Marine users have been using electronic compasses for some time. These are
fluxgate compasses and most have NEMA output so what you want is not
impossible. The marine ones are expensive circa $400 but there are a new
bread of digital compasses some of which are included in GPS handhelds but I
cannot see if any have NEMA outputs. In addition there ae some aviation
sensors coming n the market (MEMS) (see
http://www.willow.co.uk/html/heading.html) You will need a NEMA sentance
output of HDM or better HDG from such a device and a NEMA concatenator to
meld the NEMA output into the IPAQ datastream.

On the Plus side
You would have a compass that had little lag - easier to roll out of
thermals onto heading
You would get your wind data

On the downside
Expensive as one-off
Yet more battery drain
Device would need A solid state memory for an electronic version of
deviation card
Device would have to be installed in tail as they are V sensitive
You only get Magnetic heading from device - GPS is essentially True and if
flying in areas of local magnetic anomalies you will get strange results.

Given most gliders fly Track as opposed to bearing it would be easier simply
to note magnetic heading & speed once on track and make sure that the two
remain constant if they diverge then your wind direction has changed and you
can either do the mental maths (or use a flight computer) or put in a 360.

What we are all really waiting for is a Touch Single panel display system
that would include something like this along with a Head-Up display. But the
market is just too small to make something like this a real economic
proposition at this time along with the associated battery drain. You would
be lucky to sell more than 500 units.

rgds
stephen


"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