I have a layer (currently the source is a csv file) with 130,000 points. Many of these points are co-located in a building room.

How can I identify points that are within a small distance of another point on the same layer? Basically I want to add a buffer around each points and then only display points where the buffer is touching another.

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    Welcome to GIS.se! What is the overall process and result you're expecting? You mention 'co-located' in the title - will you try to reduce points to a limited set of clusters? – Simbamangu Feb 23 '16 at 17:48
  • Not exactly. I just want to highlight/segregate the points that are co-located. They will still remain as separate points. – DoDo1975 Feb 23 '16 at 18:06
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    Lets try >> Vector>Geoprocessing>Buffer with dissolve function and next spatial query with points and dissolved buffer. – Artec Feb 23 '16 at 20:25
  • I am doing something wrong because even after converting to a shapefile my buffer is just a giant polygon covering the entire screen. – DoDo1975 Feb 24 '16 at 0:05
  • Could you post an image of a section of the points, and highlight examples of how you will decide if they are co-located? You have a better chance of getting an answer (or solving it yourself) if you give more information about the exact steps and decisions you'd like to make about these points. – Simbamangu Feb 24 '16 at 5:09

Make sure the CRS you use for your points layer is measured in meters. You can change the CRS by right-clicking the points layer and selecting the Save As... option. Then:

  1. Apply a buffer with a specified distance. I made an example:

    Points and buffer layer

  2. Duplicate the buffer layer (right-click buffer layer > Duplicate):

    Duplicated buffer layer

  3. Use the Spatial Query plugin.

    • Installed from Plugins > Manage and Install Plugins
    • Accessed from Vector > Spatial Query

      Select the relevant layers as shown in the image (the overlaps function worked for me) then click the button which to Create layer with list items**:

    Spatial Query

  4. The output should show the buffers which touch each other:

Buffer output

  1. To select only the points inside those buffers, you can run another Spatial Query using the original points layer to find the intersection with the overlapping buffer layer:

    Another spatial query

    You can then close the window to see all the selected points inside those touching buffers (shown as yellow points):

    Selected points

    There are a number of ways to extract those points inside the buffers such as creating another layer with the Spatial Query, Intersect, Clip tools etc.

|improve this answer|||||
  • @DoDo1975 - Most welcome buddy! Glad it was helpful :) – Joseph Feb 25 '16 at 11:45

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