GPS

[Yogiz]

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/ImplementationAssistNowServerAndClient(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 ;-)