GPS Error
Lanny,
You probably just got info from either vested interests or GPS
"newbies". Until about 2 years ago the number of people in the whole
world who could speak authoritatively on GPS was very small. Those
working in each specialism had generally known each other for years.
Now the salesmen, and the "I heard it from the salesman" brigade are
out in force, exploiting new markets for this wonderful tool. Of
course it's going to be oversold for a while, until people catch on
that. like anything, you get what you pay for.
If I operate a Trimble 4000 in non-differential mode, my results will
fall inside the 100m ( 95% confidence level) quoted by the system
owners. These results will also be reasonably repeatable, but I won't
get centimetre level accuracies without resorting to some special
techniques. The cheaper receivers have fewer channels, so have to
sequence through satellites. Their tracking loop circuitry is also
less robust than on the more expensive models. And the antennae! For
precision geodetic work I use large ground plane extensions on the
antenna, which, unlike that of the cheaper models, already has a built
in ground plane. In fact, an antenna for the more expensive units can
cost several times the price of a whole "budget" rx!
I'm sorry you feel that you were given bum info before purchase, but
you're in the unfortunate position of entering the market at a
transition stage between the technology being used only by
specialists, and it filtering throught to general use. People in that
position "always" feel that they've had bum info, whatever they've
bought ( I still feel that I was "had" over my first CD-Rom drive!