From owner-freebsd-hackers Wed May 3 12:57:19 2000 Delivered-To: freebsd-hackers@freebsd.org Received: from ns.yogotech.com (ns.yogotech.com [206.127.123.66]) by hub.freebsd.org (Postfix) with ESMTP id BDAB637BE2D for ; Wed, 3 May 2000 12:57:15 -0700 (PDT) (envelope-from nate@yogotech.com) Received: from nomad.yogotech.com (nomad.yogotech.com [206.127.123.131]) by ns.yogotech.com (8.9.3/8.9.3) with ESMTP id NAA02186; Wed, 3 May 2000 13:57:09 -0600 (MDT) (envelope-from nate@nomad.yogotech.com) Received: (from nate@localhost) by nomad.yogotech.com (8.8.8/8.8.8) id NAA01354; Wed, 3 May 2000 13:57:08 -0600 (MDT) (envelope-from nate) Date: Wed, 3 May 2000 13:57:08 -0600 (MDT) Message-Id: <200005031957.NAA01354@nomad.yogotech.com> From: Nate Williams MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit To: Alexander Langer Cc: Matthew Dillon , hackers@FreeBSD.ORG Subject: Re: GPS heads up In-Reply-To: <20000503200006.A35116@cichlids.cichlids.com> References: <200005031744.KAA63550@apollo.backplane.com> <20000503200006.A35116@cichlids.cichlids.com> X-Mailer: VM 6.34 under 19.16 "Lille" XEmacs Lucid Reply-To: nate@yogotech.com (Nate Williams) Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG > > satellites sitting thousands of miles away in the sky. It's even more > > impressive to see the government do something right for a change! > > It's much more idiotic that the government prevented it before. > > That just means that military use is even better already, i.e. I just > imagine they are at 1m or less already. Actually, it's *REALLY* hard to get less than 1m accuracy using the frequencies that are currently in use. And, it's *really* easy to get better than standard if you're willing to spend a bit of $$, so I suspect the reason they turned it off is because anyone truly motivated can get better accuracy, so the only losers with SA are the consumers. My former employer (SRI) has done lots of research, and have gotten a receiver good to 1cm, but it takes about 24 hours for it to 'synchronize' to that accuracy. With dual receivers, you can get 2-3 mm accuracy by comparing the wavelength offsets, but it's really, really, really expensive to build the hardware, and there's very little practical use for that kind of accuracy. Nate To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message