ee.Geometry.MultiPolygon.dissolve

  • The dissolve() method returns the union of the geometries within a MultiPolygon, effectively merging them into a single, unified geometry.

  • It accepts optional parameters like maxError to control the tolerance for reprojection errors and proj to specify the projection for the union operation.

  • Single geometries remain unaffected by this operation as they are already in their simplest form.

  • This function is valuable for simplifying complex MultiPolygons by dissolving internal boundaries and creating a contiguous shape.

  • Examples in JavaScript and Python demonstrate the usage of the dissolve() method and its impact on a sample MultiPolygon.

 Returns the union of the geometry. This leaves single geometries untouched, and unions multi geometries.

UsageReturns
MultiPolygon.dissolve(maxError, proj)Geometry
ArgumentTypeDetails
this: geometryGeometryThe geometry to union.
maxErrorErrorMargin, default: nullThe maximum amount of error tolerated when performing any necessary reprojection.
projProjection, default: nullIf specified, the union will be performed in this projection. Otherwise it will be performed in a spherical coordinate system.

Examples

Code Editor (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]]]]);

// Apply the dissolve method to the MultiPolygon object.
var multiPolygonDissolve = multiPolygon.dissolve({'maxError': 1});

// Print the result to the console.
print('multiPolygon.dissolve(...) =', multiPolygonDissolve);

// Display relevant geometries on the map.
Map.setCenter(-122.085, 37.422, 15);
Map.addLayer(multiPolygon,
             {'color': 'black'},
             'Geometry [black]: multiPolygon');
Map.addLayer(multiPolygonDissolve,
             {'color': 'red'},
             'Result [red]: multiPolygon.dissolve');

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)

# 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]]],
])

# Apply the dissolve method to the MultiPolygon object.
multipolygon_dissolve = multipolygon.dissolve(maxError=1)

# Print the result.
display('multipolygon.dissolve(...) =', multipolygon_dissolve)

# 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(
    multipolygon_dissolve,
    {'color': 'red'},
    'Result [red]: multipolygon.dissolve',
)
m