1v.lidar.correction(1) Grass User's Manual v.lidar.correction(1)
2
6 v.lidar.correction - Corrects the v.lidar.growing output. It is the
7 last of the three algorithms for LIDAR filtering.
8
10 vector, LIDAR
11
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 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
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 Input observation vector map name (v.lidar.growing output)
44 output=name [required]
46 Output classified vector map name
47 terrain=name [required]
49 Name for output only ’terrain’ points vector map
50 ew_step=float
52 Length of each spline step in the east-west direction
53 Default: 25 * east-west resolution
54 ns_step=float
56 Length of each spline step in the north-south direction
57 Default: 25 * north-south resolution
58 lambda_c=float
60 Regularization weight in reclassification evaluation
61 Default: 1
62 tch=float
64 High threshold for object to terrain reclassification
65 Default: 2
66 tcl=float
68 Low threshold for terrain to object reclassification
69 Default: 1
70
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 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.
92
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)
107
109 Basic correction procedure
110 v.lidar.correction input=growing output=correction out_terrain=only_terrain
111 Second correction procedure
113 v.lidar.correction input=correction output=correction_bis terrain=only_terrain_bis
114
116 v.lidar.edgedetection, v.lidar.growing, v.surf.bspline, v.surf.rst,
117 v.in.lidar, v.in.ascii
118
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
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.
144 Last changed: $Date: 2017-07-24 23:59:39 +0200 (Mon, 24 Jul 2017) $
146
148 Available at: v.lidar.correction source code (history)
149 Main index | Vector index | Topics index | Keywords index | Graphical
151 index | Full index
152 © 2003-2019 GRASS Development Team, GRASS GIS 7.4.4 Reference Manual
154GRASS 7.4.4 v.lidar.correction(1)