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DME units report a distance based on the assumption that the ground station

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will delay it's reply by 50ms.  The ground station can change it's reply delay
to trick the airborn dme unit into reporting a distance that is offset from
the true distance by some constant value.  In FG we model this by subtracting
a fixed distance from the actual distance.

It is thus possible in our implimentation for the displayed distance to become
negative.  This patch clamp DME distance to a minimum value of 0.00 so it can
never go negative.
This commit is contained in:
curt 2004-06-09 20:21:18 +00:00
parent 225298a09e
commit 6c8f7fab01
2 changed files with 8 additions and 1 deletions
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3
src/Cockpit/dme.cxx
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@ -161,6 +161,9 @@ FGDME::update(double dt)
station = Point3D( x, y, z );
dist = aircraft.distance3D( station ) * SG_METER_TO_NM;
dist -= bias;
if ( dist < 0.0 ) {
dist = 0.0;
}
current_time.stamp();
long dMs = (current_time - last_time) / 1000;

6
src/Instrumentation/dme.cxx
View file

@ -128,7 +128,11 @@ DME::update (double delta_time_sec)
_last_distance_nm = distance_nm;
_in_range_node->setBoolValue(true);
_distance_node->setDoubleValue(distance_nm - _transmitter_bias);
double tmp_dist = distance_nm - _transmitter_bias;
if ( tmp_dist < 0.0 ) {
tmp_dist = 0.0;
}
_distance_node->setDoubleValue( tmp_dist );
_speed_node->setDoubleValue(speed_kt);
_time_node->setDoubleValue(distance_nm/speed_kt*60.0);