Andy Durbin wrote:
(Ramy Yanetz) wrote in message

These devices should be capable to tell you if you are in a collision
course, not just warn you of a nearby aircraft. Earlier someone posted
a link to a new device which also calculate collision course while
thermaling! If you thermal too close to someone else it should warn
you.



But how close is *too close*? I am perfectly comfortable cranked up
at a 50 deg bank with someone opposite me doing the same thing, but
very uncomfortable if another glider joins with the same separation
and puts me in their blind spot.

To be effective in providing warnings the device would have to
continuously predict collisions based not only on the current
trajectory of each aircraft, but also predict collisions based on all
possible future trajectories for the next say 30 seconds. Try
resolving that mess when there are 30+ gliders at the top of the same
thermal waiting for a contest start. The false alarm rate would be
unacceptable.

I think Andy is right, but I don't think that situation is the one that
produces the most collisions. My undocumented impression is the majority
involve just a few gliders, often just two. The computations for two or
three gliders should be easy compared to 6 or more. During thermalling
or beating back and forth on a ridge, gliders don't change relative
altitude very much, so this much reduces the potential paths.

So, a system that worked for 2 or 3 gliders would be useful, and as
experience was gained with it, I think it would be continually upgraded
to cover situations with more gliders. Even if it didn't work for more
than even 5 gliders, that would cover most situations.
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Eric Greenwell
Washington State
USA