[Qgis-user] GPS issue on android tablet

[Zoltan Szecsei]

On 2014/06/04 11:07, Giuseppe De Marco wrote:
> hello, I've been using Qgis on android tablet (samsung galaxy tab 2)
> and I've been experimenting GPS connection.
> The issue is that even if Qgis finds and use several satellites (9 or more)
> precision never gets under 3.0 meters but what is strange is that
> coordinates value fro the same spot varies very widely:
> Time                Coordinates                       Altitude
> 14:39:36       41.69528959 13.26464738      343.1
> 14:39:54       41.69529880 13.26466761      341.8
> 14:40:06       41.69528519 13.26470222      340.4
> 14:41:18       41.69528944 13.26472418      341.1
> 14:41:42       41.69529608 13.26471821      341.8
> 14:41:54       41.69530621 13.26470892      342.5
>
> I have colleagues who have experienced the same.
> Has anyone else experienced the same issue?
> Is that depending on GPS device or could it be a software related
> issue?
>
There are probably 10000 reasons for this.
I am surprised that you even think you are getting sub 5m accuracy.
Please plot the points on a cadastral map (or some basemap that is 
"guaranteed" accurate) and see what you are really getting.
You also don't say whether you are in a tree'd or urban (or whatever) 
area - but observing 9 satellites suggests somewhere in the open.

For professional GPSes, to get sub 10cm accuracy, you need to observe 
for 30-60 minutes, and do post processing.

I am not a surveyor, so my info may be not 100% - Please can a surveyor 
or someone well experienced in these issues chip in.

Regards,
Zoltan

-- 

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Zoltan Szecsei PrGISc [PGP0031]
Geograph (Pty) Ltd.
GIS and Photogrammetric Services

P.O. Box 7, Muizenberg 7950, South Africa.

Mobile: +27-83-6004028
Fax:    +27-86-6115323     www.geograph.co.za
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