v.lidar.correction(1)

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

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

10       vector, LIDAR
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SYNOPSIS

13       v.lidar.correction
14       v.lidar.correction help
15       v.lidar.correction  input=name  output=name  terrain=name   [sce=float]
16       [scn=float]    [lambda_c=float]    [tch=float]   [tcl=float]   [--over‐
17       write]  [--verbose]  [--quiet]
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19   Flags:
20       --overwrite
21           Allow output files to overwrite existing files
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23       --verbose
24           Verbose module output
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26       --quiet
27           Quiet module output
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29   Parameters:
30       input=name
31           Input observation vector map name (v.lidar.growing output)
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33       output=name
34           Output classified vector map name
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36       terrain=name
37           Only 'terrain' points output vector map
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39       sce=float
40           Interpolation spline step value in east direction
41           Default: 25
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43       scn=float
44           Interpolation spline step value in north direction
45           Default: 25
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47       lambda_c=float
48           Regularization weight in reclassification evaluation
49           Default: 1
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51       tch=float
52           High threshold for object to terrain reclassification
53           Default: 2
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55       tcl=float
56           Low threshold for terrain to object reclassification
57           Default: 1
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DESCRIPTION

60       v.lidar.correction is the last of three steps to filter LiDAR data. The
61       filter aims to recognize and extract attached and detached object (such
62       as buildings, bridges, power lines,  trees, etc.)  in order to create a
63       Digital Terrain Model.
64       The  module,  which could be iterated several times, makes a comparison
65       between the LiDAR observations and a bilinear spline interpolation with
66       a  Tychonov  regularization  parameter  performed on the TERRAIN SINGLE
67       PULSE points only. The gradient  is  minimized  by  the  regularization
68       parameter.   Analysis of the residuals between the observations and the
69       interpolated values results in four cases (the next  classification  is
70       referred to that of the v.lidar.growing output vector):
71       a)  Points  classified as TERRAIN differing more than a threshold value
72       are interpreted and reclassified as OBJECT, for both single and  double
73       pulse points.
74       b)  Points  classified  as OBJECT and closed enough to the interpolated
75       surface are interpreted and reclassified as TERRAIN,  for  both  single
76       and double pulse points.
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NOTES

79       The  input should be the output of v.lidar.growing module or the output
80       of this v.lidar.correction itself. That means,  this  module  could  be
81       applied more times (although, two are usually enough) for a better fil‐
82       ter solution. The outputs are a vector map with a final point classifi‐
83       cation  as as TERRAIN SINGLE PULSE, TERRAIN DOUBLE PULSE, OBJECT SINGLE
84       PULSE or OBJECT DOUBLE PULSE; and an vector map with  only  the  points
85       classified  as TERRAIN SINGLE PULSE or TERRAIN DOUBLE PULSE.  The final
86       result of the whole procedure (v.lidar.edgedetection,  v.lidar.growing,
87       v.lidar.correction) will be a point classification in four categories:
88       TERRAIN SINGLE PULSE (cat = 1, layer = 2)
89       TERRAIN DOUBLE PULSE (cat = 2, layer = 2)
90       OBJECT SINGLE PULSE (cat = 3, layer = 2)
91       OBJECT DOUBLE PULSE (cat = 4, layer = 2)
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EXAMPLES

94   Basic correction procedure
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96       v.lidar.correction     input=growing     output=correction     out_ter‐
97       rain=only_terrain
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100   Second correction procedure
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102       v.lidar.correction  input=correction   output=correction_bis   out_ter‐
103       rain=only_terrain_bis
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AUTHORS

110       Original version of program in GRASS 5.4:
111       Maria  Antonia Brovelli, Massimiliano Cannata, Ulisse Longoni and Mirko
112       Reguzzoni
113       Update for GRASS 6.X:
114       Roberto Antolin and Gonzalo Moreno
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REFERENCES

117       Antolin, R. et al., 2006. Digital terrain models determination by LiDAR
118       technology:  Po  basin experimentation. Bolletino di Geodesia e Scienze
119       Affini, anno LXV, n. 2, pp. 69-89.
120       Brovelli M. A., Cannata M., Longoni U.M., 2004.  LIDAR  Data  Filtering
121       and  DTM  Interpolation  Within GRASS, Transactions in GIS, April 2004,
122       vol. 8, iss. 2, pp. 155-174(20), Blackwell Publishing Ltd.
123       Brovelli M. A., Cannata M., 2004. Digital Terrain model  reconstruction
124       in  urban  areas  from  airborne laser scanning data: the method and an
125       example for Pavia (Northern Italy). Computers and Geosciences 30 (2004)
126       pp.325-331
127       Brovelli  M.  A.  and Longoni U.M., 2003. Software per il filtraggio di
128       dati LIDAR, Rivista dell?Agenzia del Territorio, n. 3-2003,  pp.  11-22
129       (ISSN 1593-2192).
130       Brovelli  M.  A.,  Cannata M. and Longoni U.M., 2002. DTM LIDAR in area
131       urbana, Bollettino SIFET N.2, pp. 7-26.
132       Performances of the filter can be seen in the ISPRS WG III/3 Comparison
133       of Filters report by Sithole, G. and Vosselman, G., 2003.
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135       Last changed: $Date: 2007-10-18 15:40:28 +0200 (Thu, 18 Oct 2007) $
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137       Full index
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139       © 2003-2008 GRASS Development Team
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143GRASS 6.3.0                                              v.lidar.correction(1)