ee.FeatureCollection.union

  • union() merges all geometries within a FeatureCollection into a single geometry, returning a new FeatureCollection containing one feature with an ID of 'union_result'.

  • The resulting FeatureCollection from union() will only have the merged geometry and an ID, discarding any original properties from the input features.

  • An optional maxError argument can be used to specify the maximum allowed error for reprojection during the merge process.

 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.

UsageReturns
FeatureCollection.union(maxError)FeatureCollection
ArgumentTypeDetails
this: collectionFeatureCollectionThe collection being merged.
maxErrorErrorMargin, default: nullThe 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"')

print('Original FeatureCollection:', fc.getInfo())

# 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).getInfo())