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24.1.17. Point Cloud Extraction

Výstraha

Running these algorithms requires QGIS installed with PDAL >= 2.5.0 (see Help ► About menu).

24.1.17.1. Boundary

Exports a polygon file containing point cloud layer boundary. It may contain holes and it may be a multi-part polygon.

Obr. 24.47 Extracting high vegetation and building polygons from an input point cloud layer

Parameters

Basic parameters

Label	Název	Druh	Popis
Input layer	INPUT	[point cloud]	Input point cloud layer to calculate boundary for
Resolution of cells used to calculate boundary Volitelné	RESOLUTION	[numeric: double]	Resolution of cells used to calculate boundary
Minimal number of points in a cell to consider cell occupied Volitelné	THRESHOLD	[numeric: integer]	Minimal number of points in a cell to consider cell occupied
Boundary	OUTPUT	[vector: polygon] Default: [Save to temporary file]	Specify the point cloud file to use as output. One of: Save to a Temporary File Save to File…

Advanced parameters

Label	Název	Druh	Popis
Filter expression Volitelné	FILTER_EXPRESSION	[expression]	A PDAL expression for selecting a subset of features in the point cloud data
Cropping extent Volitelné	FILTER_EXTENT	[extent]	A map extent for selecting a subset of features in the point cloud data Dostupné metody jsou: Calculate from layer…: uses extent of a layer loaded in the current project Calculate from layout map…: uses extent of a layout map item in the active project Calculate from bookmark…: uses extent of a saved bookmark Use map canvas extent Draw on canvas: click and drag a rectangle delimiting the area to take into account Enter the coordinates as xmin, xmax, ymin, ymax

Outputs

Label	Název	Druh	Popis
Boundary	OUTPUT	[vector: polygon]	Output polygon vector layer with the point cloud boundary. Currently supported format is .GPKG.

Python code

Algorithm ID: pdal:boundary

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

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

24.1.17.2. Density

Exports a raster file based on the number of points within each raster cell - useful for quality checking of point cloud datasets.

Obr. 24.48 Point density (number of points per 2x2 m) as a raster

Parameters

Basic parameters

Label	Název	Druh	Popis
Input layer	INPUT	[point cloud]	Input point cloud layer to export
Resolution of the density raster	RESOLUTION	[numeric: double] Default: 1.0	Cell size of the output raster
Tile size for parallel runs	TILE_SIZE	[numeric: integer] Default: 1000	Size of the tiles to split the data into for parallel runs
Density	OUTPUT	[raster] Default: [Save to temporary file]	Specify the raster file to export the data to. One of: Save to a Temporary File Save to File…

Advanced parameters

Label	Název	Druh	Popis
Filter expression Volitelné	FILTER_EXPRESSION	[expression]	A PDAL expression for selecting a subset of features in the point cloud data
Cropping extent Volitelné	FILTER_EXTENT	[extent]	A map extent for selecting a subset of features in the point cloud data Dostupné metody jsou: Calculate from layer…: uses extent of a layer loaded in the current project Calculate from layout map…: uses extent of a layout map item in the active project Calculate from bookmark…: uses extent of a saved bookmark Use map canvas extent Draw on canvas: click and drag a rectangle delimiting the area to take into account Enter the coordinates as xmin, xmax, ymin, ymax
X origin of a tile for parallel runs Volitelné	ORIGIN_X	[numeric: double]
Y origin of a tile for parallel runs Volitelné	ORIGIN_Y	[numeric: double]

Outputs

Label	Název	Druh	Popis
Density	OUTPUT	[raster]	Output raster layer with number of points within each cell. Currently supported format is .TIF.

Python code

Algorithm ID: pdal:density

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

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

24.1.17.3. Filter

Extracts point from the input point cloud which match PDAL expression and/or are inside of a cropping rectangle.

Obr. 24.49 Filtering of high vegetation class from an input point cloud layer

Parameters

Label	Název	Druh	Popis
Input layer	INPUT	[point cloud]	Input point cloud layer to export
Filter expression Volitelné	FILTER_EXPRESSION	[expression]	A PDAL expression for selecting a subset of features in the point cloud data
Cropping extent Volitelné	FILTER_EXTENT	[extent]	A map extent for selecting a subset of features in the point cloud data Dostupné metody jsou: Calculate from layer…: uses extent of a layer loaded in the current project Calculate from layout map…: uses extent of a layout map item in the active project Calculate from bookmark…: uses extent of a saved bookmark Use map canvas extent Draw on canvas: click and drag a rectangle delimiting the area to take into account Enter the coordinates as xmin, xmax, ymin, ymax
Filtered	OUTPUT	[point cloud] Default: [Save to temporary file]	Specify the point cloud file to export the data to. One of: Save to a Temporary File Save to File…

Outputs

Label	Název	Druh	Popis
Filtered	OUTPUT	[point cloud]	Output point cloud layer with the filtered features of the input point cloud layer. Currently supported formats are .LAS, .LAZ, .COPC.LAZ and .VPC.

Python code

Algorithm ID: pdal:filter

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

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