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

[Gora Mohanty]

On Tue, 16 Feb 2010 18:29:10 +0000
Graham Jones <grahamjones139 at googlemail.com> wrote:

> You are both right.  RF absorption is a combination of amount of
> material and its properties.   I think the issue with trains is
> limited to newer ones with special windows (I think they are
> conductive - some cars have them too).  The combination of
> shielding from the roof and windows makes it practically
> impossible to get a fix.   I was surprised that I managed to get
> a fix in a jet aircraft a few months ago - I would have expected
> this to be a good shield too.
[...]

You were probably sitting in a window seat, right? Getting a fix
from a window seat is usually not a problem, but I was not able
to get a fix elsewhere. I have tracks from several flights in
India.

As long as the windows are glass, or transparent to radio-frequency
waves, the GPS signal will diffract in, as the wavelength is much
larger than the size of the window. However, there are probably
issues like reflections within the cabin, how many satellites are
visible from the window, etc.

Regards,
Gora