thoughts on A-GPS offline

mqy meng.qingyou at
Tue Feb 17 12:28:59 CET 2009

Should be. I think the major consideration of u-blox A-GPS is to speed up
TTFF, decrease the TTFF from at 40 seconds or so to 10 seconds or so. A-GPS
online needs network connection, if network connection is unavailable,
AssistNow offline or something else are expected to provide initial aiding
data such as almanach and/or ephemeris.

Most of the time user know his/her location, but may unable to get GPS fix
due to bad environment (e.g. buildings). If we have aiding data, we can
submit them to GPS chip. What data to submit depends on your current
location and time. Location can be specified by (1) picking up from map, (2)
or last valid location recorded by GPS software (3) or from phone network
(some service providers provide this kind of service with charge fee).

I think get locations by cell id is especially useful in case of weak or no
GPS signals.
I'll have a look at opencellid, thanks.

Rikard Nilsson wrote:
>> What about if we hack the data format of u-blox AGPS offline file, and
>> extract data for current location and time? location can be specified by
>> clicking map, time from local system time. If we could, we would be able
>> to
>> submit data to GPS chip as AGPS online message on demand. What do you
>> think?
> Wouldnt it be possible to get the location from the gsm-network in some
> way?
> /Rikard
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