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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 00:25:59 -0700 (Thu, 16 Sep 2010) $

       Full index

       © 2003-2013 GRASS Development Team



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