"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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