In this case, he's been playing around with a brand new Garmin
etrex H GPS receiver. Among other things it allows you to store
a time sequence of position measurements, a so-called track,
which you can then upload on Google maps to see which part of
the forest you've been straying around in. This cute high-tech
gadget is shown in the photo. On the display (click to enlarge)
you can see a schematic map of the sky with the GPS satellites
in view, and the strengths of the signals received from these
satellites indicated in the bars at the bottom of the screen.
Moreover, the display says that the accuracy of the position
measurement is 5 meters. Now, Stefan wanted to figure out the
meaning of this accuracy, and if it can be improved by averaging
over many repeated measurements. So, he put the GPS receiver on
said patio table, and had the device measure the position every
second over a duration of a bit less than 3 hours. Then he
downloaded the measurement series with several thousand data
points, plotted them, an