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NAME

v.outlier - Removes outliers from vector point data.

KEYWORDS

vector, statistics

SYNOPSIS

v.outlier
v.outlier help
v.outlier [-e] input=name output=name outlier=name [qgis=name] [soe=float] [son=float] [lambda_i=float] [thres_o=float] [--overwrite] [--verbose] [--quiet]

Flags:

-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
--verbose
Verbose module output
--quiet
Quiet module output

Parameters:

input=name
Name of input vector map
output=name
Name for output vector map
outlier=name
Name of output outlier vector map
qgis=name
Name of vector map for visualization in QGIS
soe=float
Interpolation spline step value in east direction
Default: 10
son=float
Interpolation spline step value in north direction
Default: 10
lambda_i=float
Tykhonov regularization weight
Default: 0.1
thres_o=float
Threshold for the outliers
Default: 50

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. There is a flag to create a vector that can be visualizated by qgis. That means that topology is build and the z coordinate is considered as a category.

EXAMPLES

Basic outlier removal

v.outlier input=vector_map output=vector_output outlier=vector_outlier thres_O=25
In this case, a basic outlier removal is done with a threshold of 25 m.

Basic outlier removal

v.outlier -q input=vector_map output=vector_output outlier=vector_outlier qgis=vector_qgis
Now, the outlier removal uses the default threshold and there is also an output vector available for visualizaton in QGIS (http://www.qgis.org).

NOTES

This module is designed to work with LIDAR data, so not topology is built but in the QGIS output.

SEE ALSO

v.surf.bspline

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

Last changed: $Date: 2011-09-27 02:03:10 -0700 (Tue, 27 Sep 2011) $

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