Package 'rlas'

Check if data and headers respect the LAS specification

Description

las files are normalized files. These functions perform tests of compliance with LAS specification.

• check_las_validity tests if the data and the header contain information that cannot be written into a las file. For example it tests is the intensities do not exeed 65535. It throws an error for each deviance to the specification. It is useful for testing if modified R objects are still valid.

• check_las_compliance test if the data and the header contain information that can be written into a las file but are invalid with repect of the specification. For example it test if the RGB colors are recoded on 16 bits. It is possible to store colors recorded on 8 bits (0 to 255) but it is not correct to do that. It throws a warning for each deviance to the specification. It is useful for testing if the data read from a file are correct.

Usage

check_las_validity(header, data)

check_las_compliance(header, data)

Arguments

header	a list containing the header of a las file
data	a data.frame or a data.table containing a point cloud

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ALTREP utilities

Description

Test if an a vector is compressed using the ALTREP framework

Usage

is_compressed(x)

true_size(x)

Arguments

x	an R object

Examples

lazfile <- system.file("extdata", "example.las", package = "rlas")
las <- read.las(lazfile)
is_compressed(las)

# The difference is more substantial on bigger point clouds (~30%)
object.size(las)
true_size(las)

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Coordinate Reference System Tools

Description

Functions that update a header to describe coordinates reference system according to the LAS specifications

Usage

header_get_epsg(header)

header_set_epsg(header, epsg)

header_get_wktcs(header)

header_set_wktcs(header, WKT)

Arguments

header	list
epsg	integer. An EPSG code
WKT	string. A string of an WKT OGC CS

See Also

Other header_tools: extra_bytes_attribute_tools, fwf_interpreter(), public_header_block_tools

---

Extra Bytes Attributes Tools

Description

Functions that update a header to describe Extra Bytes Attributes according to the LAS specifications

Usage

header_add_extrabytes(header, data, name, desc)

header_add_extrabytes_manual(
  header,
  name,
  desc,
  type,
  offset = NULL,
  scale = NULL,
  max = NULL,
  min = NULL,
  NA_value = NULL
)

Arguments

header	list
data	vector. Data that must be added in the extrabytes attributes.
name	character. The name of the extrabytes attributes to add in the file.
desc	character. The description of the extrabytes attributes to add in the file.
type	integer. The data type of the extrabytes attributes (page 25 of the spec).
scale, offset	numeric. The scale and offset of the data. NULL if not relevant.
min, max	numeric or integer. The minimum and maximum value of the data. NULL if not relevant.
NA_value	numeric or integer. NA is not a valid value. At writing time it will be replaced by this value that will be considered as NA. NULL if not relevant.

See Also

Other header_tools: crs_tools, fwf_interpreter(), public_header_block_tools

Examples

data = data.frame(X = c(339002.889, 339002.983, 339002.918),
                  Y = c(5248000.515, 5248000.478, 5248000.318),
                  Z = c(975.589, 974.778, 974.471),
                  gpstime = c(269347.281418006, 269347.281428006, 269347.281438006),
                  Intensity = c(82L, 54L, 27L),
                  ReturnNumber = c(1L, 1L, 2L),
                  NumberOfReturns = c(1L, 1L, 2L),
                  ScanDirectionFlag = c(1L, 1L, 1L),
                  EdgeOfFlightline = c(1L, 0L, 0L),
                  Classification = c(1L, 1L, 1L),
                  ScanAngleRank = c(-21L, -21L, -21L),
                  UserData = c(32L, 32L, 32L),
                  PointSourceID = c(17L, 17L, 17L),
                  treeID = c(1L, 1L, 1L))

lasheader = header_create(data)
lasheader[["Variable Length Records"]]

lasheader = header_add_extrabytes(lasheader, data$treeID, "treeID", "An id for each tree")
lasheader[["Variable Length Records"]]

---

Full Waveform Interpreter

Description

This is an experimental function that may change
Raw full waveform data read from LAS files might be cryptic even with a good understanding of the LAS specifications. This function interpret the full waveform data as a set of XYZ coordinates and an amplitude which is the digitized voltage.

Usage

fwf_interpreter(header, data)

Arguments

header	list. A header
data	data.frame or data.table

Value

A list containing a data.frame per pulse with the XYZ coordinates of the waveform and the voltage of the record (Amplitude)

See Also

Other header_tools: crs_tools, extra_bytes_attribute_tools, public_header_block_tools

Examples

## Not run: 
f <- system.file("extdata", "fwf.laz", package="rlas")
head <- read.lasheader(f)
data <- read.las(f)
fwf <- fwf_interpreter(head, data)

## End(Not run)

---

A set of function to test conformance with LAS specifications

Description

Tools reserved to developpers and not intended to be used by regular users. The functions return TRUE or FALSE by default without more information. If behavior is 'warning' functions throw a warning for each fail and return FALSE if any warning TRUE otherwise. If behavior is 'stop' functions throw an error for the first fail and return TRUE if 0 error. If behavior is 'vector' returns a character vector with the decription of each error an never fail. Is it useful to make a detailed inspection.

Usage

is_defined_offsets(header, behavior = "bool")

is_valid_offsets(header, behavior = "bool")

is_defined_scalefactors(header, behavior = "bool")

is_valid_scalefactors(header, behavior = "bool")

is_defined_filesourceid(header, behavior = "bool")

is_valid_filesourceid(header, behavior)

is_defined_globalencoding(header, behavior = "bool")

is_valid_globalencoding(header, behavior = "bool")

is_defined_version(header, behavior = "bool")

is_valid_version(header, behavior = "bool")

is_defined_date(header, behavior = "bool")

is_valid_date(header, behavior = "bool")

is_defined_pointformat(header, behavior = "bool")

is_valid_pointformat(header, behavior = "bool")

is_defined_extrabytes(header, behavior = "bool")

is_valid_extrabytes(header, behavior = "bool")

is_empty_point_cloud(header, behavior = "bool")

is_defined_coordinates(data, behavior = "bool")

is_valid_XYZ(data, behavior = "bool")

is_valid_Intensity(data, behavior = "bool")

is_valid_ReturnNumber(data, header, behavior = "bool")

is_valid_NumberOfReturns(data, header, behavior = "bool")

is_valid_ScanDirectionFlag(data, behavior = "bool")

is_valid_EdgeOfFlightline(data, behavior = "bool")

is_valid_Classification(data, header, behavior = "bool")

is_valid_ScannerChannel(data, behavior = "bool")

is_valid_SyntheticFlag(data, behavior = "bool")

is_valid_KeypointFlag(data, behavior = "bool")

is_valid_WithheldFlag(data, behavior = "bool")

is_valid_OverlapFlag(data, behavior = "bool")

is_valid_ScanAngle(data, behavior = "bool")

is_valid_ScanAngleRank(data, behavior = "bool")

is_valid_UserData(data, behavior = "bool")

is_valid_gpstime(data, behavior = "bool")

is_valid_PointSourceID(data, behavior = "bool")

is_valid_RGB(data, behavior = "bool")

is_valid_NIR(data, behavior = "bool")

is_compliant_ReturnNumber(data, behavior = "bool")

is_compliant_NumberOfReturns(data, behavior = "bool")

is_compliant_ReturnNumber_vs_NumberOfReturns(data, behavior = "bool")

is_compliant_RGB(data, behavior = "bool")

is_compliant_ScanAngle(data, behavior = "bool")

is_compliant_ScanAngleRank(data, behavior = "bool")

is_NIR_in_valid_format(header, data, behavior = "bool")

is_gpstime_in_valid_format(header, data, behavior = "bool")

is_RGB_in_valid_format(header, data, behavior = "bool")

is_ScanAngle_in_valid_format(header, data, behavior = "bool")

is_ScannerChannel_in_valid_format(header, data, behavior = "bool")

is_XY_larger_than_bbox(header, data, behavior = "bool")

is_XY_smaller_than_bbox(header, data, behavior = "bool")

is_Z_in_bbox(header, data, behavior = "bool")

is_number_of_points_in_accordance_with_header(header, data, behavior = "bool")

is_number_of_points_by_return_in_accordance_with_header(
  header,
  data,
  behavior = "bool"
)

is_extrabytes_in_accordance_with_data(header, data, behavior = "bool")

Arguments

header	a list containing the header of a las file
behavior	character. Defines the behavior of the function. 'bool' returns TRUE or FALSE. 'warning' throw a warning for each fails and return FALSE if any warning TRUE otherwise. 'vector' returns a character vector of each warning but does not thrown any warning.
data	a data.frame or a data.table containing a point cloud

---

Public Header Block Tools

Description

Create or update a header for a las file from a dataset. A las file consists of two parts. A header that describes the data and the data itself. These functions make valid headers (public header block only) that can be used in write.las.

Usage

header_create(data)

header_update(header, data)

Arguments

data	data.frame or data.table
header	list. A header

Details

header_create makes a full header from data. header_update modifies the information that needs to be updated. But most of the original information is not modified, for example point data format is kept 'as is'.

Value

A list containing the metadata required to write a las file.

See Also

Other header_tools: crs_tools, extra_bytes_attribute_tools, fwf_interpreter()

Examples

lasdata = data.frame(X = c(339002.889, 339002.983, 339002.918),
                     Y = c(5248000.515, 5248000.478, 5248000.318),
                     Z = c(975.589, 974.778, 974.471),
                     gpstime = c(269347.281418006, 269347.281428006, 269347.281438006),
                     Intensity = c(82L, 54L, 27L),
                     ReturnNumber = c(1L, 1L, 2L),
                     NumberOfReturns = c(1L, 1L, 2L),
                     ScanDirectionFlag = c(1L, 1L, 1L),
                     EdgeOfFlightline = c(1L, 0L, 0L),
                     Classification = c(1L, 1L, 1L),
                     ScanAngleRank = c(-21L, -21L, -21L),
                     UserData = c(32L, 32L, 32L),
                     PointSourceID = c(17L, 17L, 17L),
                     treeID = c(1L, 1L, 1L))

lasheader = header_create(lasdata)

---

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")

---

Read header from a .las or .laz file

Description

Reads header from .las or .laz files according to LAS specifications and returns a list labeled according to LAS specifications. See the ASPRS documentation for the LAS file format.

Usage

read.lasheader(file)

Arguments

file	filepath character string to the .las or .laz file

Value

A list

See Also

Other rlas: write.las()

Examples

lazfile   <- system.file("extdata", "example.las", package="rlas")
lasheader <- read.lasheader(lazfile)

---

Write a .las or .laz file

Description

Write a .las or .laz file. The user provides a table with the data in columns. Column names must respect the specified allowed names (see details). A correct and complete header must also be provided. This header can optionally be generated with header_create.

Usage

write.las(file, header, data)

Arguments

file	character. file path to .las or .laz file
header	list. Can be partially recycled from another file (see read.lasheader) and updated with header_update or generated with header_create.
data	data.frame or data.table that contains the data to write in the file. Column names must respect the imposed nomenclature (see details)

Details

Allowed names are "X", "Y", "Z", "gpstime", "Intensity", "ReturnNumber", "NumberOfReturns", "ScanDirectionFlag", "EdgeOfFlightline", "Classification", "ScanAngle", "UserData", "PointSourceID", "R", "G", "B", "NIR". All other extra columns will be written in extra bytes attributes only if the header specifically states these data should be saved into extra bytes attributes. To use the full potential of the function write.las it is recommended users read the complete specifications of the LAS file format. Otherwise users can rely on automated procedures that are expected to be sufficient for most usages.

Value

void

See Also

Other rlas: read.lasheader()

Examples

lasdata = data.frame(X = c(339002.889, 339002.983, 339002.918),
                     Y = c(5248000.515, 5248000.478, 5248000.318),
                     Z = c(975.589, 974.778, 974.471),
                     gpstime = c(269347.281418006, 269347.281428006, 269347.281438006),
                     Intensity = c(82L, 54L, 27L),
                     ReturnNumber = c(1L, 1L, 2L),
                     NumberOfReturns = c(1L, 1L, 2L),
                     ScanDirectionFlag = c(1L, 1L, 1L),
                     EdgeOfFlightline = c(1L, 0L, 0L),
                     Classification = c(1L, 1L, 1L),
                     ScanAngleRank = c(-21L, -21L, -21L),
                     UserData = c(32L, 32L, 32L),
                     PointSourceID = c(17L, 17L, 17L))

lasheader = header_create(lasdata)
file = file.path(tempdir(), "temp.las")

write.las(file, lasheader, lasdata)

---

Write a .lax file from a .las or .laz file

Description

Write a lax file from a las or laz file. A lax file is a tiny file which can come with a las or laz and which spatially index the data to make faster spatial queries. It has been invented by Martin Isenburg in LASlib. rlas support lax file and enable to write a lax file with default settings. For more options, use lasindex from binaries provided by LASlib (for more informations see references)

Usage

writelax(file, verbose = FALSE)

Arguments

file	character. filename of .las or .laz file
verbose	boolean. Verbose switch.

References

https://rapidlasso.com/
https://rapidlasso.com/2012/12/03/lasindex-spatial-indexing-of-lidar-data/
https://github.com/LAStools/LAStools

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