NAME¶
v.lidar.correction - Correction of the v.lidar.growing output. It
is the last of the three algorithms for LIDAR filtering.
KEYWORDS¶
vector, LIDAR
SYNOPSIS¶
v.lidar.correction
v.lidar.correction help
v.lidar.correction [-
e]
input=
name
output=
name terrain=
name [
sce=
float]
[
scn=
float] [
lambda_c=
float]
[
tch=
float] [
tcl=
float] [--
overwrite]
[--
verbose] [--
quiet]
Flags:¶
- -e
-
Estimate point density and distance
Estimate point density and distance for the input vector points within the
current region extends and quit
- --overwrite
-
Allow output files to overwrite existing files
- --verbose
-
Verbose module output
- --quiet
-
Quiet module output
Parameters:¶
- input=name
-
Input observation vector map name (v.lidar.growing output)
- output=name
-
Output classified vector map name
- terrain=name
-
Only 'terrain' points output vector map
- sce=float
-
Interpolation spline step value in east direction
Default: 25
- scn=float
-
Interpolation spline step value in north direction
Default: 25
- lambda_c=float
-
Regularization weight in reclassification evaluation
Default: 1
- tch=float
-
High threshold for object to terrain reclassification
Default: 2
- tcl=float
-
Low threshold for terrain to object reclassification
Default: 1
DESCRIPTION¶
v.lidar.correction is the last of three steps to filter LiDAR data. The
filter aims to recognize and extract attached and detached object (such as
buildings, bridges, power lines, trees, etc.) in order to create a Digital
Terrain Model.
The module, which could be iterated several times, makes a comparison between
the LiDAR observations and a bilinear spline interpolation with a Tychonov
regularization parameter performed on the TERRAIN SINGLE PULSE points only.
The gradient is minimized by the regularization parameter. Analysis of the
residuals between the observations and the interpolated values results in four
cases (the next classification is referred to that of the v.lidar.growing
output vector):
a) Points classified as TERRAIN differing more than a threshold value are
interpreted and reclassified as OBJECT, for both single and double pulse
points.
b) Points classified as OBJECT and closed enough to the interpolated
surface are interpreted and reclassified as TERRAIN, for both single and
double pulse points.
NOTES¶
The input should be the output of
v.lidar.growing module or the output of
this
v.lidar.correction itself. That means, this module could be
applied more times (although, two are usually enough) for a better filter
solution. The outputs are a vector map with a final point classification as as
TERRAIN SINGLE PULSE, TERRAIN DOUBLE PULSE, OBJECT SINGLE PULSE or OBJECT
DOUBLE PULSE; and an vector map with only the points classified as TERRAIN
SINGLE PULSE or TERRAIN DOUBLE PULSE. The final result of the whole procedure
(v.lidar.edgedetection, v.lidar.growing, v.lidar.correction) will be a point
classification in four categories:
TERRAIN SINGLE PULSE (cat = 1, layer = 2)
TERRAIN DOUBLE PULSE (cat = 2, layer = 2)
OBJECT SINGLE PULSE (cat = 3, layer = 2)
OBJECT DOUBLE PULSE (cat = 4, layer = 2)
EXAMPLES¶
Basic correction procedure¶
v.lidar.correction input=growing output=correction out_terrain=only_terrain
Second correction procedure¶
v.lidar.correction input=correction output=correction_bis
out_terrain=only_terrain_bis
SEE ALSO¶
v.lidar.edgedetection,
v.lidar.growing,
v.surf.bspline
AUTHORS¶
Original version of program in GRASS 5.4:
Maria Antonia Brovelli, Massimiliano Cannata, Ulisse Longoni and Mirko Reguzzoni
Update for GRASS 6.X:
Roberto Antolin and Gonzalo Moreno
REFERENCES¶
Antolin, R. et al., 2006. Digital terrain models determination by LiDAR
technology: Po basin experimentation. Bolletino di Geodesia e Scienze Affini,
anno LXV, n. 2, pp. 69-89.
Brovelli M. A., Cannata M., Longoni U.M., 2004. LIDAR Data Filtering and DTM
Interpolation Within GRASS, Transactions in GIS, April 2004, vol. 8, iss. 2,
pp. 155-174(20), Blackwell Publishing Ltd.
Brovelli M. A., Cannata M., 2004. Digital Terrain model reconstruction in urban
areas from airborne laser scanning data: the method and an example for Pavia
(Northern Italy). Computers and Geosciences 30 (2004) pp.325-331
Brovelli M. A. and Longoni U.M., 2003. Software per il filtraggio di dati LIDAR,
Rivista dell?Agenzia del Territorio, n. 3-2003, pp. 11-22 (ISSN 1593-2192).
Brovelli M. A., Cannata M. and Longoni U.M., 2002. DTM LIDAR in area urbana,
Bollettino SIFET N.2, pp. 7-26.
Performances of the filter can be seen in the ISPRS WG III/3 Comparison of
Filters report by Sithole, G. and Vosselman, G., 2003.
Last changed: $Date: 2010-09-16 09:25:59 +0200 (Thu, 16 Sep 2010) $
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