From owner-freebsd-hackers Thu May 4 1: 7:17 2000 Delivered-To: freebsd-hackers@freebsd.org Received: from apollo.backplane.com (apollo.backplane.com [216.240.41.2]) by hub.freebsd.org (Postfix) with ESMTP id 676EB37B5BA for ; Thu, 4 May 2000 01:07:14 -0700 (PDT) (envelope-from dillon@apollo.backplane.com) Received: (from dillon@localhost) by apollo.backplane.com (8.9.3/8.9.1) id BAA67715; Thu, 4 May 2000 01:01:25 -0700 (PDT) (envelope-from dillon) Date: Thu, 4 May 2000 01:01:25 -0700 (PDT) From: Matthew Dillon Message-Id: <200005040801.BAA67715@apollo.backplane.com> To: Poul-Henning Kamp Cc: Warner Losh , hackers@FreeBSD.ORG Subject: Re: GPS heads up References: <2288.957418565@critter.freebsd.dk> Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG :SA *can* be averaged out, it has an average value of zero. But it :takes several days or even weeks to get into the centimeter range, :depending on the satelite coverage where you are. : :-- :Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 :phk@FreeBSD.ORG | TCP/IP since RFC 956 Months or years to get into the centimeter range. Days to get in the 50 ft range, weeks to get into the 14 ft range. That's based on measurements. And SA does *NOT* have an average value of 0 even if you take a month's worth of data. Try to depend on the average and you will be screwed. What you do is use the worse case error (over a couple of days) to create an area, then take the middle of the area. That will give you better results then an average (the points within the volume will not be spread evenly so taking an average will result in an offset). -Matt Matthew Dillon To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message