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From: Don Dement (no email)
Date: Wed Aug 25 1999 - 14:32:25 EDT
I previously reported my Trimble NavGraphic II as OK, but I think I know why
they said it would fail, and this may apply to other GPS brands.
It's getting fixes from satellites that it recognizes, but it's reporting
negative elevations and possibly false azimuths. That says to me it is on the
wrong date, which is hinted at by the failure prediction -- it would call
today's date to be in Jan 1980. However, it reports on the time output to the
screen what the satellites tell it the current date is, that's today's correct
date. But I don't think it's using this date as it's almanac reference for the
az/el.
Anyway, it reverts to Loran fixes every 10-15 minutes because it only recognizes
two satellites, then catches a third one and says it's a GPS fix and sits on
that for 10 minutes or so. The GDOP is generally bad even when it sees enough
satellites to pick a good geometry, so I think it has bad data into its
calculator. The position may be OK, I can't tell if it would track usefully
because I'm confined to the dock at present.
I think I should consider it dead until proven otherwise, even though I'm
getting fixes.
Regards --- Don Dement
Gerrit Houweling wrote:
> More weird stuff here, ....
> ....The only odd thing I moticed was that operation seemed erratic with
> regards
> to speed and course bearing it kept going all over the place.
>
> ___________________________________________________________________________
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