read.las {rlas}

Read data from a .las or .laz file

Description

Reads data from .las or .laz files according to LAS specifications and returns a data.table labelled according to LAS specifications. See the ASPRS documentation for the LAS file format. The optional parameters enable the user to save memory by choosing to load only the attributes they need. Moreover, the function provides a streaming filter to load only the points of interest into the memory and hence avoids allocating any superfluous memory.

Usage

read.las(files, select = "*", filter = "", transform = "")

Arguments

files

array of characters

select

character. select only columns of interest to save memory (see details)

filter

character. streaming filters - filter data while reading the file (see details)

transform

character. streaming transformation - transform data while reading the file (see details)

Details

Select: the 'select' argument specifies the data that will actually be loaded. For example, 'xyzia' means that the x, y, and z coordinates, the intensity and the scan angle will be loaded. The supported entries are t - gpstime, a - scan angle, i - intensity, n - number of returns, r - return number, c - classification, s - synthetic flag, k - keypoint flag, w - withheld flag, o - overlap flag (format 6+), u - user data, p - point source ID, e - edge of flight line flag, d - direction of scan flag, R - red channel of RGB color, G - green channel of RGB color, B - blue channel of RGB color, N - near-infrared channel, C - scanner channel (format 6+), W - Full waveform. Also numbers from 1 to 9 for the extra bytes data numbers 1 to 9. 0 enables all extra bytes to be loaded and '*' is the wildcard that enables everything to be loaded from the LAS file.
Note that x, y, z are implicit and always loaded. 'xyzia' is equivalent to 'ia'.

Filter: the 'filter' argument allows filtering of the point cloud while reading files. rlas relies on the well-known LASlib library written by Martin Isenburg to read the binary files. Thus the package inherits the filter commands available in LAStools. To use these filters the user can pass the common commands from LAStools into the parameter 'filter'. Type read.las(filter = "-help") to display the LASlib documentation and the available filters.

Transform: the 'transform' argument allows transformation of the point cloud while reading files. rlas relies on the well-known LASlib library written by Martin Isenburg to read the binary files. Thus the package inherits the transform commands available in LAStools. To use these transformations the user can pass the common commands from LAStools into the parameter 'transform'. Type read.las(transform = "-help") to display the LASlib documentation and the available transformations.

Value

A data.table

Full Waveform

The support of full waveform is still in development. The version 1.4.1 introduced the support of point formats 4, 5, 9 and 10. The current state consists in reading the raw data. We also introduced the function fwf_interpreter to interpret the raw data into something easier to manipulate (but that uses more memory). The current behaviour is not set in stone and is prone to design modification until version 1.5.0 where we aims to get enough insight to lock our engineering choices to something that suit best the needs.

Examples

lasfile <- system.file("extdata", "example.las", package="rlas")

lasdata <- read.las(lasfile)
lasdata <- read.las(lasfile, filter = "-keep_first")
lasdata <- read.las(lasfile, filter = "-drop_intensity_below 80")
lasdata <- read.las(lasfile, select = "xyzia")