I actually have the same Azimuth 1000 flux gate compass installed on
the rear instrument panel of my Janus C. It is coupled via NMEA to an
RMI microEncoder in the front panel.

One problem with the set-up is that the S/H two-place one-piece canopy
has a steel cross member, so the compass reading changes by more than 5
degrees between open and closed canopy. Also, even though it is tilt
compensated by mounting the flux gate on a gimball, it does not produce
consistent readings when tilted. I assume this is because the tilt
compensation alters the hard/soft iron compensation.

I looked at installing a remote flux gate, but there is no place in the
glider to mount it far enough from the steel flight control push/pull
rods. This is a real problem for getting accurate heading info from a
magnetic sensor in a glider.

P.S. Ray points out that with any two vectors, you can draw the vectors
tip to tail to complete the wind triangle. With one vector (GPS) and a
scalar (TAS) you can draw a circle around the tip of the vector to
create a family of wind triangles. With a second set of measurements on
another heading, you can draw another circle which intersects the first
at two places. With another set of measurements, you can remove the
ambiguity, and get a check on the error. In practice, flight computers
like the SN-10 make lots of measurements and keep a running calculation
of the wind by filtering out the measurement errors.

Capt. Geoffrey Thorpe wrote:
"Ray Roberts" wrote in message
. ..
Calculation of windspeed and wind direction without circling:

Here's my understanding. If it's not correct, doubtless someone will
straighten me out and I will have learned something. DISCLAIMER: I have
absolutely no "inside" information on the algorithms used in the SN10!

Aircraft heading (direction the nose is pointing) and airspeed together
define a velocity vector that can be drawn as an arrow on a piece of
paper, the angle of the arrow representing the direction and the length of
the
...
In the case of a sailplane with an SN10 that has input from a GPS, we have
three knowns, namely true airspeed (the SN10 can compute this from pitot
pressure, static pressure, altitude and temperature), groundspeed and
track (the last two come from the GPS). There are three unknowns, aircraft
heading, wind direction and windspeed. Basically, multiple unknowns can be
calculated by setting up and solving simultaneous equations. There are
well known mathematical and computer algorithms for doing this.
...
makes sense. If an accurate aircraft heading sensor were added to the
SN10, thus completely defining two of the vectors in the "wind triangle",
this would not be necessary. One lives in hope...



For $300 you can add a fluxgate compass that will communicate via NMEA...
Fixing the software to use it would be up to you.

Of course, the heading information will only be good when you are flying
straight and level...

http://www.westmarine.com/webapp/wcs...001/606/137/14

--
Geoff
the sea hawk at wow way d0t com
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