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And another series of extensive tests of handheld receivers in 2001 by
a geodesist:
http://home.comcast.net/~dmilbert/handacc/index.html

-- Richard Langley

Quoting Gary LaPook :

> There has been some discussion recently of GPS accuracy. I have
> attached three graphs of testing I have done. The grid is the UTM
> grid and the units are meters using NAD27 coordinates.
>
> The first shows a test I did when Selective Availability was active
> and the scatter covered 130 meters east to west and 152 meters north
> to south giving a CEP of 22.22 meters. Plus marks show one minute
> averages and the dots show single fixes. With SA on averaging did
> not improve the fix accuracy since SA swamped the effect of
> averaging since SA was not a random error.
>
> The second shows a test done on September 18, 1994 and I was shocked
> to see how small the scatter was, only 7 meters east to west and 10
> meters north to south with a CEP of 2.90 meters. I learned that the
> reason for this was that SA had been turned off because of the U.S.
> invasion of Haiti. This is a good comment on selective availability
> which was designed to allow high precision positioning for the U.S.
> military while denying it to the enemy. But, during Desert Storm and
> again when invading Haiti, our military did not have enough military
> GPSs so had to use off the shelf units so SA was turned off to allow
> greater accuracy. This is humorous since it is exactly during
> military operations that SA was developed to prevent the enemy using
> high accuracy GPS against us but, then in practice, SA was not used
> at exactly the time it was supposed to be used.
>
> The third graph was done in 2000 and includes individual fixes and
> one  minute averages. Without SA, averages were more accurate than
> single fixes with CEP of 1.50 meters for averages compared to  5.338
> meters for single fixes.
>
> Here are links to two other tests:
>
> http://www.madbavarian.org/gps/accuracy.html
>
> http://users.erols.com/dlwilson/gpswaas.htm
>
> gl
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===============================================================================
  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 5A3
      Fredericton?  Where's that?  See: http://www.city.fredericton.nb.ca/
===============================================================================

   

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