[OSM-newbies] GPS inaccuracy

[Stephen Johnson]

----- Original message -----
> Isn't the assisted technology just for the initial lock procedure?
> AFAIK the A-GPS gets the GPS information from the cellphone towers
> GPS's in order to find the satellites over my head faster.
>
> I tried to use a bluetooth GPS receiver on my N800, but 10~20 minutes
> to lock when I'm used to 30s are a great hands down.
>
> []
>
> 2009/6/9 magnus at sonic2000.org <magnus at sonic2000.org>:
> > > Anyway, I did this with my Nokia 95 and WhereAmI+ software (will try Sports
> > > Tracker next too), but this wild > result doesn't seem good enough to do
> > > mapping with.
> >
> > > Is this because I have a rubbish GPS receiver or could it be that the
> > > buildings of Islington are causing sufficient reflection/disturbance to the
> > > signal?
> >
> > That is exactly why you will never get a great accuracy with just the N95. It
> > has a A-GPS system built in, which most phones with internal GPS has. I
> > recommend spending a little money on a external Bluetooth GPS receiver.

Correct. Assisted-GPS just helps with getting data for which satellites are current visble in the sky overhead. One the GPS is locked on, it will just as accuate as other unit (within the limits of the GPS chip). Accuracy of the GPS unit is greatly affected by line of sight to the satellite constellation, trees and other foliage around, etc. Those factors will affect all GPS units.

--
Stephen Johnson <sjohnson at monsters.org>