Note: A new GRASS GIS stable version has been released: GRASS GIS 7, available here. And see the new manual page here

## 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 02:02:59 -0700 (Tue, 27 Sep 2011) $*

Main index - vector index - Full index

© 2003-2016 GRASS Development Team