ROS 2 pointcloud <-> laserscan converters

This is a ROS 2 package that provides components to convert sensor_msgs/msg/PointCloud2 messages to sensor_msgs/msg/LaserScan messages and back. It is essentially a port of the original ROS 1 package.

pointcloud_to_laserscan::PointCloudToLaserScanNode

This ROS 2 component projects sensor_msgs/msg/PointCloud2 messages into sensor_msgs/msg/LaserScan messages.

Published Topics

• scan (sensor_msgs/msg/LaserScan) - The output laser scan.

Subscribed Topics

• cloud_in (sensor_msgs/msg/PointCloud2) - The input point cloud. No input will be processed if there isn't at least one subscriber to the scan topic.

Parameters

• min_height (double, default: 2.2e-308) - The minimum height to sample in the point cloud in meters.
• max_height (double, default: 1.8e+308) - The maximum height to sample in the point cloud in meters.
• angle_min (double, default: -π) - The minimum scan angle in radians.
• angle_max (double, default: π) - The maximum scan angle in radians.
• angle_increment (double, default: π/180) - Resolution of laser scan in radians per ray.
• queue_size (double, default: detected number of cores) - Input point cloud queue size.
• scan_time (double, default: 1.0/30.0) - The scan rate in seconds. Only used to populate the scan_time field of the output laser scan message.
• range_min (double, default: 0.0) - The minimum ranges to return in meters.
• range_max (double, default: 1.8e+308) - The maximum ranges to return in meters.
• target_frame (str, default: none) - If provided, transform the pointcloud into this frame before converting to a laser scan. Otherwise, laser scan will be generated in the same frame as the input point cloud.
• transform_tolerance (double, default: 0.01) - Time tolerance for transform lookups. Only used if a target_frame is provided.
• use_inf (boolean, default: true) - If disabled, report infinite range (no obstacle) as range_max + 1. Otherwise report infinite range as +inf.

pointcloud_to_laserscan::LaserScanToPointCloudNode

This ROS 2 component re-publishes sensor_msgs/msg/LaserScan messages as sensor_msgs/msg/PointCloud2 messages.

Published Topics

• cloud (sensor_msgs/msg/PointCloud2) - The output point cloud.

Subscribed Topics

• scan_in (sensor_msgs/msg/LaserScan) - The input laser scan. No input will be processed if there isn't at least one subscriber to the cloud topic.

Parameters

• queue_size (double, default: detected number of cores) - Input laser scan queue size.
• target_frame (str, default: none) - If provided, transform the pointcloud into this frame before converting to a laser scan. Otherwise, laser scan will be generated in the same frame as the input point cloud.
• transform_tolerance (double, default: 0.01) - Time tolerance for transform lookups. Only used if a target_frame is provided.

Mid-360 Lidar

I am using the fast-lio package.

Steps to Run

1. Installation (Clone and building repo)

# Clone the repository
git clone https://github.com/20-wash/pointcloud_to_laserscan_mid360.git

# Navigate into your workspace 
cd pointcloud_to_laserscan_mid360

# Build the workspace
colcon build 

# Source the workspace
source install/setup.bash

a. Check the topic list

ros2 topic list

Analyze the topic list at beginning before running the node.

2. Play the bag file

ros2 bag play rosbag2_2024_12_14-11_49_36_MID360/

a. Check the topic list again

ros2 topic list

Analyze the topic list after playing the bag file. The topics recorded, are shown in the list.

# To view the info of 3D_clould_point topic 
ros2 topic info /cloud_registered  

# To view the message of the topic
ros2 topic echo /cloud_registered 

# To check the verbose of the topic 
ros2 topic info /cloud_registered --verbose 

We can know that the QoS of thus published node is Reliable. But, on the original repo of (ros_perception/pointcloud_to_laserscan), the output /scan topic is of BEST_EFFORT.

So, we need to make some change in original repo to account QoS problem. For that, in the node named pointcloud_to_laserscan_node.cpp inside src, an extra line is added.

// Biswash changes 
  // pub_ = this->create_publisher<sensor_msgs::msg::LaserScan>("scan", rclcpp::SensorDataQoS());
  pub_ = this->create_publisher<sensor_msgs::msg::LaserScan>("laser_scan", rclcpp::SensorDataQoS().reliability(RMW_QOS_POLICY_RELIABILITY_RELIABLE));

You can view this in thus cloned repo.

3. Launch the Node

ros2 launch pointcloud_to_laserscan sample_pointcloud_to_laserscan_launch.py

4. Visualize Data in RVIz

a. Launch RVIz

rviz2

b. Edit the configuration in RVIz

Set the frame to /camera_init

Add the topic : /scan

5. Testing (Verify the Node is Running)

a. Check active topics:

ros2 topic list

b. Confirm that /scan is being published:

#Check the info (msg types of topic /scan)
ros2 topic info /scan

#Check the message data
ros2 topic echo /scan

Changes With Respect to original repo

1. Minimal Launch File

2. Parameters defined inside the node named : pointcloud_to_laserscan_node.cpp.

// Global variables for parameters
std::string target_frame = "";
double transform_tolerance = 0.01;
double min_height = std::numeric_limits<double>::min();
double max_height = std::numeric_limits<double>::max();
double angle_min = -M_PI;
double angle_max = M_PI;
double angle_increment = M_PI / 180.0;
double scan_time = 1.0 / 30.0;
double range_min = 0.0;
double range_max = std::numeric_limits<double>::max();
bool use_inf = true;
double inf_epsilon = 1.0;

3. Suscriber and Publisher topic directly mentioned inside node named : pointcloud_to_laserscan_node.cpp

The line commented // is of the original repo.

The topics are explicitly mentioned as:

1. cloud_registered :

This topic is suscribed and then with respect to the parameters, the flattened map is made from the 3D_clould_point (/cloud_registered)

2. laser_scan This topic is published from the node, which published the flattened 2d laser message.

// pub_ = this->create_publisher<sensor_msgs::msg::LaserScan>("scan", rclcpp::SensorDataQoS());
pub_ = this->create_publisher<sensor_msgs::msg::LaserScan>("laser_scan", rclcpp::SensorDataQoS().reliability(RMW_QOS_POLICY_RELIABILITY_RELIABLE));


// sub_.subscribe(this, "cloud_in", qos.get_rmw_qos_profile());
sub_.subscribe(this, "cloud_registered", qos.get_rmw_qos_profile());