Zoltan,
I suggest you create a Csv file and plot the points on a large scale map
or hi-res satellite image.
You say "varies very widely", a quick check indicated the max. variation
between your points is approx 8m and the min. approx 1m.
I would say if you are getting 3m GPS accuracy that is pretty good if
you are outside the US or Europe. I assume you are using a dedicated
GPS unit attached to your Tablet and not a built-in GPS on your Tablet.
Bear in mind that the 3m accuracy deviation (imagine a 3m radius circle
from where you mark the point) can be in any direction, so if you are 3m
E out with first reading and 3m W with the second reading the error
between the point could be 6m.
Mike
On 04/06/2014 10:14, Zoltan Szecsei wrote:
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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