clip: Clip points in regions of interest

In lidR: Airborne LiDAR Data Manipulation and Visualization for Forestry Applications

Clip points in regions of interest

Description

Clip points within a given region of interest (ROI) from a point cloud (LAS object) or a collection of files (LAScatalog object).

Usage

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, ...)

Arguments

las	An object of class LAS or LAScatalog.
geometry	a geometric object. spatial points, spatial polygons in sp or sf/sfc format, Extent, bbox, 2x2 matrix
...	in clip_roi: optional supplementary options (see supported geometries). Unused in other functions
xleft, ybottom, xright, ytop	numeric. coordinates of one or several rectangles.
xpoly, ypoly	numeric. x coordinates of a polygon.
xcenter, ycenter	numeric. x coordinates of on or several disc centres.
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 TRUE the point cloud is reoriented to fit on XZ coordinates

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.

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, or a LAScatalog if the queries are immediately written into files without loading anything in R.

Non-supported LAScatalog options

The option ⁠chunk size⁠, buffer, ⁠chunk alignment⁠ and select are not supported by ⁠clip_*⁠ because they are meaningless in this context.

Examples

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)

lidR documentation built on Sept. 8, 2023, 5:10 p.m.