Boas, eu uso porque todas as vezes que faço sincronização ele descarrega o ficheiro. (HTC Touch Cruise)
Agora vamos ver as defenições de "A-GPS" :
Conventional standalone GPS has difficulties providing a reliable positioning - for example, when surrounded by tall buildings (resulting in
multipath), or when the
satellite signals are weakened when a GPS device is used indoors or under trees. Some newer receivers are better at handling these situations.[
citation needed] In addition, when first turned on in these conditions, some non-assisted GPS units may not be able to download the almanac and
ephemeris information from the GPS satellites, rendering them unable to function until a clear signal can be received continuously for up to 40 seconds.
An A-GPS receiver can address these problems in several ways, using network elements such as either an
assistance server or other data from a network. That assistance generally falls into two categories: a) information used to more quickly acquire satellites, or b) calculations done remotely:
- The assistance server can locate the phone roughly by which cell site it is connected to on the 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 and/or almanac for the GPS satellites to the cell phone, enabling the cell phone to lock to the satellites faster in some cases.
- The network can provide atomic time (Accurate Time Assistance)
- Simply capturing a brief snapshot of the GPS signal, with approximate time, for the server to later process into a position.[2]
- By having accurate, surveyed coordinates for the cell site towers, it has better knowledge of 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)
Uma boa opcção para ver como é que trabalha é usarem o googlemaps mobile sem gps e ele faz a triangulação atravez das antenas GSM. Claro que a posição tem maior erro de localização.
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