From owner-freebsd-hackers Sat Mar 30 6:31:26 2002 Delivered-To: freebsd-hackers@freebsd.org Received: from ussenterprise.ufp.org (ussenterprise.ufp.org [208.185.30.210]) by hub.freebsd.org (Postfix) with ESMTP id F21DD37B404 for ; Sat, 30 Mar 2002 06:31:23 -0800 (PST) Received: (from bicknell@localhost) by ussenterprise.ufp.org (8.11.1/8.11.1) id g2UESxX19388; Sat, 30 Mar 2002 09:28:59 -0500 (EST) (envelope-from bicknell) Date: Sat, 30 Mar 2002 09:28:59 -0500 From: Leo Bicknell To: Paul Halliday Cc: hackers@FreeBSD.ORG Subject: Re: GPS time. Message-ID: <20020330142859.GA19243@ussenterprise.ufp.org> References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Organization: United Federation of Planets 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 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