[Qgis-user] Finding Points which do not overlay

[Damien Stephens]

My suggestion would be to create a buffer of 3m around your original points. (vector/geoprocessing/buffer
That creates a new vector table. (vector Buffer)
Load the new vector table is it isn’t already
Then do a spatial query select source features from: new points table
Where the feature: within
Reference features of : vector buiffer

Open the attributers table  of you new points table then click on the invert selection  button (yellow triangle  with two green arrows in a circle.)
Should give you all the points that have moved, assuming that your original points were more than 3 metres apart.

Then if you want them as a separate table, just edit/copy
Then edit/paste features as
Cheers
Damien




From: qgis-user-bounces at lists.osgeo.org [mailto:qgis-user-bounces at lists.osgeo.org] On Behalf Of Carlos Cerdán
Sent: Tuesday, 23 September 2014 3:44 AM
To: henrik_f
Cc: qgis-user at lists.osgeo.org
Subject: Re: [Qgis-user] Finding Points which do not overlay

Hi Henrik:

If you still don't solve your issue, perhaps you can try this:

1. If you don't have it, Calculate X and Y coords. for your two layers

2. Make a table union, in layer properties

3. Create two new fields for calculate difference of coordinates (Xi - Xj) and (Yi - Yj)

4. Calculate the absolute distance between points in a new field, with the two previous.

5. This last field is your criterion about absolute difference between points.
Good luck

Carlos Cerdán




2014-09-19 9:35 GMT-05:00 henrik_f <henrik.feltens at gmx.de<mailto:henrik.feltens at gmx.de>>:
Hey,
So I will get right to the problem I have.
I have two different Layers with the same content from different times. Now
I want to know which points changed their location and which have been added
or deleted so I just wanted to find the points which do not overlay by using
Vector -> Geoprocessing Tools -> Difference
(I wasnt sure if the one I was looking for was Symetrical Differnce so I
tried both)
I then realzied that not a single point was overlaying due to the fact that
the points that should have the same location were all seperated by about 3
meters.

Pictures: In the first picture you see a red point. Out of these kind of
points I want to make a new layer. The second picture is a zoomed in version
of the area highlighted in the first one.

<http://osgeo-org.1560.x6.nabble.com/file/n5162929/Pic1.png>
<http://osgeo-org.1560.x6.nabble.com/file/n5162929/Pic2.png>


Here is my question: How do I find the points which are not in distance of
3m to each other?
I made some attempts with buffers and the difference tool again but non
worked.
Does anyone have an idea?

Greetings
Henrik



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