Influence of WiFi on GPS readings (200m error)

C R McClenaghan chris at
Mon Jul 21 16:54:56 CEST 2008

I'm not sure where the fault lies, but with tangogps, I seem to get a  
scatter plot displayed for my position. Initially the fix seems  
accurate, then it starts to wander, although I may not be. If I am  
moving, the trial doesn't seem to follow the route I've taken. I think  
it may be tangogps, but I thought I'd try using my garmin bluetooth in  
a "side by side" kind of test to see whether it is tangogps or the gps  


On Jul 21, 2008, at 12:02 AM, Russell Sears wrote:

> I've had this problem when the initial fix was obtained while I'm  
> inside
> a vehicle (such as a bus or car) or near a lot of metal.  Going to a
> complete stop, then moving a few times (in the car) seems to give the
> chipset a better chance to realize it's got a bogus fix.
> -Rusty
> Yaroslav Halchenko wrote:
>> Hi All,
>> Finally I got to play with FR. Flushed todays (0721) dev image and  
>> kernel.
>> Running TangoGPS. While WiFi is on (WEP encrypted. wpa_supplicant
>> powered ;)) I am having location error (never hit the right spot)  
>> around
>> 200-400m with reported speed from 0.5 to 20 km/h (while I am siting
>> steadily in 1 place).
>> When I turn WiFi Off (just on my FR, without touching access point  
>> or a
>> laptop from which I am writing) -- location moves to the right spot  
>> with
>> a bias of 10m or so.
>> Therefore, the question: is that expected? ie that we can't rely on  
>> GPS
>> readings while WiFi is on?  Or from the other side: what is
>> 'documented' precision in GPS readings while WiFi is enabled (and not
>> actually very actively used, if used at all  since I guess TangoGPS
>> already had those tiles from OSM downloaded).
>> Or may be it is just my FR which behaves that way? Did anyone observe
>> any similar behavior?
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