GPS sensitivity

Nishit Dave stargazer.dave at
Mon Oct 27 17:00:22 CET 2008

On Mon, Oct 27, 2008 at 9:18 PM, Alastair Johnson <alastair at>wrote:

> Stefan Monnier wrote:
> > The FR is the first device I use with a GPS, so I don't know what's
> > considered as "normal" w.r.t GPS function.  I find that my FR's GPS
> > never works inside a building (e.g. at home), and even outside in the
> > streets of Montreal, it seems to only be able to get a first fix if I'm
> > in a somewhat open area (i.e. not in a street but on a place, in
> > a park), and also it seems to rarely if ever be able to get a first fix
> > when it's in my pocket.
> >
> > Is that normal?  My FR does have the capacitor in the µSD slot and it
> > has a fairly recent kernel (don't know if that means it has the software
> > fix that "stops the µSD clock when possible", does it?)
> It's a little tricky to describe 'normal' since the movement of the sats
> gives some inherent variability. Getting the first fix also requires
> significantly more signal than maintaining a fix once acquired, and it
> seems to help being stationary when doing it. I don't know how limited
> the view of the sky is in Montreal, but 'urban canyon' effects have long
> been a problem for GPS systems due to limited view of the sky (can't see
> enough sats) and multiple reflected signals. That said, since the SD
> clocking fixes were added to the kernel I find the Freerunner usually at
> worst as quick as my Garmin Gecko at getting a fix, and substantially
> better at keeping it. The Freerunner will often keep a fix indoors when
> the Gecko hasn't a hope. OTOH the Gecko is hardly state of the art now,
> so expectations may be different.

I recently tested the performance of a Nokia E71 with the FR, while standing
2 feet from a window inside my office building.  Most of the view (line of
sight) was obstructed by another large building 200 ft away, although the
sky over it can be viewed from the said window.

The Nokia got a fix and started to download maps with google maps in 15
seconds.  I was unsuccessful in getting the FR to register a fix at the same
position for greater than 15 minutes, after which the experiment was
stopped. Qtextended 4.4.1, MappingDemo used.  The FR version I use is from
the time when the software fix to the hardware problem was about to be
released.  The FR still takes some minutes to get a fix when in a moving
vehicle, and anywhere inside a building, it is as if it never worked.

Nothing new.
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