> Barry King wrote:
>
> > Hmm.  Does a GPS really give you an instantaneous ground speed
> > reading that is accurate and updated often (like 1 Hz?)  The only one
> > I've played with gives erratic speeds, they seem to be long-term
> > averages, so if you are speeding up and slowing down, they aren't
> > accurate.  And they are not updated very often.  This was at approx
> > 25 mph (marine application), with I think 5 satelites in view.  Is
> > the erratic data because it was a stupid receiver, or it that a
> > limitation of the tech?
>
Roman Black Wrote
>
> No generally GPS won't give a good instantaneous road
> speed. Many customers who buy our speedo recalibrator
> product try to use a GPS to calibrate it, but you really
> need a long distance and cosntant speed for the GPS to
> give a decent average speed reading.

Hence the reason for using an Airfield Runway as well as the fact they are
well away from buildings and other structures. They are stright and flat, at
least all the ones within a 30 mile radius of me are (I'm talking proper
paved runways not the grass ones). With a bit of practice it is relatively
easy to keep a vehicle at a speed constant enough to calibrate a wind speed
indicator.

From experience, it's the cheapest and quickest way of getting fairly
accurate results, assuming  you have access to a GPS Receiver. If you
haven't then it's wood or metal work and a bicycle wheel (plus a PIC).
>
> For the wind meter caibration, you can get decent
> "hobby" wind speed meters from RadioShack, etc,
> maybe if someone is serious about building weather
> measuring equipment the $50 would be well spent?
> I have one. :o)

Suck Index Finger and stick it up in the Air. No that's for the accurate
measurement of wind direction Sorry. :-)

Chris

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