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I have a file in QGIS with 5000 points. Some of the points are really close to each other (5m). How can I cluster the point features to one point feature if they are within 5m? The new points should be centroids from the given points.

marked as duplicate by Ian Turton Nov 11 '13 at 14:09

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  • How would you like to deal with a situation where you had 50-60 points that were each within 5 m of another point, but spread out over, say 200m overall? Should they then all be merged to a single point? – Simbamangu Nov 11 '13 at 10:55
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    Do you want to delete the points or overlay them atop one another? – Simbamangu Nov 11 '13 at 11:58
  • Does merge the point features to one point feature mean calculate a new (barycentric) point feature or discard all the points except one on some basis? – Antonio Falciano Nov 11 '13 at 14:41
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    @afalciano I want to create the centroid of the point features, like the way you described in your answer. – ustroetz Nov 11 '13 at 17:58
  • @Simbamangu It is not really the case in my dataset, that the points are spread out over 200m and are within 5m distance. – ustroetz Nov 11 '13 at 19:18

One possible approach consists in the following steps:

  1. draw a buffer of 5m around points;
  2. dissolve the buffers which overlap;
  3. calculate the centroids of dissolved buffers.

You can choose the tools with which you're more comfortable.

For instance, using GDAL >= 1.10.0 compiled with SQLite and SpatiaLite you can calculate the buffer around your points.shp:

ogr2ogr buffers.shp points.shp -dialect sqlite -sql "SELECT ST_Buffer(geometry,5) from points"

Then, calculate the clusters (dissolved buffers):

ogr2ogr clusters.shp buffers.shp -dialect sqlite -sql "SELECT ST_Union(geometry) from buffers" -explodecollections

Finally, calculate result_points.shp:

ogr2ogr result_points.shp clusters.shp -dialect sqlite -sql "SELECT Centroid(geometry) FROM clusters"

Have a look at this tutorial: http://qgis.spatialthoughts.com/2013/04/tutorial-nearest-neighbor-analysis.html

  • Compute a Nearest Neighbour Analysis for your dataset
  • Add the resultant table into QGIS and join it to your dataset
  • Export your data into Excel and Sort/Filter it by distance.
  • Select all your data rows where the distance is <5 m
  • Select Data -> Delete duplicates
  • Import back into QGIS

Where any points are within 5 m of each other, this simple process will remove one and keep the other!

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