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NAME

       v.in.lidar  - Converts LAS LiDAR point clouds to a GRASS vector map with libLAS.

KEYWORDS

       vector, import, LIDAR, level1

SYNOPSIS

       v.in.lidar
       v.in.lidar --help
       v.in.lidar [-pruvetcboi] input=name output=name  [id_layer=string]   [return_layer=string]
       [class_layer=string]                                                    [rgb_layer=string]
       [spatial=xmin,ymin,xmax,ymax[,xmin,ymin,xmax,ymax,...]]                   [zrange=min,max]
       [return_filter=string]          [class_filter=integer[,integer,...]]           [mask=name]
       [mask_layer=string]        [skip=integer]        [preserve=integer]       [offset=integer]
       [limit=integer]    [location=name]    [--overwrite]   [--help]    [--verbose]    [--quiet]
       [--ui]

   Flags:
       -p
           Print LAS file info and exit

       -r
           Limit import to the current region

       -u
           Invert mask when selecting points

       -v
           Use only valid points
           Points invalid according to APSRS LAS specification will be filtered out

       -e
           Extend region extents based on new dataset

       -t
           Do not create attribute table

       -c
           Do not automatically add unique ID as category to each point
           Create only requested layers and categories

       -b
           Do not build topology
           Advantageous when handling a large number of points

       -o
           Override projection check (use current location’s projection)
           Assume that the dataset has same projection as the current location

       -i
           Create  the location specified by the "location" parameter and exit. Do not import the
           vector data.

       --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=name [required]
           LAS input file
           LiDAR input files in LAS format (*.las or *.laz)

       output=name [required]
           Name for output vector map

       id_layer=string
           Layer number to store generated point ID as category
           Set to 1 by default, use -c to not store it

       return_layer=string
           Layer number to store return information as category
           Leave empty to not store it

       class_layer=string
           Layer number to store class number as category
           Leave empty to not store it

       rgb_layer=string
           Layer number where RBG colors are stored as category
           Leave empty to not store it

       spatial=xmin,ymin,xmax,ymax[,xmin,ymin,xmax,ymax,...]
           Import subregion only
           Format: xmin,ymin,xmax,ymax - usually W,S,E,N

       zrange=min,max
           Filter range for z data (min,max)

       return_filter=string
           Only import points of selected return type
           If not specified, all points are imported
           Options: first, last, mid

       class_filter=integer[,integer,...]
           Only import points of selected class(es)
           Input is comma separated integers. If not specified, all points are imported.

       mask=name
           Areas where to import points
           Name of vector map with areas where the points should be imported

       mask_layer=string
           Layer number or name for mask option
           Vector features can have category values in different layers. This  number  determines
           which layer to use. When used with direct OGR access this is the layer name.
           Default: 1

       skip=integer
           Do not import every n-th point
           For  example,  5  will  import  80 percent of points. If not specified, all points are
           imported

       preserve=integer
           Import only every n-th point
           For example, 4 will import 25 percent of points. If  not  specified,  all  points  are
           imported

       offset=integer
           Skip first n points
           Skips the given number of points at the beginning.

       limit=integer
           Import only n points
           Imports only the given number of points

       location=name
           Name for new location to create

DESCRIPTION

       v.in.lidar  converts  LiDAR point clouds in LAS format to a GRASS vector, using the libLAS
       library.  The created vector is true 3D with x, y, z coordinates.

       For larger datasets, it is recommended to not build topology (-b flag).  Also, creating  a
       table with attributes can take some time for larger datasets.

       The  optional  spatial parameter defines spatial query extents.  This parameter allows the
       user to restrict the region to a spatial subset while importing the data. All LiDAR points
       falling  into  this  rectangle  subregion  are  imported.  The  -r  current region flag is
       identical, but uses the current region settings as the spatial bounds (see g.region).

       A LiDAR pulse can have multiple returns. The first return values can be used to  obtain  a
       digital surface model (DSM) where e.g. canopy cover is represented. The last return values
       can be used to obtain a digital terrain model (DTM) where e.g. the forest floor instead of
       canopy  cover is represented. The return_filter option allows selecting one of first, mid,
       or last returns.

       LiDAR points can be already classified  into  standardized  classes.  For  example,  class
       number 2 represents ground (for other classes see LAS format specification in references).
       The class_filter option allows selecting  one  or  more  classes,  as  numbers  (integers)
       separated by comma.

       Note  that  proper  filtering  of  the  input points in not only critical for the analysis
       itself but it can also speed up the processing significantly.

   Decimation
       Table  with  selected  percentages  of  points  to  keep  with  corresponding   decimation
       parameters:

       percentage                                                   parameters

       0.1%                                                         preserve=1000

       1%                                                           preserve=100

       5%                                                           preserve=20

       10%                                                          preserve=10

       20%                                                          preserve=5

       25%                                                          preserve=4

       50%                                                          skip=2

       75%                                                          skip=4

       80%                                                          skip=5

       90%                                                          skip=10

       Table with selected fractions of points to keep with corresponding decimation parameters:

       ratio                                                        parameters

       1/3                                                          preserve=3

       1/4                                                          preserve=4

       1/5                                                          preserve=5

       1/6                                                          preserve=6

       Table  with  selected  fractions  of  points  to  throw away with corresponding decimation
       parameters:

       ratio                                                        parameters

       1/3                                                          skip=3

       1/4                                                          skip=4

       1/5                                                          skip=5

       1/6                                                          skip=6

Location Creation

       v.in.lidar attempts to preserve projection information  when  importing  datasets  if  the
       source  format includes projection information, and if the LAS driver supports it.  If the
       projection of the source dataset does not match the projection  of  the  current  location
       v.in.lidar  will  report an error message ("Projection of dataset does not appear to match
       current location") and then report the PROJ_INFO parameters of the source dataset.

       If the user wishes to ignore the difference between the apparent coordinate system of  the
       source data and the current location, they may pass the -o flag to override the projection
       check.

       If the user wishes to import the data with the full projection definition, it is  possible
       to have v.in.lidar automatically create a new location based on the projection and extents
       of the file being read.  This is accomplished by passing the name to be used for  the  new
       location  via the location parameter.  Upon completion of the command, a new location will
       have been created (with only a PERMANENT mapset),  and  the  vector  map  will  have  been
       imported with the indicated output name into the PERMANENT mapset.

NOTES

       The  typical  file  extensions  for  the  LAS  format are .las and .laz (compressed).  The
       compressed LAS (.laz) format can be imported only if libLAS has been compiled with  laszip
       support.  It  is also recommended to compile libLAS with GDAL, needed to test for matching
       projections.

EXAMPLE

       This example is analogous to the example used in the GRASS wiki page for importing LAS  as
       vector points.

       The  sample  LAS  data  are  in  the file "Serpent Mound Model LAS Data.las", available at
       appliedimagery.com
         # print LAS file info
         v.in.lidar -p input="Serpent Mound Model LAS Data.las"
         # create location with projection information of the LAS data
         v.in.lidar -i input="Serpent Mound Model LAS Data.las" location=Serpent_Mound
         # quit and restart GRASS in the newly created location "Serpent_Mound"
         # real import of LiDAR LAS data, without topology and without attribute table
         v.in.lidar -tb input="Serpent Mound Model LAS Data.las" output=Serpent_Mound_Model_pts

SEE ALSO

        r.in.lidar, r3.in.lidar, g.region, v.vect.stats, v.in.ogr

REFERENCES

       ASPRS LAS format
       LAS library
       LAS library C API documentation

AUTHOR

       Markus Metz
       Vaclav Petras, NCSU GeoForAll Lab (decimation, cats, areas, zrange)
       based on v.in.ogr by various authors

       Last changed: $Date: 2016-08-23 04:00:20 +0200 (Tue, 23 Aug 2016) $

SOURCE CODE

       Available at: v.in.lidar source code (history)

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       © 2003-2019 GRASS Development Team, GRASS GIS 7.6.1 Reference Manual