Bill, you're absolutely right, during a dead straight glide
with constant airspeed their isn't enough information to
compute the result. With an SN10 you need to make an S-turn
at least to get an update.

The heading sensor issue is a bit difficult. Certainly it can
be done with GPS using multiple antennas (I can't remember the
commercial products that do this off-hand). Google and you'll
find a few research projects using GPS for attitude as well
as heading. Cost is not on for gliders real soon. Compasses
are very cranky beasts, especially if they need to be glider-
pilot-proof (about which I could tell stories for hours).
Making something that is low-cost, self-calibrating, immune
to stupid installations - that's the hard bit.

Hope that all makes sense,
Best Regards, Dave

PS: Haven't seen anyone suggest a sun-tracker yet ?
Or vision-system with terrain matching ?

"Bill Daniels" wrote in message news:_y8Ac.53766$0y.15362@attbi_s03...
Dave, can it give highly accurate, real-time wind data, second by second on
a straight one hour glide?

My last flight showed this problem during a long glide. For 30 miles the
wind data showed SW winds at 20 knots but then I noticed the glider drifting
to the west. Two 360 turns and the computer showed wind at 090 at 10 knots.
When I crossed the wind shift line I had a chance to change strategy. 30
miles later when the wind error became obvious it was too late.

More and more I think we need very accurate real-time wind data with no
requirement to be constantly changing heading. A cheap, reliable heading
sensor would make this possible.

Bill Daniels

"Dave Nadler YO" wrote in message
m...
Bill - The heading is not required. In the ILEC SN10 we do this
without heading, and it normally has the wind by the time you're
off tow. Pilot feedback and measurements indicate that we do
it quite accurately. We just use TAS and GPS ground track over
multiple observations (TAS requiring accurate IAS, press, temp).
Best Regards, Dave "YO"

"Bill Daniels" wrote in message
news:gw%zc.59643$HG.25574@attbi_s53...
I've been analyzing the IGC files from my flights and comparing them to
others.

Generally, in good conditions, I'm circling less than 25% of the time.
Other, far better pilots than I, are circling less than 15% of the time.
This means that wind data that depends on the glider flying circles gets
way
out of date during the long glides. OK, "S" turns can give the computer
a
chance to compute wind if you remember to fly them but there are still a
lot
of long, straight glides.

To compute real-time wind data we need Groundspeed, Ground Track (any
GPS
gives these)True Airspeed (Some computers do this if they have OAT,
Pressure
Altitude and IAS) and accurate heading data. Heading data it the tough
nut
to crack.

So, how do we get Heading? One way might be to put a GPS antenna in
each
wing and look at the carrier phase difference. If the computer saw a
constant track, it could assume the wings are level and determine a
heading
value. This heading value might update an aerospace quality MEMS
heading
gyro that would maintain a flow of heading data to the glide computer
during
times when the wings were banked.

With good heading data we could get uninterrupted high quality wind data
regardless of the gliders' maneuvering or lack of it.

OK, RAS gageteers, how about it?

Bill Daniels