[OSM-talk] fwd: Two thirds of mobile users wantdriving ANDwalking navigation

John F. Eldredge john at jfeldredge.com
Tue Feb 16 20:24:45 GMT 2010

In the case of metal, even a thin film or mesh can block RF signals if any openings are smaller than the wavelength of the signal.  Look up "Faraday cage".

John F. Eldredge -- john at jfeldredge.com
"Reserve your right to think, for even to think wrongly is better than not to think at all." -- Hypatia of Alexandria

-----Original Message-----
From: "Dave F." <davefox at madasafish.com>
Date: Tue, 16 Feb 2010 17:46:21 
To: John Smith<deltafoxtrot256 at gmail.com>
Cc: OpenStreetMap talk mailing list<talk at openstreetmap.org>
Subject: Re: [OSM-talk] fwd: Two thirds of mobile users want
 driving	ANDwalking navigation

John Smith wrote:
> On 17 February 2010 01:40, John F. Eldredge <john at jfeldredge.com> wrote:
>> Frequently you can't get a position fix at all, if the building has much metal in its structure.  I can't get a position fix from inside my house unless I am near a south-facing window, probably due to a metallic-foil vapor barrier in the attic.
> It has little to do with the material it's made of, it's all about how
> much mass an object has, the more mass the more it will absorb RF.
Is this correct?

I assumed the reason I had trouble getting reception on board trains
because of what their roofs were screened with.
I can't believe they'd put much mass up there.

Dave F.

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