GPS <--> AGPS

[Flyin_bbb8]

"An *A-GPS* receiver can address these problems in several ways, using
an *Assistance
Server*:

   - The Assistance Server can locate the phone roughly by what cell
site<http://en.wikipedia.org/wiki/Cell_site>it is connected to on the
cellular
   network <http://en.wikipedia.org/wiki/Cellular_network>.
   - The Assistance Server has a good satellite signal, and lots of
   computation power, so it can compare fragmentary signals relayed to it by
   cell phones, with the satellite signal it receives directly, and then inform
   the cell phone or emergency services of the cell phone's position.
   - It can supply orbital data <http://en.wikipedia.org/wiki/Ephemeris> for
   the GPS satellites to the cell phone, enabling the cell phone to lock to the
   satellites when it otherwise could not, and autonomously calculate its
   position.
   - It can have better knowledge of
ionospheric<http://en.wikipedia.org/wiki/Ionospheric>conditions and
other errors affecting the GPS signal than the cell phone
   alone, enabling more precise calculation of position. (See also Wide Area
   Augmentation
System<http://en.wikipedia.org/wiki/Wide_Area_Augmentation_System>)
   "

Info from http://en.wikipedia.org/wiki/AGPS ,    (I'm not 100% sure about
the precision but at least that's what alot of people have told me, and so
does other websites ), have you run any tests yet Joerg?

I know they do use D-GPS in other industries other than aviation that's
exactly why i said mainly and not only, go ahead and tell me why they made
D-GPS in the first place, and then added the small error in it by the
department of defense of the US :)

On Fri, Jun 6, 2008 at 7:46 AM, Joerg Reisenweber <joerg at openmoko.org>
wrote:

> Am Fr  6. Juni 2008 schrieb Flyin_bbb8:
> > just wanted to add, Differential GPS is mainly for aircraft GPS systems
> to
> > get better guidance on the ILS (Instrument Landing System).
> >
>
> Aaaaha, I seen it being used for all sorts of archeology and buildings
> construction purposes.
> And from the info in the uBlox-paper, regarding the protocol options it
> doesn't seem to me like there is much chance for better precision by the
> way
> they do A-GPS.
> Better precision would mean info on meteorological interference (like exact
> amount clouds on the way to sat) at the very location of the receiver. To
> get
> this, you need... a reference receiver, so we are at D-GPS again.
>
> /j
>
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