readPointCloud

Read point cloud data from LAS or LAZ file

Syntax

ptCloud = readPointCloud(lasReader)

[ptCloud,ptAttributes] = readPointCloud(lasReader)

[___] = readPointCloud(___,Name=Value)

Description

ptCloud = readPointCloud(lasReader) reads the point cloud data from the LAS or LAZ file indicated by the input lasFileReader object and returns it as a pointCloud object, ptCloud.

[ptCloud,ptAttributes] = readPointCloud(lasReader) additionally returns a lidarPointAttributes object, ptAttributes, which contains all available point attributes in the input LAS or LAZ file. (since R2025a)

[___] = readPointCloud(___,Name=Value) specifies options using one or more name-value pair arguments in addition to any of the argument combinations in previous syntaxes. For example, "ROI",[5 10 5 10 5 10] sets the region of interest (ROI) in which the function reads the point cloud.

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)

Input Arguments

lasReader — LAS or LAZ file reader

lasFileReader object

LAS or LAZ file reader, specified as a lasFileReader object.

Name-Value Arguments

Specify optional pairs of arguments as Name1=Value1,...,NameN=ValueN, where Name is the argument name and Value is the corresponding value. Name-value arguments must appear after other arguments, but the order of the pairs does not matter.

Before R2021a, use commas to separate each name and value, and enclose Name in quotes.

Example: "ROI",[5 10 5 10 5 10] sets the region of interest (ROI) in which the function reads the point cloud.

ROI — ROI to read in the point cloud

[-inf inf -inf inf -inf inf] (default) | 6-element row vector

ROI to read in the point cloud, specified as a 6-element row vector in the order, [x_min x_max y_min y_max z_min z_max]. Each element must be a real number. The values specify the ROI boundaries in the x-, y-, and z-axis.

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64

GpsTimeSpan — Range of GPS timestamps

lasReader.GPSTimeLimits (default) | 2-element vector of duration objects

Range of GPS timestamps, specified as a 2-element vector of duration objects, that denotes [startTime endTime]. The timestamps must be positive.

Data Types: duration

Classification — Classification value

lasReader.ClassificationInfo.("Classification Value") (default) | vector of valid classification numbers

Classification value, specified as a vector of valid classification numbers.

Valid classification numbers range from 0 to 255.

Classification Value	Class Name
0	Created, never classified
1	Unclassified
2	Ground
3	Low vegetation
4	Medium vegetation
5	High vegetation
6	Building
7	Low point (noise)
8	Reserved
9	Water
10	Rail
11	Road surface
12	Reserved
13	Wire guard (shield)
14	Wire conductor (phase)
15	Transmission tower
16	Wire-structure connector (insulator)
17	Bridge deck
18	High noise
19	Overhead structure
20	Ignored ground
21	Snow
22	Temporal exclusion
23- 63	Reserved
64 - 255	User-defined

These are standard class names. The class definition and mapping might differ from the standard depending on the application that created the LAS or LAZ file.

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64

LaserReturn — Number of points segregated by their return numbers

1:lasReader.NumReturn (default) | vector of valid return numbers

Number of points segregated by their return numbers, specified as a vector of valid return numbers. Valid return numbers are integers from 1 to the value of the NumReturns property of the input lasFileReader object. For each value, i, in the vector, the function returns a point cloud of only the points that have i as their return number.

The return number is the number of times a laser pulse reflects back to the sensor.

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64

Attributes — Point attributes

[ ] (default) | character vector | string scalar | vector of strings | cell array of character vectors

Point attributes, specified as a character vector, cell array of character vectors, string scalar, or vector of strings. The input must contain one or more of these options:

• "Classification"

• "GPSTimeStamp"

• "LaserReturn"

• "NumReturns"

• "NearIR"

• "ScanAngle"

• "UserData"

• "PointSourceID"

• "ScannerChannel"

• "ScanDirectionFlag"

• "EdgeOfFlightLineFlag"

• "WaveformData"

The function returns the specified attributes of each point in a lidarPointAttributes object, ptAttributes. The unspecified attributes are returned empty.

Data Types: char | string | cell

Output Arguments

ptCloud — Point cloud

pointCloud object

Point cloud, returned as a pointCloud object.

Note

Point cloud functions expect data in Cartesian coordinates, (x,y,z) as positions in a 3-D coordinate space. If a LAS or LAZ file contains data in geographic coordinates, (longitude,latitude,height), 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.

ptAttributes — Point attribute data

lidarPointAttributes object

Point attribute data, returned as a lidarPointAttributes object. By default, the object returns all attributes available in the input LAS or LAZ file for each point in the point cloud. However, if you specify the Attributes name-value argument, the object returns only the specified attributes and provides empty data for any unspecified attributes.

Version History

Introduced in R2020b

R2025a: Read all point attributes at once

You can now read all point attributes at once from an input LAS or LAZ file using this new syntax: [ptCloud,ptAttributes] = readPointCloud(lasReader). Therefore, the ptAtt argument is not required now. You can specify point attributes by using the Attributes name-value argument.

R2022a: Additional point attributes

You can now specify these additional point attributes to the ptAtt argument:

• "UserData"

• "PointSourceID"

• "ScannerChannel"

• "ScanDirectionFlag"

• "EdgeOfFlightLine"

• "WaveformData"

R2022a: LaserReturns renamed to LaserReturn

The LaserReturns is now called LaserReturn. To update your code, replace all instances of the LaserReturns argument with LaserReturn.

R2022a: Point attributes returned as object

The readPointCloud function returns the ptAttributes argument as a lidarPointAttributes object instead of as a structure.