NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: GPS as a time authority
From: Nicol�s de Hilster
Date: 2009 Sep 14, 23:13 +0200
From: Nicol�s de Hilster
Date: 2009 Sep 14, 23:13 +0200
Dear John, I think pages 30 -31of the following document will answer your question: http://www.allanstime.com/Publications/DWA/Science_Timekeeping/TheScienceOfTimekeeping.pdf The problem is that you never know for sure which time is displayed on your GPS until you check it against another source. My hand-held GPS performs similar to yours, while my car-navigation GPS shows a considerable error (about 5-6 seconds), while it tells me it should be UTC. I only found out because a series of sun shots - timed using the latter - on a known baseline did not fit within the expected accuracy. Ever since I either use a DCF-clock (Mainflingen) or the hand-held GPS. Nicol�s JKP@obec.com wrote: > I think this has been dicussed before, but I'd like to be refreshed on the list's opinion: > > While assisting the Race Committee at a regatta this weekend, I heard the timekeepers say that they were using "GPS time." I noted that my $79 wristwatch, which I check monthly against the US Bureau of Standards atomic clock (ph: 303-499-7111) and which doesn't lose a second per month, was 8 seconds ahead of the Committee's time. > > I later checked the time shown on my hand-held Gartmin GPS receiver, and it agreed with my watch. The watch was also still in sync with the Bureau's atomic clock. > > Question: Is the time displayed by GPS receivers considered a reliable and spot-on source, up to the requirements of accurate celnav? I would think that it would be, since the GPS network depends on accurate tracking of the satellites' position at a given time, yet there was that 8-second discrepancy. Perhaps the Race Committee were simply careless about setting theior clockby GPS. > > Any thoughts, List Members? > > -John Parsons > > > > > > > ------------------------------------------------------------------------ > > > No virus found in this incoming message. > Checked by AVG - www.avg.com > Version: 8.5.409 / Virus Database: 270.13.95/2368 - Release Date: 09/13/09 17:50:00 > > --~--~---------~--~----~------------~-------~--~----~ NavList message boards: www.fer3.com/arc Or post by email to: NavList@fer3.com To , email NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---
