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Alteryx designer Discussions

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Cancave Hull with polygons

Im trying to create a concave hull with a group of polygons.These polygons arent touching. I am trying to create an overall boundary but keeping the basic shape. Any Ideas?
Alteryx Alumni (Retired)


The best way to create the single boundary file for the polygons would be to use the Summarize Tool.  Select the Spatial Object field, then click on Add-->Spatial-->Create Convex Hull.  The ultimate result will be a single polygon representing the outtermost boundaries of the subject polygons.



Yes I've done that but I want a better repersentation of the shape of all the polygons as if they were one. Kind of like drawing a line along the outer most boundry of each poly gon
I have great news. I figured it out if you Buffer then re buffer a negative number then you get a general shape and all connect.
ACE Emeritus
ACE Emeritus

Does your negative buffer look like the red polygon in the image above?  Thanks Tyler.


Yes - positive and then negative buffer is almost certainly the answer to concave hull.  By changing the size (in miles) of the buffers, it will determine how much of the gaps it will fill in.  If you want the outline to track exactly around the outer portions, the positive and negative buffers should be the same size.  If you want it to extend outside a little (like the red line above), the positive buffer should be bigger than the negative.

ACE Emeritus
ACE Emeritus

Thanks Ned.