Lidar preprocessing#

Algorithm ID: hedgetools:lidarpreprocessing

Preprocess lidar point cloud COPC files. COPC files are point clouds files optimized for spatial request and can be created from common LAS/LAZ files using QGIS pdal:createcopc algorithm. Preprocessing operations available are display below panels for parameters and outputs and are calls to PDAL library algorithms.

Preprocessed point clouds files are saved in a destination folder.

Parameters#

Label	Name	Type	Description
COPC lidar files	`LIDAR_FOLDER`	[folder]	Folder with COPC lidar files.
Lidar preprocessing operations Optional	`OPERATIONS`	[string] Default: None	JSON string containing preprocessing operations with parameters. Choice of operations is made using `Lidar preprocessing operations` panel.
Mask Optional	`MASK`	[vector: polygon]	Polygon layer to clip lidar point cloud.
Parrallel threads	`WORKERS`	[numeric: integer]	Number of parrallel threads.
Destination folder	`OUTPUT`	[string] Default: `[Save in temporary folder]`	Folder to save preprocessed point cloud COPC files.

Operations#

Height Above Ground normalization#

Normalize height with nearest neighbor or delaunay filer.

PDAL documentation:

Name	Type	Description
`Strategy`	[string] Default: `nn`	Normalization strategy (`delaunay` or `nn`).

Assignment#

Assign values for a dimension range to a specified value.

PDAL documentation:

https://pdal.io/en/2.8.4/stages/filters.assign.html

Name	Type	Description
`Condition`	[string]	Condition to assign value. Must be writted with PDAl syntax.
`Assignment`	[string]	Assignation. Must be writted with PDAL syntax.

Range filter#

Filters dimension within a given range.

PDAL documentation:

https://pdal.io/en/2.8.4/stages/filters.range.html

Name	Type	Description
`Field`	[string] Default: `Classification`	Point cloud dimension/field to filter (`Classification`, `X`,`Y` or `Z`).
`Inferior bound`	[numeric: integer] Default : 1	Inferior bound for range filter. Keep values above.
`Superior bound`	[numeric: integer] Default : 99	Superior bound for range filter. Keep values below.

Statistical Outliers Removal#

Remove point cloud outliers.

PDAL documentation:

https://pdal.io/en/2.8.4/stages/filters.outlier.html

Name	Type	Description
`Mean number of neighbors`	[numeric: integer] Default: 8	Mean number of neighbors (statistical method only).
`Standard deviation threshold`	[numeric: double] Default : 2.0	Standard deviation threshold (statistical method only).
`Method`	[string] Default : `statistical`	The outlier removal method (`statistical` or `radius`).
`Radius`	[numeric: double] Default : 1.0	Radius (radius method only).