lasFileReader

Read point cloud data from LAS or LAZ file

Description

You can use a lasFileReader object to read point cloud data from a lidar aerial survey (LAS) or a LASzip (LAZ) file.

Creation

Syntax

lasReader = lasFileReader(fileName)

Description

lasReader = lasFileReader(fileName) creates a LAS file reader with properties set by the header information in the specified LAS or LAZ file fileName. The reader supports up to the LAS 1.4 specification.

Input Arguments

fileName — Name of LAS or LAZ file

character vector | string scalar

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

This argument sets the FileName property as a character vector.

Note

Point cloud functions expect data in Cartesian coordinates. If a LAS or LAZ file contains data in geographic coordinates, you must convert the data to Cartesian coordinates. For more information on how to check and convert point cloud data from geographic to Cartesian coordinates, see the Working with Geographic CRS section of the Visualize Point Clouds on Maps Using Coordinate Reference System from LAS/LAZ Files example.

Data Types: char | string

Output Arguments

lasReader — LAS or LAZ file reader

lasFileReader object

LAS or LAZ file reader, returned as a lasFileReader object. The object provides access to the point cloud data and metadata stored in the specified LAS or LAZ file. You can use the object functions such as readPointCloud, readCRS, and readVLR to read point cloud data, coordinate reference system information, and variable length records, respectively.

Properties

File Header Information

FileName — Name of LAS or LAZ file

Read-only: character vector

This property is read-only.

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, represented as a character vector.

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.

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]. When this value is set to 0, 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.

SystemIdentifier — Name of system used to generate LAS file

Read-only: string scalar

This property is read-only.

Name of the system used to generate the LAS file, 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. The name refers to the generating software used to create the LAS file.

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.

Point Data Summary

Count — Number of points

Read-only: positive integer

This property is read-only.

Number of points in the file, represented as a positive integer.

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 lasFileReader function does not populate this property as object creation. To populate this property for the lasFileReader object lasReader, enter lasReader.NumClasses in the Command Window. This command also populates the GPSTimeLimits and ClassificationInfo properties of the object.

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 in the range [0, 10]. Point data record format values between 0 and 5 contain optional information about GPS, color channels, or wave packets. Values between 6 and 10 contain optional information about color channels, near IR, or wave packets.

For more information on point data record formats, see the LAS format standard on the ASPRS LAS Working Group page.

Spatial Information

XLimits — Range of coordinates along x-axis

Read-only: two-element vector

This property is read-only.

Range of coordinates along x-axis, stored as a two-element vector.

YLimits — Range of coordinates along y-axis

Read-only: two-element vector

This property is read-only.

Range of coordinates along y-axis, stored as a two-element vector

ZLimits — Range of coordinates along z-axis

Read-only: two-element vector

This property is read-only.

Range of coordinates along z-axis, stored as a two-element 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]. The values of 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]. The values of Xoffset, Yoffset, and Zoffset represent the offset along the x-, y-, and z-axes, respectively.

Temporal Information

GPSTimeLimits — Range of GPS timestamp readings

Read-only: two-element duration vector

This property is read-only.

Range of the GPS timestamp readings, represented as a two-element duration vector.

Note

The lasFileReader function does not populate this property as object creation. To populate this property for the lasFileReader object lasReader, enter lasReader.GPSTimeLimits in the Command Window. This command also populates the NumClasses and ClassificationInfo properties of the object.

Attribute Information

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.

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 lasFileReader function does not populate this property as object creation. To populate this property for the lasFileReader object lasReader, enter 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.

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

Create a lasFileReader object to use to read point cloud data and header information from a LAZ file.

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

Create a lasFileReader object to use to read point cloud data and header information from a LAZ file.

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

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

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

Convert classification labels to RGB colors, and reshape them to match the point cloud structure.

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

Visualize the point cloud using the color information.

figure
pcshow(ptCloud.Location,colorData)

Version History

Introduced in R2020b

R2026a: Object functions for checking GPS, CRS, waveform, and near IR data have been removed

These object functions of the lasFileReader object have been removed:

• 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).

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 the 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, hasGPSData, hasWaveformData, and hasNearIRData.

R2022a: Object has additional properties

The lasFileReader object includes these additional properties:

• SystemIdentifier

• GeneratingSoftware

• FileCreationDate

• FileSourceID

• ProjectID

• PointDataFormat

• ClassificationInfo

• LaserReturnInfo

• VariableLengthRecords