Re: GPS tracking

From: HSHK (
Date: Tue Feb 10 2004 - 14:42:01 EST

  • Next message: Amaury Jacquot: "Re: GPS tracking"

    Should have read...
     would "shoot the stars" with a sextant and...
    Bill KA8VIT
    *********** REPLY SEPARATOR  ***********
    On 2/10/2004 at 2:38 PM HSHK wrote:
    >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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