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) $

       Full index

       © 2003-2013 GRASS Development Team

GRASS 6.4.3                                                                                    v.outlier(1grass)