Use FAST-LIO2

1 Overview

This document provides a detailed introduction on how to use the Hesai ROS driver to run the FAST-LIO2 algorithm on Hesai JT16 / JT128.

2 Prerequisites

• Ubuntu + ROS, with ROS Melodic or Noetic recommended.
• HesaiLidar_ROS_2.0 built successfully.
• FAST-LIO2 algorithm adaptation code from hesai_slam built successfully.
• The lidar, host network interface, and driver configuration are on the same subnet.

FAST-LIO2 algorithm reads these topics by default:

Data	Default topic
Point cloud	/lidar_points
IMU	/lidar_imu

The point cloud must use sensor_msgs/PointCloud2 and include these fields:

x, y, z, intensity, ring, timestamp

3 Application Method

3.1 Start Hesai ROS Driver

Launch the driver in the Hesai ROS driver workspace:

cd ~/hesai_ros_ws
source devel/setup.bash
roslaunch hesai_ros_driver start.launch

For a live lidar connection, enable live input and ROS topic output in the driver configuration:

lidar:
  - driver:
      source_type: 1
      lidar_udp_type:
        device_ip_address: 192.168.1.201
        udp_port: 2368
        ptc_port: 9347
      ros:
        ros_send_point_cloud_topic: /lidar_points
        ros_send_imu_topic: /lidar_imu
        send_point_cloud_ros: true
        send_imu_ros: true

Update device_ip_address, udp_port, and ptc_port according to your network.

After the driver starts, check that point cloud and IMU topics are publishing:

rostopic hz /lidar_points
rostopic hz /lidar_imu
rostopic echo -n 1 /lidar_points/fields

Confirm that /lidar_points/fields contains ring and timestamp before starting FAST-LIO2.

3.2 Start FAST-LIO2

Build and source FAST-LIO2:

cd ~/catkin_ws/src
git clone https://github.com/HesaiTechnology-Spatial-Perception/hesai_slam.git
cd hesai_slam
git submodule update --init --recursive

cd ~/catkin_ws
catkin_make
source devel/setup.bash

For JT16:

roslaunch fast_lio mapping_jt16.launch

For JT128:

roslaunch fast_lio mapping_jt128.launch

To start without RViz:

roslaunch fast_lio mapping_jt128.launch rviz:=false

For JT16, replace the launch file with mapping_jt16.launch.

4 Example Result

The following images show point cloud mapping results generated by running FAST-LIO2 with Hesai JT-series lidar.

5 Common Parameters

Parameter	Description	JT16 default	JT128 default
common/lid_topic	Point cloud topic	/lidar_points	/lidar_points
common/imu_topic	IMU topic	/lidar_imu	/lidar_imu
common/imu_gyr_unit	IMU angular velocity unit. Supports rad / deg	deg	rad
preprocess/lidar_type	lidar type. 5 means JT16, 6 means JT128	5	6
preprocess/scan_line	Number of scan lines	16	128
preprocess/timestamp_unit	Per-point timestamp unit. 0 seconds, 1 milliseconds, 2 microseconds, 3 nanoseconds	0	0
preprocess/blind	Near-field blind-zone filtering distance, in meters	1.0	0.5

If the driver publishes different topic names, update common/lid_topic and common/imu_topic in the FAST-LIO2 configuration.

6 Use a Rosbag

If the rosbag already contains /lidar_points and /lidar_imu, play the rosbag first and then start FAST-LIO2:

rosbag play your_data.bag

If the rosbag stores Hesai raw packets, use the Hesai ROS driver to parse and publish /lidar_points and /lidar_imu before starting FAST-LIO2.

7 FAQ

7.1 No FAST-LIO2 Output

Check that the topics exist and are publishing continuously:

rostopic list
rostopic hz /lidar_points
rostopic hz /lidar_imu

Also confirm that the topic names in the FAST-LIO2 configuration match the topics published by the driver.

7.2 Trajectory Diverges or Shakes Heavily

Check these items first:

• Whether lidar and IMU time are synchronized.
• Whether common/imu_gyr_unit matches the actual IMU driver output.
• Whether mapping/extrinsic_T / mapping/extrinsic_R are correct.
• Whether preprocess/timestamp_unit matches the unit of the point cloud timestamp.

7.3 Extrinsic Configuration

Extrinsics are defined as the lidar pose in the IMU coordinate frame. If accurate extrinsics are available, disable online extrinsic estimation:

mapping:
  extrinsic_est_en: false
  extrinsic_T: [0.0, 0.0, 0.0]
  extrinsic_R: [1.0, 0.0, 0.0,
                0.0, 1.0, 0.0,
                0.0, 0.0, 1.0]