3
<em>v.lidar.correction</em> is the last of three steps to filter LiDAR
4
data. The filter aims to recognize and extract attached and
5
detached object (such as buildings, bridges, power lines, trees, etc.)
6
in order to create a Digital Terrain Model.
9
The module, which could be iterated several times, makes a comparison
10
between the LiDAR observations and a bilinear spline interpolation with
11
a Tychonov regularization parameter performed on the TERRAIN SINGLE PULSE
12
points only. The gradient is minimized by the regularization parameter.
13
Analysis of the residuals between the observations and the interpolated
14
values results in four cases (the next classification is referred to that
15
of the v.lidar.growing output vector):
18
<b>a)</b> Points classified as TERRAIN differing more than a threshold
19
value are interpreted and reclassified as OBJECT, for both single and
23
<b>b)</b> Points classified as OBJECT and closed enough to the
24
interpolated surface are interpreted and reclassified as TERRAIN, for
25
both single and double pulse points.
29
The input should be the output of <em>v.lidar.growing</em> module or the
30
output of this <em>v.lidar.correction</em> itself. That means, this module
31
could be applied more times (although, two are usually enough) for a better
32
filter solution. The outputs are a vector map with a final point classification
33
as as TERRAIN SINGLE PULSE, TERRAIN DOUBLE PULSE, OBJECT SINGLE PULSE or
34
OBJECT DOUBLE PULSE; and an vector map with only the points classified as
35
TERRAIN SINGLE PULSE or TERRAIN DOUBLE PULSE.
37
The final result of the whole procedure (<em>v.lidar.edgedetection</em>,
38
<em>v.lidar.growing</em>, <em>v.lidar.correction</em>) will be a point
39
classification in four categories:
42
TERRAIN SINGLE PULSE (cat = 1, layer = 2)
44
TERRAIN DOUBLE PULSE (cat = 2, layer = 2)
46
OBJECT SINGLE PULSE (cat = 3, layer = 2)
48
OBJECT DOUBLE PULSE (cat = 4, layer = 2)
53
<h3>Basic correction procedure</h3>
54
<div class="code"><pre>
55
v.lidar.correction input=growing output=correction out_terrain=only_terrain
58
<h3>Second correction procedure</h3>
59
<div class="code"><pre>
60
v.lidar.correction input=correction output=correction_bis out_terrain=only_terrain_bis
67
<a href="v.lidar.edgedetection.html">v.lidar.edgedetection</a>,
68
<a href="v.lidar.growing.html">v.lidar.growing</a>,
69
<a href="v.surf.bspline.html">v.surf.bspline</a>
75
Original version of program in GRASS 5.4:
77
Maria Antonia Brovelli, Massimiliano Cannata, Ulisse Longoni and Mirko Reguzzoni
81
Roberto Antolin and Gonzalo Moreno
85
Antolin, R. et al., 2006. Digital terrain models determination by LiDAR
86
technology: Po basin experimentation. Bolletino di Geodesia e Scienze
87
Affini, anno LXV, n. 2, pp. 69-89.
90
Brovelli M. A., Cannata M., Longoni U.M., 2004. LIDAR Data Filtering and
91
DTM Interpolation Within GRASS, Transactions in GIS, April 2004, vol. 8,
92
iss. 2, pp. 155-174(20), Blackwell Publishing Ltd.
95
Brovelli M. A., Cannata M., 2004. Digital Terrain model reconstruction in
96
urban areas from airborne laser scanning data: the method and an example
97
for Pavia (Northern Italy). Computers and Geosciences 30 (2004) pp.325-331
100
Brovelli M. A. and Longoni U.M., 2003. Software per il filtraggio di dati
101
LIDAR, Rivista dell'Agenzia del Territorio, n. 3-2003, pp. 11-22 (ISSN 1593-2192).
104
Brovelli M. A., Cannata M. and Longoni U.M., 2002. DTM LIDAR in area urbana,
105
Bollettino SIFET N.2, pp. 7-26.
108
Performances of the filter can be seen in the
109
<a href="http://www.itc.nl/isprswgIII-3/filtertest/MainDoc.htm">ISPRS WG III/3 Comparison of Filters</a>
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report by Sithole, G. and Vosselman, G., 2003.
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<p><i>Last changed: $Date: 2015-01-12 14:37:13 +0100 (Mon, 12 Jan 2015) $</i>