GPS

[Tilman Baumann]

How accurate does this position information have to be?
With my own telephone numer, i could at least find out in which country 
i am.
Not so good for america, russia and brazil.
But in smaller countries, you culd get a ±500km position.

Al Johnson wrote:
> Gets my location wrong by 100 miles or so. Other GeoIP services put me in 
> other locations similar distances away. The BBC has had complaints from 
> people reported as being in a different country because it blocks them from 
> using the download service. Perhaps this only affects a minority, so it's 
> another option to add to the list. If we have multiple sources we can see if 
> they agree.
> 
> On Monday 07 July 2008, Francesco Cat wrote:
>> Another thing that might help: If the FR is connected to any network
>> one should also be able to use IP Locator services like
>> http://whatismyipaddress.com/ to get another extimation of the
>> location of FR. They are usually quite accurate.
>>
>> Would this help?
>>
>> 2008/7/7 Yogiz <yogizz at gmail.com>:
>>> On Mon, 7 Jul 2008 15:37:08 +0100
>>> Al Johnson <openmoko at mazikeen.demon.co.uk> wrote:
>>>
>>> Thank you for the testing. Keep doing the good work.
>>> Hopefully this idea can solve the long fix problem.
>>>
>>>> First stab uses the example perl functions from ublox for generating
>>>> the aid-ini data, replacing their hardcoded x,y,z with values for my
>>>> location. The copyright notice on the example code says you can't do
>>>> anything with it without permission so I can't give you the script,
>>>> but I can tell you how to reproduce it ;-)
>>>>
>>>> Get the AssistNow online client application note from:
>>>> http://people.openmoko.org/matt_hsu/ImplementationAssistNowServerAndClie
>>>> nt(GPS.G4-SW-05017-C).pdf
>>>>
>>>> Create a new script aid-ini.pl and start with:
>>>>
>>>> #!/usr/bin/perl
>>>> print(clientdata_prepare());
>>>>
>>>> Go to section B - Sample Server implementation and append subroutines
>>>> clientdata_prepare and ubx_checksum to aid-ini.pl
>>>>
>>>> You need to replace the $posx, $posy and $posz values in
>>>> clientdata_prepare with some that match your location. These are ECEF
>>>> coordinated in m. There's an explanation of the calculation method in:
>>>> http://www.u-blox.com/customersupport/docs/GPS.G1-X-00006.pdf
>>>>
>>>> Alternatively you can use the attached spreadsheet if it survives the
>>>> list. Just replace the lat and lon with values for your location.
>>>>
>>>> You probably want to change the time accuracy to reflect the accuracy
>>>> of the Freerunner clock, and possibly the accuracy of your location
>>>> estimate.
>>>>
>>>> Now copy the script to somewhere suitable on the Freerunner and make
>>>> it executable. I'm using /usr/local/bin. You need to install perl if
>>>> you don't have it already:
>>>> opkg install perl
>>>>
>>>> Switch on the GPS then run the script:
>>>> /usr/local/bin/aid-ini.pl > /dev/ttySAC1
>>>>
>>>> If you cat /dev/ttySAC1 you should be able to see it using the
>>>> current time according to your Freerunner. TangoGPS makes it easier
>>>> to see what it's doing. In the only test I've managed so far it got a
>>>> fix with a poor view of the sky, while my Garmin Geko was still
>>>> struggling to see 3 sats. It wasn't quick, but it was better than the
>>>> Garmin. It would be interesting if you could try 2 units side by
>>>> side, one with aid-ini and one without, to see if it really makes a
>>>> difference or if I was just lucky. I'll try to get some more testing
>>>> in, but the weather isn't good here, and I don't want to get my new
>>>> toy wet ;-)
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