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Home - General / All posts - Break apart points in a polygon
Louise James40 post(s)
#21-Feb-23 05:26

I have a polygon with many points in it. I want to edit a section of the line, however I cannot see how to break it apart. I select the points and then right click for Branch, however the Split option is greyed out. (I was thinking perhaps this option only worked on a line, rather than a polygon perhaps, but I am not certain).

How am I best to separate out and select this section of the polygon for edit (see image), so I can then edit just these points (move horizontally). Any ideas would be greatly appreciated. Many thanks

Kind regards



991 post(s)
#21-Feb-23 06:57

1)Copy duplicate geom and convert it to point you can use the points to draw. Remove them after your work is finished.give them a name using table of drawing..

2) ctrl alt open theselection in edit mode not selection mode. The tab coordinates must be active ( click on it).instead select point using drawing view in selection for edit mode you select points using table coordinates (col X,col y) .

coordinates should show height?

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Louise James40 post(s)
#21-Feb-23 18:57

Many thanks for the prompt reply - very much appreciated. I should have said I am using V8.

Some points to clarify please:

* How do I convert the poly line to points please? I see if I can extract just that section as a line could be useful.

* How do I open in selection mode 'not edit' mode please?. Perhaps just not Contrl Alt I guess. I think I am mostly in selection mode.

Thanks again for any assistance given here. Kind regards


10,391 post(s)
#21-Feb-23 08:43

Start entering the blue outline as a new area. Let it completely cover the part of the boundary that you are interested in. Before saving the new area, right-click somewhere in the window to invoke the context menu and select Clip (accept the defaults). This will reduce the area and make it neatly follow the boundary you want to have as a line. Save the area now.

Convert the new area to a line (Ctrl-click the area to select it, go to the Transform pane, Convert - Convert to = line, Transform selection only, maybe Preview, then Transform).

Start editing the line (Alt-click it). Select all coordinates that are not on the boundary (Ctrl-click or Ctrl-drag), then delete them (eg, in the Info pane, see the Coordinates tab).

Also, check out this help topic: Start > User Manual > Editing > Clip

Louise James40 post(s)
#21-Feb-23 19:02

Thanks for the prompt response here. Apologies I should have confirmed I am using V8. I think the idea of clipping the area to another area will do just what I am chasing here.

Few questions please:

I right click on the area and see context menu but I dont see a Clip option?

I dont seem to see a Convert option in the transform pane. Perhaps there is a V8 option to achieve the same here please.

Any assistance here is very much appreciated. Many thanks Kind regards


2,065 post(s)
#21-Feb-23 19:35

If you want to expand that section horizontally, why not create a new area covering the required expansion and add that to the original polygon?

Aussie Nature Shots

Louise James40 post(s)
#21-Feb-23 20:03

Thanks Colin, I am wanting to reduce the area. Move the border of the green polygon to the west. Hope this clarification helps. Many thanks

image 2.jpg


2,065 post(s)
#21-Feb-23 20:21

In that case you would use the Split With transform splitting by the line you have drawn. Can either draw the line in a separate drawing or over the same drawing and use Saved Selection.

Aussie Nature Shots

Louise James40 post(s)
#21-Feb-23 23:13

Thanks Colin. Yes. That is what I was trying to do. Yes, using the Split with option. Great. Many thanks folks

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