From owner-freebsd-hackers Thu May 4 14:56:53 2000 Delivered-To: freebsd-hackers@freebsd.org Received: from rover.village.org (rover.village.org [204.144.255.49]) by hub.freebsd.org (Postfix) with ESMTP id 5323737B666 for ; Thu, 4 May 2000 14:56:46 -0700 (PDT) (envelope-from imp@harmony.village.org) Received: from harmony.village.org (harmony.village.org [10.0.0.6]) by rover.village.org (8.9.3/8.9.3) with ESMTP id PAA26398; Thu, 4 May 2000 15:56:42 -0600 (MDT) (envelope-from imp@harmony.village.org) Received: from harmony.village.org (localhost.village.org [127.0.0.1]) by harmony.village.org (8.9.3/8.8.3) with ESMTP id PAA43697; Thu, 4 May 2000 15:56:40 -0600 (MDT) Message-Id: <200005042156.PAA43697@harmony.village.org> To: nate@yogotech.com (Nate Williams) Subject: Re: GPS heads up Cc: hackers@FreeBSD.ORG In-reply-to: Your message of "Thu, 04 May 2000 08:11:06 MDT." <200005041411.IAA17374@nomad.yogotech.com> References: <200005041411.IAA17374@nomad.yogotech.com> <2288.957418565@critter.freebsd.dk> <200005040801.BAA67715@apollo.backplane.com> Date: Thu, 04 May 2000 15:56:40 -0600 From: Warner Losh Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG In message <200005041411.IAA17374@nomad.yogotech.com> Nate Williams writes: : That's very different from what the GPS experts at SRI tell me. They : start to average things out in a matter of hours, and within a week can : have it almost gone. However, they're also using multiple satellites, : which allows them to more quickly find the center. The experts here tell me that professional surveyers get sub meter accuracy with in about an hour with commercially available hardware. This was with SA. He estimates that now it would take about 6-10 minutes to do the same thing since SA is turned off. It was very abruptly turned off if you look at the graph of the cutover. Looks like timing information from GPS is now +- 20ns or so. This is 10x better than with SA where the timing information was +- 200-250ns. These numbers are the average of all the birds in the sky at any given time. Warner To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message