lidR (version 3.1.1)

classify_ground: Classify points as 'ground'

Description

Classify points as 'ground' with several possible algorithms. The function updates the attribute Classification of the LAS object. The points classified as 'ground' are assigned a value of 2 according to las specifications.

Usage

classify_ground(las, algorithm, last_returns = TRUE)

Arguments

las

An object of class LAS or LAScatalog.

algorithm

a ground-segmentation function. lidR has: pmf and csf. The lidRplugins package has 'mcc'.

last_returns

logical. The algorithm will use only the last returns (including the first returns in cases of a single return) to run the algorithm. If FALSE all the returns are used. If the attribute 'ReturnNumber' or 'NumberOfReturns' are absent, 'last_returns' is turned to FALSE automatically.

Value

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

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: How much data is loaded at once.

• chunk buffer*: Mandatory to get a continuous output without edge effects. The buffer is always removed once processed and will never be returned either in R or in files.

• 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

# NOT RUN {
LASfile <- system.file("extdata", "Topography.laz", package="lidR")
las <- readLAS(LASfile, select = "xyzrn", filter = "-inside 273450 5274350 273550 5274450")

# Using the Progressive Morphological Filter
# --------------------------------------

# (Parameters chosen mainly for speed)
ws  <- seq(3,12, 4)
th  <- seq(0.1, 1.5, length.out = length(ws))

las <- classify_ground(las, pmf(ws, th))
#plot(las, color = "Classification")

#' # Using the Cloth Simulation Filter
# --------------------------------------

# (Parameters chosen mainly for speed)
mycsf <- csf(TRUE, 1, 1, time_step = 1)
las <- classify_ground(las, mycsf)
#plot(las, color = "Classification")
# }