76CS...Problems with Altimeter...and other....HELP!!!

Hi All,

I Just bought a 76CS to replace my older 3+. I am trying to get the
altimeter to work (its probably just my errors). The first thing I did, was
I calibrated it to 11 feet, b/c I know that the top of the deck that I laid
it flat on, was 11 feet above sea level. It said it calibrated. The next
thing I know is I'm looking at the altitude page, and its going back and
forth between 12 and 8 and 13 and 12 again, maybe 11 at some point (still in
the same spot I set it in). My question is, if I just set the altitude,
shouldn't it know its 11 feet?

Okay, so it seems its off something < 10 (which the specs say it should be
like < 10'). I turn off and go to bed. The next day I participated in a 5
mile walking event where I carried it with me. The Altimeter several times
showed negative readings (I did not calibrate it again when I turned it on
after the initial calibration). In the track log, it also had me going 350+
mph (only one point for 00:01), but weird nonetheless.

Later that afternoon, I begin my ride home, I had the GPS on pretty much the
whole way (altitude where I noticed problem should have been around 240) I
think the 76cs (again, without another calibration since the "outdoor deck
calibration" it was around 40 or 50. I do a calibration on the fly to the
GPS altitude. It is more like it should be, and within 15 feet of what my
old 3+ says.

How often do you have to calibrate these? It seems unrealistic to calibrate
it every time you turn it on and off. What if you're taking a several day
long hiking trip, and you're relying on the altitude, but don't have
anything but the GPS to calibrate it by? Does the sensor make it more
accurate, or just able to be used when there isn't a GPS signal available?
How does it use barometric pressure to determine altitude.

Thanks in advance for the responses.....I am a "why" kind of person.


.

Relevant Pages

  • Re: 76CS...Problems with Altimeter...and other....HELP!!!
    ... The first thing I did, was I calibrated it to 11 feet, b/c I know that the top of the deck that I laid it flat on, was 11 feet above sea level. ... My question is, if I just set the altitude, shouldn't it know its 11 feet? ... But the pressure change isn't very much whether you're at 8' above sea level or 13', so it's not at all surprising that you see fluctuations of a few feet back and forth. ... whole way I think the 76cs (again, without another calibration since the "outdoor deck calibration" it was around 40 or 50. ...
    (sci.geo.satellite-nav)
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    ... However, since the actual sea-level atmospheric pressure at any point on the journey is unlikely to be exactly 29.92 inches Hg, then the ACTUAL altitude will NOT be 36,000 feet and it will vary continuously. ... your in-cabin hand-held GPS will show the true altitude. ...
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  • Re: Bicycle Computer Altimeter Accuracy
    ... It appears they don't use GPS for altitude unless the main ... Take a GPS altimeter reading. ... almost always within 20 feet or so of the correct altitude and NEVER ... So while the barometric altimeter under ideal ...
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  • Re: 76CS...Problems with Altimeter...and other....HELP!!!
    ... reads 30.04" where the correct reading is 30.07" The altitude is about ... 24 feet in error... ... > calibration" it was around 40 or 50. ... > GPS altitude. ...
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