R: Classify points of interest

classify_poi {lidR}

R Documentation

Classify points of interest

Description

Classify points that meet some logical criterion and/or that belong in a region of interest. The function updates the attribute Classification of the LAS object.

Usage

classify_poi(
  las,
  class,
  poi = NULL,
  roi = NULL,
  inverse_roi = FALSE,
  by_reference = FALSE,
  ...
)

Arguments

`las`	An object of class LAS or LAScatalog.
`class`	The ASPRS class to attribute to the points that meet the criterion.
`poi`	a formula of logical predicates. The points that are `TRUE` will be classified `class`.
`roi`	A `SpatialPolygons`, `SpatialPolygonDataFrame` from `sp` or a `POLYGON` from `sf`. The points that are in the region of interest delimited by the polygon(s) are classified `class`.
`inverse_roi`	bool. Inverses the `roi`. The points that are outside the polygon(s) are classified `class`
`by_reference`	bool. Updates the classification in place (LAS only).
`...`	Unused

Value

If the input is a LAS object, return a LAS object. If the input is a LAScatalog, returns a LAScatalog.

Working with a `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

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

chunk size: How much data is loaded at once.
chunk buffer: A buffer is not need for this function to works thus buffer = 0 and cannot be changed.
chunk alignment: Align the processed chunks.
progress: Displays a progression estimation.
output files*: Mandatory because the output is likely to be too big to be returned in R and needs to be written in las/laz files. Supported templates are {XLEFT}, {XRIGHT}, {YBOTTOM}, {YTOP}, {XCENTER}, {YCENTER} {ID} and, if chunk size is equal to 0 (processing by file), {ORIGINALFILENAME}.
select: The function will write files equivalent to the original ones. Thus select = "*" and cannot be changed.
filter: Read only points of interest.

Examples

LASfile <- system.file("extdata", "Megaplot.laz", package="lidR")
shp     <- system.file("extdata", "lake_polygons_UTM17.shp", package = "lidR")

las  <- readLAS(LASfile, filter = "-keep_random_fraction 0.1")
lake <- sf::st_read(shp, quiet = TRUE)

# Classifies the points that are NOT in the lake and that are NOT ground points as class 5
poi <- ~Classification != LASGROUND
las <- classify_poi(las, LASHIGHVEGETATION, poi = poi, roi = lake, inverse = TRUE)

# Classifies the points that are in the lake as class 9
las <- classify_poi(las, LASWATER, roi = lake, inverse = FALSE)

#plot(las, color = "Classification")

[Package lidR version 3.2.2 Index]