1v.lidar.correction(1)       GRASS GIS User's Manual      v.lidar.correction(1)
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NAME

6       v.lidar.correction   -  Corrects  the v.lidar.growing output. It is the
7       last of the three algorithms for LIDAR filtering.
8

KEYWORDS

10       vector, LIDAR
11

SYNOPSIS

13       v.lidar.correction
14       v.lidar.correction --help
15       v.lidar.correction    [-e]    input=name    output=name    terrain=name
16       [ew_step=float]     [ns_step=float]     [lambda_c=float]    [tch=float]
17       [tcl=float]   [--overwrite]  [--help]  [--verbose]  [--quiet]  [--ui]
18
19   Flags:
20       -e
21           Estimate point density and distance and quit
22           Estimate point density and distance in map units for the input vec‐
23           tor points within the current region extents and quit
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25       --overwrite
26           Allow output files to overwrite existing files
27
28       --help
29           Print usage summary
30
31       --verbose
32           Verbose module output
33
34       --quiet
35           Quiet module output
36
37       --ui
38           Force launching GUI dialog
39
40   Parameters:
41       input=name [required]
42           Name of input vector map
43           Input observation vector map name (v.lidar.growing output)
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45       output=name [required]
46           Output classified vector map name
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48       terrain=name [required]
49           Name for output only ’terrain’ points vector map
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51       ew_step=float
52           Length of each spline step in the east-west direction
53           Default: 25 * east-west resolution
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55       ns_step=float
56           Length of each spline step in the north-south direction
57           Default: 25 * north-south resolution
58
59       lambda_c=float
60           Regularization weight in reclassification evaluation
61           Default: 1
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63       tch=float
64           High threshold for object to terrain reclassification
65           Default: 2
66
67       tcl=float
68           Low threshold for terrain to object reclassification
69           Default: 1
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DESCRIPTION

72       v.lidar.correction is the last of three steps to filter LiDAR data. The
73       filter aims to recognize and extract attached and detached object (such
74       as buildings, bridges, power lines,  trees, etc.)  in order to create a
75       Digital Terrain Model.
76       The module, which could be iterated several times, makes  a  comparison
77       between the LiDAR observations and a bilinear spline interpolation with
78       a Tychonov regularization parameter performed  on  the  TERRAIN  SINGLE
79       PULSE  points  only.  The  gradient  is minimized by the regularization
80       parameter.  Analysis of the residuals between the observations and  the
81       interpolated  values  results in four cases (the next classification is
82       referred to that of the v.lidar.growing output vector):
83       a) Points classified as TERRAIN differing more than a  threshold  value
84       are  interpreted and reclassified as OBJECT, for both single and double
85       pulse points.
86       b) Points classified as OBJECT and closed enough  to  the  interpolated
87       surface  are  interpreted  and reclassified as TERRAIN, for both single
88       and double pulse points.
89
90       The length (in mapping units) of each spline step is defined by ew_step
91       for the east-west direction and ns_step for the north-south direction.
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NOTES

94       The  input should be the output of v.lidar.growing module or the output
95       of this v.lidar.correction itself. That means,  this  module  could  be
96       applied more times (although, two are usually enough) for a better fil‐
97       ter solution. The outputs are a vector map with a final point classifi‐
98       cation  as as TERRAIN SINGLE PULSE, TERRAIN DOUBLE PULSE, OBJECT SINGLE
99       PULSE or OBJECT DOUBLE PULSE; and an vector map with  only  the  points
100       classified  as TERRAIN SINGLE PULSE or TERRAIN DOUBLE PULSE.  The final
101       result of the whole procedure (v.lidar.edgedetection,  v.lidar.growing,
102       v.lidar.correction) will be a point classification in four categories:
103       TERRAIN SINGLE PULSE (cat = 1, layer = 2)
104       TERRAIN DOUBLE PULSE (cat = 2, layer = 2)
105       OBJECT SINGLE PULSE (cat = 3, layer = 2)
106       OBJECT DOUBLE PULSE (cat = 4, layer = 2)
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EXAMPLES

109   Basic correction procedure
110       v.lidar.correction input=growing output=correction out_terrain=only_terrain
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112   Second correction procedure
113       v.lidar.correction input=correction output=correction_bis terrain=only_terrain_bis
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SEE ALSO

116         v.lidar.edgedetection,  v.lidar.growing,  v.surf.bspline, v.surf.rst,
117       v.in.lidar, v.in.ascii
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AUTHORS

120       Original version of program in GRASS 5.4:
121       Maria Antonia Brovelli, Massimiliano Cannata, Ulisse Longoni and  Mirko
122       Reguzzoni
123       Update for GRASS 6.X:
124       Roberto Antolin and Gonzalo Moreno
125

REFERENCES

127       Antolin, R. et al., 2006. Digital terrain models determination by LiDAR
128       technology: Po basin experimentation. Bolletino di Geodesia  e  Scienze
129       Affini, anno LXV, n. 2, pp. 69-89.
130       Brovelli  M.  A.,  Cannata M., Longoni U.M., 2004. LIDAR Data Filtering
131       and DTM Interpolation Within GRASS, Transactions in  GIS,  April  2004,
132       vol. 8, iss. 2, pp. 155-174(20), Blackwell Publishing Ltd.
133       Brovelli  M. A., Cannata M., 2004. Digital Terrain model reconstruction
134       in urban areas from airborne laser scanning data:  the  method  and  an
135       example for Pavia (Northern Italy). Computers and Geosciences 30 (2004)
136       pp.325-331
137       Brovelli M. A. and Longoni U.M., 2003. Software per  il  filtraggio  di
138       dati  LIDAR,  Rivista dell’Agenzia del Territorio, n. 3-2003, pp. 11-22
139       (ISSN 1593-2192).
140       Brovelli M. A., Cannata M. and Longoni U.M., 2002. DTM  LIDAR  in  area
141       urbana, Bollettino SIFET N.2, pp. 7-26.
142       Performances of the filter can be seen in the ISPRS WG III/3 Comparison
143       of Filters report by Sithole, G. and Vosselman, G., 2003.
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SOURCE CODE

146       Available at: v.lidar.correction source code (history)
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148       Main index | Vector index | Topics index | Keywords index  |  Graphical
149       index | Full index
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151       © 2003-2020 GRASS Development Team, GRASS GIS 7.8.5 Reference Manual
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155GRASS 7.8.5                                              v.lidar.correction(1)
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