
Date: Wed, 28 Sep 2011 09:06:31 +0100
Subject: [PATCH] Switch ATCmgr comm station search to filter by range in
 cartesian, not geodetic, space, to avoid numerical instability with extremely
 distant stations.

---
 src/ATC/CMakeLists.txt    | 11 +++++++++--
 src/ATCDCL/ATCmgr.cxx     | 22 ++++++++++++++++------
 src/ATCDCL/CMakeLists.txt | 16 ++++++++++++++--
 3 files changed, 39 insertions(+), 10 deletions(-)

diff --git a/src/ATC/CMakeLists.txt b/src/ATC/CMakeLists.txt
index e055ec6dd..f7dd1f2df 100644
--- a/src/ATC/CMakeLists.txt
+++ b/src/ATC/CMakeLists.txt
@@ -6,5 +6,12 @@ set(SOURCES
 	trafficcontrol.cxx
 	CommStation.cxx
 	)
-	
-flightgear_component(ATC "${SOURCES}")
+
+set(HEADERS
+	atc_mgr.hxx
+	atcdialog.hxx
+	trafficcontrol.hxx
+	CommStation.hxx
+	)
+    	
+flightgear_component(ATC "${SOURCES}" "${HEADERS}")
diff --git a/src/ATCDCL/ATCmgr.cxx b/src/ATCDCL/ATCmgr.cxx
index 7a3da5969..dc0901153 100644
--- a/src/ATCDCL/ATCmgr.cxx
+++ b/src/ATCDCL/ATCmgr.cxx
@@ -253,16 +253,26 @@ void FGATCMgr::FreqSearch(const string navcomm, const int unit) {
 
     class RangeFilter : public CommStation::Filter {
     public:
-        RangeFilter( const SGGeod & pos ) : CommStation::Filter(), _pos(pos) {}
-        virtual bool pass(FGPositioned* aPos) const {
+        RangeFilter( const SGGeod & pos ) : 
+          CommStation::Filter(), 
+          _cart(SGVec3d::fromGeod(pos)),
+          _pos(pos)
+        {}
+      
+        virtual bool pass(FGPositioned* aPos) const
+        {
             flightgear::CommStation * stn = dynamic_cast<flightgear::CommStation*>(aPos);
             if( NULL == stn ) return false;
-            double dist = SGGeodesy::distanceNm( stn->geod(), _pos );
-            // if range is not configured, assume at least 10NM range
-            // TODO: maybe ramp down range with proximity to ground?
-            return dist <= SGMiscd::max( stn->rangeNm(), 10.0 );
+          // do the range check in cartesian space, since the distances are potentially
+          // large enough that the geodetic functions become unstable
+          // (eg, station on opposite side of the planet)
+            double rangeM = SGMiscd::max( stn->rangeNm(), 10.0 ) * SG_NM_TO_METER;
+            double d2 = distSqr( aPos->cart(), _cart);
+          
+            return d2 <= (rangeM * rangeM);
         }
     private:
+        SGVec3d _cart;
         SGGeod _pos;
     };
 
diff --git a/src/ATCDCL/CMakeLists.txt b/src/ATCDCL/CMakeLists.txt
index d0dde266a..8f0363135 100644
--- a/src/ATCDCL/CMakeLists.txt
+++ b/src/ATCDCL/CMakeLists.txt
@@ -9,5 +9,17 @@ set(SOURCES
 	ATCutils.cxx
 	ATCProjection.cxx
 	)
-	
-flightgear_component(ATCDCL "${SOURCES}")
+
+set(HEADERS
+	ATC.hxx
+	atis.hxx
+	ATCDialogOld.hxx
+	ATCVoice.hxx
+	ATCmgr.hxx
+	ATCutils.hxx
+	ATCProjection.hxx
+	atis_lexicon.hxx
+	atis_remap.hxx
+	)
+    	
+flightgear_component(ATCDCL "${SOURCES}" "${HEADERS}")
-- 
2.39.5