readCartesian

(To be removed) Read laser scan ranges in Cartesian coordinates

readCartesian will be removed in a future release. Use rosReadCartesian instead. For more information, see ROS Message Structure Functions.

Syntax

cart = readCartesian(scan)

cart = readCartesian(___,Name,Value)

[cart,angles] = readCartesian(___)

Description

cart = readCartesian(scan) converts the polar measurements of the laser scan object, scan, into Cartesian coordinates, cart. This function uses the metadata in the message, such as angular resolution and opening angle of the laser scanner, to perform the conversion. Invalid range readings, usually represented as NaN, are ignored in this conversion.

cart = readCartesian(___,Name,Value) provides additional options specified by one or more Name,Value pair arguments. Name must appear inside single quotes (''). You can specify several name-value pair arguments in any order as Name1,Value1,...,NameN,ValueN.

[cart,angles] = readCartesian(___) returns the scan angles, angles, that are associated with each Cartesian coordinate. Angles are measured counterclockwise around the positive z-axis, with the zero angle along the x-axis. The angles is returned in radians and wrapped to the [ –pi, pi] interval.

Examples

Get Cartesian Coordinates from Laser Scan

Connect to ROS network. Subscribe to a laser scan topic, and receive a message.

rosinit('192.168.17.129')

Initializing global node /matlab_global_node_40737 with NodeURI http://192.168.17.1:56343/

sub = rossubscriber('/scan');
scan = receive(sub);

Read the Cartesian points from the laser scan. Plot the laser scan.

cart = readCartesian(scan);
plot(cart(:,1),cart(:,2))

Shutdown ROS network.

rosshutdown

Shutting down global node /matlab_global_node_40737 with NodeURI http://192.168.17.1:56343/

Get Cartesian Coordinates from Laser Scan With Scan Range

Connect to ROS network. Subscribe to a laser scan topic, and receive a message.

rosinit('192.168.17.129')

Initializing global node /matlab_global_node_12735 with NodeURI http://192.168.17.1:56572/

sub = rossubscriber('/scan');
scan = receive(sub);

Read the Cartesian points from the laser scan with specified range limits. Plot the laser scan.

cart = readCartesian(scan,'RangeLimit',[0.5 6]);
plot(cart(:,1),cart(:,2))

Shutdown ROS network.

rosshutdown

Shutting down global node /matlab_global_node_12735 with NodeURI http://192.168.17.1:56572/

Input Arguments

scan — Laser scan message

LaserScan object handle

'sensor_msgs/LaserScan' ROS message, specified as a LaserScan object handle.

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: 'RangeLimits',[-2 2]

RangeLimits — Minimum and maximum range for scan in meters

[scan.RangeMin scan.RangeMax] (default) | 2-element [min max] vector

Minimum and maximum range for a scan in meters, specified as a 2-element [min max] vector. All ranges smaller than min or larger than max are ignored during the conversion to Cartesian coordinates.

Output Arguments

cart — Cartesian coordinates of laser scan

n–by–2 matrix in meters

Cartesian coordinates of laser scan, returned as an n-by-2 matrix in meters.

angles — Scan angles for laser scan data

n–by–1 matrix in radians

Scan angles for laser scan data, returned as an n-by-1 matrix in radians. Angles are measured counterclockwise around the positive z-axis, with the zero angle along the x-axis. The angles is returned in radians and wrapped to the [ –pi, pi] interval.

Version History

Introduced in R2019b

R2021a: ROS Message Structure Functions

You can now create messages as structures with fields matching the message object properties. Using structures typically improves performance of creating, updating, and using ROS messages, but message fields are no longer validated when set. Message types and corresponding field values from the structures are validated when sent across the network.

To support message structures as inputs, new functions that operate on specialized ROS messages have been provided. These new functions are based on the existing object functions of message objects, but support ROS and ROS 2 message structures as inputs instead of message objects.

The object functions will be removed in a future release.

Message Types	Object Function Name	New Function Name
Image CompressedImage	readImage writeImage	rosReadImage rosWriteImage
LaserScan	readCartesian readScanAngles lidarScan plot	rosReadCartesian rosReadScanAngles rosReadLidarScan rosPlot
PointCloud2	apply readXYZ readRGB readAllFieldNames readField scatter3	rosApplyTransform rosReadXYZ rosReadRGB rosReadAllFieldNames rosReadField rosPlot
Quaternion	readQuaternion	rosReadQuaternion
OccupancyGrid	readBinaryOccupanyGrid readOccupancyGrid writeBinaryOccupanyGrid writeOccupanyGrid	rosReadOccupancyGrid rosReadBinaryOccupancyGrid rosReadOccupancyGrid rosWriteBinaryOccupancyGrid rosWriteOccupancyGrid
Octomap	readOccupancyMap3D	rosReadOccupancyMap3D
PointStamped PoseStamped QuaternionStamped Vector3Stamped TransformStamped	apply	rosApplyTransform
All messages	showdetails	rosShowDetails