GPS

[Federico Lorenzi]

An interesting idea would be to acquire a fix, then bring the phone
under cover, so it loses the fix, then bring it back in the open and
see how long it will take to reacquire the fix.

On 7/7/08, Kai Römer <smirfi at googlemail.com> wrote:
> 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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