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Old May 29th 15, 01:16 AM posted to rec.aviation.soaring
pcool
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Posts: 69
Default Help us with this petition for security on anti-collision systems

oh com'on, at the beginning of this thread I stated I did not sign the
petition. There is no deliberate action of any kind.
Simply you keep calling prediction what is really a projection.
If you are turning, it projects accordingly . It doesnt predict you are
turning.
"prediction" is a marketing word here. There is no computational power to
predict anything, inside the flarm.
But let it go, it does work, this is out of any question. We have been using
it since 2005.


"Andy Blackburn" wrote in message
...

On Thursday, May 28, 2015 at 2:16:55 PM UTC-7, Tango Eight wrote:
On Thursday, May 28, 2015 at 4:00:06 PM UTC-4, Buddy Bob wrote:
At 18:35 28 May 2015, pcool wrote:

Two flarm equipped gliders fly parallel to one another at 80 kts with 300'
separation and -- as long as the flight paths are not convergent -- flarm
gives no alarm. If the paths become convergent, alarms result very
quickly. As soon as the paths become parallel or divergent, the alarms
cease. The same two gliders now fly a head on approach, again at 80 kts.
Flarm gives a warning at significant range... over a mile... and the
warning ceases almost immediately when one glider changes his track. From
this I believe it should be clear to anyone that the way flarm works is
most likely just how they've said it works: by estimating what airspace
any given glider is capable of occupying in the next +/-30 seconds and
looking for potential conflicts.

-Evan Ludeman / T8


Yes. I'm surprised this is even coming up, except as a deliberate effort to
obfuscate important differences between the various technologies and why
they may not be compatible.

Anyone with a rudimentary knowledge of aircraft dynamics and even a single
day's flying with FLARM has to conclude that it is making path-dependent
collision prediction estimates. You have to fly in a few thermals to pick up
that the path prediction is curved when you are turning.

Flarm engineers have told me explicitly that the prediction is done on the
transmit side and I can see why this would work better for the reasons
previously raised. The specification may or may not need to specify this as
a communications protocol generally needn't include a specification of the
data payload or the algorithm to create or interpret it.

9B