24.1.16. Vector geometry

24.1.16.1. Add geometry attributes

Computes geometric properties of the features in a vector layer and includes them in the output layer.

It generates a new vector layer with the same content as the input one, but with additional attributes, containing geometric measurements based on a selected CRS.

The attributes added to the table depend on the geometry type and dimension of the input layer:

• for point layers: X (xcoord), Y (ycoord), Z (zcoord) coordinates and/or M value (mvalue)

• for line layers: length and, for the LineString and CompoundCurve geometry types, the feature sinuosity and straight distance (straightdis)

• for polygon layers: perimeter and area

Default menu: Vector ► Geometry Tools

Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: any]	Input vector layer
Calculate using	CALC_METHOD	[enumeration] Default: 0	Calculation parameters to use for the geometric properties. One of: 0 — Layer CRS 1 — Project CRS 2 — Ellipsoidal
Added geom info	OUTPUT	[same as input] Default: [Create temporary layer]	Specify the output (input copy with geometry) layer. One of: Create Temporary Layer (TEMPORARY_OUTPUT) Save to File… Save to Geopackage… Save to PostGIS Table… The file encoding can also be changed here.

Outputs

Label	Name	Type	Description
Added geom info	OUTPUT	[same as input]	Copy of the input vector layer with the addition of the geometry fields

Python code

Algorithm ID: qgis:exportaddgeometrycolumns

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.

24.1.16.2. Affine transform

Applies an affine transformation to the layer geometries. Affine transformations can include translation, scaling and rotation. The operations are performed in the following order: scale, rotation, and translation.

Z and M values (if present) can be translated and scaled.

Fig. 24.40 Vector point layer (green dots) before (left), and after (rigth) an affine transformation (translation).

See also

Translate

Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: any]	Input vector layer
Translation (x-axis)	DELTA_X	[number ] Default: 0	Displacement to apply on the X axis.
Translation (y-axis)	DELTA_Y	[number ] Default: 0	Displacement to apply on the Y axis.
Translation (z-axis)	DELTA_Z	[number ] Default: 0	Displacement to apply on the Z axis.
Translation (m-values)	DELTA_M	[number ] Default: 0	Offset to apply on m values.
Scale factor (x-axis)	SCALE_X	[number ] Default: 1	Scaling value (expansion or contraction) to apply on the X axis.
Scale factor (y-axis)	SCALE_Y	[number ] Default: 1	Scaling value (expansion or contraction) to apply on the Y axis.
Scale factor (z-axis)	SCALE_Z	[number ] Default: 1	Scaling value (expansion or contraction) to apply on the Z axis.
Scale factor (m-values)	SCALE_M	[number ] Default: 1	Scaling value (expansion or contraction) to apply on m values.
Rotation around z-axis (degrees counter-clockwise)	ROTATION_Z	[number ] Default: 0	Angle of the rotation in degrees.
Transformed	OUTPUT	[same as input] Default: [Create temporary layer]	Specify the output vector layer. One of: Create Temporary Layer (TEMPORARY_OUTPUT) Save to File… Save to Geopackage… Save to PostGIS Table… The file encoding can also be changed here.

Outputs

Label	Name	Type	Description
Transformed	OUTPUT	[same as input]	Output (transformed) vector layer.

Python code

Algorithm ID: native:affinetransform

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.

24.1.16.3. Aggregate

Takes a vector or table layer and creates a new layer by aggregating features based on a group by expression.

Features for which group by expression returns the same value are grouped together.

It is possible to group all source features together using constant value in group by parameter, example: NULL.

It is also possible to group features by multiple fields using Array function, example: Array(“Field1”, “Field2”).

Geometries (if present) are combined into one multipart geometry for each group. Output attributes are computed depending on each given aggregate definition.

This algorithm allows to use the default aggregates functions of the QGIS Expression engine.

See also

Collect geometries, Dissolve

Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: any]	Input vector layer
Group by expression	GROUP_BY	[tablefield: any] Default: ‘NULL’	Choose the grouping field. If NULL all features will be grouped.
Aggregates	AGGREGATES	[list]	List of output layer field definitions. Example of a field definition: {‘aggregate’: ‘sum’, ‘delimiter’: ‘,’, ‘input’: ‘ $area’, ‘length’: 10, ‘name’: ‘totarea’, ‘precision’: 0, ‘type’: 6} By default, the list contains all the fields of the input layer. In the GUI, you can edit these fields and their definitions, and you can also: Click the button to add a new field. Click to delete the selected field. Use and to change order of the fields. Click to reset to the default (the fields of the input layer). For each of the fields you’d like to retrieve information from, you need to define the following: Input expression [expression] (input) Field or expression from the input layer. Aggregate function [enumeration] (aggregate) Function to use on the input expression to return the aggregated value. Default: concatenate (for string data type), sum (for numeric data type) Delimiter [string] (delimiter) Text string to separate aggregated values, for example in case of concatenation. Default: , Output field name [string] (name) Name of the aggregated field in the output layer. By default input field name is kept. Type [enumeration] (type) Data type of the output field. One of: 1 — Boolean 2 — Integer 4 — Integer64 6 — Double 10 — String 14 — Date 16 — DateTime Length [number] (length) Length of the output field. Precision [number] (precision) Precision of the output field.
Load fields from layer	GUI only	[vector: any]	You can load fields from another layer and use them for the aggregation
Aggregated	OUTPUT	[same as input] Default: [Create temporary layer]	Specify the output (aggregate) layer One of: Create Temporary Layer (TEMPORARY_OUTPUT) Save to File… Save to Geopackage… Save to PostGIS Table… The file encoding can also be changed here.

Outputs

Label	Name	Type	Description
Aggregated	OUTPUT	[same as input]	Multigeometry vector layer with the aggregated values

Python code

Algorithm ID: native:aggregate

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.

24.1.16.4. Boundary

Returns the closure of the combinatorial boundary of the input geometries (i.e. the topological boundary of the geometry).

Only for polygon and line layers.

For polygon geometries , the boundary consists of all the lines making up the rings of the polygon.

Fig. 24.41 Boundaries (black dashed line) of the source polygon layer

For lines geometries, the boundaries are their end points.

Fig. 24.42 Boundary layer (red points) for lines. In yellow a selected feature.

Parameters

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

Outputs

Label	Name	Type	Description
Boundary	OUTPUT	[vector: point, line]	Boundaries from the input layer (point for line, and line for polygon)

Python code

Algorithm ID: native:boundary

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.

24.1.16.5. Bounding boxes

Calculates the bounding box (envelope) of each feature in an input layer. Polygon and line geometries are supported.

Fig. 24.43 Black lines represent the bounding boxes of each polygon feature

Allows features in-place modification

See also

Minimum bounding geometry

Parameters

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

Outputs

Label	Name	Type	Description
Bounds	OUTPUT	[vector: polygon]	Bounding boxes of input layer

Python code

Algorithm ID: native:boundingboxes

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.

24.1.16.6. Buffer

Computes a buffer area for all the features in an input layer, using a fixed distance.

It is possible to use a negative distance for polygon input layers. In this case the buffer will result in a smaller polygon (setback).

Fig. 24.44 Buffer (in yellow) of points, line and polygon

Allows features in-place modification

Default menu: Vector ► Geoprocessing Tools

See also

Variable distance buffer, Multi-ring buffer (constant distance), Variable width buffer (by M value)

Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: any]	Input vector layer
Distance	DISTANCE	[number ] Default: 10.0	Buffer distance (from the boundary of each feature). You can use the Data Defined button on the right to choose a field from which the radius will be calculated. This way you can have different radius for each feature (see Variable distance buffer).
Segments	SEGMENTS	[number] Default: 5	Controls the number of line segments to use to approximate a quarter circle when creating rounded offsets.
End cap style	END_CAP_STYLE	[enumeration] Default: 0	Controls how line endings are handled in the buffer. One of: 0 — Round 1 — Flat 2 — Square Fig. 24.45 Round, flat and square cap styles
Join style	JOIN_STYLE	[enumeration] Default: 0	Specifies whether round, miter or beveled joins should be used when offsetting corners in a line. Options are: 0 — Round 1 — Miter 2 — Bevel
Miter limit	MITER_LIMIT	[number] Default: 2.0	Controls the maximum distance from the offset curve to use when creating a mitered join (only applicable for miter join styles). Minimum: 1.
Dissolve result	DISSOLVE	[boolean] Default: False	Dissolve the final buffer. If True (checked), overlapping buffers will be dissolved (combined) into a new feature. Fig. 24.46 Standard and dissolved buffer
Buffered	OUTPUT	[vector: polygon] Default: [Create temporary layer]	Specify the output (buffer) layer. One of: Create Temporary Layer (TEMPORARY_OUTPUT) Save to File… Save to Geopackage… Save to PostGIS Table… The file encoding can also be changed here.

Outputs

Label	Name	Type	Description
Buffered	OUTPUT	[vector: polygon]	Output (buffer) polygon layer

Python code

Algorithm ID: native:buffer

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.

24.1.16.7. Centroids

Creates a new point layer, with points representing the centroids of the geometries of the input layer.

The centroid is a single point representing the barycenter (of all parts) of the feature, so it can be outside the feature borders. But can also be a point on each part of the feature.

The attributes of the points in the output layer are the same as for the original features.

Fig. 24.47 The red stars represent the centroids of the features of the input layer.

Allows features in-place modification

Default menu: Vector ► Geometry Tools

See also

Point on Surface

Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: any]	Input vector layer
Create centroid for each part	ALL_PARTS	[boolean ] Default: False	If True (checked), a centroid will be created for each part of the geometry
Centroids	OUTPUT	[vector: point] Default: [Create temporary layer]	Specify the output (centroid) layer. One of: Create Temporary Layer (TEMPORARY_OUTPUT) Save to File… Save to Geopackage… Save to PostGIS Table… The file encoding can also be changed here.

Outputs

Label	Name	Type	Description
Centroids	OUTPUT	[vector: point]	Output point vector layer (centroids)

Python code

Algorithm ID: native:centroids

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.

24.1.16.8. Check validity

Performs a validity check on the geometries of a vector layer.

The geometries are classified in three groups (valid, invalid and error) and for each group, a vector layer with its features is generated:

• The Valid output layer contains only the valid features (without topological errors).

• The Invalid output layer contains all the invalid features found by the algorithm.

• The Error output layer is a point layer that points to where the invalid features were found.

The attribute tables of the generated layers will contain some additional information (“message” for the error layer, “FID” and “_errors” for the invalid layer and only “FID” for the valid layer):

The attribute table of each generated vector layer will contain some additional information (number of errors found and types of error):

Fig. 24.48 Left: the input layer. Right: the valid layer (green), the invalid layer (orange)

Default menu: Vector ► Geometry Tools

See also

Fix geometries and the core plugin Geometry Checker Plugin

Parameters

Label	Name	Type	Description
Input layer	INPUT_LAYER	[vector: any]	Input vector layer
Method	METHOD	[enumeration] Default: 2	Method to use to check validity. Options: 0: The one selected in digitizing settings 1: QGIS 2: GEOS
Ignore ring self intersection	IGNORE_RING_SELF_INTERSECTION	[boolean] Default: False	Ignore self intersecting rings when checking for validity.
Valid output	VALID_OUTPUT	[same as input] Default: [Create temporary layer]	Specify the vector layer to contain a copy of the valid features of the source layer. One of: Skip output Create Temporary Layer (TEMPORARY_OUTPUT) Save to File… Save to Geopackage… Save to PostGIS Table… The file encoding can also be changed here.
Invalid output	INVALID_OUTPUT	[same as input] Default: [Create temporary layer]	Vector layer containing copy of the invalid features of the source layer with the field _errors listing the summary of the error(s) found. One of: Skip output Create Temporary Layer (TEMPORARY_OUTPUT) Save to File… Save to Geopackage… Save to PostGIS Table… The file encoding can also be changed here.
Error output	ERROR_OUTPUT	[vector: point] Default: [Create temporary layer]	Point layer of the exact position of the validity problems detected with the message field describing the error(s) found. One of: Skip output Create Temporary Layer (TEMPORARY_OUTPUT) Save to File… Save to Geopackage… Save to PostGIS Table… The file encoding can also be changed here.

Outputs

Label	Name	Type	Description
Count of errors	ERROR_COUNT	[number]	The number of geometries that caused errors.
Error output	ERROR_OUTPUT	[vector: point]	Point layer of the exact position of the validity problems detected with the message field describing the error(s) found.
Count of invalid features	INVALID_COUNT	[number]	The number of invalid geometries.
Invalid output	INVALID_OUTPUT	[same as input]	Vector layer containing copy of the invalid features of the source layer with the field _errors listing the summary of the error(s) found.
Count of valid features	VALID_COUNT	[number]	The number of valid geometries.
Valid output	VALID_OUTPUT	[same as input]	Vector layer containing a copy of the valid features of the source layer.

Python code

Algorithm ID: qgis:checkvalidity

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.

Types of error messages and their meanings

Table 24.1 If the GEOS method is used the following error messages can occur:

Error message	Explanation	Example
Repeated point	This error happens when a given vertex is repeated.
Ring self-intersection	This error happens when a geometry touches itself and generates a ring.
Self-intersection	This error happens when a geometry touches itself.
Topology validation error
Hole lies outside shell
Holes are nested
Interior is disconnected
Nested shells	This error happens when a polygon geometry is on top of another polygon geometry.
Duplicate rings	This error happens when two rings (exterior or interior) of a polygon geometry are identical
Too few points in geometry component
Invalid coordinate	For a point geometry, this error happens when the geometry does not have a proper coordinate pair. The coordinate pair does not contain a latitude value and a longitude value in that order.
Ring is not closed

Table 24.2 If the QGIS method is used the following error messages can occur:

Error message	Explanation	Example
Segment %1 of ring %2 of polygon %3 intersects segment %4 of ring %5 of polygon %6 at %7
Ring %1 with less than four points
Ring %1 not closed
Line %1 with less than two points
Line %1 contains %n duplicate node(s) at %2	This error happens when consecutive points on a line have the same coordinates.
Segments %1 and %2 of line %3 intersect at %4	This error happens when a line self intersects (two segments of the line intersect each other).
Ring self-intersection	This error happens when an outer or inner (island) ring / boundary of a polygon geometry intersects itself.
Ring %1 of polygon %2 not in exterior ring
Polygon %1 lies inside polygon %2	This error happens when a part of a MultiPolygon geometry is inside a hole of a MultiPolygon geometry.

24.1.16.9. Collect geometries

Takes a vector layer and collects its geometries into new multipart geometries.

One or more attributes can be specified to collect only geometries belonging to the same class (having the same value for the specified attributes), alternatively all geometries can be collected.

All output geometries will be converted to multi geometries, even those with just a single part. This algorithm does not dissolve overlapping geometries - they will be collected together without modifying the shape of each geometry part.

See the ‘Promote to multipart’ or ‘Aggregate’ algorithms for alternative options.

Default menu: Vector ► Geometry Tools

See also

Aggregate, Promote to multipart, Dissolve

Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: any]	Input vector layer
Unique ID fields	FIELD	[tablefield: any] [list]	Choose one or more attributes to collect the geometries
Collected	OUTPUT	[same as input]	Vector layer with collected geometries

Outputs

Label	Name	Type	Description
Collected	OUTPUT	[same as input] Default: [Create temporary layer]	Specify the output vector layer for the collected geometries. One of: Create Temporary Layer (TEMPORARY_OUTPUT) Save to File… Save to Geopackage… Save to PostGIS Table… The file encoding can also be changed here.

Python code

Algorithm ID: native:collect

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.

24.1.16.10. Concave hull (alpha shapes)

Computes the concave hull of the features in an input point layer.

Fig. 24.49 Concave hulls with different thresholds (0.3, 0.6, 0.9)

See also

Convex hull, Concave hull (k-nearest neighbor)

Parameters

Label	Name	Type	Description
Input point layer	INPUT	[vector: point]	Input point vector layer
Threshold	ALPHA	[number] Default: 0.3	Number from 0 (maximum concave hull) to 1 (convex hull).
Allow holes	HOLES	[boolean] Default: True	Choose whether to allow holes in the final concave hull
Split multipart geometry into singlepart geometries	NO_MULTIGEOMETRY	[boolean] Default: True	Check if you want to have singlepart geometries instead of multipart ones.
Concave hull	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 PostGIS Table… The file encoding can also be changed here.

Outputs

Label	Name	Type	Description
Concave hull	OUTPUT	[vector: polygon]	The output vector layer

Python code

Algorithm ID: qgis:concavehull

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.

24.1.16.11. Concave hull (k-nearest neighbor)

Generates a concave hull polygon from a set of points. If the input layer is a line or polygon layer, it will use the vertices.

The number of neighbors to consider determines the concaveness of the output polygon. A lower number will result in a concave hull that follows the points very closely, while a higher number will have a smoother shape. The minimum number of neighbor points to consider is 3. A value equal to or greater than the number of points will result in a convex hull.

If a field is selected, the algorithm will group the features in the input layer using unique values in that field and generate individual polygons in the output layer for each group.

See also

Concave hull (alpha shapes)

Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: any]	Input vector layer
Number of neighboring points to consider (a lower number is more concave, a higher number is smoother)	KNEIGHBORS	[number] Default: 3	Determines the concaveness of the output polygon. A small number will result in a concave hull that follows the points very closely, while a high number will make the polygon look more like the convex hull (if the number is equal to or larger than the number of features, the result will be the convex hull). Minimum value: 3.
Field Optional	FIELD	[tablefield: any] Default: None	If specified, one concave hull polygon is generated for each unique value of the field (by selecting features using this value).
Concave hull	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 PostGIS Table… The file encoding can also be changed here.

Outputs

Label	Name	Type	Description
Concave hull	OUTPUT	[vector: polygon]	The output vector layer

Python code

Algorithm ID: qgis:knearestconcavehull

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.

24.1.16.12. Convert geometry type

Generates a new layer based on an existing one, with a different type of geometry.

The attribute table of the output layer is the same as the one of the input layer.

Not all conversions are possible. For instance, a line layer can be converted to a point layer, but a point layer cannot be converted to a line layer.

See also

Polygonize, Lines to polygons, Polygons to lines, Points to path

Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: any]	Input vector layer
New geometry type	TYPE	[enumeration] Default: 0	Geometry type to apply to the output features. One of: 0 — Centroids 1 — Nodes 2 — Linestrings 3 — Multilinestrings 4 — Polygons
Converted	OUTPUT	[vector: any] Default: [Create temporary layer]	Specify the output vector layer. One of: Create Temporary Layer (TEMPORARY_OUTPUT) Save to File… Save to Geopackage… Save to PostGIS Table… The file encoding can also be changed here.

Outputs

Label	Name	Type	Description
Converted	OUTPUT	[vector: any]	Output vector layer - the type depends on the parameters

Python code

Algorithm ID: qgis:convertgeometrytype

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.

24.1.16.13. Convert to curved geometries

Converts a geometry into its curved geometry equivalent.

Already curved geometries will be retained without change.

Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: line or polygon]	Input vector layer
Maximum distance tolerance	DISTANCE	[number] Default: 0.000001	The maximum distance allowed between the original location of vertices and where they would fall on the converted curved geometries
Maximum angle tolerance	ANGLE	[number] Default: 0.000001	Segments are considered as suitable for replacing with an arc if the points are all regularly spaced on the candidate arc. This parameter specifies the maximum angular deviation (in degrees) allowed when testing for regular point spacing. Between 0 and 45°.
Curves	OUTPUT	[vector: compoundcurve or curvepolygon] 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… Append to Layer… The file encoding can also be changed here.

Outputs

Label	Name	Type	Description
Curves	OUTPUT	[vector: compoundcurve or curvepolygon]	Output vector layer with curved geometries

Python code

Algorithm ID: native:converttocurves

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.

24.1.16.14. Convex hull

Calculates the convex hull for each feature in an input layer.

See the ‘Minimum bounding geometry’ algorithm for a convex hull calculation which covers the whole layer or grouped subsets of features.

Fig. 24.50 Black lines identify the convex hull for each layer feature

Allows features in-place modification

Default menu: Vector ► Geoprocessing Tools

See also

Minimum bounding geometry, Concave hull (alpha shapes)

Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: any]	Input vector layer
Convex hull	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 PostGIS Table… The file encoding can also be changed here.

Outputs

Label	Name	Type	Description
Convex hull	OUTPUT	[vector: polygon]	The output (convex hull) vector layer

Python code

Algorithm ID: native:convexhull

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.

24.1.16.15. Create layer from extent

Creates a new vector layer that contains a single feature with geometry matching the extent of the input layer.

It can be used in models to convert a literal extent (xmin, xmax, ymin, ymax format) into a layer which can be used for other algorithms which require a layer based input.

See also

Create layer from point

Parameters

Label	Name	Type	Description
Extent (xmin, xmax, ymin, ymax)	INPUT	[extent]	Input extent
Extent	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 PostGIS Table… The file encoding can also be changed here.

Outputs

Label	Name	Type	Description
Extent	OUTPUT	[vector: polygon]	The output (extent) vector layer

Python code

Algorithm ID: native:extenttolayer

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.

24.1.16.16. Create layer from point

Creates a new vector layer that contains a single feature with geometry matching a point parameter. It can be used in models to convert a point into a point layer for algorithms which require a layer based input.

See also

Create layer from extent

Parameters

Label	Name	Type	Description
Point	INPUT	[coordinates]	Input point, including CRS info (example: 397254,6214446 [EPSG:32632]). If the CRS is not provided, the Project CRS will be used. The point can be specified by clicking on the map canvas.
Point	OUTPUT	[vector: point] Default: [Create temporary layer]	Specify the output layer. One of: Create Temporary Layer (TEMPORARY_OUTPUT) Save to File… Save to Geopackage… Save to PostGIS Table… The file encoding can also be changed here.

Outputs

Label	Name	Type	Description
Point	OUTPUT	[vector: point]	The output point vector layer containing the input point.

Python code

Algorithm ID: native:pointtolayer

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.

24.1.16.17. Create wedge buffers

Creates wedge shaped buffers from input points.

Fig. 24.51 Wedge buffers

The native output from this algorithm are CurvePolygon geometries, but these may be automatically segmentized to Polygons depending on the output format.

See also

Buffer, Variable width buffer (by M value), Tapered buffers

Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: point]	Input point vector layer
Azimuth (degrees from North)	AZIMUTH	[number ] Default: 0.0	Angle (in degrees) as the middle value of the wedge
Wedge width (in degrees)	WIDTH	[number ] Default: 45.0	Width (in degrees) of the buffer. The wedge will extend to half of the angular width either side of the azimuth direction. Fig. 24.52 Azimuth and width values of the wedge buffer
Outer radius	OUTER_RADIUS	[number ] Default: 1.0	The outer size (length) of the wedge: the size is meant from the source point to the edge of the wedge shape.
Inner radius Optional	INNER_RADIUS	[number ] Default: 0.0	Inner radius value. If 0 the wedge will begin from the source point.
Buffers	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 PostGIS Table… The file encoding can also be changed here.

Outputs

Label	Name	Type	Description
Buffers	OUTPUT	[vector: polygon]	The output (wedge buffer) vector layer

Python code

Algorithm ID: native:wedgebuffers

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.

24.1.16.18. Delaunay triangulation

Creates a polygon layer with the Delaunay triangulation corresponding to the input point layer.

Fig. 24.53 Delaunay triangulation on points

Default menu: Vector ► Geometry Tools

Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: point]	Input point vector layer
Delaunay triangulation	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 PostGIS Table… The file encoding can also be changed here.

Outputs

Label	Name	Type	Description
Delaunay triangulation	OUTPUT	[vector: polygon]	The output (Delaunay triangulation) vector layer

Python code

Algorithm ID: qgis:delaunaytriangulation

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.

24.1.16.19. Delete holes

Takes a polygon layer and removes holes in polygons. It creates a new vector layer in which polygons with holes have been replaced by polygons with only their external ring. Attributes are not modified.

An optional minimum area parameter allows removing only holes which are smaller than a specified area threshold. Leaving this parameter at 0.0 results in all holes being removed.

Fig. 24.54 Before and after the cleaning

Allows features in-place modification

Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: polygon]	Input polygon vector layer
Remove holes with area less than Optional	MIN_AREA	[number ] Default: 0.0	Only holes with an area less than this threshold will be deleted. With a value of 0.0, all the holes will be deleted.
Cleaned	OUTPUT	[same as input] Default: [Create temporary layer]	Specify the output vector layer. One of: Create Temporary Layer (TEMPORARY_OUTPUT) Save to File… Save to Geopackage… Save to PostGIS Table… The file encoding can also be changed here.

Outputs

Label	Name	Type	Description
Cleaned	OUTPUT	[same as input]	The output (cleaned) vector layer

Python code

Algorithm ID: native:deleteholes

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.

24.1.16.20. Densify by count

Takes a polygon or line layer and generates a new one in which the geometries have a larger number of vertices than the original one.

If the geometries have Z or M values present then these will be linearly interpolated at the added vertices.

The number of new vertices to add to each segment is specified as an input parameter.

Fig. 24.55 Red points show the vertices before and after the densify

Allows features in-place modification

Default menu: Vector ► Geometry Tools

See also

Densify by interval

Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: line, polygon]	Input line or polygon vector layer
Vertices to add	VERTICES	[number] Default: 1	Number of vertices to add to each segment
Densified	OUTPUT	[same as input] Default: [Create temporary layer]	Specify the output vector layer. One of: Create Temporary Layer (TEMPORARY_OUTPUT) Save to File… Save to Geopackage… Save to PostGIS Table… The file encoding can also be changed here.

Outputs

Label	Name	Type	Description
Densified	OUTPUT	[same as input]	The output (densified) vector layer

Python code

Algorithm ID: native:densifygeometries

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.

24.1.16.21. Densify by interval

Takes a polygon or line layer and generates a new one in which the geometries have a larger number of vertices than the original one.

The geometries are densified by adding regularly placed extra vertices inside each segment so that the maximum distance between any two vertices does not exceed the specified distance.

If the geometries have Z or M values present then these will be linearly interpolated at the added vertices.

Example

Specifying a distance of 3 would cause the segment [0 0] -> [10 0] to be converted to [0 0] -> [2.5 0] -> [5 0] -> [7.5 0] -> [10 0], since 3 extra vertices are required on the segment and spacing these at 2.5 increments allows them to be evenly spaced over the segment.

Fig. 24.56 Densify geometry at a given interval

Allows features in-place modification

See also

Densify by count

Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: line, polygon]	Input line or polygon vector layer
Interval between vertices to add	INTERVAL	[number ] Default: 1.0	Maximum distance between two consecutive vertices
Densified	OUTPUT	[same as input] Default: [Create temporary layer]	Specify the output vector layer. One of: Create Temporary Layer (TEMPORARY_OUTPUT) Save to File… Save to Geopackage… Save to PostGIS Table… The file encoding can also be changed here.

Outputs

Label	Name	Type	Description
Densified	OUTPUT	[same as input]	The output (densified) vector layer

Python code

Algorithm ID: native:densifygeometriesgivenaninterval

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.

24.1.16.22. Dissolve

Takes a vector layer and combines its features into new features. One or more attributes can be specified to dissolve features belonging to the same class (having the same value for the specified attributes), alternatively all features can be dissolved to a single feature.

All output geometries will be converted to multi geometries. In case the input is a polygon layer, common boundaries of adjacent polygons being dissolved will get erased.

The resulting attribute table will have the same fields as the input layer. The values in the output layer’s fields are the ones of the first input feature that happens to be processed.

Fig. 24.57 Dissolve the polygon layer on a common attribute

Default menu: Vector ► Geoprocessing Tools

See also

Aggregate, Collect geometries

Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: any]	Input vector layer
Dissolve field(s) Optional	FIELD	[tablefield: any] [list] Default: []	Features having the same value for the selected field(s) will be replaced with a single one and their geometries are merged. If no field is provided then all the features are dissolved, resulting in a single (multipart) feature.
Dissolved	OUTPUT	[same as input] Default: [Create temporary layer]	Specify the output vector layer. One of: Create Temporary Layer (TEMPORARY_OUTPUT) Save to File… Save to Geopackage… Save to PostGIS Table… The file encoding can also be changed here.

Outputs

Label	Name	Type	Description
Dissolved	OUTPUT	[same as input]	The output vector layer with dissolved geometries

Python code

Algorithm ID: native:dissolve

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.

24.1.16.23. Drape (set Z value from raster)

Uses values sampled from a band within a raster layer to set the Z value for every overlapping vertex in the feature geometry. The raster values can optionally be scaled by a preset amount.

If Z values already exist in the layer, they will be overwritten with the new value. If no Z values exist, the geometry will be upgraded to include the Z dimension.

See also

Set M value from raster, Set Z value

Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: any]	Input vector layer
Raster layer	RASTER	[raster]	Raster layer with Z values
Band number	BAND	[raster band] Default: 1	The raster band to take the Z values from
Value for nodata or non-intersecting vertices	NODATA	[number ] Default: 0	Value to use in case the vertex does not intersect (a valid pixel of) the raster
Scale factor	SCALE	[number ] Default: 1.0	Scaling value: the band values are multiplied by this value.
Updated	OUTPUT	[same as input] Default: [Create temporary layer]	Specify the output vector layer (with Z values from the raster layer). One of: Create Temporary Layer (TEMPORARY_OUTPUT) Save to File… Save to Geopackage… Save to PostGIS Table… The file encoding can also be changed here.

Outputs

Label	Name	Type	Description
Updated	OUTPUT	[same as input]	The output vector layer with Z values from the raster layer

Python code

Algorithm ID: native:setzfromraster

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.

24.1.16.24. Drop M/Z values

Removes M (measure) or Z (altitude) values from input geometries.

See also

Set M value, Set Z value

Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: any]	Input vector layer with M or Z values
Drop M Values	DROP_M_VALUES	[boolean] Default: False	Removes the M values from the geometries
Drop Z Values	DROP_Z_VALUES	[boolean] Default: False	Removes the Z values from the geometries
Z/M Dropped	OUTPUT	[same as input] Default: [Create temporary layer]	Specify the output vector layer. One of: Create Temporary Layer (TEMPORARY_OUTPUT) Save to File… Save to Geopackage… Save to PostGIS Table… The file encoding can also be changed here.

Outputs

Label	Name	Type	Description
Z/M Dropped	OUTPUT	[same as input]	The output vector layer (identical to the input layer, except that the M and/or Z dimensions have been removed from the geometries).

Python code

Algorithm ID: native:dropmzvalues

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.

24.1.16.25. Eliminate selected polygons

Combines selected polygons of the input layer with certain adjacent polygons by erasing their common boundary. The adjacent polygon can be either the one with the largest or smallest area or the one sharing the largest common boundary with the polygon to be eliminated.

Eliminate is normally used to get rid of sliver polygons, i.e. tiny polygons that are a result of polygon intersection processes where boundaries of the inputs are similar but not identical.

Default menu: Vector ► Geoprocessing Tools

See also

Fix geometries

Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: polygon]	Input polygon vector layer
Merge selection with the neighboring polygon with the	MODE	[enumeration] Default: None	Choose the parameter to use in order to get rid of the selected polygons: 0 — Largest Area 1 — Smallest Area 2 — Largest Common Boundary
Eliminated	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 PostGIS Table… The file encoding can also be changed here.

Outputs

Label	Name	Type	Description
Eliminated	OUTPUT	[vector: polygon]	The output polygon vector layer.

Python code

Algorithm ID: qgis:eliminateselectedpolygons

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.

24.1.16.26. Explode lines

Takes a lines layer and creates a new one in which each line layer is replaced by a set of lines representing the segments in the original line.

Each line in the resulting layer contains only a start and an end point, with no intermediate vertices between them.

Fig. 24.58 The original line layer and the exploded one

Allows features in-place modification

See also

Subdivide, Line substring

Parameters

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

Outputs

Label	Name	Type	Description
Exploded	OUTPUT	[vector: line]	The output line vector layer with features representing each segment of the input layer.

Python code

Algorithm ID: native:explodelines

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.

24.1.16.27. Extend lines

Extends line geometry by a specified amount at the start and end of the line.

Lines are extended using the bearing of the first and last segment in the line.

Fig. 24.59 The red dashes represent the initial and final extension of the original layer

Allows features in-place modification

See also

Line substring

Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: line]	Input line vector layer
Start distance	START_DISTANCE	[number ]	Distance by which to extend the first segment of the line (starting point)
End distance	END_DISTANCE	[number ]	Distance by which to extend the last segment of the line (ending point)
Extended	OUTPUT	[vector: line] Default: [Create temporary layer]	Specify the output vector layer. One of: Create Temporary Layer (TEMPORARY_OUTPUT) Save to File… Save to Geopackage… Save to PostGIS Table… The file encoding can also be changed here.

Outputs

Label	Name	Type	Description
Extended	OUTPUT	[vector: line]	The output (extended) line vector layer.

Python code

Algorithm ID: native:extendlines

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.

24.1.16.28. Extract M values

Extracts M values from geometries into feature attributes.

By default only the M value from the first vertex of each feature is extracted, however the algorithm can optionally calculate statistics on all of the geometry’s M values, including sum, mean, minimum and maximum.

See also

Extract Z values, Set M value, Drop M/Z values

Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: any]	Input vector layer
Summaries to calculate	SUMMARIES	[enumeration] Default: [0]	Statistics on the M values of a geometry. One or more of: 0 — First 1 — Last 2 — Count 3 — Sum 4 — Mean 5 — Median 6 — St.dev (pop) 7 — Minimum 8 — Maximum 9 — Range 10 — Minority 11 — Majority 12 — Variety 13 — Q1 14 — Q3 15 — IQR
Output column prefix	COLUMN_PREFIX	[string] Default: ‘m_’	The prefix for the output (M) column
Extracted	OUTPUT	[same as input] Default: [Create temporary layer]	Specify the output layer. One of: Create Temporary Layer (TEMPORARY_OUTPUT) Save to File… Save to Geopackage… Save to PostGIS Table… The file encoding can also be changed here.

Outputs

Label	Name	Type	Description
Extracted	OUTPUT	[same as input]	The output vector layer (with M values)

Python code

Algorithm ID: native:extractmvalues

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.

24.1.16.29. Extract specific vertices

Takes a vector layer and generates a point layer with points representing specific vertices in the input geometries.

For instance, this algorithm can be used to extract the first or last vertices in the geometry. The attributes associated to each point are the same ones associated to the feature that the vertex belongs to.

The vertex indices parameter accepts a comma separated string specifying the indices of the vertices to extract. The first vertex corresponds to an index of 0, the second vertex has an index of 1, etc. Negative indices can be used to find vertices at the end of the geometry, e.g., an index of -1 corresponds to the last vertex, -2 corresponds to the second last vertex, etc.

Additional fields are added to the vertices indicating the specific vertex position (e.g., 0, -1, etc), the original vertex index, the vertex’s part and its index within the part (as well as its ring for polygons), distance along the original geometry and bisector angle of vertex for the original geometry.

See also

Extract vertices, Filter vertices by M value, Filter vertices by Z value

Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: any]	Input vector layer
Vertex indices	VERTICES	[string] Default: ‘0’	Comma-separated string of the indices of the vertices to extract.
Vertices	OUTPUT	[vector: point] Default: [Create temporary layer]	Specify the output vector layer. One of: Create Temporary Layer (TEMPORARY_OUTPUT) Save to File… Save to Geopackage… Save to PostGIS Table… The file encoding can also be changed here.

Outputs

Label	Name	Type	Description
Vertices	OUTPUT	[vector: point]	The output (point) vector layer containing the specified vertices from the input layer geometries.

Python code

Algorithm ID: native:extractspecificvertices

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.

24.1.16.30. Extract vertices

Takes a vector layer and generates a point layer with points representing the vertices in the input geometries.

The attributes associated to each point are the same ones associated to the feature that the vertex belongs to.

Additional fields are added to the vertices indicating the vertex index (beginning at 0), the feature’s part and its index within the part (as well as its ring for polygons), distance along original geometry and bisector angle of vertex for original geometry.

Fig. 24.60 Vertices extracted for line and polygon layer

Default menu: Vector ► Geometry Tools

See also

Extract specific vertices, Filter vertices by M value, Filter vertices by Z value

Parameters

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

Outputs

Label	Name	Type	Description
Vertices	OUTPUT	[vector: point]	The output (point) vector layer containing the vertices from the input layer geometries.

Python code

Algorithm ID: native:extractvertices

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.

24.1.16.31. Extract Z values

Extracts Z values from geometries into feature attributes.

By default only the Z value from the first vertex of each feature is extracted, however the algorithm can optionally calculate statistics on all of the geometry’s Z values, including sum, mean, minimum and maximum.

See also

Extract M values, Set Z value, Drop M/Z values

Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: any]	Input vector layer
Summaries to calculate	SUMMARIES	[enumeration] Default: [0]	Statistics on the Z values of a geometry. One or more of: 0 — First 1 — Last 2 — Count 3 — Sum 4 — Mean 5 — Median 6 — St.dev (pop) 7 — Minimum 8 — Maximum 9 — Range 10 — Minority 11 — Majority 12 — Variety 13 — Q1 14 — Q3 15 — IQR
Output column prefix	COLUMN_PREFIX	[string] Default: ‘z_’	The prefix for the output (Z) column
Extracted	OUTPUT	[same as input] Default: [Create temporary layer]	Specify the output layer. One of: Create Temporary Layer (TEMPORARY_OUTPUT) Save to File… Save to Geopackage… Save to PostGIS Table… The file encoding can also be changed here.

Outputs

Label	Name	Type	Description
Extracted	OUTPUT	[same as input]	The output vector layer (with Z values)

Python code

Algorithm ID: native:extractzvalues

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.

24.1.16.32. Filter vertices by M value

Filters away vertices based on their M value, returning geometries with only vertex points that have a M value greater than or equal to the specified minimum value and/or less than or equal to the maximum value.

If the minimum value is not specified then only the maximum value is tested, and similarly if the maximum value is not specified then only the minimum value is tested.

Fig. 24.61 The red line represents the black line with only vertices whose M value is <=10.

Note

Depending on the input geometry attributes and the filters used, the resultant geometries created by this algorithm may no longer be valid.

See also

Filter vertices by Z value, Extract vertices, Extract specific vertices

Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: line, polygon]	Input line or polygon vector layer to remove vertices from
Minimum Optional	MIN	[number ] Default: Not set	Minimum of M values allowed
Maximum Optional	MAX	[number ] Default: Not set	Maximum of M values allowed
Filtered	OUTPUT	[same as input] Default: [Create temporary layer]	Specify the output vector layer. One of: Create Temporary Layer (TEMPORARY_OUTPUT) Save to File… Save to Geopackage… Save to PostGIS Table… The file encoding can also be changed here.

Outputs

Label	Name	Type	Description
Filtered	OUTPUT	[same as input]	The output vector layer of features with only the filtered vertices.

Python code

Algorithm ID: native:filterverticesbym

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.

24.1.16.33. Filter vertices by Z value

Filters away vertices based on their Z value, returning geometries with only vertex points that have a Z value greater than or equal to the specified minimum value and/or less than or equal to the maximum value.

If the minimum value is not specified then only the maximum value is tested, and similarly if the maximum value is not specified then only the minimum value is tested.

Fig. 24.62 The red line represents the black line with only vertices whose Z value is <=10.

Note

Depending on the input geometry attributes and the filters used, the resultant geometries created by this algorithm may no longer be valid. You may need to run the Fix geometries algorithm to ensure their validity.

See also

Filter vertices by M value, Extract vertices, Extract specific vertices

Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: line, polygon]	Input line or polygon vector layer to remove vertices from
Minimum Optional	MIN	[number ] Default: Not set	Minimum of Z values allowed
Maximum Optional	MAX	[number ] Default: Not set	Maximum of Z values allowed
Filtered	OUTPUT	[same as input] Default: [Create temporary layer]	Specify the output vector layer. One of: Create Temporary Layer (TEMPORARY_OUTPUT) Save to File… Save to Geopackage… Save to PostGIS Table… The file encoding can also be changed here.

Outputs

Label	Name	Type	Description
Filtered	OUTPUT	[same as input]	The output vector layer of features with only the filtered vertices.

Python code

Algorithm ID: native:filterverticesbyz

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.

24.1.16.34. Fix geometries

Attempts to create a valid representation of a given invalid geometry without losing any of the input vertices. Already valid geometries are returned without further intervention. Always outputs multi-geometry layer.

Note

M values will be dropped from the output.

Allows features in-place modification

See also

Check validity

Parameters

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

Outputs

Label	Name	Type	Description
Fixed geometries	OUTPUT	[same as input]	The output vector layer with fixed geometries.

Python code

Algorithm ID: native:fixgeometries

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.

24.1.16.35. Force right-hand-rule

Forces polygon geometries to respect the Right-Hand-Rule, in which the area that is bounded by a polygon is to the right of the boundary. In particular, the exterior ring is oriented in a clockwise direction and any interior rings in a counter-clockwise direction.

Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: polygon]	Input vector layer
Reoriented	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 PostGIS Table… The file encoding can also be changed here.

Outputs

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

Python code

Algorithm ID: native:forcerhr

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.

24.1.16.36. Geodesic line split at antimeridian

Splits a line into multiple geodesic segments, whenever the line crosses the antimeridian (±180 degrees longitude).

Splitting at the antimeridian helps the visual display of the lines in some projections. The returned geometry will always be a multi-part geometry.

Whenever line segments in the input geometry cross the antimeridian, they will be split into two segments, with the latitude of the breakpoint being determined using a geodesic line connecting the points either side of this segment. The current project ellipsoid setting will be used when calculating this breakpoint.

If the input geometry contains M or Z values, these will be linearly interpolated for the new vertices created at the antimeridian.

Parameters

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

Outputs

Label	Name	Type	Description
Split	OUTPUT	[vector: line]	The output line vector layer split at the antimeridian.

Python code

Algorithm ID: native:antimeridiansplit

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.

24.1.16.37. Geometry by expression

Updates existing geometries (or creates new geometries) for input features by use of a QGIS expression.

This allows complex geometry modifications which can utilize all the flexibility of the QGIS expression engine to manipulate and create geometries for output features.

For help with QGIS expression functions, see the inbuilt help available in the expression builder.

Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: any]	Input vector layer
Output geometry type	OUTPUT_GEOMETRY	[enumeration] Default: 0	The output geometry strongly depends on the expression: for instance, if you create a buffer the geometry type has to be polygon. One of: 0 — Polygon 1 — Line 2 — Point
Output geometry has z values	WITH_Z	[boolean] Default: False	Choose if the output geometry should include the Z dimension
Output geometry has m values	WITH_M	[boolean] Default: False	Choose if the output geometry should include the M dimension
Geometry expression	EXPRESSION	[expression] Default: ‘$geometry’	Add the geometry expression you want to use. You can use the button to open the Expression Dialog. The dialog lists all the relevant expressions, together with their help and guide.
Modified geometry	OUTPUT	[vector: any] Default: [Create temporary layer]	Specify the output vector layer. One of: Create Temporary Layer (TEMPORARY_OUTPUT) Save to File… Save to Geopackage… Save to PostGIS Table… The file encoding can also be changed here.

Outputs

Label	Name	Type	Description
Modified geometry	OUTPUT	[vector: any]	The output vector layer

Python code

Algorithm ID: native:geometrybyexpression

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.

24.1.16.38. Interpolate point on line

Creates a point geometry interpolated at a set distance along line or curve geometries.

Z and M values are linearly interpolated from existing values.

If a multipart geometry is encountered, only the first part is considered when calculating the substring.

If the specified distance is greater than the input feature’s length, the resultant feature will have a null geometry.

Fig. 24.63 Interpolated point at 500m of the beginning of the line

See also

Points along geometry

Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: line, polygon]	Input line or polygon vector layer
Distance	DISTANCE	[number ] Default: 0.0	Distance from the beginning of the line
Interpolated points	OUTPUT	[vector: point] Default: [Create temporary layer]	Specify the output vector layer. One of: Create Temporary Layer (TEMPORARY_OUTPUT) Save to File… Save to Geopackage… Save to PostGIS Table… The file encoding can also be changed here.

Outputs

Label	Name	Type	Description
Interpolated points	OUTPUT	[vector: point]	The output point vector layer with features at a set distance along the line or polygon boundary

Python code

Algorithm ID: native:interpolatepoint

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.

24.1.16.39. Keep N biggest parts

Takes a layer with polygons or multipolygons and returns a new layer in which only the n largest polygons of each multipolygon feature are kept. If a feature has n or fewer parts, the feature will just be copied.

Fig. 24.64 Clockwise from top left: original multipart feature, one, two and three biggest parts kept

Parameters

Label	Name	Type	Description
Polygons	INPUT	[vector: polygon]	Input polygon vector layer
Parts to keep	PARTS	[number] Default: 1	Number of parts to keep. If 1, only the biggest part of the feature will be kept.
Parts	OUTPUT	[vector: polygon] Default: [Create temporary layer]	Specify the output polygon vector layer. One of: Create Temporary Layer (TEMPORARY_OUTPUT) Save to File… Save to Geopackage… Save to PostGIS Table… The file encoding can also be changed here.

Outputs

Label	Name	Type	Description
Parts	OUTPUT	[vector: polygon]	The output polygon vector layer with the N biggest parts of each feature

Python code

Algorithm ID: qgis:keepnbiggestparts

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.

24.1.16.40. Line substring

Returns the portion of a line (or curve) which falls between the specified start and end distances (measured from the beginning of the line).

Z and M values are linearly interpolated from existing values.

If a multipart geometry is encountered, only the first part is considered when calculating the substring.

Fig. 24.65 Substring line with starting distance set at 0 meters and the ending distance at 250 meters.

Allows features in-place modification

See also

Extend lines

Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: line]	Input line vector layer
Start distance	START_DISTANCE	[number ]	Distance along the input line to the start point of the output feature
End distance	END_DISTANCE	[number ]	Distance along the input line to the end point of the output feature
Substring	OUTPUT	[vector: line] Default: [Create temporary layer]	Specify the output line vector layer. One of: Create Temporary Layer (TEMPORARY_OUTPUT) Save to File… Save to Geopackage… Save to PostGIS Table… The file encoding can also be changed here.

Outputs

Label	Name	Type	Description
Substring	OUTPUT	[vector: line]	The output line vector layer.

Python code

Algorithm ID: native:linesubstring

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.

24.1.16.41. Lines to polygons

Generates a polygon layer using as polygon rings the lines from an input line layer.

The attribute table of the output layer is the same as the one of the input layer.

Default menu: Vector ► Geometry Tools

See also

Polygons to lines, Polygonize, Convert geometry type

Parameters

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

Outputs

Label	Name	Type	Description
Polygons	OUTPUT	[vector: polygon]	The output polygon vector layer.

Python code

Algorithm ID: qgis:linestopolygons

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.

24.1.16.42. Merge lines

Joins all connected parts of MultiLineString geometries into single LineString geometries.

If any parts of the input MultiLineString geometries are not connected, the resultant geometry will be a MultiLineString containing any lines which could be merged and any non-connected line parts.

Allows features in-place modification

Parameters

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

Outputs

Label	Name	Type	Description
Merged	OUTPUT	[vector: line]	The output (merged) line vector layer.

Python code

Algorithm ID: native:mergelines

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.

24.1.16.43. Minimum bounding geometry

Creates geometries which enclose the features from an input layer. The features can be grouped by a field. The output layer will then contain one feature per group value with a geometry (MBB) that covers the geometries of the features with matching value.

The following enclosing geometry types are supported:

• bounding box (envelope)

• oriented rectangle

• circle

• convex hull

Fig. 24.66 Clockwise from top left: envelope, oriented rectangle, circle, convex hull

See also

Minimum enclosing circles

Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: any]	Input vector layer
Field Optional	FIELD	[tablefield: any]	Features can be grouped by a field. If set, this causes the output layer to contain one feature per grouped value with a minimal geometry covering only the features with matching values.
Geometry type	TYPE	[enumeration] Default: 0	Enclosing geometry types. One of: 0 — Envelope (Bounding Box) 1 — Minimum Oriented Rectangle 2 — Minimum Enclosing Circle 3 — Convex Hull
Bounding geometry	OUTPUT	[vector: polygon] Default: [Create temporary layer]	Specify the output polygon vector layer. One of: Create Temporary Layer (TEMPORARY_OUTPUT) Save to File… Save to Geopackage… Save to PostGIS Table… The file encoding can also be changed here.

Outputs

Label	Name	Type	Description
Bounding geometry	OUTPUT	[vector: polygon]	The output (bounding) polygon vector layer.

Python code

Algorithm ID: qgis:minimumboundinggeometry

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.

24.1.16.44. Minimum enclosing circles

Calculates the minimum enclosing circles of the features in the input layer.

Fig. 24.67 Enclosing circles for each feature

Allows features in-place modification

See also

Minimum bounding geometry

Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: any]	Input vector layer
Number of segment in circles	SEGMENTS	[number] Default: 72	The number of segment used to approximate a circle. Minimum 8, maximum 100000.
Minimum enclosing circles	OUTPUT	[vector: polygon] Default: [Create temporary layer]	Specify the output polygon vector layer. One of: Create Temporary Layer (TEMPORARY_OUTPUT) Save to File… Save to Geopackage… Save to PostGIS Table… The file encoding can also be changed here.

Outputs

Label	Name	Type	Description
Minimum enclosing circles	OUTPUT	[vector: polygon]	The output polygon vector layer.

Python code

Algorithm ID: native:minimumenclosingcircle

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.

24.1.16.45. Multi-ring buffer (constant distance)

Computes multi-ring (donut) buffer for the features of the input layer, using a fixed or dynamic distance and number of rings.

Fig. 24.68 Multi-ring buffer for a line, point and polygon layer

Allows features in-place modification

See also

Buffer, Variable distance buffer, Rectangles, ovals, diamonds, Single sided buffer

Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: any]	Input vector layer
Number of rings	RINGS	[number ] Default: 1	The number of rings. It can be a unique value (same number of rings for all the features) or it can be taken from features data (the number of rings depends on feature values).
Distance between rings	DISTANCE	[number ] Default: 1.0	Distance between the rings. It can be a unique value (same distance for all the features) or it can be taken from features data (the distance depends on feature values).
Multi-ring buffer (constant distance)	OUTPUT	[vector: polygon] Default: [Create temporary layer]	Specify the output polygon vector layer. One of: Create Temporary Layer (TEMPORARY_OUTPUT) Save to File… Save to Geopackage… Save to PostGIS Table… The file encoding can also be changed here.

Outputs

Label	Name	Type	Description
Multi-ring buffer (constant distance)	OUTPUT	[vector: polygon]	The output polygon vector layer.

Python code

Algorithm ID: native:multiringconstantbuffer

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.

24.1.16.46. Multipart to singleparts

Splits multipart features in the input layer into singlepart features.

The attributes of the output layer are the same as the original ones but divided into single features.

Fig. 24.69 Left the multipart source layer and right the single part output result

Allows features in-place modification

Default menu: Vector ► Geometry Tools

See also

Collect geometries, Promote to multipart

Parameters

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

Outputs

Label	Name	Type	Description
Single parts	OUTPUT	[same as input]	The output vector layer.

Python code

Algorithm ID: native:multiparttosingleparts

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.

24.1.16.47. Offset lines

Offsets lines by a specified distance. Positive distances will offset lines to the left, and negative distances will offset them to the right.

Fig. 24.70 In blue the source layer, in red the offset one

Allows features in-place modification

See also

Array of offset (parallel) lines, Translate

Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: line]	Input line vector layer
Distance	DISTANCE	[number ] Default: 10.0	Offset distance. You can use the Data Defined button on the right to choose a field from which the radius will be calculated. This way you can have different radius for each feature (see Variable distance buffer).
Segments	SEGMENTS	[number] Default: 8	Controls the number of line segments to use to approximate a quarter circle when creating rounded offsets.
Join style	JOIN_STYLE	[enumeration] Default: 0	Specifies whether round, miter or beveled joins should be used when offsetting corners in a line. Options are: 0 — Round 1 — Miter 2 — Bevel
Miter limit	MITER_LIMIT	[number] Default: 2.0	Controls the maximum distance from the offset curve to use when creating a mitered join (only applicable for miter join styles). Minimum: 1.
Offset	OUTPUT	[vector: line] Default: [Create temporary layer]	Specify the output (offset) layer. One of: Create Temporary Layer (TEMPORARY_OUTPUT) Save to File… Save to Geopackage… Save to PostGIS Table… The file encoding can also be changed here.

Outputs

Label	Name	Type	Description
Offset	OUTPUT	[vector: line]	Output (offset) line layer

Python code

Algorithm ID: native:offsetline

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.

24.1.16.48. Oriented minimum bounding box

Calculates the minimum area rotated rectangle for each feature in the input layer.

Fig. 24.71 Oriented minimum bounding box

Allows features in-place modification

See also

Minimum bounding geometry

Parameters

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

Outputs

Label	Name	Type	Description
Bounding boxes	OUTPUT	[vector: polygon]	The output polygon vector layer.

Python code

Algorithm ID: native:orientedminimumboundingbox

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.

24.1.16.49. Orthogonalize

Attempts to orthogonalize the geometries of the input line or polygon layer. This process shifts the vertices in the geometries to try to make every angle in the geometry either a right angle or a straight line.

Fig. 24.72 In blue the source layer and in the red orthogonalized result

Allows features in-place modification

Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: line, polygon]	Input line or polygon vector layer
Maximum angle tolerance (degrees)	ANGLE_TOLERANCE	[number] Default: 15	Specify the maximum deviation from a right angle or straight line a vertex can have for it to be adjusted. Smaller tolerances mean that only vertices which are already closer to right angles will be adjusted, and larger tolerances mean that vertices which deviate further from right angles will also be adjusted.
Maximum algorithm iterations	MAX_ITERATIONS	[number] Default: 1000	Setting a larger number for the maximum number of iterations will result in a more orthogonal geometry at the cost of extra processing time.
Orthogonalized	OUTPUT	[same as input] Default: [Create temporary layer]	Specify the output polygon vector layer. One of: Create Temporary Layer (TEMPORARY_OUTPUT) Save to File… Save to Geopackage… Save to PostGIS Table… The file encoding can also be changed here.

Outputs

Label	Name	Type	Description
Orthogonalized	OUTPUT	[same as input]	The output polygon vector layer with adjusted angles.

Python code

Algorithm ID: native:orthogonalize

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.

24.1.16.50. Point on Surface

For each feature of the input layer, returns a point that is guaranteed to lie on the surface of the feature geometry.

Allows features in-place modification

See also

Centroids

Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: any]	Input vector layer
Create point on surface for each part	ANGLE_TOLERANCE	[boolean ]	If checked, a point will be created for each part of the geometry.
Point	OUTPUT	[vector: point] Default: [Create temporary layer]	Specify the output point vector layer. One of: Create Temporary Layer (TEMPORARY_OUTPUT) Save to File… Save to Geopackage… Save to PostGIS Table… The file encoding can also be changed here.

Outputs

Label	Name	Type	Description
Point	OUTPUT	[vector: point]	The output point vector layer.

Python code

Algorithm ID: native:pointonsurface

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.

24.1.16.51. Points along geometry

Creates points at regular intervals along line or polygon geometries. Created points will have new attributes added for the distance along the geometry and the angle of the line at the point.

An optional start and end offset can be specified, which controls how far from the start and end of the geometry the points should be created.

Fig. 24.73 Points created along the source line layer

See also

Interpolate point on line

Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: line, polygon]	Input line or polygon vector layer
Distance	DISTANCE	[number ] Default: 1.0	Distance between two consecutive points along the line
Start offset	START_OFFSET	[number ] Default: 0.0	Distance from the beginning of the input line, representing the position of the first point.
End offset	END_OFFSET	[number ] Default: 0.0	Distance from the end of the input line, representing the position beyond which no point feature shoud be created.
Interpolated points	OUTPUT	[vector: point] Default: [Create temporary layer]	Specify the output vector layer. One of: Create Temporary Layer (TEMPORARY_OUTPUT) Save to File… Save to Geopackage… Save to PostGIS Table… The file encoding can also be changed here.

Outputs

Label	Name	Type	Description
Interpolated points	OUTPUT	[vector: point]	Point vector layer with features placed along lines or polygon boundaries of the input layer.

Python code

Algorithm ID: native:pointsalonglines

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.

24.1.16.52. Points displacement

Given a distance of proximity, identifies nearby point features and radially distributes them over a circle whose center represents their barycenter. A convenient tool to scatter overlaid features.

Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: point]	Input point vector layer
Minimum distance to other points	PROXIMITY	[number] Default: 1.0	Distance below which point features are considered close. Close features are distributed altogether.
Displacement distance	DISTANCE	[number] Default: 1.0	Radius of the circle on which close features are placed
Horizontal distribution for two point case	HORIZONTAL	[boolean] Default: False	When only two points are identified as close, aligns them horizontally on the circle instead of vertically.
Displaced	OUTPUT	[vector: point] Default: [Create temporary layer]	Specify the output vector layer. One of: Create Temporary Layer (TEMPORARY_OUTPUT) Save to File… Save to Geopackage… Save to PostGIS Table… The file encoding can also be changed here.

Outputs

Label	Name	Type	Description
Displaced	OUTPUT	[vector: point]	Output point vector layer

Python code

Algorithm ID: qgis:pointsdisplacement

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.

24.1.16.53. Pole of inaccessibility

Calculates the pole of inaccessibility for a polygon layer, which is the most distant internal point from the boundary of the surface.

This algorithm uses the ‘polylabel’ algorithm (Vladimir Agafonkin, 2016), which is an iterative approach guaranteed to find the true pole of inaccessibility within a specified tolerance. A more precise tolerance (lower value) requires more iterations and will take longer to calculate.

The distance from the calculated pole to the polygon boundary will be stored as a new attribute in the output layer.

Fig. 24.74 Pole of inaccessibility

Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: polygon]	Input vector layer
Tolerance	TOLERANCE	[number] Default: 1.0	Set the tolerance for the calculation
Point	OUTPUT	[vector: point] Default: [Create temporary layer]	Specify the output polygon vector layer. One of: Create Temporary Layer (TEMPORARY_OUTPUT) Save to File… Save to Geopackage… Save to PostGIS Table… The file encoding can also be changed here.

Outputs

Label	Name	Type	Description
Point	OUTPUT	[vector: point]	The output point vector layer

Python code

Algorithm ID: native:poleofinaccessibility

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.

24.1.16.54. Polygonize

Creates a polygon layer whose features boundaries are generated from a line layer of closed features.

Fig. 24.75 The yellow polygons generated from the closed lines

Note

The line layer must have closed shapes in order to be transformed into a polygon.

See also

Polygons to lines, Lines to polygons, Convert geometry type

Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: line]	Input line vector layer
Keep table structure of line layer Optional	KEEP_FIELDS	[boolean] Default: False	Check to keep the fields (only the table structure, not the values) of the input layer
Polygons from lines	OUTPUT	[vector: polygon] Default: [Create temporary layer]	Specify the output polygon vector layer. One of: Create Temporary Layer (TEMPORARY_OUTPUT) Save to File… Save to Geopackage… Save to PostGIS Table… The file encoding can also be changed here.

Outputs

Label	Name	Type	Description
Polygons from lines	OUTPUT	[vector: polygon]	The output polygon vector layer from lines

Python code

Algorithm ID: native:polygonize

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.

24.1.16.55. Polygons to lines

Takes a polygon layer and creates a line layer, with lines representing the boundaries of the polygons in the input layer.

The attribute table of the output layer is the same as the one of the input layer.

Fig. 24.76 Black lines as the result of the algorithm

Default menu: Vector ► Geometry Tools

See also

Lines to polygons, Polygonize, Convert geometry type

Parameters

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

Outputs

Label	Name	Type	Description
Lines	OUTPUT	[vector: line]	The output line vector layer from polygons

Python code

Algorithm ID: native:polygonstolines

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.

24.1.16.56. Project points (Cartesian)

Projects point geometries by a specified distance and bearing (azimuth).

Allows features in-place modification

Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: point]	Input point vector layer
Bearing (degrees from North)	BEARING	[number ] Default: 0.0	Clockwise angle starting from North, in degree (°) unit
Distance	DISTANCE	[number ] Default: 1.0	Distance to offset geometries, in layer units
Projected	OUTPUT	[vector: point] Default: [Create temporary layer]	Specify the output point vector layer. One of: Create Temporary Layer (TEMPORARY_OUTPUT) Save to File… Save to Geopackage… Save to PostGIS Table… The file encoding can also be changed here.

Outputs

Label	Name	Type	Description
Projected	OUTPUT	[vector: point]	The output (projected) point vector layer

Python code

Algorithm ID: native:projectpointcartesian

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.

24.1.16.57. Promote to multipart

Takes a vector layer with singlepart geometries and generates a new one in which all geometries are multipart.

Input features which are already multipart features will remain unchanged.

This algorithm can be used to force geometries to multipart types in order to be compatible with data providers that require multipart features.

Allows features in-place modification

See also

Aggregate, Collect geometries

Parameters

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

Outputs

Label	Name	Type	Description
Multiparts	OUTPUT	[same as input]	The output multipart vector layer

Python code

Algorithm ID: native:promotetomulti

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.

24.1.16.58. Rectangles, ovals, diamonds

Creates a buffer area with a rectangle, oval or diamond shape for each feature of the input point layer.

The shape parameters can be fixed for all features or dynamic using a field or an expression.

Fig. 24.77 Different buffer shapes with dynamic parameters

Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: point]	Input point vector layer
Buffer shape	SHAPE	[enumeration]	The shape to use. One of: 0 — Rectangles 1 — Ovals 2 — Diamonds
Width	WIDTH	[number ] Default: 1.0	Width of the buffer shape
Height	HEIGHT	[number ] Default: 1.0	Height of the buffer shape
Rotation Optional	ROTATION	[number ] Default: None	Rotation of the buffer shape
Number of segment	SEGMENTS	[number] Default: 36	Number of segments for a full circle (Ovals shape)
Output	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 PostGIS Table… The file encoding can also be changed here.

Outputs

Label	Name	Type	Description
Output	OUTPUT	[vector: polygon]	The output vector layer (with the buffer shapes)

Python code

Algorithm ID: native:rectanglesovalsdiamonds

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.

24.1.16.59. Remove duplicate vertices

Removes duplicate vertices from features, wherever removing the vertices does not result in a degenerate geometry.

The tolerance parameter specifies the tolerance for coordinates when determining whether vertices are identical.

By default, Z values are not considered when detecting duplicate vertices. E.g. two vertices with the same X and Y coordinate but different Z values will still be considered duplicate and one will be removed. If the Use Z Value parameter is true, then the Z values are also tested and vertices with the same X and Y but different Z will be maintained.

Note

Duplicate vertices are not tested between different parts of a multipart geometry, e.g. a multipoint geometry with overlapping points will not be changed by this method.

Allows features in-place modification

See also

Extract vertices, Extract specific vertices, Delete duplicate geometries

Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: any]	Input vector layer
Tolerance	TOLERANCE	[number ] Default: 0.000001	Vertices closer than the specified distance are considered duplicates
Use Z value	USE_Z_VALUE	[boolean ] Default: False	If the Use Z Value parameter is true, then the Z values are also tested and vertices with the same X and Y but different Z will be maintained.
Cleaned	OUTPUT	[same as input] Default: [Create temporary layer]	Specify the output vector layer. One of: Create Temporary Layer (TEMPORARY_OUTPUT) Save to File… Save to Geopackage… Save to PostGIS Table… The file encoding can also be changed here.

Outputs

Label	Name	Type	Description
Cleaned	OUTPUT	[same as input]	The output vector layer (without duplicate vertices)

Python code

Algorithm ID: native:removeduplicatevertices

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.

24.1.16.60. Remove null geometries

Removes any features which do not have a geometry from a vector layer. All other features will be copied unchanged.

The features with null geometries can be saved to a separate layer.

If Also remove empty geometries is checked, the algorithm removes features whose geometries have no coordinates, i.e., geometries that are empty. In that case, also the null output will reflect this option, containing both null and empty geometries.

See also

Delete duplicate geometries

Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: any]	Input vector layer (with non-NULL geometries)
Also remove empty geometries	REMOVE_EMPTY	[boolean]
Non null geometries	OUTPUT	[same as input] Default: [Create temporary layer]	Specify the output vector layer for the non-NULL (and non-empty) geometries. One of: Create Temporary Layer (TEMPORARY_OUTPUT) Save to File… Save to Geopackage… Save to PostGIS Table… The file encoding can also be changed here.
Null geometries	NULL_OUTPUT	[same as input] Default: [Skip output]	Specify the output vector layer for the NULL (and empty) geometries. One of: Skip Output Create Temporary Layer (TEMPORARY_OUTPUT) Save to File… Save to Geopackage… Save to PostGIS Table… The file encoding can also be changed here.

Outputs

Label	Name	Type	Description
Null geometries	NULL_OUTPUT	[same as input]	Output vector layer (for NULL and, if chosen, empty geometries)
Non null geometries	OUTPUT	[same as input]	The output vector layer (without NULL and, if chosen, empty geometries)

Python code

Algorithm ID: native:removenullgeometries

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.

24.1.16.61. Reverse line direction

Inverts the direction of a line layer.

Fig. 24.78 Before and after the direction inversion

Allows features in-place modification

Parameters

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

Outputs

Label	Name	Type	Description
Reversed	OUTPUT	[vector: line]	The output line vector layer (with reversed lines)

Python code

Algorithm ID: native:reverselinedirection

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.

24.1.16.62. Rotate

Rotates feature geometries by the specified angle clockwise. The rotation occurs around each feature’s centroid, or optionally around a unique preset point.

Allows features in-place modification

See also

Translate, Swap X and Y coordinates

Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: any]	Input vector layer
Rotation (degrees clockwise)	ANGLE	[number ] Default: 0.0	Angle of the rotation in degrees
Rotation anchor point (x, y) Optional	ANCHOR	[point] Default: None	X,Y coordinates of the point to rotate the features around. If not set the rotation occurs around each feature’s centroid.
Rotated	OUTPUT	[same as input] Default: [Create temporary layer]	Specify the output vector layer (with rotated geometries). One of: Create Temporary Layer (TEMPORARY_OUTPUT) Save to File… Save to Geopackage… Save to PostGIS Table… The file encoding can also be changed here.

Outputs

Label	Name	Type	Description
Rotated	OUTPUT	[same as input]	The output vector layer with rotated geometries

Python code

Algorithm ID: native:rotatefeatures

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.

24.1.16.63. Segmentize by maximum angle

Segmentizes a geometry by converting curved sections to linear sections.

The segmentization is performed by specifying the maximum allowed radius angle between vertices on the straightened geometry (e.g the angle of the arc created from the original arc center to consecutive output vertices on the linearized geometry). Non-curved geometries will be retained without change.

See also

Segmentize by maximum distance, Simplify, Smooth

Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: line, polygon]	Input line or polygon vector layer
Maximum angle between vertices (degrees)	ANGLE	[number ] Default: 5.0	Maximum allowed radius angle between vertices on the straightened geometry
Segmentized	OUTPUT	[same as input] Default: [Create temporary layer]	Specify the output vector layer (with segmentized geometries). One of: Create Temporary Layer (TEMPORARY_OUTPUT) Save to File… Save to Geopackage… Save to PostGIS Table… The file encoding can also be changed here.

Outputs

Label	Name	Type	Description
Segmentized	OUTPUT	[same as input]	The output vector layer with segmentized geometries

Python code

Algorithm ID: native:segmentizebymaxangle

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.

24.1.16.64. Segmentize by maximum distance

Segmentizes a geometry by converting curved sections to linear sections.

The segmentization is performed by specifying the maximum allowed offset distance between the original curve and the segmentized representation. Non-curved geometries will be retained without change.

See also

Segmentize by maximum angle, Simplify, Smooth

Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: line, polygon]	Input line or polygon vector layer
Maximum offset distance	DISTANCE	[number ] Default: 1.0	Maximum allowed offset distance between the original curve and the segmentized representation, in the layer units.
Segmentized	OUTPUT	[same as input] Default: [Create temporary layer]	Specify the output vector layer (with segmentized geometries). One of: Create Temporary Layer (TEMPORARY_OUTPUT) Save to File… Save to Geopackage… Save to PostGIS Table… The file encoding can also be changed here.

Outputs

Label	Name	Type	Description
Segmentized	OUTPUT	[same as input]	The output vector layer with segmentized geometries

Python code

Algorithm ID: native:segmentizebymaxdistance

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.

24.1.16.65. Set M value

Sets the M value for geometries in a layer.

If M values already exist in the layer, they will be overwritten with the new value. If no M values exist, the geometry will be upgraded to include M values and the specified value used as the initial M value for all geometries.

Tip

Use the ^{Identify Features} button to check the added M value: the results are available in the Identify Results dialog.

See also

Set M value from raster, Set Z value, Drop M/Z values

Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: any]	Input vector layer
M Value	M_VALUE	[number ] Default: 0.0	M value to assign to the feature geometries
M Added	OUTPUT	[same as input] Default: [Create temporary layer]	Specify the output vector layer. One of: Create Temporary Layer (TEMPORARY_OUTPUT) Save to File… Save to Geopackage… Save to PostGIS Table… The file encoding can also be changed here.

Outputs

Label	Name	Type	Description
M Added	OUTPUT	[same as input]	The output vector layer (with M values assigned to the geometries)

Python code

Algorithm ID: native:setmvalue

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.

24.1.16.66. Set M value from raster

Uses values sampled from a band within a raster layer to set the M value for every overlapping vertex in the feature geometry. The raster values can optionally be scaled by a preset amount.

If M values already exist in the layer, they will be overwritten with the new value. If no M values exist, the geometry will be upgraded to include M values.

See also

Drape (set Z value from raster), Set M value

Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: any]	Input vector layer
Raster layer	RASTER	[raster]	Raster layer with M values
Band number	BAND	[raster band] Default: 1	The raster band from which the M values are taken
Value for nodata or non-intersecting vertices	NODATA	[number ] Default: 0.0	Value to use in case the vertex does not intersect (a valid pixel of) the raster
Scale factor	SCALE	[number ] Default: 1.0	Scaling value: the band values are multiplied by this value.
Updated	OUTPUT	[same as input] Default: [Create temporary layer]	Specify the output vector layer (with updated M values). One of: Create Temporary Layer (TEMPORARY_OUTPUT) Save to File… Save to Geopackage… Save to PostGIS Table… The file encoding can also be changed here.

Outputs

Label	Name	Type	Description
Updated	OUTPUT	[same as input]	The output vector layer (with updated M values)

Python code

Algorithm ID: native:setmfromraster

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.

24.1.16.67. Set Z value

Sets the Z value for geometries in a layer.

If Z values already exist in the layer, they will be overwritten with the new value. If no Z values exist, the geometry will be upgraded to include Z values and the specified value used as the initial Z value for all geometries.

Tip

Use the ^{Identify Features} button to check the added Z value: the results are available in the Identify Results dialog.

See also

Drape (set Z value from raster), Set M value, Drop M/Z values

Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: any]	Input vector layer
Z Value	Z_VALUE	[number ] Default: 0.0	Z value to assign to the feature geometries
Z Added	OUTPUT	[same as input] Default: [Create temporary layer]	Specify the output vector layer. One of: Create Temporary Layer (TEMPORARY_OUTPUT) Save to File… Save to Geopackage… Save to PostGIS Table… The file encoding can also be changed here.

Outputs

Label	Name	Type	Description
Z Added	OUTPUT	[same as input]	The output vector layer (with Z values assigned)

Python code

Algorithm ID: native:setzvalue

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.

24.1.16.68. Simplify

Simplifies the geometries in a line or polygon layer. It creates a new layer with the same features as the ones in the input layer, but with geometries containing a lower number of vertices.

The algorithm gives a choice of simplification methods, including distance based (the “Douglas-Peucker” algorithm), area based (“Visvalingam” algorithm) and snapping geometries to grid.

Fig. 24.79 Clockwise from top left: source layer and increasing simplification tolerances

Allows features in-place modification

Default menu: Vector ► Geometry Tools

See also

Smooth, Densify by count, Densify by interval

Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: line, polygon]	Input line or polygon vector layer
Simplification method	METHOD	[enumeration] Default: 0	Simplification method. One of: 0 — Distance (Douglas-Peucker) 1 — Snap to grid 2 — Area (Visvalingam)
Tolerance	TOLERANCE	[number ] Default: 1.0	Threshold tolerance (in units of the layer): if the distance between two nodes is smaller than the tolerance value, the segment will be simplified and vertices will be removed.
Simplified	OUTPUT	[same as input] Default: [Create temporary layer]	Specify the output (simplified) vector layer. One of: Create Temporary Layer (TEMPORARY_OUTPUT) Save to File… Save to Geopackage… Save to PostGIS Table… The file encoding can also be changed here.

Outputs

Label	Name	Type	Description
Simplified	OUTPUT	[same as input]	The output (simplified) vector layer

Python code

Algorithm ID: native:simplifygeometries

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.

24.1.16.69. Single sided buffer

Computes a buffer on lines by a specified distance on one side of the line only.

Buffer always results in a polygon layer.

Fig. 24.80 Left versus right side buffer on the same vector line layer

See also

Buffer

Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: line]	Input line vector layer
Distance	DISTANCE	[number] Default: 10.0	Buffer distance.
Side	SIDE	[enumeration]	Which side to create the buffer on. One of: 0 – Left 1 – Right
Segments	SEGMENTS	[number] Default: 8	Controls the number of line segments to use to approximate a quarter circle when creating rounded offsets.
Join style	JOIN_STYLE	[enumeration]	Specifies whether round, miter or beveled joins should be used when offsetting corners in a line. Options are: 0 — Round 1 — Miter 2 — Bevel
Miter limit	MITER_LIMIT	[number] Default: 2.0	Controls the maximum distance from the offset curve to use when creating a mitered join (only applicable for miter join styles). Minimum: 1.0
Buffer	OUTPUT	[vector: polygon] Default: [Create temporary layer]	Specify the output (buffer) layer. One of: Create Temporary Layer (TEMPORARY_OUTPUT) Save to File… Save to Geopackage… Save to PostGIS Table… The file encoding can also be changed here.

Outputs

Label	Name	Type	Description
Buffer	OUTPUT	[vector: polygon]	Output (buffer) polygon layer

Python code

Algorithm ID: native:singlesidedbuffer

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.

24.1.16.70. Smooth

Smooths the geometries in a line or polygon layer by adding more vertices and corners to the feature geometries.

The iterations parameter dictates how many smoothing iterations will be applied to each geometry. A higher number of iterations results in smoother geometries with the cost of greater number of nodes in the geometries.

Fig. 24.81 Increasing number of iterations causes smoother geometries

The offset parameter controls how “tightly” the smoothed geometries follow the original geometries. Smaller values results in a tighter fit, and larger values will create a looser fit.

Fig. 24.82 Blue: the input layer. Offset 0.25 gives the red line, while offset 0.50 gives the green line.

The maximum angle parameter can be used to prevent smoothing of nodes with large angles. Any node where the angle of the segments to either side is larger than this will not be smoothed. For example, setting the maximum angle to 90 degrees or lower would preserve right angles in the geometry.

Allows features in-place modification

See also

Simplify, Densify by count, Densify by interval

Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: line, polygon]	Input line or polygon vector layer
Iterations	ITERATIONS	[number ] Default: 1	Increasing the number of iterations will give smoother geometries (and more vertices).
Offset	OFFSET	[number ] Default: 0.25	Increasing values will move the smoothed lines / boundaries further away from the input lines / boundaries.
Maximum node angle to smooth	MAX_ANGLE	[number ] Default: 180.0	Every node below this value will be smoothed
Smoothed	OUTPUT	[same as input] Default: [Create temporary layer]	Specify the output (smoothed) layer. One of: Create Temporary Layer (TEMPORARY_OUTPUT) Save to File… Save to Geopackage… Save to PostGIS Table… The file encoding can also be changed here.

Outputs

Label	Name	Type	Description
Smoothed	OUTPUT	[same as input]	Output (smoothed) vector layer

Python code

Algorithm ID: native:smoothgeometry

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.

24.1.16.71. Snap geometries to layer

Snaps the geometries in a layer either to the geometries from another layer, or to geometries within the same layer.

Matching is done based on a tolerance distance, and vertices will be inserted or removed as required to make the geometries match the reference geometries.

See also

Snap points to grid

Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: any]	Input vector layer
Reference layer	REFERENCE_LAYER	[vector: any]	Vector layer to snap to
Tolerance	TOLERANCE	[number] Default: 10.0	Control how close input vertices need to be to the reference layer geometries before they are snapped.
Behavior	BEHAVIOR	[enumeration] Default: 0	Snapping can be done to an existing node or a segment (its closest point to the vertex to move). Available snapping options: 0 — Prefer aligning nodes, insert extra vertices where required Prefer to snap to nodes, even when a segment may be closer than a node. New nodes will be inserted to make geometries follow each other exactly when inside allowable tolerance. 1 — Prefer closest point, insert extra vertices where required Snap to closest point, regardless of it is a node or a segment. New nodes will be inserted to make geometries follow each other exactly when inside allowable tolerance. 2 — Prefer aligning nodes, don’t insert new vertices Prefer to snap to nodes, even when a segment may be closer than a node. No new nodes will be inserted. 3 — Prefer closest point, don’t insert new vertices Snap to closest point, regardless of it is a node or a segment. No new nodes will be inserted. 4 — Move end points only, prefer aligning nodes Only snap start/end points of lines (point features will also be snapped, polygon features will not be modified), prefer to snap to nodes. 5 — Move end points only, prefer closest point Only snap start/end points of lines (point features will also be snapped, polygon features will not be modified), snap to closest point 6 — Snap end points to end points only Only snap the start/end points of lines to other start/end points of lines 7 — Snap to anchor nodes (single layer only)
Snapped geometry	OUTPUT	[same as input] Default: [Create temporary layer]	Specify the output (snapped) layer. One of: Create Temporary Layer (TEMPORARY_OUTPUT) Save to File… Save to Geopackage… Save to PostGIS Table… The file encoding can also be changed here.

Outputs

Label	Name	Type	Description
Snapped geometry	OUTPUT	[same as input]	Output (snapped) vector layer

Python code

Algorithm ID: native:snapgeometries

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.

24.1.16.72. Snap points to grid

Modifies the coordinates of geometries in a vector layer, so that all points or vertices are snapped to the closest point of a grid.

If the snapped geometry cannot be calculated (or is totally collapsed) the feature’s geometry will be cleared.

Snapping can be performed on the X, Y, Z or M axis. A grid spacing of 0 for any axis will disable snapping for that axis.

Note

Snapping to grid may generate an invalid geometry in some corner cases.

Allows features in-place modification

See also

Snap geometries to layer

Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: any]	Input vector layer
X Grid Spacing	HSPACING	[number ] Default: 1.0	Grid spacing on the X axis
Y Grid Spacing	VSPACING	[number ] Default: 1.0	Grid spacing on the Y axis
Z Grid Spacing	ZSPACING	[number ] Default: 0.0	Grid spacing on the Z axis
M Grid Spacing	MSPACING	[number ] Default: 0.0	Grid spacing on the M axis
Snapped	OUTPUT	[same as input] Default: [Create temporary layer]	Specify the output (snapped) layer. One of: Create Temporary Layer (TEMPORARY_OUTPUT) Save to File… Save to Geopackage… Save to PostGIS Table… The file encoding can also be changed here.

Outputs

Label	Name	Type	Description
Snapped	OUTPUT	[same as input]	Output (snapped) vector layer

Python code

Algorithm ID: native:snappointstogrid

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.

24.1.16.73. Split lines by maximum length

Takes a line (or curve) layer and splits each feature into multiple parts, where each part is of a specified maximum length. Z and M values at the start and end of the new line substrings are linearly interpolated from existing values.

Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: line]	The input line vector layer
Maximum line length	LENGTH	[number ] Default: 10.0	The maximum length of a line in the output.
Split	OUTPUT	[vector: line] Default: [Create temporary layer]	Specify the output line vector layer. One of: Create Temporary Layer (TEMPORARY_OUTPUT) Save to File… Save to Geopackage… Save to PostGIS Table… The file encoding can also be changed here.

Outputs

Label	Name	Type	Description
Split	OUTPUT	[vector: line]	The new line vector layer - the length of the feature geometries is less than or equal to the length specified in the LENGTH parameter.

Python code

Algorithm ID: native:splitlinesbylength

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.

24.1.16.74. Subdivide

Subdivides the geometry. The returned geometry will be a collection containing subdivided parts from the original geometry, where no part has more than the specified maximum number of nodes.

This is useful for dividing a complex geometry into less complex parts, easier to spatially index and faster to perform spatial operations. Curved geometries will be segmentized before subdivision.

Fig. 24.83 Left the input layer, middle maximum nodes value is 100 and right maximum value is 200

Note

Subdividing a geometry can generate geometry parts that may not be valid and may contain self-intersections.

Allows features in-place modification

See also

Explode lines, Line substring

Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: any]	The input vector layer
Maximum nodes in parts	MAX_NODES	[number ] Default: 256	Maximum number of vertices each new geometry part is allowed to have. Fewer sub-parts for higher values.
Subdivided	OUTPUT	[same as input] Default: [Create temporary layer]	Specify the output (subdivided) vector layer. One of: Create Temporary Layer (TEMPORARY_OUTPUT) Save to File… Save to Geopackage… Save to PostGIS Table… The file encoding can also be changed here.

Outputs

Label	Name	Type	Description
Subdivided	OUTPUT	[same as input]	Output vector layer

Python code

Algorithm ID: native:subdivide

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.

24.1.16.75. Swap X and Y coordinates

Switches the X and Y coordinate values in input geometries.

It can be used to repair geometries which have accidentally had their latitude and longitude values reversed.

Allows features in-place modification

See also

Translate, Rotate

Parameters

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

Outputs

Label	Name	Type	Description
Swapped	OUTPUT	[same as input]	Output (swapped) vector layer

Python code

Algorithm ID: native:swapxy

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.

24.1.16.76. Tapered buffers

Creates tapered buffer along line geometries, using a specified start and end buffer diameter.

Fig. 24.84 Tapered buffer example

See also

Variable width buffer (by M value), Buffer, Create wedge buffers

Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: line]	Input line vector layer
Start width	START_WIDTH	[number ] Default: 0.0	Represents the radius of the buffer applied at the start point of the line feature
End width	END_WIDTH	[number ] Default: 0.0	Represents the radius of the buffer applied at the end point of the line feature.
Segments	SEGMENTS	[number ] Default: 16	Controls the number of line segments to use to approximate a quarter circle when creating rounded offsets.
Buffered	OUTPUT	[vector: polygon] Default: [Create temporary layer]	Specify the output (buffer) layer. One of: Create Temporary Layer (TEMPORARY_OUTPUT) Save to File… Save to Geopackage… Save to PostGIS Table… The file encoding can also be changed here.

Outputs

Label	Name	Type	Description
Buffered	OUTPUT	[vector: polygon]	Output (buffer) polygon layer

Python code

Algorithm ID: native:taperedbuffer

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.

24.1.16.77. Tessellate

Tessellates a polygon geometry layer, dividing the geometries into triangular components.

The output layer consists of multipolygon geometries for each input feature, with each multipolygon consisting of multiple triangle component polygons.

Fig. 24.85 Tessellated polygon (right)

Allows features in-place modification

Parameters

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

Outputs

Label	Name	Type	Description
Tesselated	OUTPUT	[vector: polygon]	Output multipolygonZ layer

Python code

Algorithm ID: 3d:tessellate

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.

24.1.16.78. Transect

Creates transects on vertices for (multi)linestring.

A transect is a line oriented from an angle (by default perpendicular) to the input polylines (at vertices).

Field(s) from feature(s) are returned in the transect with these new fields:

• TR_FID: ID of the original feature

• TR_ID: ID of the transect. Each transect have an unique ID

• TR_SEGMENT: ID of the segment of the linestring

• TR_ANGLE: Angle in degrees from the original line at the vertex

• TR_LENGTH: Total length of the transect returned

• TR_ORIENT: Side of the transect (only on the left or right of the line, or both side)

Fig. 24.86 Dashed red lines represent the transect of the input line layer

Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: line]	Input line vector layer
Length of the transect	LENGTH	[number ] Default: 5.0	Length in map unit of the transect
Angle in degrees from the original line at the vertices	ANGLE	[number ] Default: 90.0	Change the angle of the transect
Side to create the transect	SIDE	[enumeration]	Choose the side of the transect. Available options are: 0 — Left 1 — Right 2 — Both
Transect	OUTPUT	[vector: line] Default: [Create temporary layer]	Specify the output line layer. One of: Create Temporary Layer (TEMPORARY_OUTPUT) Save to File… Save to Geopackage… Save to PostGIS Table… The file encoding can also be changed here.

Outputs

Label	Name	Type	Description
Transect	OUTPUT	[vector: line]	Output line layer

Python code

Algorithm ID: native:transect

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.

24.1.16.79. Translate

Moves the geometries within a layer, by offsetting with a predefined X and Y displacement.

Z and M values present in the geometry can also be translated.

Fig. 24.87 Dashed lines represent the translated geometry of the input layer

Allows features in-place modification

See also

Array of translated features, Offset lines, Rotate, Swap X and Y coordinates

Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: any]	Input vector layer
Offset distance (x-axis)	DELTA_X	[number ] Default: 0.0	Displacement to apply on the X axis
Offset distance (y-axis)	DELTA_Y	[number ] Default: 0.0	Displacement to apply on the Y axis
Offset distance (z-axis)	DELTA_Z	[number ] Default: 0.0	Displacement to apply on the Z axis
Offset distance (m values)	DELTA_M	[number ] Default: 0.0	Displacement to apply on the M axis
Translated	OUTPUT	[same as input] Default: [Create temporary layer]	Specify the output vector layer. One of: Create Temporary Layer (TEMPORARY_OUTPUT) Save to File… Save to Geopackage… Save to PostGIS Table… The file encoding can also be changed here.

Outputs

Label	Name	Type	Description
Translated	OUTPUT	[same as input]	Output vector layer

Python code

Algorithm ID: native:translategeometry

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.

24.1.16.80. Variable distance buffer

Computes a buffer area for all the features in an input layer.

The size of the buffer for a given feature is defined by an attribute, so it allows different features to have different buffer sizes.

Note

This algorithm is only available from the Graphical modeler.

See also

Buffer

Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: any]	Input vector layer
Distance field	DISTANCE	[tablefield: numeric]	Attribute for the distance radius of the buffer
Segments	SEGMENTS	[number] Default: 5	Controls the number of line segments to use to approximate a quarter circle when creating rounded offsets.
Dissolve result	DISSOLVE	[boolean] Default: False	Choose to dissolve the final buffer, resulting in a single feature covering all input features. Fig. 24.88 Normal and dissolved buffer
End cap style	END_CAP_STYLE	[enumeration]	Controls how line endings are handled in the buffer. Fig. 24.89 Round, flat and square cap styles
Join style	JOIN_STYLE	[enumeration]	Specifies whether round, miter or beveled joins should be used when offsetting corners in a line.
Miter limit	MITER_LIMIT	[number] Default: 2.0	Only applicable for mitered join styles, and controls the maximum distance from the offset curve to use when creating a mitered join.

Outputs

Label	Name	Type	Description
Buffer	OUTPUT	[vector: polygon]	Buffer polygon vector layer.

Python code

Algorithm ID: qgis:variabledistancebuffer

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.

24.1.16.81. Variable width buffer (by M value)

Creates variable width buffers along lines, using the M value of the line geometries as the diameter of the buffer at each vertex.

Fig. 24.90 Variable buffer example

See also

Tapered buffers, Buffer, Set M value

Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: line]	Input line vector layer
Segments	SEGMENTS	[number ] Default: 16	Number of the buffer segments per quarter circle. It can be a unique value (same value for all the features), or it can be taken from features data (the value can depend on feature attributes).
Buffered	OUTPUT	[vector: polygon] Default: [Create temporary layer]	Specify the output (buffer) layer. One of: Create Temporary Layer (TEMPORARY_OUTPUT) Save to File… Save to Geopackage… Save to PostGIS Table… The file encoding can also be changed here.

Outputs

Label	Name	Type	Description
Buffered	OUTPUT	[vector: polygon]	Variable buffer polygon layer

Python code

Algorithm ID: native:bufferbym

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.

24.1.16.82. Voronoi polygons

Takes a point layer and generates a polygon layer containing the Voronoi polygons (known also as Thiessen polygons) corresponding to those input points.

Any location within a Voronoi polygon is closer to the associated point than to any other point.

Fig. 24.91 Voronoi polygons

Default menu: Vector ► Geometry Tools

Parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: point]	Input point vector layer
Buffer region (% of extent)	BUFFER	[number] Default: 0.0	The extent of the output layer will be this much bigger than the extent of the input layer
Voronoi polygons	OUTPUT	[vector: polygon] Default: [Create temporary layer]	Specify the output layer (with the Voronoi polygons). One of: Create Temporary Layer (TEMPORARY_OUTPUT) Save to File… Save to Geopackage… Save to PostGIS Table… The file encoding can also be changed here.

Outputs

Label	Name	Type	Description
Voronoi polygons	OUTPUT	[vector: polygon]	Voronoi polygons of the input point vector layer

Python code

Algorithm ID: qgis:voronoipolygons

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.