Sensor calibration for LiDAR calibration

1、 Introduction

With the continuous progress of technology and the development of intelligence, the application of sensor technology in various fields is becoming increasingly widespread. Among them, LiDAR, as a high-precision and highly reliable sensor, is widely used in fields such as autonomous driving, robot navigation, and terrain surveying. However, in order to ensure the accurate and stable operation of the LiDAR, precise calibration is crucial. This article will provide a detailed discussion on the concept, methods, steps, and application of LiDAR calibration in autonomous driving.



2、 The concept of LiDAR calibration

Lidar calibration refers to the detection, measurement, and feature parameter adjustment of a lidar system to ensure that the system can operate normally according to regulations. The core of LiDAR calibration is to calibrate the functional parameters and performance characteristics of LiDAR, including internal parameters such as laser beam rotation center, scanning surface tilt angle, laser beam divergence, as well as external parameters such as the position and direction of LiDAR relative to the vehicle coordinate system. By accurately calibrating these parameters, it can be ensured that the point cloud data collected by the LiDAR is accurately represented in the vehicle coordinate system, providing reliable data support for subsequent SLAM, target detection, and path planning tasks.



3、 The calibration method of LiDAR

Method based on calibration board

The calibration board based method is one of the most commonly used methods in lidar calibration. This method requires preparing a special calibration board, such as a chessboard calibration board, and then using the correspondence between the points on the calibration board in the LiDAR and camera (or other sensors), obtaining the external parameters of the LiDAR by solving the PnP problem or minimizing the reprojection error. The advantage of this method is that it is relatively simple and intuitive, but the disadvantage is that it requires the production and use of calibration plates, and there are certain requirements for the quality and position of the calibration plates.
Motion based methods

The motion based method does not require a calibration board, but utilizes multiple frames of data captured by LiDAR during the motion process to estimate the motion of each sensor and solve the transformation between the two sensors. This method does not require additional calibration equipment and can be calibrated in practical application scenarios. However, this method has certain requirements for the motion trajectory and speed of LiDAR, and is easily affected by environmental noise and interference.

A method based on multi-sensor fusion

The method based on multi-sensor fusion utilizes data fusion between LiDAR and other sensors (such as cameras, IMUs, etc.) to achieve LiDAR calibration. This method can obtain more accurate and stable calibration results by matching and fusing data between multiple sensors. However, this method requires data synchronization and calibration between multiple sensors, and requires high performance and accuracy of the sensors.

4、 Steps for LiDAR calibration

Determine calibration scenarios and targets

Before conducting LiDAR calibration, it is necessary to determine the calibration scenario and target. The calibration scene should have sufficient feature points and structural information so that the LiDAR can accurately collect data. The calibration target can be a known object or scene for comparison and validation with data collected by LiDAR.

Installation and debugging of LiDAR

Before calibration, it is necessary to install and debug the LiDAR. Including the selection of installation position, adjustment of installation angle, calibration of laser beam, etc. Ensure that the LiDAR can function properly and collect accurate data.
Collect calibration data


Collect corresponding calibration data based on the selected calibration method. For example, for calibration board based methods, it is necessary to take photos of the calibration board and obtain the corresponding relationship between the LiDAR and the camera; For motion based methods, it is necessary to control the LiDAR to move and collect multiple frames of data; For multi-sensor fusion based methods, it is necessary to collect data from both LiDAR and other sensors simultaneously.

Data processing and calibration calculation

Process and analyze the collected data to extract key feature points and structural information. Then, based on the selected calibration method, use these feature points and structural information for calibration calculation to obtain the external and internal parameters of the LiDAR.

Verification and calibration

Apply the calibration results to actual scenarios for verification and calibration. Evaluate the accuracy and stability of calibration results by comparing the differences between the data collected by LiDAR and the actual scene. If there are differences or significant errors, recalibration or adjustment is necessary.

5、 Application of LiDAR Calibration in Autonomous Driving

In the field of autonomous driving, LiDAR calibration plays an important role. Firstly, LiDAR calibration can accurately determine the position and direction of the LiDAR relative to the vehicle coordinate system, thereby achieving accurate positioning and navigation of the vehicle. This is crucial for the safe driving and path planning of autonomous vehicles. Secondly, LiDAR calibration can improve the accuracy and stability of point cloud data collected by LiDAR, thereby achieving more accurate detection and tracking of obstacles in the environment. This is of great significance for obstacle avoidance and driving safety of autonomous vehicles. Finally, LiDAR calibration can accurately convert the point cloud data collected by LiDAR into coordinates in the vehicle coordinate system, thereby constructing a more accurate map and providing more reliable environmental information for autonomous driving.


6、 Conclusion

Lidar calibration is a crucial step in ensuring the accurate and stable operation of a lidar system. This article introduces the concept, method, steps, and application of LiDAR calibration in autonomous driving. Through precise LiDAR calibration, the performance and safety of autonomous vehicles can be improved, providing strong support for the future development of intelligent transportation and autonomous driving technology.