How To: Split a circle polygon into half in ArcMap


In some instances, it is necessary to split a circular area in half. The image below shows a circle with its attribute table before it is split. The total area is roughly 8,631,337 square feet.

A full circle.


To split a circle into half using Cut Polygons Tool, follow the steps below:

  1. In ArcMap, start an edit session. Select the circle 'polygon' to split.
If the Editor toolbar does not appear, click Customize > Toolbars > Editor.
  1. In the Editor toolbar, click the Cut Polygons Tool icon The Cut Polygons tool icon.. The Straight Segment icon is automatically selected The Straight Segment icon..
  2. Click Editor > Options. In the Editing Options window, enable the Show feature construction toolbar option, and click OK.
Enable the feature construction tooolbar.
  1. Click anywhere at the edge of the circle. The Feature Construction toolbar appears.
This is the Feature Constructions toolbar.
To ease line construction, enable snapping options by clicking Editor > Snapping > Snapping Toolbar.
  1. In the Feature Construction toolbar, click the Constrain Perpendicular icon the Constrain Perpendicular icon.. Creating a straight line that is perpendicular to any edge of a circle draws across the centroid to split the circle in half. For more information on creating a line at an angle, refer to ArcMap: Creating a segment using an angle and a length.
  2. Draw a straight line across the circle and snap the line at the other edge of the circle. The circle automatically splits. Opening the attribute table shows the circle is split into two. In this example, each half has an area of roughly 4,315,668 square feet.
The circle is split into two.

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