Clip points in regions of interest
Clip points within a given region of interest (ROI) 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. 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.
clip_roi(las, geometry, ...) clip_rectangle(las, xleft, ybottom, xright, ytop, ...) clip_polygon(las, xpoly, ypoly, ...) clip_circle(las, xcenter, ycenter, radius, ...) clip_transect(las, p1, p2, width, xz = FALSE, ...)
las |
An object of class LAS or LAScatalog. |
geometry |
a geometric object. Many types are supported, see section 'supported geometries'. |
... |
in |
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 disc centers. |
ycenter |
numeric. y coordinates of disc centers. |
radius |
numeric. disc radius or radii. |
p1, p2 |
numeric vectors of length 2 that gives the coordinates of two points that define a transect |
width |
numeric. width of the transect. |
xz |
bool. If |
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.
WKT string: describing a POINT, a POLYGON or
a MULTIPOLYGON. If points, a parameter 'radius' must be passed in ...
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 ...
matrix 2 x 2 describing a bounding box following this order:
min max x 684816 684943 y 5017823 5017957
LAScatalog
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 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.
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
clip_* are {XLEFT}, {XRIGHT}, {YBOTTOM}, {YTOP}, {ID}, {XCENTER},
{YCENTER}. In addition clip_roi supports any names from the table of attributes of a spatial object given as
input such as {PLOTID}, {YEAR}, {SPECIES}, for examples, if these attributes exist. If empty everything
is returned into R.
laz_compression: write las or laz files
select: The function will write files equivalent to the originals. This option is not respected.
filter: Read only the points of interest.
LASfile <- system.file("extdata", "Megaplot.laz", package="lidR")
# Load the file and clip the region of interest
las = readLAS(LASfile, select = "xyz", filter = "-keep_first")
subset1 = clip_rectangle(las, 684850, 5017850, 684900, 5017900)
# Do not load the file(s), extract only the region of interest
# from a bigger dataset
ctg = readLAScatalog(LASfile, progress = FALSE, filter = "-keep_first")
subset2 = clip_rectangle(ctg, 684850, 5017850, 684900, 5017900)
# Extract all the polygons from a shapefile
f <- system.file("extdata", "lake_polygons_UTM17.shp", package = "lidR")
lakes <- sf::st_read(f, quiet = TRUE)
subset3 <- clip_roi(las, lakes)
# Extract the polygons for a catalog, 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 = clip_roi(ctg, lakes)
plot(new_ctg)
# Extract a transect
p1 <- c(684800, y = 5017800)
p2 <- c(684900, y = 5017900)
tr1 <- clip_transect(las, p1, p2, width = 4)
## Not run:
plot(subset1)
plot(subset2)
plot(subset3)
plot(tr1, axis = TRUE, clear_artifacts = FALSE)
## End(Not run)Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.