Skip site navigation (1)Skip section navigation (2)

FreeBSD Manual Pages

  
 
  

home | help
v.lidar.correction(1)	    GRASS GIS User's Manual	 v.lidar.correction(1)

NAME
       v.lidar.correction   -  Corrects	 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
       [ew_step=float]	   [ns_step=float]     [lambda_c=float]	   [tch=float]
       [tcl=float]   [--overwrite]  [--help]  [--verbose]  [--quiet]  [--ui]

   Flags:
       -e
	   Estimate point density and distance and quit
	   Estimate point density and distance in map units for	the input vec-
	   tor points within the current region	extents	and quit

       --overwrite
	   Allow output	files to overwrite existing files

       --help
	   Print usage summary

       --verbose
	   Verbose module output

       --quiet
	   Quiet module	output

       --ui
	   Force launching GUI dialog

   Parameters:
       input=nameA [required]
	   Name	of input vector	map
	   Input observation vector map	name (v.lidar.growing output)

       output=nameA [required]
	   Output classified vector map	name

       terrain=nameA [required]
	   Name	for output only	'terrain' points vector	map

       ew_step=float
	   Length of each spline step in the east-west direction
	   Default: 25 * east-west resolution

       ns_step=float
	   Length of each spline step in the north-south direction
	   Default: 25 * north-south resolution

       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 pa-
       rameter.	 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 length (in mapping units) of	each spline step is defined by ew_step
       for the east-west direction and ns_step for the north-south direction.

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 ap-
       plied more times	(although, two are usually enough) for a better	filter
       solution. The outputs are a vector map with a final  point  classifica-
       tion  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 terrain=only_terrain_bis

SEE ALSO
	 v.lidar.edgedetection,	 v.lidar.growing,  v.surf.bspline, v.surf.rst,
       v.in.lidar, v.in.ascii

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.

SOURCE CODE
       Available at: v.lidar.correction	source code (history)

       Main index | Vector index | Topics index	| Keywords index  |  Graphical
       index | Full index

       A(C) 2003-2020 GRASS Development	Team, GRASS GIS	7.8.3 Reference	Manual

GRASS 7.8.3						 v.lidar.correction(1)

NAME | KEYWORDS | SYNOPSIS | DESCRIPTION | NOTES | EXAMPLES | SEE ALSO | AUTHORS | REFERENCES | SOURCE CODE

Want to link to this manual page? Use this URL:
<https://www.freebsd.org/cgi/man.cgi?query=v.lidar.correction&sektion=1&manpath=FreeBSD+12.2-RELEASE+and+Ports>

home | help