Affordable GPS systems -Reply

[Rodham E. Tulloss]

I found that, in the neovolcanic region of Mexico, I got very good lat/long
readings.  I usually repeated a reading 6 times.  Usually, there was stability
within a few minutes.  Altitude is meaningless at lower elevations; however,
at 1600 m or more, I found that I usually matched the altimeter that a colleague
was using within 25 - 100 m (this in the same region of Mexico).  I did the
experiment of plotting the sites on a map and found that, at the scale of
the State of Mexico on a single folded sheet, the accuracy was quite
sufficient.

I have noticed that under conditions that I do not understand the GPS will
slowly start to drift very far off even in very well-covered regions like
central New Jersey.  I powercycle the thing when this happens (it is very
noticeable when it does), and that seems to work.

My system is a Magellan 2000.

Rod Tulloss