[QtMoko] adding agps support

[Paul Fertser]

tomas nackaerts <tomas.nackaerts at gmail.com> writes:
>> If the ephemiri data is fresh enough (2-4 hours max), the
>> effect is the same as downloading the data from the internet. Other
>> than that, there's no agps integration yet afaik.
>>
>
> Don't know why, but i thought this data was useful for a couple of
> days, not couple of hours

Almanac can be used for a couple of days, right, but almanac is not
used for the real fix (though some receivers can provide a rough
approximatation based on almanac), rather it's used to find to which
sattelites it's worth listening to to get their ephemeri (every
sattelite transfers its own ephemeri on its own channel). AFAIK modern
receivers can listen on all the channels at the same time (they have
enough correlators), so having almanac provides no advantage. In an
ideal conditions you can get a fix in ~40 seconds without any data.

U-blox has some "offline AGPS" trick allowing computation of ephemeris
for the nearest feature, but i haven't heard about anyone had it
working.

At least that's what i think about GPS atm, i might be wrong in some
details.

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