GPS

[Kai Römer]

Hi Al,
If you need testers, please contact me. I have several gta02v5
available and can do tests in Germany Munich.

thanks
Kai

2008/7/7 Al Johnson <openmoko at mazikeen.demon.co.uk>:
> I'm not saying there isn't an antenna issue, but that we may be able to
> mitigate the effects on startup time.
>
> On Monday 07 July 2008, Kai Römer wrote:
>> Hi Al,
>>
>> Sounds really convincing, but how do you explain the constantly fast
>> fix via external antenna then. I really think its an antenna issue.
>>
>> Also the difference of the GPGSV values support this idea.
>>
>> Tomorrow evening i will ask a specialist to check the antenna signal
>> qualities. Maybe a cable is broken or there is a short circuit on the
>> main board.
>>
>> I ll report about the results.
>>
>> CU Kai
>>
>> 2008/7/6 Al Johnson <openmoko at mazikeen.demon.co.uk>:
>> > 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
>
>
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