Note: A new GRASS GIS stable version has been released: GRASS GIS 7, available here. And see the new manual page here
v.lidar.correction - Correction of the v.lidar.growing output. It is the last of the three algorithms for LIDAR filtering.
v.lidar.correction [-e] input=name output=name terrain=name [sce=float] [scn=float] [lambda_c=float] [tch=float] [tcl=float] [--overwrite] [--verbose] [--quiet]
- Estimate point density and distance
- Estimate point density and distance for the input vector points within the current region extends and quit
- Allow output files to overwrite existing files
- Verbose module output
- Quiet module output
- Input observation vector map name (v.lidar.growing output)
- Output classified vector map name
- Only 'terrain' points output vector map
- Interpolation spline step value in east direction
- Default: 25
- Interpolation spline step value in north direction
- Default: 25
- Regularization weight in reclassification evaluation
- Default: 1
- High threshold for object to terrain reclassification
- Default: 2
- Low threshold for terrain to object reclassification
- Default: 1
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.
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
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)
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
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
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 00:25:59 -0700 (Thu, 16 Sep 2010) $
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