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) $

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