Date: Wed, 3 May 2000 13:57:08 -0600 (MDT) From: Nate Williams <nate@yogotech.com> To: Alexander Langer <alex@big.endian.de> Cc: Matthew Dillon <dillon@apollo.backplane.com>, hackers@FreeBSD.ORG Subject: Re: GPS heads up Message-ID: <200005031957.NAA01354@nomad.yogotech.com> In-Reply-To: <20000503200006.A35116@cichlids.cichlids.com> References: <200005031744.KAA63550@apollo.backplane.com> <20000503200006.A35116@cichlids.cichlids.com>
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> > 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
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