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:
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.