ee.FeatureCollection.union

Page Summary

• The union function merges all geometries in a collection into a single feature with a single geometry and an ID of 'union_result'.

• The union function returns a FeatureCollection containing this single merged feature.

• The maxError argument allows specifying the maximum error for reprojections, defaulting to the output's requested error margin if not provided.

Merges all geometries in a given collection into one and returns a collection containing a single feature with only an ID of 'union_result' and a geometry.

Usage	Returns
FeatureCollection.union(maxError)	FeatureCollection

Argument	Type	Details
this: collection	FeatureCollection	The collection being merged.
maxError	ErrorMargin, default: null	The maximum error allowed when performing any necessary reprojections. If not specified, defaults to the error margin requested from the output.

Examples

Code Editor (JavaScript)

// FeatureCollection of power plants in Belgium.
var fc = ee.FeatureCollection('WRI/GPPD/power_plants')
            .filter('country_lg == "Belgium"');

print('Original FeatureCollection', fc);

// Merge all geometries into one. A FeatureCollection with a single feature
// with no properties is returned.
print('All geometries merged into one', fc.union(1));

Python setup

See the Python Environment page for information on the Python API and using geemap for interactive development.

import ee
import geemap.core as geemap

Colab (Python)

# FeatureCollection of power plants in Belgium.
fc = ee.FeatureCollection('WRI/GPPD/power_plants').filter(
    'country_lg == "Belgium"')

display('Original FeatureCollection:', fc)

# Merge all geometries into one. A FeatureCollection with a single feature
# with no properties is returned.
display('All geometries merged into one:', fc.union(1))