From 28b847da097882cb2eb299a5095aee517d0b6388 Mon Sep 17 00:00:00 2001
From: curt <curt>
Date: Wed, 30 Sep 2009 20:53:22 +0000
Subject: [PATCH] Smooth out the time-to-intercept radial computation so it's a
 bit more useful.

---
 src/Instrumentation/navradio.cxx | 4 +++-
 src/Instrumentation/navradio.hxx | 1 +
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/Instrumentation/navradio.cxx b/src/Instrumentation/navradio.cxx
index 3e779bbcd..404bb7300 100644
--- a/src/Instrumentation/navradio.cxx
+++ b/src/Instrumentation/navradio.cxx
@@ -137,6 +137,7 @@ FGNavRadio::FGNavRadio(SGPropertyNode *node) :
     last_x(0.0),
     last_loc_dist(0.0),
     last_xtrack_error(0.0),
+    xrate_ms(0.0),
     _localizerWidth(5.0),
     _name(node->getStringValue("name", "nav")),
     _num(node->getIntValue("number", 0)),
@@ -686,7 +687,8 @@ void FGNavRadio::updateCDI(double dt)
   //////////////////////////////////////////////////////////
   double t = 0.0;
   if ( inrange && cdi_serviceable ) {
-    double xrate_ms = (last_xtrack_error - _cdiCrossTrackErrorM) / dt;
+    double cur_rate = (last_xtrack_error - _cdiCrossTrackErrorM) / dt;
+    xrate_ms = 0.99 * xrate_ms + 0.01 * cur_rate;
     if ( fabs(xrate_ms) > 0.00001 ) {
         t = _cdiCrossTrackErrorM / xrate_ms;
     } else {
diff --git a/src/Instrumentation/navradio.hxx b/src/Instrumentation/navradio.hxx
index 116a90ce7..d88f0d876 100644
--- a/src/Instrumentation/navradio.hxx
+++ b/src/Instrumentation/navradio.hxx
@@ -135,6 +135,7 @@ class FGNavRadio : public SGSubsystem
     double last_x;
     double last_loc_dist;
     double last_xtrack_error;
+    double xrate_ms;
     double _localizerWidth; // cached localizer width in degrees
     
     string _name;