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 11:02:59 +0200 (Tue, 27 Sep 2011) $
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