> On 09/12/09 10:08, James Turner wrote:
> > I was wondering if we should increase the GS range cutoff to 1.2 *
> > range-fom-nav.dat (or 1.4, or 1.8, or 2.0 ... essentially give a
> > margin of reception beyond the published limit)
> >
> > I guess it depends what the nav.dat value should be taken as : a
> > published maximum, or a guaranteed (with a tolerance) reception area,
> > or something else?
> >
> > Otherwise I think we'll have to edit a very large number of entries in
> > nav.dat.
>
> Why do you think it will be a "large number" of edits?
> How many approaches do you know of that require
> intercepting the glideslope more than 5 or 6 miles out?
> As of today, I know of two, namely the one that Torsten
> alluded to this morning, and Jackson Hole:
> http://naco.faa.gov/d-tpp/0909/00504ILY19.PDF
>
> I reckon there are more than two total, but not a very
> large number.
Hmm - almost every standard ILS in Germany starts out of roughly 3000ft GND on
a 3deg slope resulting in approx. 10NM final. I can't actually remember a
single ILS I flew in Europe having less than 6 NM for the FAF to the
threshold.
A quick check at airnav.com showed me
KSFO 28L: 7.3 NM
KMYF 28R: 7 NM
KLAS 1L: 9.3NM
>
> I know of several approaches with expanded LOC volumes,
> but GS is a horse of a different color.
>
> > I was wondering if we should increase the GS range cutoff to 1.2 *
> > range-fom-nav.dat
Some time ago, I added a simple (very simple) decay function to the VOR
reception, reducing the signal-quality by distance-squared beyond it's range.
It's definitely not the best radio-signal-decay model on earth, but probably
better than a binary on/off at the boundary of the service volume.
Maybe just drop
if (gsDist > (_gs->get_range() * SG_NM_TO_METER)) {
return;
}
and let the gsNeedleDeflection drop with distance from the station, which is
already imlemented some lines below:
_gsNeedleDeflection *= signal_quality_norm;
This might also be useful for reduced signal strengths of side lobes.
Thanks for working on and improving the navradio code. It's highy appreciated!
Torsten
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