lasFileReader

Read point cloud data from LAS or LAZ file

Since R2020b

Description

A lasFileReader object stores the metadata present in the LAS or LAZ file as read-only properties. The object function, readPointCloud, uses these properties to read point cloud data from the file. The lasFileReader object supports up to the LAS 1.4 specification.

A LAS file contains a public header, which has lidar metadata, followed by lidar point records. Each point record contains attributes such as 3-D coordinates, intensity, and GPS timestamp.

The LAS file format is an industry-standard binary format for storing lidar data, developed and maintained by the American Society for Photogrammetry and Remote Sensing (ASPRS). The LAZ file format is a compressed version of the LAS file format.

Creation

Syntax

lasReader = lasFileReader(fileName)

Description

lasReader = lasFileReader(fileName) creates a lasFileReader object with properties set by reading the metadata present in the LAS or LAZ file fileName. The fileName input sets the FileName property.

Input Arguments

fileName — Name of LAS or LAZ file

string scalar | character vector

Name of the LAS or LAZ file, specified as a character vector or string scalar. You must specify the full file path if the LAS or LAZ file is not in your MATLAB^® path.

This argument sets the FileName property as a character vector.

Data Types: char | string

Properties

FileName — Name of LAS or LAZ file

character vector | string scalar

This property is read-only after object creation. To set this property, use the fileName argument when calling the lasFileReader function.

Name of the LAS or LAZ file, specified as a character vector or string scalar.

Count — Number of available point records

Read-only: positive integer

This property is read-only.

Number of available point records in the file, represented as a positive integer.

LasVersion — LAS or LAZ file version

Read-only: character vector

This property is read-only.

LAS or LAZ file version, represented as a character vector.

XLimits — Range of coordinates along x-axis

Read-only: two-element real-valued row vector

This property is read-only.

Range of coordinates along the x-axis, represented as a two-element real-valued row vector.

YLimits — Range of coordinates along y-axis

Read-only: two-element real-valued row vector

This property is read-only.

Range of coordinates along the y-axis, represented as a two-element real-valued row vector.

ZLimits — Range of coordinates along z-axis

Read-only: two-element real-valued row vector

This property is read-only.

Range of coordinates along the z-axis, represented as a two-element real-valued row vector.

Scale — Scale of XYZ coordinates

Read-only: three-element real-valued row vector

Since R2025a

This property is read-only.

Scale of the XYZ coordinates, represented as a three-element real-valued row vector of the form [Xscale Yscale Zscale]. Xscale, Yscale, and Zscale represent the scale along the X-, Y-, and Z-axes, respectively.

Offset — Offset of XYZ coordinates

Read-only: three-element real-valued row vector

Since R2025a

This property is read-only.

Offset of the XYZ coordinates, represented as a three-element real-valued row vector of the form [Xoffset Yoffset Zoffset]. Xoffset, Yoffset, and Zoffset represent the offset along the X-, Y-, and Z-axes, respectively.

Attributes — List of available attributes

Read-only: string array

Since R2025a

This property is read-only.

List of the available attributes, represented as a string array. Use this property to identify all the attributes present in the file. You can also read all available attributes by using the readPointCloud object function.

GPSTimeLimits — Range of GPS timestamps

Read-only: 1-by-2 duration vector

This property is read-only.

Range of GPS timestamp readings, represented as a 1-by-2 duration vector.

Note

The value of this property is not immediately available. To get the this property for the lasFileReader object, lasReader, type lasReader.GPSTimeLimits in the Command Window. This command also populates the NumClasses and ClassificationInfo properties of the object.

NumReturns — Maximum of all point laser returns

Read-only: 1 (default) | positive integer

This property is read-only.

Maximum of all point laser returns, represented as a positive integer.

NumClasses — Maximum of all point classification values

Read-only: 1 (default) | positive integer

This property is read-only.

Maximum of all point classification values, represented as a positive integer.

Note

The value of this property is not immediately available. To get the this property for the lasFileReader object, lasReader, type lasReader.NumClasses in the Command Window. This command also populates the GPSTimeLimits and ClassificationInfo properties of the object.

SystemIdentifier — Name of hardware sensor system identifier

Read-only: string scalar

This property is read-only.

Name of the hardware sensor system identifier that generated the LAS files, represented as a string scalar.

GeneratingSoftware — Name of generating software

Read-only: string scalar

This property is read-only.

Name of the generating software, represented as a string scalar. This property specifies the generating software package used when the LAS file was created.

FileCreationDate — Date of file creation

Read-only: datetime object

This property is read-only.

Date of file creation, represented as a datetime object.

FileSourceID — LAS file source identifier

Read-only: nonnegative integer

This property is read-only.

LAS file source identifier, represented as a nonnegative integer. Values are in the range 0 to 65535. This defines the flight line number if this file was created from an original flight line. A value 0 specifies that no ID has been assigned. Use the ProjectID and FileSourceID properties to uniquely identify each point in a LAS file.

ProjectID — Project ID

Read-only: string scalar

This property is read-only.

Project ID, represented as a string scalar. This value is a globally unique identifier (GUID). Use the ProjectID and FileSourceID properties to uniquely identify each point in a LAS file.

PointDataFormat — Point data record format ID

Read-only: nonnegative integer

This property is read-only.

Point data record format ID, represented as a nonnegative integer. Values are in the range 0 to 10. For more information, see Point Data Record Format.

ClassificationInfo — Classification information

Read-only: table

This property is read-only.

Classification information, represented as a table. Each row of the table contains this information describing a point class:

• Classification Value — Unique classification ID number for the class, represented as a positive integer.

• Class Name — Label associated with the class, represented as a string scalar.

• Number of Points by Class — Number of points in the class, represented as a positive integer.

Note

The value of this property is not immediately available. To get the this property for the lasFileReader object, lasReader, type lasReader.ClassificationInfo in the Command Window. This command also populates the GPSTimeLimits and NumClasses properties of the object.

LaserReturnInfo — Laser return information

Read-only: table

This property is read-only.

Laser return information, represented as a table. Each row of the table contains this information describing a laser return:

• Laser Return Number — Laser return number, represented as a positive integer.

• Number of Points by Return — Number of points per laser return, represented as a positive integer.

VariableLengthRecords — Variable length record information

Read-only: table

This property is read-only.

Variable length record (VLR) or extended VLR information, represented as a table. Each row of the table contains this information describing a record:

• Record ID — Record identification number, represented as a positive integer.

• User ID — User identification associated with record ID, represented as a string scalar.

• Description — Description of record, represented as a string scalar.

Object Functions

readPointCloud	Read point cloud data from LAS or LAZ file
readCRS	Read coordinate reference system data from LAS or LAZ file
readVLR	Read variable length record from LAS or LAZ file

Examples

Read Point Cloud Data from LAZ File

This example shows how to read and visualize point cloud data from a LAS / LAZ file.

Create a lasFileReader object for a LAZ file. Then, use the readPointCloud function to read point cloud data from the LAZ file and generate a pointCloud object.

Create a lasFileReader object to access the LAZ file data.

filepath = fullfile(toolboxdir("lidar"),"lidardata", ...
    "las","aerialLidarData.laz");
lasReader = lasFileReader(filepath);

Read point cloud data from the LAZ file using the readPointCloud function.

ptCloud = readPointCloud(lasReader);

Visualize the point cloud.

figure
pcshow(ptCloud.Location)

Visualize Point Cloud Based on Classification Data from LAZ File

Segregate and visualize point cloud data based on classification data from a LAZ file.

Create a lasFileReader object to access data from the LAZ file.

path = fullfile(toolboxdir("lidar"),"lidardata", ...
    "las","aerialLidarData.laz");
lasReader = lasFileReader(path);

Read point cloud data and associated classification point attributes from the LAZ file using the readPointCloud function.

[ptCloud,pointAttributes] = readPointCloud(lasReader,"Attributes","Classification");

Color the points based on their classification attributes. Reshape the label image into the shape of the point cloud.

labels = label2rgb(pointAttributes.Classification);
colorData = reshape(labels,[],3);

Visualize the color-coded point cloud.

figure
pcshow(ptCloud.Location,colorData)

More About

Point Data Record Format

A LAS file contains point cloud data as a collection of point data records, as well as a public header block and optional metadata information about the records. The public header block indicates the point numbers and point data bounds of the LAS file, as well as the point data record format.

As of the LAS 1.4 specification, there are 11 point data record formats, ranging from Point Data Record Format 0 to Point Data Record Format 10, divided into two major groups.

• Point Data Record Format 0 to Point Data Record Format 5 — These formats contain 20 core bytes, with formats 1–5 adding optional information about GPS time, color channels, or wave packets.

• Point Data Record Format 6 to Point Data Record Format 10 — These formats contain 30 core bytes, with formats 7–10 adding optional information about color channels, near IR, or wave packets.

For more information, including which point data record formats are available for each version of the LAS file specification, see the ASPRS LASER (LAS) File Format Exchange Activities page.

Version History

Introduced in R2020b

R2025a: Read scale and offset of coordinates, and list of available attributes

The lasFileReader object includes these additional properties to read scale and offset values of the XYZ coordinates from the input LAS or LAZ file.

• Scale

• Offset

The object also includes Attributes property. Use this property to get the list of available attributes in the input LAS or LAZ file.

R2025a: Improved performance

The lasFileReader function shows improved performance for creating a lasFileReader object. The performance improvement increases as the number of available point records increases in the input LAS or LAZ file. For example, this code is about 118x faster than in the previous release:

function t = timingTest
    pcfile = fullfile(toolboxdir("lidar"),"lidardata","las","aerialLidarData.laz");
    lasReader = @()lasFileReader(pcfile);
    t = timeit(lasReader);
end

The approximate execution times are:

• R2024b: 0.39 s

• R2025a: 0.0033 s

The code was timed on a Windows^® 10, Intel^® Xeon^® Gold 6240R CPU@ 2.40 GHz test system by calling the function timingTest.

The object shows improved performance because it does not immediately populate the GPSTimeLimits, NumClasses, and ClassificationInfo properties after creation. Therefore, unlike the previous release, the creation time for the object is independent of the number of point records in the input file. To populate these properties, view or extract one of them. For example, using this command to view the GPSTimeLimits property of a lasFileReader object, lasReader, also populates the NumClasses and ClassificationInfo properties of the object.

R2025a: Object functions for checking GPS, CRS, waveform, and near IR data will be removed in future release

These object functions of the lasFileReader object will be removed in a future release:

• hasCRSData — To check for CRS data in a LAS or LAZ file, use ~isempty(readCRS(lasReader)) instead of hasCRSData(lasReader).

• hasGPSData — To check for GPS data in a LAS or LAZ file, use any(lasReader.Attributes == "GPSTimeStamp") instead of hasGPSData(lasReader).

• hasWaveformData — To check for waveform data in a LAS or LAZ file, use any(lasReader.Attributes == "WaveformData") instead of hasWaveformData(lasReader).

• hasNearIRData — To check for near IR data in a LAS or LAZ file, use any(lasReader.Attributes == "NearIR") instead of hasNearIRData(lasReader).

R2022a: Object has additional properties

The lasFileReader object includes these additional properties:

• SystemIdentifier

• GeneratingSoftware

• FileCreationDate

• FileSourceID

• ProjectID

• PointDataFormat

• ClassificationInfo

• LaserReturnInfo

• VariableLengthRecords