Study Area polygon

I extracted the study area polygon using raster to polygon tool in ArcGIS from a binary raster mask. However, I can only extract a polygon with fills outside of my study area. I tried using editor tool to draw along the needed area, but fail to plot precisely as extracted.

Is there any way to invert the polygon values so that it could be used as a mask for the central area?

  • It seems Singapore :) – Shiko Dec 5 '16 at 2:17
  • @Shiko This is actually Northern Ontario, Canada :) – Yuyun He Dec 5 '16 at 2:23
  • 3
    Use it to Erase a rectangle with the same extent. Or Union and select out the -1 polygon. – Vince Dec 5 '16 at 2:25
  • Interesting, Shape is very similar to Singapore :) – Shiko Dec 5 '16 at 2:26
  • 1
    Use auto complete polygon in editor – FelixIP Dec 5 '16 at 4:35

There are a few ways you could do this.

Method 1

Like @Vince suggested, you could draw a rectangle and use the Erase tool if your license level allows it.

Method 2

Or, draw a rectangle of the same extent and perform a Union analysis and select the polygon in the middle (including the little islands).

Method 3

Or, you could draw a rectangle of the same extent, then select your complex polygon. With your original polygon selected, select the Clip tool in the Editor toolbar:

enter image description here enter image description here

Choose "Discard the area that intersects." enter image description here

Then select the original polygon and delete it:

enter image description here

Method 4

Another way you could do it would be to edit the vertices of your polygon and delete the four outer corners. This will give you the inverse polygon. Note, this might not always work, but it worked for this example.

enter image description here

Edit the vertices and select the four corners: enter image description here

Delete the four vertices by right clicking on one of the selected ones: enter image description here

Note, the result is a multipart polygon: enter image description here

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  • 3
    method 5: Start editing and there is a method "trace" just start the first point and click "Trace" than just move the mouse on one side it will trace the edge automatically. – Florjan Dec 5 '16 at 9:17
  • @Florjan, good point. Just be aware, that it may be difficult to pick up the smaller "islands" that appear to be in the original screenshot. – Fezter Dec 6 '16 at 0:59
  • you are right but as soon as he want to extract the border of a country, city or area of interest there should not be small polygon inside or outside :)... whatever my comment was excessive with all these method that you have listed – Florjan Dec 6 '16 at 15:22

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