Re: GPS tracking

From: HSHK (
Date: Tue Feb 10 2004 - 14:38:00 EST

  • Next message: HSHK: "Re: GPS tracking"

    Inside GPS really won't work.  At the frequencies GPS uses
    the attenuation by the buildings will be significant and you probably
    won't get a lock.
    Also, any "bouncing" or propagation of the GPS signals will increase
    the time they take to reach the receiver thus causing error
    in the positon the GPS unit calculates. 
    GPS satellites themselves do not track anyone.  They send out
    identifiable signals along with a very accurate time signal and
    the satellite's current postion.
    The signals from 3 or more satellites are received by a GPS unit,
    then the GPS unit, using the encoded time signal, the sat's known
    postion, then figures out how long it took for the signal to hit the
    GPS unit.
    It then triangulates this into postion information...  the same way a sea
    faring navagator would "shoot the starts" with a sextant and a book
    of star positions and triangulate his position.
    If the signals to a cell phone in the tube, took a few bounces before
    the cell phone...  you would never notice the propagtion delay.
    In GPS, the propagation delays would result in errors to great for
    your (or most any) application.
    Bill  KA8VIT
    *********** REPLY SEPARATOR  ***********
    On 2/10/2004 at 7:23 PM Stan Wijnans wrote:
    >This might be the wrong list, but I thought I try as I think somebody 
    >might know !
    >I am interested in developing a GPS tracking system to trigger people 
    >for an art project. I'm trying to find out if this is possible inside a 
    >building as I am aware that GPS tracking has already been developed for 
    >outside but seems to be weak inside  ...
    >Does anybody know how to make the GPS sensitive enough to go through 
    >walls, do I need a differential GPS or has anybody suggestions ? I have 
    >seen people on mobile phones in the tube in Asia, so something should 
    >be possible .... but how :-)) ??
    >Any help is much appreciated
    >Thanks, Stan
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