Blur the boundary of polygons in ArcGIS Pro

Summary

In ArcGIS Pro, the boundary of polygons can be blurred to create the effect of an undefined edge. This is useful for mapping boundaries without definitive borders such as an animal’s habitat.

This article provides two workflows to blur the boundary of polygons in ArcGIS Pro. The image below shows a polygon layer representing the areas of an animal’s habitat on the map.

Procedure

Blur polygon boundaries by applying the Offset effect

Blur polygon boundaries by applying the Offset effect and creating multiple duplicates of the polygon layer.

1. Open the ArcGIS Pro project.
2. Increase the polygon layer transparency.
   1. In the Contents pane, click the symbol of the polygon layer to open the Format Polygon Symbol pane.

2. In the Format Polygon Symbol pane, on the Properties tab, click the Symbol button.
3. Under Appearance, click the Color drop-down arrow, and click Color Properties.
4. In the Color Editor window, increase the Transparency percentage. In this example, the transparency is increased to 50%. Click OK.
5. In the Format Polygon Symbol pane, change Outline color to No color, and click Apply.

3. Create duplicates of the polygon layer and use the Offset effect to blur the polygon boundaries.
   1. In the Format Polygon Symbol pane, on the Properties tab, click the Structure button.
   2. Under Layers, browse to the polygon layer and click Add effect > Offset.
   3. Click the Duplicate Layer button to create multiple duplicates of the layer as needed. In this example, the polygon layer is duplicated six times.

Note:
A greater number of duplicate layers creates a smoother blurring transition of the polygon boundaries.

4. Click the Layers button. Under Offset effect of the original polygon layer, specify a value for Offset. Gradually increase or decrease the offset value by the same interval for every subsequent layer. In this example, the offset values of the polygon layers are 0 pt, -2 pt, -4 pt, and so forth.

Note:
A negative offset value pulls the polygon boundary inwards, whereas a positive offset value pushes the polygon boundary outwards.

5. Click Apply.

The image below shows the polygon layer with blurred polygon boundaries on the map.

Blur polygon boundaries by using the Multiple Ring Buffer tool

Blur polygon boundaries by using the Multiple Ring Buffer tool and adjusting the buffer transparency.

1. Use the Multiple Ring Buffer tool to create ring buffers on the polygon layer.
   1. In ArcGIS Pro, navigate to Analysis > Tools to open the Geoprocessing pane.
   2. In the Geoprocessing pane, search for and click Multiple Ring Buffer (Analysis Tools).
   3. For Input Features, select the polygon layer.
   4. For Output Feature class, specify a name.
   5. For Distances, specify a value for the distance coverage of the ring buffer from the polygon boundary. Click Add another to create more ring buffers as necessary and increase the distance value of each ring buffer by the same interval. In this example, six ring buffers are added and their distance values are 150, 300, 450, and so forth.
   6. For Distance Unit, select a unit for the distances of the ring buffers.
   7. Optionally, specify a name for Buffer Distance Field Name. The default field name is ‘distance’.
   8. Click Run.

2. Hide the ring buffer outlines from the map.
   1. In the Contents pane, click the symbol of the multiple ring buffer layer to open the Format Polygon Symbol pane.
   2. In the Format Polygon Symbol pane, on the Properties tab, click the Layers button.
   3. Uncheck the outline layer and click Apply.

3. Increase the transparency of the ring buffer layer.

Note:
Uncheck the initial polygon layer in the Contents pane to hide the polygon layer and distinguish the ring buffer layer on the map.

1. Right-click the ring buffer layer in the Contents pane > Symbology.
2. On the Vary symbology by attribute tab of the Symbology pane, expand Transparency and select the field containing the ring buffer distance values from Step 1(g)for Field.
3. Under Transparency range, increase the High values percentage and decrease the Low values percentage. In this example, the High values percentage is increased to 90% and the Low values percentage is decreased to 5%.
4. Optionally, adjust the histogram to vary the transparency range.

The image below shows the polygon boundary blurred by adjusting the buffer transparency.