Increasing GPS accuracy with EGNOS

Baruch Even baruch at
Wed Oct 7 12:20:19 CEST 2009

Christian wrote:
> Al Johnson schrieb:
>> On Sunday 04 October 2009, Erik Lundin wrote:
>>> Good news, indeed. Does the Neo FreeRunner support EGNOS signals? Both
>>> the hardware and software?
>> According to this the Antaris 4 is capable of using WAAS, EGNOS and MSAS, 
>> collectively known as SBAS, and the signal is received through the GPS 
>> antenna. By default it is enabled, with one search channel, although this can 
>> be configured through the ubx protocol. The status can also be shown in ubx 
>> messages. This is probably worth checking to see what is actually happening 
>> when in Europe, as when it was written EGNOS was in test mode, and its use was 
>> disabled by default. It is unclear whether this was because of a 'test mode' 
>> flag in the signal or hardcoding in the firmware.
> I found this in the source of ogpsd on my Freerunner:
> def initializeDevice( self ):
>     # Use high sensitivity mode
>     #self.send("CFG-RXM", 2, {"gps_mode" : 2, "lp_mode" : 0})
>     # Enable use of SBAS (even in testmode)
>     self.send("CFG-SBAS", 8, {"mode" : 1, "usage" : 7, "maxsbas" : 3,
> "scanmode" : 0})
> So it seems that SBAS has always been enabled even in test mode. Does
> anybody know where we can get information if sbas is really active and
> used by the chip?

The comment is wrong, the mode value of 1 means that it uses SBAS but 
not if its in test mode. The comment is a left over from the time the 
value was 3, but then the whole line was commented out.

You can get SBAS status messages if you set it in the debug interface with:
mdbus -s org.freesmartphone.ogpsd /org/freedesktop/Gypsy 
org.freesmartphone.GPS.UBX.SetDebugFilter NAV-SBAS True

and then listen to the signals with:
mdbus -l -s rg.freesmartphone.ogpsd /org/freedesktop/Gypsy

Look for DebugPacket signals.

I tried it for other signals, didn't have time yet to test if it works 


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