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[aprssig] GPS Signals in a Tunnel?

Stephen H. Smith wa8lmf2 at aol.com
Sun Nov 25 23:31:40 UTC 2007


Ralph Milnes wrote:
> I'm curious -- while driving through the Lincoln Tunnel (New York City) the
> other day, my GPS seemed to be accurately tracking where I was in the
> tunnel. 
>
> Was it really getting some GPS signals? How?
>
> I'm pretty sure my 2m APRS beacon didn't make it out of the tunnel, however.
> :-)
>
>
>   
 Most GPS devices will dead-reckon for 15-30 secs when they loose the 
satellite signals. Typically, in a tunnel, this would tend to be the 
same speed and heading you were on before you entered since most tunnels 
are straight.  This would tend to look as through the GPS is still 
tracking. 


--

Stephen H. Smith    wa8lmf (at) aol.com
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