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Computes geometric properties of the features in a vector 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.
Depending on the geometry type of the vector layer, the attributes added to the table will be different:
- for point layers: X and Y coordinates called
xcoordandycoord - for line layers:
lengthand,NEW in 3.2particularly for LineString and CompoundCurve geometry type also adds feature'ssinuosityand straight distance (straightdis) - for polygon layers:
perimeterandarea
Default menu: Vector --> Geometry Tools
Input layer[vector: any]Vector layer in input
Calculate using[selection]Choose different calculation type for the geometric properties:
- Layer CRS
- Project CRS
- Ellipsoidal
Added geom info[vector]Copy of the input vector layer with the addition of the geometry fields
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 using 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 aggregation functions of the QGIS Expression engine.
Input layer[vector: any]Vector layer in input to aggregate the features from
Group by expression[tablefield: any]Choose the grouping field. If NULL all features will be grouped
Default: NULL
Aggregates[fieldsmapping]Summary of all fields of the source layer, aggregation function available, delimiter and output field name
Load fields from layer[vector: any]You can also load the fields from another layer and use these fields for the aggregation.
Aggregated[vector]Multigeometry vector layer with the aggregated values
For a complete description of the aggregates function, refer to the dedicated aggregates_function chapter.
Returns the closure of the combinatorial boundary of the input geometries (i.e. the topological boundary of the geometry).
Only valid for polygon or line layers.
For polygon geometries , the boundary consists of all the line strings for each ring of the polygon.
For lines geometries, the boundaries are the vertices between each features.
Input layer[vector: line, polygon]Input vector layer
Boundary[vector: point, line]Boundary from the input layer (point for line, and line for polygon).
Calculates the bounding box (envelope) of each feature in an input layer. Polygon and line geometries are supported.
Input layer[vector: polygon, line]Input vector layer
Bounds[vector: polygon]Bounding boxes of input layer.
qgisminimumboundinggeometry
Computes a buffer area for all the features in an input layer, using a fixed distance.
It is possible to define also a negative distance for polygon input layers: in this case the buffer will result in a smaller polygon.
Default menu: Vector --> Geoprocessing Tools
Input layer[vector: any]Input vector layer
Distance[number]Distance radius of the buffer calculated from the boundary of each feature. Moreover you can use the Data Defined button on the right to choose a field of from which the radius will be calculated: this way you can have different radius for each feature (see
qgisvariabledistancebuffer).Default: 10.0
Segments[number]Controls the number of line segments to use to approximate a quarter circle when creating rounded offsets.
Default: 5
End cap style[selection]Controls how line endings are handled in the buffer.
Round, flat and square cap styles
Join style[selection]Specifies whether round, miter or beveled joins should be used when offsetting corners in a line.
Miter limit[number]Only applicable for miter join styles
Default: 2.0
Dissolve result[boolean]Choose to dissolve the final buffer. If chosen each buffer that overlaps with another one will be dissolved and an unique feature will be created.
Default: False
Standard and dissolved buffer
Buffer[vector: polygon]Buffer polygon vector layer
qgisvariabledistancebuffer, qgismultiringconstantbuffer
Creates a new point layer, with points representing the centroid of the geometries of the input layer.
The attributes associated to each point in the output layer are the same ones associated to the original features.
In case of a multigeometry layer a single centroid will be calculated for each feature. The resulting centroid represents the barycenter of all parts, so the centroid can be outside the feature borders.
Default menu: Vector --> Geometry Tools
Input layer[vector: any]Vector layer in input.
Centroids[vector: point]Points vector layer in output.
Performs a validity check on the geometries of a vector layer.
The geometries are classified in three groups (valid, invalid and error) and a vector layer is generated with the features in each of these categories:
- the valid layer contains only the valid features (without topological errors)
- the invalid layer contains all the invalid features found by the algorithm
- the error layer is the point layer where the invalid features have been found
The attribute table of each generated vector layer will contain some additional information (numbers of error found and type of error):
Default menu: Vector --> Geometry Tools
Input layer[vector: any]Source layer to check.
Method[selection]Check validity method.
Options:
- The one selected in digitizing settings
- QGIS
- GEOS
Default: The one selected in digitizing settings
Valid output[vector: any]Vector layer containing copy of the valid features of the source layer.
Invalid output[vector: any]Vector layer containing copy of the invalid features of the source layer with the field
_errorslisting the summary of the error found.Error output[vector: point]Point layer of the exact position of the validity problems detected with the
messagefield describing the error(s) found.
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
Input layer[vector: any]Vector layer to be transformed
Unique ID fields[multipleinput]Optional
Choose one or more attributes to collect the geometries
Collected [vector]
qgisaggregate and qgispromotetomulti
Computes the concave hull of the features in an input point layer.
Input point layer[vector: point]Point vector layer to calculate the concave hull
Threshold[number]Number from 0 (maximum concave hull) to 1 (convex hull)
Default: 0.3
Different thresholds used (0.3, 0.6, 0.9)
Allow holes[boolean]Choose whether to allow holes in the final concave hull
Default: True
Split multipart geometry into singlepart geometries[boolean]Check if you want to have singlepart geometries instead of multipart ones
Default: False
Concave hull[vector: polygon]Output concave hull
qgisconvexhull
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.
Input layer[vector: any]Input vector layer to transform
New geometry type[selection]List of all the conversions supported:
- Centroids
- Vertices
- Linestrings
- Multilinestrings
- Polygons
Note
Conversion types availability depends on the input layer and the conversion chosen: e.g. it is not possible to convert a point to a line
Converted[vector]Converted vector layer depending on the parameters chosen
qgispolygonize, qgislinestopolygons
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.
Default menu: Vector --> Geoprocessing Tools
Input point layer[vector: any]Point vector layer to calculate the convex hull
Convex hull[vector: polygon]Output convex hull
qgisminimumboundinggeometry, qgisconcavehull
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 an literal extent (xmin, xmax, ymin, ymax format) into a layer which can be used for other algorithms which require a layer based input.
Extent (xmin, xmax, ymin, ymax)[extent]Output layer as result of the chosen extent
ExtentFinal extent of the layer
Creates a polygon layer with the delaunay triangulation corresponding to a points layer.
Default menu: Vector --> Geometry Tools
Input layer[vector: point]Point vector layer to compute the triangulation on
Delaunay triangulation[vector: polygon]Resulting polygon layer of delaunay triangulation
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.
Input layer[vector: polygon]Polygon layer with holes.
Remove holes with area less than[number]Optional.
Only holes with an area less than this threshold will be deleted. If
0.0is added, all the holes will be deleted.Default: 0.0
Cleaned[vector: polygon]Vector layer without holes or holes larger than specified area
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 feature geometry is specified as an input parameter.
Vertices will be added to each segment of the layer.
Default menu: Vector --> Geometry Tools
Input layer[vector: polygon, line]Polygon or line vector layer.
Vertices to add[number]Number of vertices to add.
Default: 1
Densified[vector: polygon, line]Densified layer with vertices added.
To add vertices at specific intervals look at qgisdensifygeometriesgivenaninterval.
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.
The distance is expressed in the same units used by the layer CRS.
If the geometries have z or m values present then these will be linearly interpolated at the added vertices.
Specifying a distance 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.
Input layer[vector: polygon, line]Polygon or line vector layer.
Interval between vertices to add[number]Distance between the vertices. Units are taken from the layer CRS.
Default: 1.0
Densified[vector: plygon, line]Densified layer with vertices added at specified intervals
To add a specific number of vertices, look at qgisdensifygeometries.
Takes a polygon or line vector layer and combines their geometries into new geometries creating a new layer.
One or more attributes can be specified to dissolve only geometries belonging to the same class (having the same value for the specified attributes), alternatively all geometries can be dissolved.
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 of the input layer while the features are aggregated.
Default menu: Vector --> Geoprocessing Tools
Input layer[vector: polygon, line]Line or polygon layer to be dissolved.
Unique ID fields[tablefield: any]Optional.
If features share a common value in all selected field(s) their geometries will be combined.
Values in the output layer's fields are the ones of the first input feature that happens to be processed. Returns one feature for each unique value in the field. The feature's geometry represents all input geometries with this value.
Dissolved[vector: polygon, line]Output layer, either (multi) line or (multi) polygon
Removes any M (measure) or Z (altitude) values from input geometries.
Input layer[vector: any]Input vector layer to clean
Drop M Values[boolean]Check to remove the M values
Default: False
Drop Z Values[boolean]Check to remove the Z values
Default: False
Z/M Dropped[vector]Cleaned vector layer without M and/or Z values
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
Input layer[vector: polygon]Input polygon vector layer to clean
Merge selection with the neighboring polygon with the[selection]Choose the parameter to use in order to get rid of the selected polygons:
- Largest Area
- Smallest Area
- Largest Common Boundary
Eliminated[vector: polygon]Cleaned vector layer as result of the parameters chosen
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.
Input layer[vector: line]Line vector layer in input to explode
Exploded [vector: line]
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.
Input layer[vector: line]Line vector layer to extend
Start distance[number]Starting distance to extend the line by (starting point)
End distance[number]Ending distance of the extension
Extended[vector: line]Extended vector line layer
Takes a line or polygon layer and generates a point layer with points representing specific vertices in the input lines or polygons.
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 line or polygon that the point 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.
Input layer[vector]Vector layer in input to extract the vertices from
Vertex indices[number]Type the indices of the vertices to extract. The algorithm accepts comma separated values for many vertices to extract (e.g.
-2, 3, 5, 7)Default: 0
Vertices[vector: point]Extracted vertices of input layer
Takes a line or polygon layer and generates a point layer with points representing the vertices in the input lines or polygons.
The attributes associated to each point are the same ones associated to the line or polygon that the point 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.
Default menu: Vector --> Geometry Tools
Input layer[vector: any]Vector layer in input to extract the vertices from
Vertices[vector: point]Vector layer of extracted vertices
This algorithm 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.
Input layer[vector: polygon, line]Polygon or vector layer in input.
Fixed geometries[vector: polygon, line]Layer with fixed geometries.
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 for specific functions which is available in the expression builder.
Input layer[vector: any]Vector input layer
Output geometry type[selection]The output geometry strongly depends on the expression you will choose: for instance, if you want to create a buffer than the geometry type has to be a polygon
- Polygon
- Line
- Point
Output geometry has z dimension[boolean]Choose if the output geometry should have the z dimension
Default: False
Output geometry has m dimension[boolean]Choose if the output geometry should have the z dimension
Default: False
Geometry expression[expression]Add the geometry expression you want to use. You can use the button to open the Expression Dialog: the dialog has a lists of all the usable expression together with their help and guide
Default: $geometry
Modified geometry[vector]Vector layer resulting from the expression added
Cuts the n biggest parts of the input layer.
This algorithm is particularly useful if a single layer is very complicated and made of many different parts.
Polygons[vector: polygon]Input polygon layer.
To keep[number]Choose how many biggest parts have to be kept. If 1 is selected, only the biggest part of the whole layer will be saved.
Default: 1
Biggest parts[vector: polygon]Resulting polygon layer with the biggest parts chosen.
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
Input layer[vector: line]Line vector layer to convert
Polygons[vector: polygon]Polygon vector layer from the line input vector layer
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.
Input layer[vector: line]MultiLineString vector layer
Merged[vector: lines]Single Linestring vector layer
Creates geometries which enclose the features from an input layer.
Input layer[vector: any]Input vector layer
Field[tablefield: any]Optional
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 just the features with matching values
Geometry type[selection]Numerous enclosing geometry types are supported:
- Envelopes (bounding boxes)
- Minimum oriented rectangle
- Minimum enclosing circles
- Convex hulls
Clockwise from left-up: envelopes, oriented rectangle, circle, convex hull
Bounding geometry[vector: polygon]Bounding polygon layer
Calculates the minimum enclosing circle which covers each feature in an input layer.
Input layer[vector: any]Input vector layer
Number of segment in circles[number]Choose the number of segment for each circle
Default: 72
Minimum enclosing circles[vector: polygon]Enclosing circles for each polygon feature
qgisminimumboundinggeometry
Computes multi-ring (donuts) buffer for all the features in an input layer, using a fixed or dynamic distance and ring numbers.
Input layer[vector: any]Input vector layer.
Number of rings[number]Total number of rings that the buffer must have. It can be an unique value (same ring number for all the features) or it can be taken from features data (different ring number depending on the feature values).
Distance between rings[number]Distance between the single rings. It can be an unique value (same distance for all the the features) or it can be taken from features data (different distance depending on the feature values).
Multi-ring buffer (constant distance)Multi ring buffer polygon vector layer
qgisbuffer, qgisvariabledistancebuffer, qgisrectanglesovalsdiamondsfixed, qgisrectanglesovalsdiamondsvariable, qgissinglesidedbuffer
Splits the multipart input layers into single features.
The attributes of the output layers are the same of the original ones but divided into single features.
Default menu: Vector --> Geometry Tools
Input layer[vector: any]Multipart input layer.
Single parts[vector: any]Singlepart layer in output with updated attribute table.
qgiscollect and qgispromotetomulti
Offsets lines by a specified distance. Positive distances will offset lines to the left, and negative distances will offset to the right of lines.
Input layer[vector: line]Line vector layer in input to elaborate the offset on
Distance[number]Distance of the offset. Negative distances are also supported: for instance a negative distance will create the offset to the other part of the layer
Default: 10.0
Segment[number]Number of line segments to use to approximate a quarter circle when creating rounded offsets
Default: 8
Join style[selection]Specify whether round, miter or beveled joins should be used when offsetting corners in a line
Default: Round
Miter limit[number]Only applicable for mitered join styles, and controls the maximum distance from the offset curve to use when creating a mitered join
Default: 2.0
Offset[vector: line]Offset line layer
Calculates the minimum area rotated rectangle which covers each feature in an input layer.
Input layer[vector: any]Input vector layer
Bounding boxes[vector: polygon]Oriented minimum bounding boxes for each polygon feature
qgisminimumboundinggeometry
Takes a line or polygon layer and attempts to orthogonalize all the geometries in the 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.
Input layer[vector: polygon, line]Input vector layer
Maximum angle tolerance (degrees)[number]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[number]Setting a larger number for the maximum iterations will result in a more orthogonal geometry at the cost of extra processing time
Orthogonalized[vector]Final layer with angles adjusted depending on the parameters chosen
Returns a point guaranteed to lie on the surface of a geometry.
Input layer[vector: any]Input vector layer
Create point on surface for each part[boolean]NEW in 3.2If checked a point for each different part of the geometry will be created.
Default: False
Point[vector: point]Point vector layer
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.
Input layer[vector: line, polygon]Input vector layer
Distance[number]Set the distance between each point
Default: 100
Start offset[number]Specify an eventual offset where the first point should start
Default: 0
End offset[number]Specify an eventual offset where the last point should end
Default: 0
Points[vector: point]Point vector layer
Offsets nearby point features by moving nearby points by a preset amount to minimize overlapping features.
Input layer[vector: point]Input point vector layer
Minimum distance to other points[number]Set the distance between each point
Default: 0,000150
Displacement distance[number]Specify an eventual offset where the first point should start
Default: 0,000150
Horizontal distribution for two point case[boolean]Specify an eventual offset where the last point should end
Default: False
Displaced[vector: point]Point vector layer
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 (in layer units). More precise tolerances require 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.
Input layer[vector: polygon]Input polygon vector layer
Tolerance (layer units)[number]Set the tolerance for the calculation
Default: 1.0
Point[vector: point]Point as pole of inaccessibility for the source polygon vector layer
Creates a polygon layer whose features boundaries are generated from a closed line layer features.
Note
the line layer must have closed shapes in order to be transformed into a polygon
Input layer[vector: line]Input line vector layer
Keep table structure of line layer[boolean]Optional
Check to copy the original attribute of the line layer
Default: False
Polygons from lines[vector: polygon]Vector layer with polygonized features
Takes a polygon layer and creates a line layer, with lines representing the boundaries of the polygons in the input layer.
Default menu: Vector --> Geometry Tools
Input layer[vector: polygon]Input polygon vector layer
Lines[vector: line]Lines from the polygon layer
Projects point geometries by a specified distance and bearing (azimuth), creating a new point layer with the projected points.
Input layer[vector: point]Point vector layer to project
Bearing (degrees from North)[number]Clockwise angle starting from North, in degree (°) unit
Distance[number]Distance to offset geometries, in layer units
Projected[vector: point]Projected layer at given degrees and distance
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.
Input layer[vector]Input vector layer
Multiparts[vector]Multiparts vector layer
qgisaggregate and qgiscollect
Creates a buffer area for all the features in an input layer with different shape choice.
Parameters can vary depending on the shape chosen.
Input layer[vector: point]Input point vector layer
Buffer shape[selection]Different shape available:
- Rectangles
- Ovals
- Diamonds
Default: Rectangles
Width[number]Width of the buffer shape
Default: 1.0
Height[number]Height of the buffer shape
Default: 1.0
Rotation[number]Optional
Rotation of the buffer shape
Default: 0.0
Number of segment[number]How many segment should have the buffer shape
Default: 36
Output[vector: polygon]Buffer shape in output
qgisrectanglesovalsdiamondsvariable
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.
Input layer[vector: point]Input point vector layer
Buffer shape[selection]Different shape available:
- Rectangles
- Ovals
- Diamonds
Default: Rectangles
Width[tablefield: numeric]Width of the buffer shape
Default: 1.0
Height[tablefield: numeric]Height of the buffer shape
Default: 1.0
Rotation[tablefield: numeric]Optional
Rotation of the buffer shape
Default: 0.0
Number of segment[number]How many segment should have the buffer shape
Default: 36
Output[vector: polygon]Buffer shape in output
qgisrectanglesovalsdiamondsfixed
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.
Input layer[vector: any]Input vector layer with NULL geometries
Non null geometries[vector]Vector layer without NULL geometries
Null geometries[vector]Vector layer with only NULL geometries
Inverts the direction of a line layer.
Input layer[vector: line]Input line vector layer to invert the direction
Reversed[vector: line]Inverted line vector layer
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.
Use the 
Identify Features button to check the added M value: the results are available in the Identify Results dialog.
Input layer[vector: any]Input vector layer
M Added[vector]Vector layer in output with M 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.
Use the Identify Features button to check the added Z value: the results are available in the Identify Results dialog.
Input layer[vector: any]Input vector layer
Z Added[vector]Vector layer in output with Z value
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.
Default menu: Vector --> Geometry Tools
Input layer[vector: polygon, line]Polygon or line vector to simplify.
Simplification method[selection]Method of the simplification.
Options:
- Distance (Douglas-Peucker)
- Snap to grid
- Area (Visvalingam)
Default: Distance (Douglas-Peucker)
Tolerance[number]Threshold tolerance: if the distance between two nodes is smaller than the tolerance value, the segment will be simplified and vetices will be removed.
Value in map unit of the layer
Default: 1.0
Simplified[vector: polygon, line]Simplified vector layers in output.
Computes a buffer on lines by a specified distance on one side of the line only.
Buffer always results in a polygon layer.
Input layer[vector: line]Input line vector layer
Distance[number]Distance radius of the buffer
Default: 10.0
Side[selection]Choose which side the buffer should be created
- Left
- Right
Default: Left
Segments[number]Controls the number of line segments to use to approximate a quarter circle when creating rounded offsets
Default: 5
Join style[selection]Specifies whether round, miter or beveled joins should be used when offsetting corners in a line.
- Round
- Miter
- Bevel
Default: Round
Miter limit[number]Only applicable for mitered join styles, and controls the maximum distance from the offset curve to use when creating a mitered join
Default: 2.0
Buffer[vector: polygon]One side buffer polygon vector layer
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.
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.
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.
Input layer[vector: polygon, line]Polygon or line vector to smooth.
Iterations[number]With many iterations the resulting layer will have many nodes.
Default: 1
Different number of iterations cause smoother geometries
Offset[number]Larger values will move the resulting layer borders from the input layer ones.
Default: 0.25
In blue the input layer. Offset value of 0.25 results in the red line while offset value of 0.50 results in the green line
Maximum angle to smooth[number]Every node below this value will be smoothed.
Default: 180
Smoothed[vector]The smoothed vector layer.
Snaps the geometries in a layer.
Given a tolerance distance, snapping can be done either to the geometries from another layer, or to geometries within the same layer.
Vertices will be inserted or removed as required to make the geometries match the reference geometries.
Input layer[vector: any]Vector layer to align
Reference layer[vector: any]Vector layer to snap to
Tolerance[number]Control how close input vertices need to be to the reference layer geometries before they are snapped. This distance is specified in layer units.
Default: 10.0
Behavior[selection]Snapping can be done on an existing node or a segment (its closest point). Choose between different snapping options:
- Prefer aligning nodes, insert extra vertices where required
- Prefer closest point, insert extra vertices where required
- Prefer aligning nodes, don't insert new vertices
- Prefer closest point, don't insert new vertices
- Move end points only, prefer aligning nodes
- Move end points only, prefer closest point
- Snap end points to end points only
Default: Prefer aligning nodes, insert extra vertices where required
Snapped geometry[vector]Vector layer with snapped geometries
Modifies the coordinates of geometries in a vector layer, so that all points or vertices are snapped to the closest point of the grid.
If the snapped geometry cannot be calculated (or is totally collapsed) the feature's geometry will be cleared.
Note that snapping to grid may generate an invalid geometry in some corner cases.
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.
Input layer[vector: any]Input vector layer to snap
X Grid Spacing[number]X snapping parameter
Default: 1.0
Y Grid Spacing[number]Y snapping parameter
Default: 1.0
Z Grid Spacing[number]Z snapping parameter
Default: 0.0
M Grid Spacing[number]M snapping parameter
Default: 0.0
Snapped[vector]Vector layer with snapped geometries
Subdivides the geometry. The returned geometry will be a collection containing subdivided parts from the original geometry, where no part has more then 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. The returned geometry parts may not be valid and may contain self-intersections.
Curved geometries will be segmentized before subdivision.
Input layer [vector: any]
Maximum nodes in parts[number]Less sub-parts for higher values
Default: 256
Subdivided[vector: any]Output vector with sub-parts.
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)
Input layer[vector: line]Input line vector layer
Length of the transect[number]Length in map unit of the transect
Default: 5.0
Angle in degrees from the original line at the vertices[number]Change the angle of the transect
Default: 90.0
Side to create the transect[selection]Choose the side of the transect. Three different options available:
- Left
- Right
- Both
Default: Left
Transect[vector: line]Transect of the source line vector layer
Creates an offset of the source layer depending on the parameters chosen.
Input layer[vector: any]Vector layer in input
Offset distance (x-axis)[number]X axis offset distance
Default: 0.0
Offset distance (y-axis)[number]Y axis offset distance
Default: 0.0
Translated[vector]Translated (offset) vector layer
Takes a points 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.
Default menu: Vector --> Geometry Tools
Input layer[vector: point]Input point vector layer
Buffer region[number]Area of the Voronoi polygons or of the input layer
Default: 0.0
Voronoi polygons[vector: polygon]Voronoi polygons of the input point vector layer