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GPS receivers can compute position and velocity updates at rates of 1
Hz or more. Velocity is determined from Doppler-shift measurements and
so are quite precise (and accurate).
-- Richard Langley

On 22-Feb-11, at 2:45 PM, Patrick Goold wrote:

>
>
> I put down my calculator and my almanac on Sunday and went sailing.
> I had spent spent several hours that morning reducing and plotting a
> series of sunsights taken the day before,  preparing to ease myself
> into the arcana of running fixes.
>
> Just past the coal dock in Norfolk harbor, I was tinkering with the
> sail trim. I asked my wife to watch the handheld gps to see if my
> adjustments made any difference in our speed.  We were loping along
> at 4 knots.  She was at the stern, I was in the front of the
> cockpit.  I asked her to hand me the unit.   When she did, just for
> a second, it registered our speed over the ground as 6 knots.  I
> could not believe that satellite info was refreshed so frequently
> that the unit would detect the increased velocity northward as it
> was passed from hand to hand.  I stepped onto the side deck and
> walked to the bow, carrying the gps.  Sure enough the speed reading
> increased to 6.4 knots while I walked and returned to 4 the moment I
> stopped.  Oddly, while my first reaction was to laugh with delight,
> my second was to throw the thing overboard.  Damned creepy, these
> machines!
>
> If nothing else, they sap a man's motivation to learn about running
> fixes.
>
> Best,
> Patrick
>
> --
> Dr. Patrick Goold
> Department of Philosophy
> Virginia Wesleyan College
> Norfolk, VA 23502
> 757 455 3357
>
> Charles Olson: "Love the World -- and stay inside it."
>

-----------------------------------------------------------------------------
| Richard B. Langley                            E-mail:
lang@unb.ca         |
| Geodetic Research Laboratory                  Web: http://www.unb.ca/GGE/
  |
| Dept. of Geodesy and Geomatics Engineering    Phone:    +1 506
453-5142   |
| University of New Brunswick                   Fax:      +1 506
453-4943   |
| Fredericton, N.B., Canada  E3B
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|        Fredericton?  Where's that?  See: http://
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