Date: Sat, 06 May 2000 12:07:10 -0700 From: Mike Smith <msmith@freebsd.org> To: nate@yogotech.com (Nate Williams) Cc: Mike Smith <msmith@FreeBSD.ORG>, hackers@FreeBSD.ORG Subject: Re: [OT] Finding people with GSM phones (was Re: GPS heads up ) Message-ID: <200005061907.MAA07403@mass.cdrom.com> In-Reply-To: Your message of "Sat, 06 May 2000 12:50:04 MDT." <200005061850.MAA18384@nomad.yogotech.com>
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> > Well, assuming they have 100% antenna overlap (not unlikely) you could > > just do phase comparisons between the antennae getting the squirt. If > > these guys are as smart as you say (and I have no doubt at all about > > that), 25m at near distance is probably not unrealistic. > > True. Up close, you can triangulate. You can do it further out, too, the issue is angle (and accuracy of measurement of the angle). We used to do something similar for tiny grains of dust hitting the stratosphere using nothing more than a few pieces of clothesline wire; the dust doesn't do TDMA but the principle is the same. 8) > > Ask him if they can still do it at 35km out (the outer limit for a normal > > GSM cell). That'd really spook me. 8) > > He wasn't interested in talking about it when I started asking about > single cell towers, so I never pressed him on the issue. Maybe he was > afraid that the 100m accuracy claim would be found out to be un-doable, > but the Feds claim 'it must be that accurate', and they aren't > interested in spending the $$ for GPS receivers in the handhelds. What's the actual background behind this? The FBI wants to be able to track down people using cellphones? I assume that it's all hidden behind some "public safety" smokescreen, right? -- \\ Give a man a fish, and you feed him for a day. \\ Mike Smith \\ Tell him he should learn how to fish himself, \\ msmith@freebsd.org \\ and he'll hate you for a lifetime. \\ msmith@cdrom.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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