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I'm using ArcMap to draw polygons around some geologic features. I want to know the length of the semi major and semi minor axes of the smallest ellipse that would fit around the polygons.

I'm a new Arc user, so it's possible that there's a simple way to do this, but not that I've yet found. Maybe the buffer tool could do the trick, but I'm not sure how.

  • Did you want to create the ellipse manually or derive it from a tool automatically? – whyzar Oct 30 '17 at 16:02
  • Automatically - I have the length and x-y coordinates of my polygons in the attributes table. But if I use that information to make ellipses, it'll just draw ellipses at those coordinates, but not necessarily encompass the polygons. I'm looking for a more specific application of the "create ellipse" feature in which it draws an ellipse around my polygons. – M. Phillips Oct 30 '17 at 16:50
  • As far as I'm aware it is possible to draw manually as mentioned above. Use the table to bring into ArcMap. Creating a bounding box using ellipse in ArcMap I believe is not currently available – whyzar Oct 30 '17 at 16:52
  • I've updated my answer and added a few more resources and alternatives – whyzar Oct 30 '17 at 18:36
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You could refer to Esri's documentation Creating an ellipse feature

The Ellipse tool is used to create ellipse features.

  • These steps can be used to create lines or polygons:

    • To create lines, click a line feature template in the Create Features window.
    • To create polygons, click a polygon feature template in the Create Features window.
  • Click the Ellipse construction tool Ellipse on the Create Features window.

  • Click to place the center of the ellipse, then drag.
  • Click to set the major or minor radius, then drag.
  • You can also right-click or use keyboard shortcuts to enter x,y coordinates, set a direction angle, choose whether the ellipse is constructed from the center or an endpoint, or enter a major or minor radius. The radius is given in map units by default, but you can give the value in other units by specifying a distance units abbreviation with the value that you enter. Click once to finish the ellipse.

Alternatively, you may try as this user Make a minimum bound ellipse? suggests, you would need an extension via ArcMap

the spatial statistics tool "Directional Distribution (Standard Deviational Ellipse)" may help

To add from my comments:

As far as I'm aware it is possible to draw manually as mentioned above. Use the [table to bring into ArcMap] (http://pro.arcgis.com/en/pro-app/tool-reference/data-management/table-to-ellipse.htm). Creating a bounding box using ellipse in ArcMap I believe is not currently available

Here is an Esri idea page [Minimum bound ellipse](https://community.esri.com/ideas/6118

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