28.1.20. Vector coverage

28.1.20.1. Dissolve coverage

Operates on a coverage (represented as a set of polygon features with exactly matching edge geometry) to dissolve (union) the geometries. It provides a heavily optimized approach for unioning these features compared with the standard Dissolve tools.

See also

Dissolve

Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: polygon]	Input polygon vector layer
Dissolved	OUTPUT	[vector: polygon] Default: [Create temporary layer]	Specify the output vector layer. One of: Create Temporary Layer (TEMPORARY_OUTPUT) Save to File… Save to Geopackage… Save to Database Table… The file encoding can also be changed here.

Outputs

Label	Name	Type	Description
Dissolved	OUTPUT	[vector: polygon]	The output polygon vector layer with dissolved geometries.

Python code

Algorithm ID: native:coverageunion

import processing
processing.run("algorithm_id", {parameter_dictionary})

The algorithm id is displayed when you hover over the algorithm in the Processing Toolbox. The parameter dictionary provides the parameter NAMEs and values. See Using processing algorithms from the console for details on how to run processing algorithms from the Python console.

28.1.20.2. Simplify coverage

Operates on a coverage (represented as a set of polygon features with exactly matching edge geometry) to apply a Visvalingam–Whyatt simplification to the edges, reducing complexity in proportion with the provided tolerance, while retaining a valid coverage (i.e. no edges will cross or touch after the simplification). Geometries will never be removed, but they may be simplified down to just a triangle. Also, some geometries (such as polygons which have too few non-repeated points) will be returned unchanged.

If the input dataset is not a valid coverage due to overlaps, it will still be simplified, but invalid topology such as crossing edges will still be invalid.

Requires version of GEOS >= 3.12

See also

Simplify, qgissmoothgeometry

Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: polygon]	Input polygon vector layer
Tolerance	TOLERANCE	[number] Default: 0.0	The maximum distance (in unit of choice) between two consecutive vertices to get merged.
Preserve boundary	PRESERVE_BOUNDARY	[number] Default: False	When enabled, the outside edges of the coverage will be preserved without simplification
Simplified	OUTPUT	[vector: polygon] Default: [Create temporary layer]	Specify the output vector layer. One of: Create Temporary Layer (TEMPORARY_OUTPUT) Save to File… Save to Geopackage… Save to Database Table… The file encoding can also be changed here.

Outputs

Label	Name	Type	Description
Simplified	OUTPUT	[vector: polygon]	The output polygon vector layer, with a lower number of vertices.

Python code

Algorithm ID: native:coveragesimplify

import processing
processing.run("algorithm_id", {parameter_dictionary})

The algorithm id is displayed when you hover over the algorithm in the Processing Toolbox. The parameter dictionary provides the parameter NAMEs and values. See Using processing algorithms from the console for details on how to run processing algorithms from the Python console.

28.1.20.3. Validate coverage

Analyzes a coverage (represented as a set of polygon features with exactly matching edge geometry) to find places where the assumption of exactly matching edges is not met. Invalidity includes polygons that overlap or that have gaps smaller than the specified gap width.

Requires version of GEOS >= 3.12

See also

Check validity

Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: polygon]	Input polygon vector layer
Gap width	GAP_WIDTH	[number] Default: 0.0	The maximum width of gap to detect
Invalid edges	INVALID_EDGES	[vector: line] Default: [Create temporary layer]	Specify the output vector layer. One of: Skip Output Create Temporary Layer (TEMPORARY_OUTPUT) Save to File… Save to Geopackage… Save to Database Table… The file encoding can also be changed here.

Outputs

Label	Name	Type	Description
Invalid edges	OUTPUT	[vector: line]	The output line vector layer showing error edges for each invalid polygon.
Validity result	IS_VALID	[boolean]	Returns whether the coverage is valid or not.

Python code

Algorithm ID: native:coveragevalidate

import processing
processing.run("algorithm_id", {parameter_dictionary})

The algorithm id is displayed when you hover over the algorithm in the Processing Toolbox. The parameter dictionary provides the parameter NAMEs and values. See Using processing algorithms from the console for details on how to run processing algorithms from the Python console.