[Qgis-user] Minimum bounding circle from cluster of points

[Nicolas Cadieux]

Hi,
This could work but there may be a more efficient way.   Here are my ideas.
1) Split vector layer using the  ID for each plot/cluster.2) Create a polygone from the file extent. (use the processing toolbox), merge all the polygone into 1 file.3) Find the centroid of this shape and the maximum extent of the file or the maximum extent of the shape (field calculator). 4) Use the Create Buffers tools (on the centroid file) in the MMQGIS plugin.  You can create a circle based on a Radius specified in a column (the max file extent).
Step 1 could also be create convex hull for every group of points. Perhaps this can be done by aggregating the points into a multi point files. (vector/geometry tool/single part to multipart).
Nicolas    
From: ml-node+s1560n5275434h15 at n6.nabble.com
To: nicolas.cadieux at archeotec.ca
Date: Fri, 8 Jul 2016 07:33:36 -0600
Subject: Minimum bounding circle from cluster of points



	Hi all,
Looking for help aggregating some field data subplots to the plot level. In the attached screenshot, you can see clusters of 4 points (4 subplots = 1 plot). I'd like to create a circle around each cluster that is the smallest circle that would encompass all 4 points. Sort of like a convex hull, but a circle (convex hull, in this case, would give me a triangle). Is there a tool or a series of steps to accomplish this without doing it manually? In the attribute table, I have a unique ID for each plot/cluster. So for each plot ID (in this case, consisting of 4 subplots), I'd like to build a circle around all of the subplots.
I should also mention that it's not always 4 points (subplots), and they aren't always covering the same size area on the ground.
I have QGIS 2.14.2 as well as one of the nightly builds from a few weeks ago (can download the newest one if necessary).
Thanks in advance for any ideas/insights! Google has not helped me so much yet with this one!Tina




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