v.outlier
Removes outliers from vector point data.
v.outlier [-e] input=name output=name outlier=name [qgis=name] [ew_step=float] [ns_step=float] [lambda=float] [threshold=float] [filter=string] [--overwrite] [--verbose] [--quiet] [--qq] [--ui]
Example:
v.outlier input=name output=name outlier=name
grass.script.run_command("v.outlier", input, output, outlier, qgis=None, ew_step=None, ns_step=None, lambda=0.1, threshold=50, filter="both", flags=None, overwrite=False, verbose=False, quiet=False, superquiet=False)
Example:
gs.run_command("v.outlier", input="name", output="name", outlier="name")
Parameters
input=name [required]
Name of input vector map
Or data source for direct OGR access
output=name [required]
Name for output vector map
outlier=name [required]
Name for output outlier vector map
qgis=name
Name for vector map for visualization in QGIS
ew_step=float
Length of each spline step in the east-west direction
Default: 10 * east-west resolution
ns_step=float
Length of each spline step in the north-south direction
Default: 10 * north-south resolution
lambda=float
Tykhonov regularization weight
Default: 0.1
threshold=float
Threshold for the outliers
Default: 50
filter=string
Filtering option
Allowed values: both, positive, negative
Default: both
-e
Estimate point density and distance
Estimate point density and distance for the input vector points within the current region extends and quit
--overwrite
Allow output files to overwrite existing files
--help
Print usage summary
--verbose
Verbose module output
--quiet
Quiet module output
--qq
Very quiet module output
--ui
Force launching GUI dialog
input : str, required
Name of input vector map
Or data source for direct OGR access
Used as: input, vector, name
output : str, required
Name for output vector map
Used as: output, vector, name
outlier : str, required
Name for output outlier vector map
Used as: output, vector, name
qgis : str, optional
Name for vector map for visualization in QGIS
Used as: output, vector, name
ew_step : float, optional
Length of each spline step in the east-west direction
Default: 10 * east-west resolution
ns_step : float, optional
Length of each spline step in the north-south direction
Default: 10 * north-south resolution
lambda : float, optional
Tykhonov regularization weight
Default: 0.1
threshold : float, optional
Threshold for the outliers
Default: 50
filter : str, optional
Filtering option
Allowed values: both, positive, negative
Default: both
flags : str, optional
Allowed values: e
e
Estimate point density and distance
Estimate point density and distance for the input vector points within the current region extends and quit
overwrite: bool, optional
Allow output files to overwrite existing files
Default: False
verbose: bool, optional
Verbose module output
Default: False
quiet: bool, optional
Quiet module output
Default: False
superquiet: bool, optional
Very quiet module output
Default: False
DESCRIPTION
v.outlier removes outliers in a 3D point cloud. By default, the outlier identification is done by a bicubic spline interpolation of the observation with a high regularization parameter and a low resolution in south-north and east-west directions. Those points that differ in an absolute value more than the given threshold from a fixed value, reckoned from its surroundings by the interpolation, are considered as an outlier, and hence are removed.
The filter option specifies if all outliers will be removed (default), or only positive or only negative outliers. Filtering out only positive outliers can be useful to filter out vegetation returns (e.g. from forest canopies) from LIDAR point clouds, in order to extract digital terrain models (DTMs). Filtering out only negative outliers can be useful to estimate vegetation height.
There is a flag to create a vector that can be visualized in QGIS. That means that topology is built and the z coordinate is considered as a category.
EXAMPLES
Basic outlier removal
In this case, a basic outlier removal is done with a threshold of 25 m:
v.outlier input=vector_map output=vector_output outlier=vector_outlier thres_O=25
Now, the outlier removal uses the default threshold and there is also an output vector available for visualization in QGIS:
v.outlier input=vector_map output=vector_output outlier=vector_outlier qgis=vector_qgis
North Carolina dataset example
v.outlier input=elev_lid792_bepts output=elev_lid792_bepts_nooutliers \
outlier=elev_lid792_bepts_outliers ew_step=5 ns_step=5 thres_o=0.1
NOTES
This module is designed to work with LIDAR data, so not topology is built but in the QGIS output.
SEE ALSO
AUTHORS
Original version of the program in GRASS 5.4:
Maria Antonia Brovelli, Massimiliano Cannata, Ulisse Longoni and Mirko
Reguzzoni
Updates for GRASS 6:
Roberto Antolin
SOURCE CODE
Available at: v.outlier source code
(history)
Latest change: Saturday Mar 29 14:59:39 2025 in commit 0bfa813