NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Time and cel nav, a stupid question
From: Lu Abel
Date: 2008 May 14, 08:43 -0700
From: Lu Abel
Date: 2008 May 14, 08:43 -0700
Anabasis wrote: > This is really quite simple. Use the GPS. GPS birds have atomic > clocks on them and the only error in the time signal is from the > transmission delay between the sat and your receiver. The only necessary word of caution here is that you must make sure that your GPS receiver is set to display UTC and not GPS time (which is 1980 UT without subsequent leap-seconds and hence is now off by about seven seconds). The default, out-of-the-box setting for most GPS receivers is to show UTC, but it can be changed. > A website has > all sorts of network delays as packets get sent to and fro. These delays can be accounted for by simply measuring the round-trip delay from the time source to the web browser and back. www.time.gov does exactly this, and will even display any remaining uncertainty in the time display. For my broadband connection, this number is typically 0.2 or 0.3 seconds. I doubt one can set a hack watch this accurately regardless of the time source. Lu Abel --~--~---------~--~----~------------~-------~--~----~ Navigation List archive: www.fer3.com/arc To post, email NavList@fer3.com To , email NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---