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v.outlier

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v.outlier: Removes outliers from vector point data.

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   outlier   points.   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
       (//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: 2010-09-16 09:25:59 +0200 (Thu, 16 Sep 2010) $

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       (C) 2003-2010 GRASS Development Team

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