1v.outlier(1) GRASS GIS User's Manual v.outlier(1)
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6 v.outlier - Removes outliers from vector point data.
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9 vector, statistics, extract, select, filter, LIDAR
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12 v.outlier
13 v.outlier --help
14 v.outlier [-e] input=name output=name outlier=name [qgis=name]
15 [ew_step=float] [ns_step=float] [lambda=float] [threshold=float]
16 [filter=string] [--overwrite] [--help] [--verbose] [--quiet]
17 [--ui]
18 Flags:
20 -e
21 Estimate point density and distance
22 Estimate point density and distance for the input vector points
23 within the current region extends and quit
24 --overwrite
26 Allow output files to overwrite existing files
27 --help
29 Print usage summary
30 --verbose
32 Verbose module output
33 --quiet
35 Quiet module output
36 --ui
38 Force launching GUI dialog
39 Parameters:
41 input=name [required]
42 Name of input vector map
43 Or data source for direct OGR access
44 output=name [required]
46 Name for output vector map
47 outlier=name [required]
49 Name for output outlier vector map
50 qgis=name
52 Name for vector map for visualization in QGIS
53 ew_step=float
55 Length of each spline step in the east-west direction
56 Default: 10 * east-west resolution
57 ns_step=float
59 Length of each spline step in the north-south direction
60 Default: 10 * north-south resolution
61 lambda=float
63 Tykhonov regularization weight
64 Default: 0.1
65 threshold=float
67 Threshold for the outliers
68 Default: 50
69 filter=string
71 Filtering option
72 Options: both, positive, negative
73 Default: both
74
76 v.outlier removes outliers in a 3D point cloud. By default, the outlier
77 identification is done by a bicubic spline interpolation of the obser‐
78 vation with a high regularization parameter and a low resolution in
79 south-north and east-west directions. Those points that differ in an
80 absolute value more than the given threshold from a fixed value, reck‐
81 oned from its surroundings by the interpolation, are considered as an
82 outlier, and hence are removed.
83 The filter option specifies if all outliers will be removed (default),
85 or only positive or only negative outliers. Filtering out only positive
86 outliers can be useful to filter out vegetation returns (e.g. from for‐
87 est canopies) from LIDAR point clouds, in order to extract Digital Ter‐
88 rain Models. Filtering out only negative outliers can be useful to
89 estimate vegetation height.
90 There is a flag to create a vector that can be visualizated by qgis.
92 That means that topology is build and the z coordinate is considered as
93 a category.
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96 Basic outlier removal
97 v.outlier input=vector_map output=vector_output outlier=vector_outlier thres_O=25
98 In this case, a basic outlier removal is done with a threshold of 25 m.
99 Basic outlier removal
101 v.outlier input=vector_map output=vector_output outlier=vector_outlier qgis=vector_qgis
102 Now, the outlier removal uses the default threshold and there is also
103 an output vector available for visualizaton in QGIS
104 (http://www.qgis.org).
105 North carolina location example
107 v.outlier input=elev_lid792_bepts output=elev_lid792_bepts_nooutliers \
108 outlier=elev_lid792_bepts_outliers ew_step=5 ns_step=5 thres_o=0.1
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111 This module is designed to work with LIDAR data, so not topology is
112 built but in the QGIS output.
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115 v.surf.bspline
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118 Original version of the program in GRASS 5.4:
119 Maria Antonia Brovelli, Massimiliano Cannata, Ulisse Longoni and Mirko
120 Reguzzoni
121 Updates for GRASS 6:
122 Roberto Antolin
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125 Available at: v.outlier source code (history)
126 Main index | Vector index | Topics index | Keywords index | Graphical
128 index | Full index
129 © 2003-2020 GRASS Development Team, GRASS GIS 7.8.5 Reference Manual
131GRASS 7.8.5 v.outlier(1)