[OSM-talk] fwd: Two thirds of mobile users want driving ANDwalking navigation
jochen at plumeyer.org
Tue Feb 16 19:52:48 GMT 2010
On Mar 16 Feb 2010, ce-test, qualified testing bv - Gert Gremmen wrote:
> No it ain't correct.
> Satellite signals are blocked by conductive materials
> such as metals, and to a limited extend by materials
> containing humidity (= limited conductivity) such as leaves
> and possibly concrete.
> Due to their high frequency GPS signal tend to behave like light,
> meaning that when there is metal in the line of sight between
> GPS and satellite, there is decreased reception quality.
> Most satellites can be seen (in west Europe and USA) in the southern
> direction, and an uncovered horizon will give better signals.
I just want to add, that as well meshes of conductive material with a mesh
distance narrower than about 19 cm will tend to block GPS signals (most but
not all steel armed concrete).
19 cm = lambda = c/f = 3*10^8/1575.42 m/s/Mhz
It seems there are certain GPS chips (SiRFstar-III) that use additionally
other GPS channels/ protocols and are capable to compensate signal loss of
the main GPS channel.
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