From owner-freebsd-hackers Sat Mar 30 10:58:51 2002 Delivered-To: freebsd-hackers@freebsd.org Received: from virtual-voodoo.com (bdsl.66.12.217.106.gte.net [66.12.217.106]) by hub.freebsd.org (Postfix) with ESMTP id 4877837B432 for ; Sat, 30 Mar 2002 10:58:38 -0800 (PST) Received: from virtual-voodoo.com (steve@localhost [127.0.0.1]) by virtual-voodoo.com (8.12.2/8.12.2) with ESMTP id g2UIwZFt070467; Sat, 30 Mar 2002 13:58:36 -0500 (EST) (envelope-from steve@virtual-voodoo.com) Received: (from steve@localhost) by virtual-voodoo.com (8.12.2/8.12.2/Submit) id g2UIwYfm070189; Sat, 30 Mar 2002 13:58:34 -0500 (EST) Date: Sat, 30 Mar 2002 13:58:34 -0500 From: Steve Ames To: Leo Bicknell Cc: Paul Halliday , hackers@FreeBSD.ORG Subject: Re: GPS time. Message-ID: <20020330185834.GB77994@virtual-voodoo.com> References: <20020330142859.GA19243@ussenterprise.ufp.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20020330142859.GA19243@ussenterprise.ufp.org> User-Agent: Mutt/1.3.28i Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG http://www.gpsclock.com/ is $380US and does PPS pulses accurate to plus or minus 1 microsecond of UTC. On Sat, Mar 30, 2002 at 09:28:59AM -0500, Leo Bicknell wrote: > In a message written on Fri, Mar 29, 2002 at 06:04:11PM -0600, Paul Halliday wrote: > > I just connected my gps (garmin gps III plus) to my serial port > > and realized that simply cat'ing cua0 displays date/time/position of the > > unit. (neato). Anyway, how accurate would it be to use the time from this > > output for ntp as opposed to my current setup using ntp servers. > > Your NTP servers are better. > > I tested a III Plus, and without a 1 PPS source (which that model > doesn't provide) it's accurate to about 100ms, give or take. Since > real NTP servers are < 1ms, they really aren't that good. It's > not that the time isn't accurate, it's that they were not designed > to communicate with that accuracy to an external device. > > If you NTP off the Internet, and want a local backup clock it might > be an acceptable solution. However clocks that can achieve < 1ms > accuracy can be had for < $1000, so if you really care you should > get one of those. > > You might want to do some searches for NTP in google. > > -- > Leo Bicknell - bicknell@ufp.org - CCIE 3440 > PGP keys at http://www.ufp.org/~bicknell/ > Read TMBG List - tmbg-list-request@tmbg.org, www.tmbg.org > > To Unsubscribe: send mail to majordomo@FreeBSD.org > with "unsubscribe freebsd-hackers" in the body of the message To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message