Vector geometry

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

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.

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 newAttribute button to add a new field.
  • Click deleteAttribute to delete the selected field.
  • Use arrowUp and arrowDown to change order of the fields.
  • Click clearText 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

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.

../../../../_images/boundary_polygon.png

Boundaries (black dashed line) of the source polygon layer

For lines geometries, the boundaries are their end points.

../../../../_images/boundary_lines.png

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)

Bounding boxes

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

../../../../_images/bounding_box.png

Black lines represent the bounding boxes of each polygon feature

checkbox Allows features in-place modification

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

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).

../../../../_images/buffer2.png

Buffer (in yellow) of points, line and polygon

checkbox Allows features in-place modification

Default menu: Vector ‣ Geoprocessing Tools

Parameters

Label Name Type Description
Input layer INPUT [vector: any] Input vector layer
Distance DISTANCE

[number dataDefined]

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 (Graphical Modeler only)).
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
../../../../_images/buffer_cap_style.png

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.

../../../../_images/buffer_dissolve1.png

Standard and dissolved buffer

Buffered OUTPUT

[vector: polygon]

Default: [Create temporary layer]

Specify the output (buffer) 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.

Outputs

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

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.

../../../../_images/centroids2.png

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

checkbox 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 dataDefined]

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)

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):

../../../../_images/check_validity.png

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.

Types of error messages and their meanings

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.
../../../../_images/geos_rep_point.png
Ring self-intersection This error happens when a geometry touches itself and generates a ring.
../../../../_images/geos_ring_inter.png
Self-intersection This error happens when a geometry touches itself.
../../../../_images/geos_self_inter.png
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.
../../../../_images/geos_nest_shell.png
Duplicate rings This error happens when two rings (exterior or interior) of a polygon geometry are identical
../../../../_images/geos_dupl_rings.png
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    

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.
../../../../_images/geos_rep_point.png
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).
../../../../_images/qgis_seg_line_int.png
Ring self-intersection This error happens when an outer or inner (island) ring / boundary of a polygon geometry intersects itself.
../../../../_images/geos_ring_inter.png
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.
../../../../_images/qgis_poliinside_.png

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

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.

Concave hull (alpha shapes)

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

../../../../_images/concave_hull_threshold.png

Concave hulls with different thresholds (0.3, 0.6, 0.9)

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

Concave hull (k-nearest neighbor)

This algorithm 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.

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

Convert geometry type

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

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.

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

Note

The available conversion types depend on the input layer and the conversion chosen: e.g. it is not possible to convert a point to a line.

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

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.

../../../../_images/convex_hull1.png

Black lines identify the convex hull for each layer feature

checkbox Allows features in-place modification

Default menu: Vector ‣ Geoprocessing Tools

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

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.

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

Create wedge buffers

Creates wedge shaped buffers from input points.

../../../../_images/wedge_buffers.png

Wedge buffers

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

Parameters

Label Name Type Description
Input layer INPUT [vector: point] Input point vector layer
Azimuth (degrees from North) AZIMUTH

[number dataDefined]

Default: 0.0

Angle (in degrees) as the middle value of the wedge
Wedge width (in degrees) WIDTH

[number dataDefined]

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.

../../../../_images/wedge_buffers_azimuth_width.png

Azimuth and width values of the wedge buffer

Outer radius OUTER_RADIUS

[number dataDefined]

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 dataDefined]

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

Delaunay triangulation

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

../../../../_images/delaunay1.png

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
../../../../_images/delete_holes.png

Before and after the cleaning

checkbox 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 dataDefined]

Default: 0.0

Only holes with an area less than this threshold will be deleted. If 0.0 is added, 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

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.

../../../../_images/delete_holes.png

Before and after the cleaning

checkbox 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 dataDefined]

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

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.

../../../../_images/densify_geometry.png

Red points show the vertices before and after the densify

checkbox Allows features in-place modification

Default menu: Vector ‣ Geometry Tools

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

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.

../../../../_images/densify_geometry_interval.png

Densify geometry at a given interval

checkbox 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 dataDefined]

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

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.

../../../../_images/dissolve1.png

Dissolve the polygon layer on a common attribute

Default menu: Vector ‣ Geoprocessing Tools

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

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.

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 dataDefined]

Default: 0

Value to use in case the vertex does not intersect (a valid pixel of) the raster
Scale factor SCALE

[number dataDefined]

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
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).

Drop M/Z values

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

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).

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.

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.

../../../../_images/explode_lines.png

The original line layer and the exploded one

checkbox Allows features in-place modification

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.

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.

../../../../_images/extend_lines.png

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

checkbox 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 dataDefined] Distance by which to extend the first segment of the line (starting point)
End distance END_DISTANCE [number dataDefined] 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.

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.

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.

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.

../../../../_images/extract_nodes1.png

Vertices extracted for line and polygon layer

Default menu: Vector ‣ Geometry Tools

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.

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.

../../../../_images/filter_zm.png

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.

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 dataDefined]

Default: Not set

Minimum of M values allowed

Maximum

Optional

MAX

[number dataDefined]

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.

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.

../../../../_images/filter_zm.png

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.

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 dataDefined]

Default: Not set

Minimum of Z values allowed

Maximum

Optional

MAX

[number dataDefined]

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.

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.

checkbox 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.

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

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.

../../../../_images/interpolated_point.png

Interpolated point at 500m of the beginning of the line

Parameters

Label Name Type Description
Input layer INPUT [vector: line, polygon] Input line or polygon vector layer
Distance DISTANCE

[number dataDefined]

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

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.

../../../../_images/n_biggest.png

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

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.

../../../../_images/substring.png

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

checkbox 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 dataDefined] Distance along the input line to the start point of the output feature
End distance END_DISTANCE [number dataDefined] 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.

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 from of the input line layer.

Default menu: Vector ‣ Geometry Tools

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.

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.

checkbox 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.

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
../../../../_images/minimum_bounding.png

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

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.

Minimum enclosing circles

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

../../../../_images/minimum_enclosing_circles.png

Enclosing circles for each feature

checkbox Allows features in-place modification

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.

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.

../../../../_images/multiringbuffer.png

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

checkbox Allows features in-place modification

Parameters

Label Name Type Description
Input layer INPUT [vector: any] Input vector layer
Number of rings RINGS

[number dataDefined]

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 dataDefined]

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.

Multipart to singleparts

Splits multipart features in the input layer into singlepart features.

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

../../../../_images/multipart.png

Left the multipart source layer and right the single part output result

checkbox Allows features in-place modification

Default menu: Vector ‣ Geometry Tools

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.

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.

../../../../_images/offset_lines.png

In blue the source layer, in red the offset one

checkbox Allows features in-place modification

Parameters

Label Name Type Description
Input layer INPUT [vector: line] Input line vector layer
Distance DISTANCE

[number dataDefined]

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 (Graphical Modeler only)).
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:

  • 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
Offset OUTPUT [vector: line] Output (offset) line layer

Oriented minimum bounding box

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

../../../../_images/oriented_minimum_bounding_box.png

Oriented minimum bounding box

checkbox Allows features in-place modification

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.

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.

../../../../_images/orthogonize.png

In blue the source layer and in the red orthogonalized result

checkbox 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.

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.

checkbox 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 dataDefined] 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.

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.

../../../../_images/points_along_line.png

Points created along the source line layer

Parameters

Label Name Type Description
Input layer INPUT [vector: line, polygon] Input line or polygon vector layer
Distance DISTANCE

[number dataDefined]

Default: 1.0

Distance between two consecutive points along the line
Start offset START_OFFSET

[number dataDefined]

Default: 0.0

Distance from the beginning of the input line, representing the position of the first point.
End offset END_OFFSET

[number dataDefined]

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.

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

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.

../../../../_images/pole_inaccessibility.png

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

Polygonize

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

../../../../_images/polygonize.png

The yellow polygons generated from the closed lines

Note

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

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 copy the original attributes 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

Polygons to lines

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

../../../../_images/polygon_to_lines.png

Black lines as the result of the algorithm

Default menu: Vector ‣ Geometry Tools

See also

Polygonize

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

Project points (Cartesian)

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

checkbox 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 dataDefined]

Default: 0.0

Clockwise angle starting from North, in degree (°) unit
Distance DISTANCE

[number dataDefined]

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

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.

checkbox Allows features in-place modification

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

Rectangles, ovals, diamonds (fixed)

Creates a buffer area for all the features in an input layer with different shape choice.

Parameters can vary depending on the shape chosen.

../../../../_images/rectangles_ovals_diamond.png

Different buffer shapes

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)

Rectangles, ovals, diamonds (variable)

Creates a buffer area for all the features in an input layer with different shape choice.

Buffer shape parameters are specified through attribute of the input layer.

../../../../_images/rectangles_ovals_diamond_variable.png

Different buffer shapes with different parameters

Parameters

Label Name Type Description
Input layer INPUT [vector: point] Input point vector layer
Buffer shape SHAPE

[enumeration]

Default: 0

The shape to use. One of:

  • 0 — Rectangles
  • 1 — Ovals
  • 2 — Diamonds
Width field WIDTH

[tablefield: numeric]

Default: First

Width of the buffer shape
Height field HEIGHT

[tablefield: numeric]

Default: First

Height of the buffer shape

Rotation field

Optional

ROTATION [tablefield: numeric] 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)

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 :guilabel;`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.

checkbox Allows features in-place modification

Parameters

Label Name Type Description
Input layer INPUT [vector: any] Input vector layer
Tolerance TOLERANCE

[number dataDefined]

Default: 0.000001

Vertices closer than the specified distance are considered duplicates
Use Z value USE_Z_VALUE

[boolean dataDefined]

Default: False

If the :guilabel;`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)

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.

Parameters

Label Name Type Description
Input layer INPUT [vector: any] Input vector layer (with non-NULL geometries)
Non null geometries OUTPUT

[same as input]

Default: [Create temporary layer]

Specify the output vector layer for the non-NULL 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 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] The output vector layer (only NULL geometries)
Non null geometries OUTPUT [same as input] The output vector layer (without NULL geometries)

Reverse line direction

Inverts the direction of a line layer.

../../../../_images/reverse_line.png

Before and after the direction inversion

checkbox 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)

Rotate

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

checkbox Allows features in-place modification

Parameters

Label Name Type Description
Input layer INPUT [vector: any] Input vector layer
Rotation (degrees clockwise) ANGLE

[number dataDefined]

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

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.

Parameters

Label Name Type Description
Input layer INPUT [vector: line, polygon] Input line or polygon vector layer
Maximum angle between vertices (degrees) ANGLE

[number dataDefined]

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

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.

Parameters

Label Name Type Description
Input layer INPUT [vector: line, polygon] Input line or polygon vector layer
Maximum offset distance DISTANCE

[number dataDefined]

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

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 identifyIdentify Features button to check the added M value: the results are available in the Identify Results dialog.

Parameters

Label Name Type Description
Input layer INPUT [vector: any] Input vector layer
M Value M_VALUE

[number dataDefined]

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)

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.

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 dataDefined] Default: 0.0 Value to use in case the vertex does not intersect (a valid pixel of) the raster
Scale factor SCALE

[number dataDefined]

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)

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 identifyIdentify Features button to check the added Z value: the results are available in the Identify Results dialog.

Parameters

Label Name Type Description
Input layer INPUT [vector: any] Input vector layer
Z Value Z_VALUE

[number dataDefined]

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)

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.

../../../../_images/simplify_geometries.png

Clockwise from top left: source layer and increasing simplification tolerances

checkbox Allows features in-place modification

Default menu: Vector ‣ Geometry Tools

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 dataDefined]

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

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.

../../../../_images/single_side_buffer.png

Left versus right side buffer on the same vector line layer

See also

Buffer

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).
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

Smooth

Smooths 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 higher number of vertices and corners in the geometries smoothed out.

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.

../../../../_images/smooth_geometry_1.png

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.

../../../../_images/smooth_geometry_2.png

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.

checkbox Allows features in-place modification

Parameters

Label Name Type Description
Input layer INPUT [vector: line, polygon] Input line or polygon vector layer
Iterations ITERATIONS

[number dataDefined]

Default: 1

Increasing the number of iterations will give smoother geometries (and more vertices).
Offset OFFSET

[number dataDefined]

Default: 0.25

Increasing values will move the smoothed lines / boundaries further away from the input lines / booundaries.
Maximum node angle to smooth MAX_ANGLE

[number dataDefined]

Default: 180.0

Every node below this value will be smoothed
Smoothed OUTPUT

[same as input]

Default: [Create temporary layer]

Specify the output (buffer) 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.

Outputs

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

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.

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. This distance is specified in layer units.
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
  • 1 — Prefer closest point, insert extra vertices where required
  • 2 — Prefer aligning nodes, don’t insert new vertices
  • 3 — Prefer closest point, don’t insert new vertices
  • 4 — Move end points only, prefer aligning nodes
  • 5 — Move end points only, prefer closest point
  • 6 — Snap end points to end points only
  • 7 — Snap to anchor nodes (single layer only)
Snapped geometry OUTPUT

[same as input]

Default: [Create temporary layer]

Specify the output (buffer) 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.

Outputs

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

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.

checkbox Allows features in-place modification

Parameters

Label Name Type Description
Input layer INPUT [vector: any] Input vector layer
X Grid Spacing HSPACING

[number dataDefined]

Default: 1.0

Grid spacing on the X axis
Y Grid Spacing VSPACING

[number dataDefined]

Default: 1.0

Grid spacing on the Y axis
Z Grid Spacing ZSPACING

[number dataDefined]

Default: 0.0

Grid spacing on the Z axis
M Grid Spacing MSPACING

[number dataDefined]

Default: 0.0

Grid spacing on the M axis
Snapped OUTPUT

[same as input]

Default: [Create temporary layer]

Specify the output (buffer) 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.

Outputs

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

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.

../../../../_images/subdivide.png

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.

checkbox Allows features in-place modification

Parameters

Label Name Type Description
Input layer INPUT [vector: any] The input vector layer
Maximum nodes in parts MAX_NODES

[number dataDefined]

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 line vector 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.

Outputs

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

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.

checkbox 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 line vector 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.

Outputs

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

Tapered buffers

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

../../../../_images/tapered_buffer.png

Tapered buffer example

Parameters

Label Name Type Description
Input layer INPUT [vector: line] Input line vector layer
Start width START_WIDTH

[number dataDefined]

Default: 0.0

Represents the radius of the buffer applied at the start point of the line feature
End width END_WIDTH

[number dataDefined]

Default: 0.0

Represents the radius of the buffer applied at the end point of the line feature.
Segments SEGMENTS

[number dataDefined]

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

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.

../../../../_images/tessellated.png

Tessellated polygon (right)

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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

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)
../../../../_images/transect.png

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 dataDefined]

Default: 5.0

Length in map unit of the transect
Angle in degrees from the original line at the vertices ANGLE

[number dataDefined]

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

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.

../../../../_images/translate_geometry.png

Dashed lines represent the translated geometry of the input layer

checkbox Allows features in-place modification

Parameters

Label Name Type Description
Input layer INPUT [vector: any] Input vector layer
Offset distance (x-axis) DELTA_X

[number dataDefined]

Default: 0.0

Displacement to apply on the X axis
Offset distance (y-axis) DELTA_Y

[number dataDefined]

Default: 0.0

Displacement to apply on the Y axis
Offset distance (z-axis) DELTA_Z

[number dataDefined]

Default: 0.0

Displacement to apply on the Z axis
Offset distance (m values) DELTA_M

[number dataDefined]

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

Variable distance buffer (Graphical Modeler only)

Computes a buffer area for all the features in an input layer. This algorithm is only available from the The graphical modeler.

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

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.

../../../../_images/buffer_dissolve1.png

Normal and dissolved buffer

End cap style END_CAP_STYLE [enumeration]

Controls how line endings are handled in the buffer.

../../../../_images/buffer_cap_style.png

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.

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.

../../../../_images/variable_buffer_m.png

Variable buffer example

Parameters

Label Name Type Description
Input layer INPUT [vector: line] Input line vector layer
Segments SEGMENTS

[number dataDefined]

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

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.

../../../../_images/voronoi1.png

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