lidR (version 2.2.5)

lasground: Classify points as 'ground' or 'not ground'

Description

Classify points as 'ground' or 'not 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

lasground(las, algorithm, last_returns = TRUE)

Arguments

las

An object of class LAS or LAScatalog.

algorithm

a ground-segmentation function. lidR has: pmf and csf.

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")

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

ws  <- seq(3,12, 3)
th  <- seq(0.1, 1.5, length.out = length(ws))

las <- lasground(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 <- lasground(las, mycsf)
plot(las, color = "Classification")
# }