GPS

[Al Johnson]

From what I've seen on the wiki the version of the Antares4 on the GTA02 
doesn't have the memory needed to store almanac and ephemeris, last known 
position or time. This means that every start is a true cold start, unlike 
every other reasonably modern GPS we're comparing it to. It starts up 
thinking the time is midnight on 30th November 1999 and seems to need a fair 
bit of decent signal to convince it otherwise, contributing to the long 
startup time.

It looks like there is a way around this if you look at the documentation for 
the assist. The AID-INI message needn't be supplied by a remote server; we 
can generate it locally to provide the sort of data that's stored internally 
most of the time. At the very least we have a fair idea of the current time 
and date. We should also be able to store location, almanac and ephemeris 
when we shut down the GPS, and provide it at the next startup. We can also 
have a stab at current location, based perhaps on cell ID or wifi data as 
discussed by some of the other threads, or on user input.

I'll try to patch together something to do this based on the example perl 
client and server code, and see how much difference it makes. 

On Friday 04 July 2008, Kai Römer wrote:
> I can affirm this for 6 opemoko devices. i guess its an internal
> antenna issue. as soon as you connect a external antenna to it works
> like a charm. but fur me thats no solution.
>
> TTFF with external antenna (perfect condition): 40 to 60 seconds
> TTFF with internal antenna AGPS (perfect condition): more than 1:20
> minute but not always. its like gambling.
>
> I guess a miss design of the internal antenna.
>
> CU Kai
>
> 2008/6/23 Peter Kraker <peter.kraker at volja.net>:
> > This timings are insane unless you don't even have a valid almanac, which
> > is rare. This doesn't look right.
> >
> > Yorick Matthys pravi:
> >
> > Marcus Bauer said:
> >
> >
> > My experience with the Freerunner is ~12 minutes TTFF (time to first
> > fix) without use of agps and ~4-8 minutes TTFF with agps from
> > agps.u-blox.com using the software from openmoko.
> >
> > The Neo1973 (GTA01) had a TTFF without agps assistance of ~2 min.
> >
> >
> > 12 minutes without AGPS and 4-8min with AGPS??
> > I hope there was a thunderstorm inside the basement where you tested
> > this...
> >
> > :)
> >
> > Seriously, these just don't seem realistic.
> > Compare them for example with some other devices from 2003:
> > http://www.pocketgpsworld.com/ttffcomparisons.php.
> > Or from ublox: http://www.u-blox.com/technology/assistnow/ (table at the
> > bottom of the page)
> >
> > Surely there must be something wrong with your
> > software/settings/hardware/environment...
> > (or maybe they still have a lot of work to do on the GPS :))
> >
> > y