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
--
===========================================
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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