[amsat-bb] Re: GPS Time observation
alancresswell at xtra.co.nz
Thu Feb 2 12:12:03 PST 2012
Well the most likely explanation would seem to be related to your GPS
display routine. If you are getting accurate position information the
timing from the satellites must be within a few nanoseconds. The satellite
time currently differs from UTC by plus 15 seconds because UTC is retarded
by one leap second on a regular basis but the satellite time is not altered.
The satellites broadcast this offset from UTC but only every 12.5 minutes.
It is not unusual for a GPS display to have a relatively low priority
compared to the intensive position calculations and give a time display that
differs by a second or two from UTC.
From: amsat-bb-bounces at amsat.org [mailto:amsat-bb-bounces at amsat.org] On
Behalf Of Dave Guimont
Sent: Thursday, 2 February 2012 18:29
To: Vince Fiscus, KB7ADL
Cc: amsat-bb at amsat.org
Subject: [amsat-bb] Re: GPS Time observation
Interesting question, Vince...am sure someone on here will be able to
answer it. I know at one time the civilian population was restricted
from the most accurate location, and as I also remember the military
accuracy was within a centimeter if several observations were
taken...Nice to see your smiling face on here, my friend...
>I have an old GPS unit, a Magellan explorist 210. It's fairly
>accurate determining position. After it has acquired about eight to
>ten satellites the position error averages between 20 to 35
>feet. Now the question, the other day I was looking at one of the
>information pages the unit can display and on it, it gives the time
>in UTC. Just for fun I thought I would see how close the time was to
>WWV. I was surprised to see the unit was between one to four seconds
>off over various tests compared to WWV. IS this typical of all GPS
>units or do some display the time of day more accurately?
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73, Dave, WB6LLO
dguimon1 at san.rr.com
Disagree: I learn....
Pulling for P3E...
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