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RE: Time references (UT vs. GPS) Whoa, there!




Leap second corrections have not been applied to GPS time.
Therefore the raw GPS time is 13 seconds off UTC.

Bob
N4HY

-----Original Message-----
From: owner-AMSAT-BB@AMSAT.Org [mailto:owner-AMSAT-BB@AMSAT.Org]On
Behalf Of laura halliday
Sent: Wednesday, July 09, 2003 15:45
To: amsat-bb@AMSAT.Org
Subject: Re: [amsat-bb] Time references (UT vs. GPS) Whoa, there!


Wayne Day <n5wd@charter.net> wrote without thinking:

>OK, this has been bugging me no end - I simply don't see any
>13-second difference between (a) my receiver hearing WWV over the
>air, (b) an atomic clock that synchs up with WWVB every evening and
>(c) my Garman GPS-12.  There IS NO 13 SECOND DIFFERENCE that I can
>see!
>
>Now, I saw the reference to the 13 second difference on the web page
>that Scott referenced, but I can't find it anywhere else in the
>references I've looked at.  Is this merely another urban legend?

Far be for me to have a clue what I'm doing, but the systems
I work with are industrial GPS receivers (e.g. Trimble Palisade)
which output raw GPS data. The correction information is there
if you want to use it, but you must apply it yourself in the software
that digests the data stream.

All commercial/industrial/OEM GPS receivers I've ever
seen work like this. Only consumer receivers automatically
apply leap-second correction.

I scored a couple of surplus Palisades from my employers
(tehy look like white mushrooms, and are intended to sit
on top of a mast), with cables and documentation. The manuals
are interesting - even the cable length is taken in to account
when defining the accuracy of the 1 PPS output.

Laura Halliday VE7LDH     "Que les nuages soient notre
Grid: CN89mg                       pied a terre..."
ICBM: 49 16.05 N 122 56.92 W     - Hospital/Shafte

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