Date: Thu, 04 May 2000 15:56:40 -0600 From: Warner Losh <imp@village.org> To: nate@yogotech.com (Nate Williams) Cc: hackers@FreeBSD.ORG Subject: Re: GPS heads up Message-ID: <200005042156.PAA43697@harmony.village.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>
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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
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