4

I am aware that this question has been asked here: Removing unnecessary vertices?.

I want to focus a different point. How to remove unnecessary vertices without changing the shape at all. As you can see in the example below I want to get rid of vertex 2 and 3. All generalize or smooth functions I saw so far, will somehow alter the shape of the polygon/polyline. So they will mess with vertex 5,6 and 7 in the example.

enter image description here

  • I think you may be out of luck. Someone correct me if I'm wrong, but I believe the Verticies exist whenever there is a change in direction of a polygon extent. The link you referenced contains the only way to get rid of these verticies (that I know of). What is the specific reason you want to reduce the number of verticies? – Goldring Apr 18 '16 at 13:28
  • Of course nobody would digitize polygons like this. In my case the unnecessary vertices appear as a result of geoprocessing steps. Why remove? I could reduce the size of my dataset approx. 20%. – EikeMike Apr 18 '16 at 13:45
  • get a civil 3d licence and use the command weed. They have trial lics.docs.autodesk.com/CIV3D/2013/ENU/index.html?url=filesCUG/… – risail Apr 18 '16 at 13:46
  • You give no indication on how many polygons you need to alter. If it is just a few and they are as simple as you have depicted, why not simply use the edit vertices tool bar, click on the delete vertex tool and draw a box around 2 and 3, that is literally a 5 second job? – Hornbydd Apr 18 '16 at 14:06
  • Well, I do have more than a few polygons :-). Looking for a function or similar procedure. – EikeMike Apr 18 '16 at 14:09
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I can only speak for ArcGIS, but since you didn't mention any specific software, here's my answer.

The Simplify Polygon tool with the POINT_REMOVE option should do what you want. From the help:

POINT_REMOVE—Keeps the so-called critical points that depict the essential shape of a polygon and removes all other points

  • As you can see in the depicted example of the tool resources.arcgis.com/en/help/main/10.1/index.html#//… it will mess with the shape. – EikeMike Apr 18 '16 at 13:48
  • 4
    In the tool, you can set the tolerance to a very small distance so it wouldn't affect vertices 5, 6, and 7 – kenbuja Apr 18 '16 at 13:54
  • Berend and kenbuja you are right, thanks for the effort. – EikeMike Apr 25 '16 at 6:58
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Have a look at this page. Follow the instructions, you can select multiple polygons by drawing a box around them with the tool and then run the generalize edge tool.

Here is a polygon with "extra" vertices:

A polygon with extra vertices

After running the Generalize edge tool and fiddling around with the tolerance scroll bar I created this:

Vertices removed

Your question gives no indication of the scale of your data, are they houses or national parks? I ask that as the tolerance may not be appropriate for all of your polygons, but you can certain do batches of them. You can see the effect of the tolerance if you have preview ticked on, useful before committing to the generalization.

  • 1 Up and thanks, for idea. I did not state in the question that I would prefer "automatic" solutions. – EikeMike Apr 25 '16 at 6:57

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