ee.FeatureCollection.merge

Page Summary

• FeatureCollection.merge() combines two collections into one, including all elements from both.

• Elements from the first collection have IDs prefixed with "1*" and the second with "2*".

• For merging many collections, using FeatureCollection.flatten() is recommended over repeated merging for better performance.

Merges two collections into one. The result has all the elements that were in either collection.

Elements from the first collection will have IDs prefixed with "1" and elements from the second collection will have IDs prefixed with "2".

Note: If many collections need to be merged, consider placing them all in a collection and using FeatureCollection.flatten() instead. Repeated use of FeatureCollection.merge() will result in increasingly long element IDs and reduced performance.

Usage	Returns
FeatureCollection.merge(collection2)	FeatureCollection

Argument	Type	Details
this: collection1	FeatureCollection	The first collection to merge.
collection2	FeatureCollection	The second collection to merge.

Examples

Code Editor (JavaScript)

// FeatureCollection of points representing forest cover.
var fcForest = ee.FeatureCollection([
  ee.Feature(ee.Geometry.Point([-122.248, 37.238]),
             {'id': 0, 'cover_class': 'forest'}),
  ee.Feature(ee.Geometry.Point([-122.204, 37.222]),
             {'id': 1, 'cover_class': 'forest'}),
  ee.Feature(ee.Geometry.Point([-122.110, 37.199]),
             {'id': 2, 'cover_class': 'forest'})
]);

// FeatureCollection of points representing urban cover.
var fcUrban = ee.FeatureCollection([
  ee.Feature(ee.Geometry.Point([-121.953, 37.372]),
             {'id': 0, 'cover_class': 'urban'}),
  ee.Feature(ee.Geometry.Point([-121.861, 37.308]),
             {'id': 1, 'cover_class': 'urban'}),
  ee.Feature(ee.Geometry.Point([-121.984, 37.372]),
             {'id': 2, 'cover_class': 'urban'})
]);

// Merge the two FeatureCollections into one.
var fcMerged = fcForest.merge(fcUrban);

// Display FeatureCollections on the map.
Map.setCenter(-122.034, 37.296, 11);
Map.addLayer(fcForest, {color: 'green'}, 'Forest points');
Map.addLayer(fcUrban, {color: 'grey'}, 'Urban points');
Map.addLayer(fcMerged, {color: 'yellow'}, 'Protected areas merged');

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 points representing forest cover.
fc_forest = ee.FeatureCollection([
    ee.Feature(
        ee.Geometry.Point([-122.248, 37.238]),
        {
            'id': 0,
            'cover_class': 'forest',
            'id': 0,
            'cover_class': 'forest',
        },
    ),
    ee.Feature(
        ee.Geometry.Point([-122.204, 37.222]),
        {
            'id': 1,
            'cover_class': 'forest',
            'id': 1,
            'cover_class': 'forest',
        },
    ),
    ee.Feature(
        ee.Geometry.Point([-122.110, 37.199]),
        {
            'id': 2,
            'cover_class': 'forest',
            'id': 2,
            'cover_class': 'forest',
        },
    ),
])

# FeatureCollection of points representing urban cover.
fc_urban = ee.FeatureCollection([
    ee.Feature(
        ee.Geometry.Point([-121.953, 37.372]),
        {'id': 0, 'cover_class': 'urban', 'id': 0, 'cover_class': 'urban'},
    ),
    ee.Feature(
        ee.Geometry.Point([-121.861, 37.308]),
        {'id': 1, 'cover_class': 'urban', 'id': 1, 'cover_class': 'urban'},
    ),
    ee.Feature(
        ee.Geometry.Point([-121.984, 37.372]),
        {'id': 2, 'cover_class': 'urban', 'id': 2, 'cover_class': 'urban'},
    ),
])

# Merge the two FeatureCollections into one.
fc_merged = fc_forest.merge(fc_urban)

# Display FeatureCollections on the map.
m = geemap.Map()
m.set_center(-122.034, 37.296, 11)
m.add_layer(fc_forest, {'color': 'green'}, 'Forest points')
m.add_layer(fc_urban, {'color': 'grey'}, 'Urban points')
m.add_layer(fc_merged, {'color': 'yellow'}, 'Protected areas merged')
m