ee.FeatureCollection.union

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));