[ntp:questions] Re: Good and cheap GPS receivers (was: Reference clocks - which?)
Wolfgang S. Rupprecht
wolfgang+gnus20041030T140650 at dailyplanet.dontspam.wsrcc.com
Sat Oct 30 21:18:44 UTC 2004
Bjorn Gabrielsson <bg at lysator.liu.se> writes:
> "Wolfgang S. Rupprecht" <wolfgang+gnus20041030T125048 at dailyplanet.dontspam.wsrcc.com> writes:
> > Helmut Wollmersdorfer <helmut at wollmersdorfer.at> writes:
> > Unless you can mount the antenna and/or the whole gps on the roof,
> > getting a GPS will be nothing but an aggravation. GPS is roughly 1.5
> > Ghz and line of sight.
> A window on first floor might be much worse than an antenna on the
> addict, especially if you do position hold. A friend can usually
> "navigate" his eTrex in his appartment. Obviously sheet metal roofs
> are bad, but if you have other materials - try it out. Borrow a
> handheld to check satellite reception out.
One thing to keep in mind is that Garmin GPS's which will extrapolate
for 30 seconds whenever it loses lock. That tends to give a false
impression that things are working better than they really are.
Graphing the time (or positional) jitter will show you that things
aren't working all that well.
I can walk around the house with my eMap and it will usually stay
locked too. The positional solution it provides isn't worth crap
BTW. The Motorola Oncore m12 is fairly unfiltered. It won't beat
around the bush when it is unhappy with the signal strength. Expect
it to complain long before the garmin complains.
Wolfgang S. Rupprecht http://www.wsrcc.com/wolfgang/
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