My sampling design requires me to do a couple of things:

First I need to determine the mid-point of an irregular polygon feature. Then I'd need to create a layer of 4 line features, that intersect in the mid-point of said polygon and are all oriented N-S, NE-SW, E-W and SE-NW. As a third and final step I need to highling a point on each line that lies exactly halfway between the midpoint of the polygon and the edge of it, plus one additional point at the very center. In the end, it should look something like this: THIS

Is this feasible at all? Thing is, I have to do this for 32 polygons and it's just a small step for my project, so I want to spend as little time for it as necessary and thus need a method that works fast. The lines are actually just a tool to get to the 9 plot points, as plots determine the locations where I will do my sampling. So if anyone has any idea to get my 9 sampling-spots to be aligned the way I described, I'm open for all suggestions.

  • This should be relatively straight forward using ArcPy and polygon centroids as long as your polygons are not overly complex.
    – PolyGeo
    Commented May 24, 2016 at 12:34
  • And how exactly would I use it? I don't have any experience with it so far.
    – Metlieb
    Commented May 24, 2016 at 12:58
  • We help with code snippets but are not a code writing service. If you want to use custom functionality like this with ArcGIS for Desktop and/or ArcGIS Pro I recommend learning ArcPy.
    – PolyGeo
    Commented May 24, 2016 at 13:04

2 Answers 2


Create centre points using one of possible technique. I suggest centre of largest inscribed circle. You can find solution in here:

Checking if polygon fits inside another polygon using ArcGIS or QGIS?

Create 8 same length long lines starting from same point outside any of your polygons. Select them, copy,paste and drag to the centre points. They'll snap.

Clip your lines by polygon. Compute midpoints for remaining segments

  1. -Calculate the centroid of the polygon (x,y) 2.- Draw lines from centroid for angles of 0º, 45º, 90º,...315º 3.- Find the points of intersection (xi,yi) of the lines with the polygon 4.- Determine the midpoints for each line: ((x+xi)/2,(y+yi)/2) 5.- End

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