# ee.Geometry.MultiPolygon.union

Returns the union of the two geometries.

<br />

| Usage | Returns |
|---|---|
| `MultiPolygon.union(right, *maxError*, *proj*)` | Geometry |

| Argument | Type | Details |
|---|---|---|
| this: `left` | Geometry | The geometry used as the left operand of the operation. |
| `right` | Geometry | The geometry used as the right operand of the operation. |
| `maxError` | ErrorMargin, default: null | The maximum amount of error tolerated when performing any necessary reprojection. |
| `proj` | Projection, default: null | The projection in which to perform the operation. If not specified, the operation will be performed in a spherical coordinate system, and linear distances will be in meters on the sphere. |

## Examples

### Code Editor (JavaScript)

```javascript
// Define a MultiPolygon object.
var multiPolygon = ee.Geometry.MultiPolygon(
    [[[[-122.092, 37.424],
       [-122.086, 37.418],
       [-122.079, 37.425],
       [-122.085, 37.423]]],
     [[[-122.081, 37.417],
       [-122.086, 37.421],
       [-122.089, 37.416]]]]);

// Define other inputs.
var inputGeom = ee.Geometry.BBox(-122.085, 37.415, -122.075, 37.425);

// Apply the union method to the MultiPolygon object.
var multiPolygonUnion = multiPolygon.union({'right': inputGeom, 'maxError': 1});

// Print the result to the console.
print('multiPolygon.union(...) =', multiPolygonUnion);

// Display relevant geometries on the map.
Map.setCenter(-122.085, 37.422, 15);
Map.addLayer(multiPolygon,
             {'color': 'black'},
             'Geometry [black]: multiPolygon');
Map.addLayer(inputGeom,
             {'color': 'blue'},
             'Parameter [blue]: inputGeom');
Map.addLayer(multiPolygonUnion,
             {'color': 'red'},
             'Result [red]: multiPolygon.union');
```
Python setup

See the [Python Environment](https://developers.google.com/earth-engine/guides/python_install) page for information on the Python API and using
`geemap` for interactive development.

```python
import ee
import geemap.core as geemap
```

### Colab (Python)

```python
# Define a MultiPolygon object.
multipolygon = ee.Geometry.MultiPolygon([
    [[
        [-122.092, 37.424],
        [-122.086, 37.418],
        [-122.079, 37.425],
        [-122.085, 37.423],
    ]],
    [[[-122.081, 37.417], [-122.086, 37.421], [-122.089, 37.416]]],
])

# Define other inputs.
input_geom = ee.Geometry.BBox(-122.085, 37.415, -122.075, 37.425)

# Apply the union method to the MultiPolygon object.
multipolygon_union = multipolygon.union(right=input_geom, maxError=1)

# Print the result.
display('multipolygon.union(...) =', multipolygon_union)

# Display relevant geometries on the map.
m = geemap.Map()
m.set_center(-122.085, 37.422, 15)
m.add_layer(
    multipolygon, {'color': 'black'}, 'Geometry [black]: multipolygon'
)
m.add_layer(input_geom, {'color': 'blue'}, 'Parameter [blue]: input_geom')
m.add_layer(
    multipolygon_union, {'color': 'red'}, 'Result [red]: multipolygon.union'
)
m
```