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.
73 Alan ZL2BX
-----Original Message----- From: amsat-bb-bounces@amsat.org [mailto:amsat-bb-bounces@amsat.org] On Behalf Of Dave Guimont Sent: Thursday, 2 February 2012 18:29 To: Vince Fiscus, KB7ADL Cc: amsat-bb@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...
Anyone?
73 Dave
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?
KB7ADL
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73, Dave, WB6LLO dguimon1@san.rr.com
Disagree: I learn....
Pulling for P3E... _______________________________________________ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb