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Working on modeling VOR range as per AIM.

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curt 2001-03-14 01:31:04 +00:00
parent d116eb2a62
commit 6e0a10b757
1 changed files with 63 additions and 4 deletions
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67
src/Cockpit/radiostack.cxx
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@ -35,16 +35,19 @@ static int nav1_play_count = 0;
static time_t nav1_last_time = 0;
FGRadioStack *current_radiostack;
/**
* Boy, this is ugly! Make the VOR range vary by altitude difference.
*/
static inline double
kludgeRange (double stationElev, double aircraftElev, double nominalRange)
static double kludgeRange ( double stationElev, double aircraftElev,
double nominalRange)
{
// Assume that the nominal range (usually
// 50nm) applies at a 5,000 ft difference.
// Just a wild guess!
double factor = ((aircraftElev*METER_TO_FEET) - stationElev) / 1000.0;
double factor = ((aircraftElev*METER_TO_FEET) - stationElev) / 5000.0;
double range = fabs(nominalRange * factor);
// Clamp the range to keep it sane; for
@ -60,7 +63,63 @@ kludgeRange (double stationElev, double aircraftElev, double nominalRange)
}
FGRadioStack *current_radiostack;
// model standard VOR/DME/TACAN service volumes as per AIM 1-1-8
static double adjustNavRange( double stationElev, double aircraftElev,
double nominalRange )
{
// assumptions we model the standard service volume, plus
// ... rather than specifying a cylinder, we model a cone that
// contains the cylinder. Then we put an upside down cone on top
// to model diminishing returns at too-high altitudes.
// altitude difference
double alt = ( aircraftElev - stationElev ) * METER_TO_FEET;
if ( nominalRange < 25.0 + FG_EPSILON ) {
// Standard Terminal Service Volume
if ( alt <= 1000.0 ) {
return nominalRange;
} else if ( alt <= 12000.0 ) {
return nominalRange + nominalRange * ( alt - 1000.0 ) / 11000.0;
} else if ( alt <= 18000.0 ) {
return nominalRange * 2 * ( 1 - ( alt - 12000.0 ) / 6000.0 );
} else {
return 0.0;
}
} else if ( nominalRange < 50.0 + FG_EPSILON ) {
// Standard Low Altitude Service Volume
if ( alt <= 1000.0 ) {
return nominalRange;
} else if ( alt <= 18000.0 ) {
return nominalRange + nominalRange * ( alt - 1000.0 ) / 17000.0;
} else if ( alt <= 18000.0 ) {
return nominalRange * 2 * ( 1 - ( alt - 18000.0 ) / 9000.0 );
} else {
return 0.0;
}
} else {
// Standard High Altitude Service Volume
double lc = nominalRange * 0.31;
double mc = nominalRange * 0.77;
double hc = nominalRange;
if ( alt <= 1000.0 ) {
return lc;
} else if ( alt <= 14500.0 ) {
return lc + (mc-lc) * ( alt - 1000.0 ) / 13500.0;
} else if ( alt <= 18000.0 ) {
return mc + (hc-mc) * ( alt - 14500.0 ) / 3500.0;
} else if ( alt <= 45000.0 ) {
return hc + hc * ( 1 - fabs(alt - 31500.0) / 13500.0 );
} else if ( alt <= 60000.0 ) {
return mc + (hc-mc) * (60000.0 - alt) / 15000.0;
} else if ( alt <= 75000.0 ) {
return mc * ( 75000.0 - alt ) / 15000.0;
} else {
return 0.0;
}
}
}
// periodic radio station search wrapper