[maemo-users] Diablo released (AGPS)

From: Andrew Daviel advax at triumf.ca
Date: Thu Jun 26 10:28:06 EEST 2008
On Wed, 25 Jun 2008, Nils Faerber wrote:

> Using the ephimeris data from ublox a ublox Antaris 5 receiver can have
> a time to first after cold start of less than three seconds!

Now that's impressive! (thanks for the info; I stand corrected re. AGPS 
in non-cellphone devices..)

> We already wondered what this GUI is good for ;)
> Choosing your region? Oh well...

>From running supld on the command line (it normally runs as a daemon 
from startup) :

SUPL daemon version is Mon May  5 12:12:24 UTC 2008
SLP address: supl.nokia.com
SLP port: 7275
A-GPS srv address: supl.nokia.com
Position timestamp: 1214410112.000000
Position latitude: 49.162067
Position longitude: -123.119614
Position uncertainty: 300
Previous A-GPS req time: 0
Previous A-GPS req status: 0
A-GPS support: 1
NW INIT enabled: 0
Cached assistance data support: 1
Packet data for assistance data allowed: 1
Preferred connection id: Rogers Internet
SetId NAI: JohnDoe at nokia.com
Wimax BSID:
GSM Cell ID by BT support: 0
Debug SLP IP source: provisioned
Debug mode: 0
Debug log folder: /media/mmc2/supllog/

agps-ui allows you to choose the "preferred connection id" (it only 
offered my EDGE connection), but supld downloaded data over the WLAN.
agps-ui also has a checkbox to enable "Packet data ..". I presume it 
means "do you want to incur cellular data charges for downloading an 
ephemeris?". I don't know how to turn on debugging (DBUS?); nothing is 
written to /media/mmc2/supllog/.

I'm not sure where the positions came from; I suspect from the last 
position saved by gpsdriver. It's more accurate than geosearching my ip 

I think that supld is exchanging data on DBUS with gpsdriver; the new 
version links libsupld.so

I presume from this that some location data is 
available from WiMax on the new device, and also from the GPS cell ID. I 
know the cell ID is available from my 
Nokia cellphone (I had gnokii running on my laptop via USB, and I built 
it for the tablet), and I believe Google has been mapping
cell locations by driving around (Rogers told me the tower locations were 
confidential when I asked a couple of years back).

Pointing a browser at supl.nokia.com doesn't get you far; I don't know 
the path, and it may be using a client-side SSL certificate for

I haven't actually tried this much in real life so far. From what you say 
about ephemeris lifetime, I would hope to get a 30-second fix going 
outside from somewhere with WLAN but no sky (like my home, or office). I 
would hope that one could also take an 8-hour plane trip, then use 
agps-ui to set my approximate location, and get a fix in a minute or two 
instead of "never". If true, it should go a long way to fixing the GPS 
woes (thanks, Zoltan).

Andrew Daviel, TRIUMF, Canada

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