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 second gap, as shown in the image below, is a thin slit that exists between two 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.
- Open the project in ArcGIS Pro.
- On the Edit tab, in the Features group, click Create.
- 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.
- Draw a line from one edge to another to complete the gap, as shown below.
- Click the Clear icon to remove the selection.
- On the Edit tab, in the Manage Edits group, click Save to save the changes.
- In the Selection group, click Select and select the recently filled polygon and the adjacent polygon by pressing the keyboard Shift key.
- In the Tools group, click Merge.
- 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.
- Click Merge.
- In the Selection group, click the Clear icon to view the merged polygons.
- 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.
- In the Tools group, click Merge.
- 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.
- Click Merge.
The image below shows the gap between the polygons filled.
Using the Union tool
Use this workflow when a gap exists between two polygons and requires merging with only one existing polygon.
- Open the project in ArcGIS Pro.
- On the Analysis tab, in the Geoprocessing group, click Tools.
- In the Geoprocessing pane, search for and select Union (Analysis Tools).
- In the Geoprocessing pane, specify Parameters as follows:
- For Input Features, click the drop-down list and select the polygon layer. In this example, CropField is selected.
- The Output Feature Class is auto-filled. Alternatively, specify a name for the output feature class.
- For Attributes To Join, click the drop-down list and select All attributes.
- Uncheck the Gaps Allowed check box.
- Click Run.
- 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.
- In the Tools group, select Merge.
- 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.
- Click Merge.
The image below shows the gap is filled and merged with the selected polygon.