v.lidar.correction(1)

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 input=name output=name out_terrain=name [database=string] [driver=string] [sce=float] scn=float [lambda_c=float] [tch=float] [tcl=float] [--overwrite]

  Flags:

--overwrite

  Parameters:

input=name
    Input observation vector map name (v.lidar.growing output)

output=name
    Output classified vector map name

out_terrain=name
    Output terrain only vector map name

database=string
    Database name

driver=string
    Driver name Options: dbf,pg,ogr

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 step to filter LIDAR data. It makes a comparison between the LIDAR observations and an interpolated surface in which only terrain points have been used. Once the new reference surface is obtained, a point reclassification is done:
a) Points classified as TERRAIN differing more than a threshold value are interpreted and reclassified as OBJECT.
b) Points classified as OBJECT and closed enough to the interpolated surface are interpreted and reclassified as TERRAIN.
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 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.

NOTES
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
TERRAIN DOUBLE PULSE
OBJECT SINGLE PULSE
OBJECT DOUBLE PULSE

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

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
Brovelli M. A., Cannata M., and 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. and 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, pp.325-331
Brovelli M. A e 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, 2002, pp. 7-26

Last changed: $Date: 2007/04/16 21:36:04 $

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