thoughts on A-GPS offline

Helge Hafting helge.hafting at
Fri Feb 20 11:57:51 CET 2009

Cédric Berger wrote:
> On Wed, Feb 18, 2009 at 17:49, Al Johnson <openmoko at> wrote:
>> I may be misunderstanding the suggestion, but I don't think it had anything to
>> do with data from ublox. The suggestion was to use data sent by other
>> freerunner users instead of the data supplied by ublox.
> As I understood the suggestion was in reply to :
>>> It is not a problem that user account is required when download u-blox online
>>> aiding data.
>> It is a problem since u-blox might go out of business and you might
>> not want to tell them where you are all time. Their server also might
>> be down. There are plenty of reasons to remove dependency to any
>> single party.
> The problem is that data from u-blox is a proprietary format, and as
> far as I know, we do not know yet how to create the same data that can
> be pushed to the GPS chip.

As far as I know - we do know the format. The SHR distribution
already saves such data before turning the gps off, and restores it when 
you turn it on so you get the first fix quicker.

Not all the data is used at the moment, because the process sometimes 
fail yelding long startup times. But that should only be a debugging 

It is already possible to set up a free server for almanac data, as 
saving and loading almanac data works well and speed up TTFF some.

Helge Hafting

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