vectorgeoprocessing.rst

Vector geoprocessing

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Buffer vectors

Create buffers around the features of a vector layer.

Parameters

Basic parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: any]	The input vector layer
Geometry column name	GEOMETRY	[string] Default: 'geometry'	The name of the input layer geometry column to use
Buffer distance	DISTANCE	[number] Default: 10.0	Minimum: 0.0
Dissolve by attribute Optional	FIELD	[tablefield: any] Default: None	Field to use for dissolving
Dissolve results	DISSOLVE	[boolean] Default: False	If set, the result is dissolved. If no field is set for dissolving, all the buffers are dissolved into one feature.
Produce one feature for each geometry in any kind of geometry collection in the source file	EXPLODE_COLLECTIONS	[boolean] Default: False
Buffer	OUTPUT	[vector: polygon] Default: [Save to temporary file]	Specify the output buffer layer. One of:

Advanced parameters

Label	Name	Type	Description
Additional creation options Optional	OPTIONS	[string] Default: '' (no additional options)	Additional GDAL creation options.

Outputs

Label	Name	Type	Description
Buffer	OUTPUT	[vector: polygon]	The output buffer layer

Python code

Algorithm ID: gdal:buffervectors

Clip vector by extent

Clips any OGR-supported vector file to a given extent.

This algorithm is derived from the GDAL ogr2ogr utility.

Parameters

Basic parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: any]	The input vector layer
Clip extent	EXTENT	[extent]	Defines the bounding box that should be used for the output vector file. It has to be defined in target CRS coordinates.
Clipped (extent)	OUTPUT	[same as input] Default: [Save to temporary file]	Specify the output (clipped) layer. One of:

Advanced parameters

Label	Name	Type	Description
Additional creation options Optional	OPTIONS	[string] Default: '' (no additional options)	Additional GDAL creation options.

Outputs

Label	Name	Type	Description
Clipped (extent)	OUTPUT	[same as input]	The output (clipped) layer. The default format is "ESRI Shapefile".

Python code

Algorithm ID: gdal:clipvectorbyextent

Clip vector by mask layer

Clips any OGR-supported vector layer by a mask polygon layer.

This algorithm is derived from the GDAL ogr2ogr utility.

Parameters

Basic parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: any]	The input vector layer
Mask layer	MASK	[vector: polygon]	Layer to be used as clipping extent for the input vector layer.
Clipped (mask)	OUTPUT	[same as input] Default: [Save to temporary file]	The output (masked) layer. One of:

Advanced parameters

Label	Name	Type	Description
Additional creation options Optional	OPTIONS	[string] Default: '' (no additional options)	Additional GDAL creation options.

Outputs

Label	Name	Type	Description
Clipped (mask)	OUTPUT	[same as input]	The output (masked) layer. The default format is "ESRI Shapefile".

Python code

Algorithm ID: gdal:clipvectorbypolygon

Dissolve

Dissolve (combine) geometries that have the same value for a given attribute / field. The output geometries are multipart.

Parameters

Basic parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: any]	The input layer to dissolve
Dissolve field Optional	FIELD	[tablefield: any]	The field of the input layer to use for dissolving
Geometry column name	GEOMETRY	[string] Default: 'geometry'	The name of the input layer geometry column to use for dissolving.
Dissolved	OUTPUT	[same as input] Default: [Save to temporary file]	Specify the output layer. One of:

Advanced parameters

Label	Name	Type	Description
Produce one feature for each geometry in any kind of geometry collection in the source file	EXPLODE_COLLECTIONS	[boolean] Default: False	Produce one feature for each geometry in any kind of geometry collection in the source file
Keep input attributes	KEEP_ATTRIBUTES	[boolean] Default: False	Keep all attributes from the input layer
Count dissolved features	COUNT_FEATURES	[boolean] Default: False	Count the dissolved features and include it in the output layer.
Compute area and perimeter of dissolved features	COMPUTE_AREA	[boolean] Default: False	Compute the area and perimeter of dissolved features and include them in the output layer
Compute min/max/sum/mean for attribute	COMPUTE_STATISTICS	[boolean] Default: False	Calculate statistics (min, max, sum and mean) for the numeric attribute specified and include them in the output layer
Numeric attribute to calculate statistics on Optional	STATISTICS_ATTRIBUTE	[tablefield: numeric]	The numeric attribute to calculate statistics on
Additional creation options Optional	OPTIONS	[string] Default: '' (no additional options)	Additional GDAL creation options.

Outputs

Label	Name	Type	Description
Dissolved	OUTPUT	[same as input]	The output multipart geometry layer (with dissolved geometries)

Python code

Algorithm ID: gdal:dissolve

Offset curve

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

Parameters

Basic parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: line]	The input line layer
Geometry column name	GEOMETRY	[string] Default: 'geometry'	The name of the input layer geometry column to use
Offset distance (left-sided: positive, right-sided: negative)	DISTANCE	[number] Default: 10.0
Offset curve	OUTPUT	[vector: line] Default: [Save to temporary file]	Specify the output line layer. One of:

Advanced parameters

Label	Name	Type	Description
Additional creation options Optional	OPTIONS	[string] Default: '' (no additional options)	Additional GDAL creation options.

Outputs

Label	Name	Type	Description
Offset curve	OUTPUT	[vector: line]	The output offset curve layer

Python code

Algorithm ID: gdal:offsetcurve

One side buffer

Creates a buffer on one side (right or left) of the lines in a line vector layer.

Parameters

Basic parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: line]	The input line layer
Geometry column name	GEOMETRY	[string] Default: 'geometry'	The name of the input layer geometry column to use
Buffer distance	DISTANCE	[number] Default: 10.0
Buffer side	BUFFER_SIDE	[enumeration] Default: 0	One of: 0 --- Right 1 --- Left
Dissolve by attribute Optional	FIELD	[tablefield: any] Default: None	Field to use for dissolving
Dissolve all results	DISSOLVE	[boolean] Default: False	If set, the result is dissolved. If no field is set for dissolving, all the buffers are dissolved into one feature.
Produce one feature for each geometry in any kind of geometry collection in the source file	EXPLODE_COLLECTIONS	[boolean] Default: False
One-sided buffer	OUTPUT	[vector: polygon] Default: [Save to temporary file]	Specify the output buffer layer. One of:

Advanced parameters

Label	Name	Type	Description
Additional creation options Optional	OPTIONS	[string] Default: '' (no additional options)	Additional GDAL creation options.

Outputs

Label	Name	Type	Description
One-sided buffer	OUTPUT	[vector: polygon]	The output buffer layer

Python code

Algorithm ID: gdal:onesidebuffer

Points along lines

Generates a point on each line of a line vector layer at a distance from start. The distance is provided as a fraction of the line length.

Parameters

Basic parameters

Label	Name	Type	Description
Input layer	INPUT	[vector: line]	The input line layer
Geometry column name	GEOMETRY	[string] Default: 'geometry'	The name of the input layer geometry column to use
Distance from line start represented as a fraction of line length	DISTANCE	[number] Default: 0.5 (middle of the line)
Points along lines	OUTPUT	[vector: point] Default: [Save to temporary file]	Specify the output point layer. One of:

Advanced parameters

Label	Name	Type	Description
Additional creation options Optional	OPTIONS	[string] Default: '' (no additional options)	Additional GDAL creation options.

Outputs

Label	Name	Type	Description
Points along line	OUTPUT	[vector: point]	The output point layer

Python code

Algorithm ID: gdal:pointsalonglines