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v.outlier - Removes outliers from vector point data.
vector, statistics, extract, select, filter, LIDAR
v.outlier v.outlier --help v.outlier [-e] input=name output=name outlier=name [qgis=name] [ew_step=float] [ns_step=float] [lambda=float] [threshold=float] [filter=string] [--overwrite] [--help] [--verbose] [--quiet] [--ui] 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 --help Print usage summary --verbose Verbose module output --quiet Quiet module output --ui Force launching GUI dialog Parameters: input=name [required] Name of input vector map Or data source for direct OGR access output=name [required] Name for output vector map outlier=name [required] Name for output outlier vector map qgis=name Name for vector map for visualization in QGIS ew_step=float Length of each spline step in the east-west direction Default: 10 * east-west resolution ns_step=float Length of each spline step in the north-south direction Default: 10 * north-south resolution lambda=float Tykhonov regularization weight Default: 0.1 threshold=float Threshold for the outliers Default: 50 filter=string Filtering option Options: both, positive, negative Default: both
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. The filter option specifies if all outliers will be removed (default), or only positive or only negative outliers. Filtering out only positive outliers can be useful to filter out vegetation returns (e.g. from forest canopies) from LIDAR point clouds, in order to extract Digital Terrain Models. Filtering out only negative outliers can be useful to estimate vegetation height. 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.
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 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). North carolina location example v.outlier input=elev_lid792_bepts output=elev_lid792_bepts_nooutliers \ outlier=elev_lid792_bepts_outliers ew_step=5 ns_step=5 thres_o=0.1
This module is designed to work with LIDAR data, so not topology is built but in the QGIS output.
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: 2014-08-05 08:59:29 +0200 (Tue, 05 Aug 2014) $
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