lidR (version 2.2.5)

lasclip: Clip LiDAR points

Description

Clip LiDAR points within a given geometry from a point cloud (LAS object) or a catalog (LAScatalog object). With a LAS object, the user first reads and loads a point-cloud into memory and then can clip it to get a subset within a region of interest (ROI). With a LAScatalog object, the user can extract any arbitrary ROI for a set of las/laz files, loading only the points of interest. This is faster, easier and much more memory-efficient for extracting ROIs.

Usage

lasclip(las, geometry, ...)
lasclipRectangle(las, xleft, ybottom, xright, ytop, ...)
lasclipPolygon(las, xpoly, ypoly, ...)
lasclipCircle(las, xcenter, ycenter, radius, ...)

Arguments

las

An object of class LAS or LAScatalog.

geometry

a geometric object. Many types are supported, see section 'supported geometries'.

...

in lasclip: optional supplementary options (see supported geometries). Unused in other functions

xleft

numeric. left x coordinates of rectangles.

ybottom

numeric. bottom y coordinates of rectangles.

xright

numeric. right x coordinates of rectangles.

ytop

numeric. top y coordinates of rectangles.

xpoly

numeric. x coordinates of a polygon.

ypoly

numeric. y coordinates of a polygon.

xcenter

numeric. x coordinates of discs centers.

ycenter

numeric. y coordinates of discs centers.

radius

numeric. disc radius or radii.

Value

If the input is a LAS object: an object of class LAS, or a list of LAS objects if the query implies several regions of interest will be returned. If the input is a LAScatalog object: an object of class LAS, or a list of LAS objects if the query implies several regions of interest will be returned, or a LAScatalog if the queries are immediately written into files without loading anything in R.

Supported geometries

• WKT string: describing a POINT, a POLYGON or a MULTIPOLYGON. If points a parameter 'radius' must be passed in ...

• Polygon or Polygons

• SpatialPolygons or SpatialPolygonsDataFrame

• SpatialPoints or SpatialPointsDataFrame in that case a parameter 'radius' must be passed in ...

• SimpleFeature that consistently contains POINT or POLYGON/MULTIPOLYGON. In case of POINT a parameter 'radius' must be passed in ...

• Extent

• matrix 2 x 2 describing a bounding box following this order:

    min     max
  x 684816  684943
  y 5017823 5017957

Working with a <code>LAScatalog</code>

This section appears in each function that supports a LAScatalog as input.

In lidR when the input of a function is a LAScatalog the function uses the LAScatalog processing engine. The user can modify the engine options using the available options. A careful reading of the engine documentation is recommended before processing LAScatalogs. Each lidR function should come with a section that documents the supported engine options.

The LAScatalog engine supports .lax files that significantly improve the computation speed of spatial queries using a spatial index. Users should really take advantage a .lax files, but this is not mandatory.

Supported processing options

Supported processing options for a LAScatalog (in bold). For more details see the LAScatalog engine documentation:

• chunk_size: Does not make sense here.

• buffer: Not supported yet.

• alignment: Does not makes sense here.

• progress: Displays a progress estimation.

• stop_early: Leave this 'as-is' unless you are an advanced user.

• output_files: If 'output_files' is set in the catalog, the ROIs will not be returned in R. They will be written immediately in files. See LAScatalog-class and examples. The allowed templates in lasclip are {XLEFT}, {XRIGHT}, {YBOTTOM}, {YTOP}, {ID}, {XCENTER}, {YCENTER} or any names from the table of attributes of a spatial object given as input such as {PLOT_ID} or {YEAR}, for example, if these attributes exist. If empty everything is returned into R.

• laz_compression: write las or laz files

• drivers: Leave this 'as-is' unless you are an advanced user.

• select: The function will write files equivalent to the originals. This option is not respected.

• filter: Read only the points of interest.

Examples

# NOT RUN {
LASfile <- system.file("extdata", "Megaplot.laz", package="lidR")

# Load the file and clip the region of interest
las = readLAS(LASfile)
subset1 = lasclipRectangle(las, 684850, 5017850, 684900, 5017900)

# Do not load the file(s), extract only the region of interest
# from a bigger dataset
ctg = readLAScatalog(LASfile)
subset2 = lasclipRectangle(ctg, 684850, 5017850, 684900, 5017900)

# Extract all the polygons from a shapefile
shapefile_dir <- system.file("extdata", package = "lidR")
lakes = shapefile(paste0(shapefile_dir, "/lake_polygons_UTM17.shp"))
subset3 = lasclip(ctg, lakes)

# Extract the polygons, write them in files named after the lake names,
# do not load anything in R
opt_output_files(ctg) <- paste0(tempfile(), "_{LAKENAME_1}")
new_ctg = lasclip(ctg, lakes)

# }
# NOT RUN {
plot(subset1)
plot(subset2)
plot(subset3)
# }