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Quite a straightforward question:

I have a point layer that consists of a few thousand points. These points are heterogeneously positioned in or very close to polygons that are water bodies. These polygons differ in size. I would like to cut the polygon based on the location of these points.

Please look at the example below. Blue polygon (water body) and black point is what I have right now. The purple, red or green lined polygon (or line) is a example of what the result can look like in order to clip the blue polygon. Which approach do you suggest?

Perhaps that a buffer around a point would help. The tricky part is that the buffer should match the two closest edges of the surrounding polygon. Or maybe to create a line to both sides?

enter image description here

Other suggestions?

Working with both QGIS and GIS (arcmap 10.0)

  • Can you add an image depicting your desired result? – OGmaps Jul 8 at 7:09
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    Certainly! Hopefully this clarifies it. – Mark Jul 8 at 7:16
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    Don't forget to take the Tour to learn about the site and its protocols. By asking how to do the same thing in either of two products you are effectively asking two questions which makes this too broad for focused Q&A. Please use the edit button beneath your question to focus your question on one or other. I recommend asking about the one you are most likely to use. You can always ask about the other one in a separate question. – PolyGeo Jul 8 at 7:21
  • Perhaps I phrased the question wrong. The purple, red or green lined polygon (or line) is what the results can look like. I do not have a specific preference. Would like to know how to approach this. – Mark Jul 8 at 7:29
  • I assume the blue polygons differ in size? So a buffer would not always fit the polygons? – gHupf Jul 8 at 8:22
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The solution for QGIS,

I propose to act on the following scenario,

"while I am kind :-)",

If I understand you correctly, the initial situation is as shown in Figure 1 and my test layers are called "pts" and "polygon_exp". enter image description here

Action 1, using the new virtual layer with the SQL script in the form window add 2 layers to the screen form and run the SQL script see Figure 2. enter image description here

SELECT ShortestLine(a.geometry, b.geometry) geom FROM pts a, polygon_exp b

result is shown in Figure 3 enter image description here

save it by giving it a new name.

Action 2, using on the result of Action 1 start the geoinstrument, see Figure 4 enter image description here

The result is shown in Figure 5.

enter image description here

Action 3, using cut your pond with the result obtained in Action 2, see Figure 6 enter image description here

and see Figure 7 for the result: enter image description here

Quite a straightforward question :-)...

We've all reached our goal, before we meet again...

Translated with www.DeepL.com/Translator (free version)

| improve this answer | |
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    Are you answering philosophical or geo related questions ?! 🙂 – Taras Jul 8 at 19:52
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    @Taras, Try not to burn out in life, i.e. not to burn out emmotionally, it's very important... it's the philosophy of life... Try to do what develops you and what interests you... – Cyril Mikhalchenko Jul 8 at 20:20
  • Great! Thanks for the elaborate response to this "straightforward question" – Mark Jul 9 at 7:04
  • I'm pleased that this solution is clear to you and most importantly, that one of the solutions to your question... – Cyril Mikhalchenko Jul 9 at 7:10

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