On Fri, 6 Dec 2002, Christopher Allen wrote: > Yes, it is possible. But not without accurate clocks located onsite at > each of multiple beacons (or at each of multiple receivers, depending > on whether one is measuring ping time from cell towers to vehicle or > from vehicle to cell towers). The clock doesn't have to be accurate as not much time passes during a relativistic pingpong over ~km distances. After all, you're clocking 300 Mm/s, after all... > This is a mesh that doesn't know where it's nodes are if said nodes > don't each and independently know exactly what time it is. "Gentlemen, While it is possible to achieve a much higher aggregate precision by synchronizing a distributed cloud of oscillators this is strictly unnecessary. Even bad oscilators don't drift much during ms to us duration. > let's syncronize our watches." Why do heavily choreographed > organized-crime scenarios require each node to wear a syncronized > watch if it isn't imperative for the successful execution of the crime > scheme that each node at all times know exactly what time it is? Because mutual positioning is a crime comitted in a very brief, immediate time slot. > The onboard atomic clocks don't just tell us where -- with the help of > precalculated, periodically calibrated, time-plotted trajectories -- > GPS satellites are. The atomic clocks tell us when their time code was > launched, so we the receivers of the time code can figure out where we > are, based on that and on the satellites' separately calculated > positions. What are you going to do with a piece of time code or a > ping, even if it was broadcast from a stationary beacon of known > accurate location, if you don't know what _time_ it was broadcast? Because it is not being broadcast. The ID of the node doing a pingpong is encoded in the signal. That signal is only visible in a very short range, and ideally only to the node you're pinging (directional aerials or optics for ~VIS range). You're mired in the GPS old-think, which is based on expensive birds high above, which are centralistic and a single point of failure (are operated by people who can and do degrade service of make it unavailable at certain times in a certain area). Check out http://www.aetherwire.com/ -- Subscription/unsubscription/info requests: send e-mail with subject of "subscribe", "unsubscribe", or "info" toWear-Hard Mailing List Archive (searchable): http://wearables.blu.org Please, *PLEASE* don't subscribe through a forward/expander/false domain
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