At 09:56 AM 8/13/02 -0700, you wrote:
>Curious, then, why two different Garmins (etrex units) gave two
>different readings (altitude and location) from the same position.
>Has the Clinton order been rescinded? We were in the open, and were
>getting signals from 4 different satellites.
>
>BK
>
That may be your problem, for any kind of accuracy six good signals is
minimum.
The tree problem, BTW, is called multiple-path reflections, and resembles
the kind of distortion woodland leaves impose on our nature sound audio
recordings.
I have owned two Garmin machines, the GPS-40 for four years and now the GPS
III+ for three. Both are ,as I keep saying, laughably incompetent at
altitude. In familiar lowland terrain, I can often guess the altitude
better than these machines.
For example this morning my Suunto altimeter, with no calibration, said 200
ft altitude when I took it out of the drawer. The first floor of my house
is actually 195 ft. This happened (air pressure wise) to need no
calibrating today, by chance. The GPS III+ read 279, then settled down to
245, then, half an hour later read 260. All without moving it, with five
or six satellites.
I wonder why the E-trex ($ 119 at REI Coop) is so much better at altitude
than the high priced spread III+ ($ 300 at REI)? I think I will call REI
about it. Maybe I have something mis-set in the many option settings . . .
If you think about the triangluation process, with all the satellites ABOVE
you, the altitude reading should be at least as accurate as the Lat Long,
usually better.
Marty
Marty Michener
MIST Software Associates
PO Box 269, Hollis, NH 03049
coming soon : EnjoyBirds, bird identification software for all AOU area.
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