HOW TO

Fill gaps or holes between polygons in ArcGIS Pro

Last Published: June 9, 2023

Summary

In some cases, a map layer can have gaps or holes between polygons due to inaccurate data mapping, or to represent specific features of a given area. To represent the polygon boundaries concisely, the gaps between the polygons must be filled, and the polygon features merged. This article provides two workarounds to fill the gaps between polygons, using the Autocomplete Polygon tool, or the Union tool, in ArcGIS Pro.

There are two examples used to demonstrate the workflows in this article. The first gap, as shown in the image below, represents a lake located in the middle of crop fields.

The gaps between polygons.

The second gap, as shown in the image below, is a thin slit that exists between two polygons.

The gap or thin slit between polygons.

Procedure

Using the Autocomplete Polygon tool

Use this workflow when a gap exists between two polygons and requires the newly filled polygon to be merged with more than one existing polygon.

  1. Open the project in ArcGIS Pro.
  2. On the Edit tab, in the Features group, click Create.
The Create button in the Features group.
  1. In the Create Features pane, under Templates, select the polygon adjacent to the gap, and click the Autocomplete Polygon icon. In this example, the polygon, 10 is selected.
The Create Features pane.
  1. Draw a line from one edge to another to complete the gap, as shown below.
The gap autocompleted as a polygon.
  1. Click the Clear icon to remove the selection.
The Clear button in the Selection group.
  1. On the Edit tab, in the Manage Edits group, click Save to save the changes.
The Save button in the Manage Edits group.
  1. In the Selection group, click Select and select the recently filled polygon and the adjacent polygon by pressing the keyboard Shift key.
The newly filled polygon and the adjacent polygon selected.
  1. In the Tools group, click Merge.
The Merge tool in the Tools group.
  1. In the Modify Features pane, under Merged Feature Attributes, click the Choose Symbol Class button, and select the adjacent polygon for the newly filled polygon to be merged. In this example, the polygon, 10 is selected.
  2. Click Merge.
The Modify Features pane.
  1. In the Selection group, click the Clear The Clear icon icon to view the merged polygons.
The merged polygons.
  1. In the Selection group, click Select and select the other half of the recently filled polygon and the adjacent polygon by pressing the keyboard Shift key.
The newly filled polygon and the adjacent polygon selected.
  1. In the Tools group, click Merge.
  2. In the Modify Features pane, under Merged Feature Attributes, click the Choose Symbol Class button, and select the adjacent polygon for the newly filled polygon to be merged. In this example, the polygon, 12 is selected.
  3. Click Merge.
The Modify Features pane.

The image below shows the gap between the polygons filled.

The merged polygons.

Using the Union tool

Use this workflow when a gap exists between two polygons and requires merging with only one existing polygon.

  1. Open the project in ArcGIS Pro.
  2. On the Analysis tab, in the Geoprocessing group, click Tools.
  3. In the Geoprocessing pane, search for and select Union (Analysis Tools).
  4. In the Geoprocessing pane, specify Parameters as follows:
    1. For Input Features, click the drop-down list and select the polygon layer. In this example, CropField is selected.
    2. The Output Feature Class is auto-filled. Alternatively, specify a name for the output feature class.
    3. For Attributes To Join, click the drop-down list and select All attributes.
    4. Uncheck the Gaps Allowed check box.
    5. Click Run.
The Union tool parameters in the Geoprocessing pane.
  1. On the Edit tab, in the Selection group, click Select and select the recently filled polygon and the adjacent polygon by pressing the keyboard Shift key.
The selected polygons.
  1. In the Tools group, select Merge.
  2. In the Modify Features pane, under Merged Feature Attributes, click the Choose Symbol Class button, and select the attribute for the selected polygon to be merged. In this example, the polygon, 13 is selected.
  3. Click Merge.
The Modify Features pane.

The image below shows the gap is filled and merged with the selected polygon.

The merged polygons.

Article ID: 000030410

Software:
  • ArcGIS Pro 3 1
  • ArcGIS Pro 3 0
  • ArcGIS Pro 2 x

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