"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 <[EMAIL PROTECTED]> 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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