On Fri, 6 Dec 2002, Eugen Leitl wrote: > It is possible to do relativistic pings (time of flight mutual > triangulation) with ~cm accuracy. 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). > This is something ultrabroadband/digital pulse radio best excels in. > Here you don't even need base stations, as the architecture is ad hoc: > if you're in the area, you're a node in a mesh. 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, 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? > Base stations don't need ephemerides nor nuke clocks, being statical. > Their mutual drift will be ~mm year tops. 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? -Chris You know what time it is? It's Twiddler o'clock! -- 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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