GPS sensitivity

Iain B. Findleton ifindleton at
Mon Oct 27 17:26:05 CET 2008

I find the FR more or less equivalent to other GPS devices I have. The
biggest factor I notice is weather conditions. In overcast conditions I
can use the GPS anywhere inside my house, as well as outside. Under
clear sky conditions, the GPS will only work outside and will not
acquire a first fix unless I am more or less in the open, away from
trees, houses, etc.

Some people claim that there are newer GPS chips that work better.
Perhaps its the nature of the beast.

Nishit Dave wrote:
> On Mon, Oct 27, 2008 at 9:18 PM, Alastair Johnson
> <alastair at <mailto: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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Iain B. Findleton
Tel: 514-457-0744

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