Re: Trimble Geoexplorer 1,2 date problems

Thanks very much to all the posters. I kept on being told by everybody
including Trimble that it doesnt matter!
Interesting that the problem was flagged in 1993 ie 7 years before the
event.
One authority made the pertinent observation that if a manufacturer did not
account for the rollover then they would be "non-compliant".
Looks like Trimble sold "non-compliant" GPS receivers and their excuse is
that it doesnt matter.
In their Support Note they say "The issue does not affect the GPS positions
or the ability to differentially correct the data. "
Well if you are using rinex formatted data from a third party source to do
post processing differential correction then it does!

"Sam Wormley" <swormley1@xxxxxxxxx> wrote in message
news:gpqzl.35278$DP1.21644@xxxxxxxxxxxx
Terje Mathisen wrote:
Sam Wormley wrote:
Roman Szeremeta wrote:
Their excuse for producing incorrect data is that it doesn't matter!!!

Because of the GPS Week Number Rollover, it is impossible with the
current
navigation message to determine the correct date for more than 1024
weeks
(19.6 years), with out an external date source or an internal clock
set by
the user... no matter who is the manufacturer.
http://www.navcen.uscg.gov/gps/geninfo/y2k/gpsweek.htm

That isn't quite true:

It is in fact trivial to check the current UTC-TAI offset and use that to
determine that the 10-bit week count must have rolled over.

Yes, Terje, you are correct! Too bad the receiver manufacturers didn't
anticipate that units would be in use for a very long time.

-Sam






You can even use the known offset at the last (first) rollover to check
if a second rollover must have occured.

This would allow the firmware to last for 70+ years from now.

Terje



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