terra Livox Lidar Auto Extrinsics Calibration User Guide

: June 6, 2024
: terra

Table of Contents

Introduction
Auto Extrinsics Calibration Procedure
- Calibration Data Collection Requirements
- Calibration Data Collection Scenario Requirements
Documents / Resources
- Read User Manual Online (PDF format)
- Download This Manual (PDF format)

terra Livox Lidar Auto Extrinsics Calibration

Introduction

Auto extrinsics calibration enables users to automatically calibrate the extrinsics of multiple LiDAR sensors at the same time. It is particularly useful for LiDAR sensors with little or no FOV overlap.

Auto Extrinsics Calibration Procedure

Click to open the extrinsic parameter tool and select Auto Calibrating.
Click to import the calibration data of lvx file. Check Calibration Data Collection Requirements and Calibration Data Collection Scenario Requirements for more information.
Click Mapping and wait until the point cloud reconstruction is completed.
Select a LiDAR sensor as the Benchmark LiDAR. The extrinsics of the benchmark LiDAR will remain zero during the auto extrinsics calibration. Users can adjust the extrinsics of the remaining LiDAR sensors where necessary.
Uncheck the box in column V to hide a LiDAR on the display.
Select the extrinsic in the table to adjust. The point cloud data of the selected LiDAR will change to red in the display. Hold Shift and press Up/Down or scroll the mouse wheel to adjust extrinsics by 0.01° or 0.001 m. Hold Ctrl and press Up/Down or scroll the mouse wheel to adjust extrinsics by 0.1° or 0.05 m. The real-time point cloud data will be updated immediately after the extrinsic is adjusted.
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- When adjusting extrinsics, it is recommended to keep the margin of error within 2° or 0.5 m.
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Once all extrinsics are adjusted, select Calibrating to perform auto extrinsics calibration.

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  * For improved accuracy, repeat Steps 5-7. If calibration fails or the extrinsics are inaccurate, check if the point cloud data was recorded properly. Check Calibration Data Collection Requirements and Calibration Data Collection Scenario Requirements for more information.

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8. After calibration, users can adjust the extrinsics of all LiDAR sensors as a group by checking one of the boxes in column G. Follow Step 6 to perform a coarse or fine adjustment of extrinsics.

Click to save the current extrinsics or click Apply to confirm and update the extrinsics in Livox Viewer and all connected LiDAR sensors.

Calibration Data Collection Requirements

Currently, only Horizon LiDAR sensors support auto extrinsics calibration. Make sure no other models are connected to the Livox Viewer at the same time. Otherwise, calibration cannot be performed.
Two to five LiDAR sensors can be calibrated at the same time.
Make sure to clear the extrinsics of the LiDAR before recording point cloud data.
Make sure to record the point cloud data in lvx format.
Record at least 10 seconds but no more than 30 seconds of point cloud data.
Use Livox Hub to ensure the time of all LiDAR sensors are synchronized.
It is not necessary for the FOVs of the LiDAR sensors to overlap, but the point cloud data should have an overlap of at least 80% after mapping.
If there is less than 80% overlap between the FOVs of two LiDAR sensors, scan and keep the surface that the LiDAR sensors are attached to stationary for 3 seconds before completing a 360° rotation. Make sure the ground is flat and the rotational speed is slow.
If there is more than 80% overlap between the FOVs of two LiDAR sensors, scan for 10 seconds and keep the surface that the LiDAR sensors are attached to stationary for the entire period.

Calibration Data Collection Scenario Requirements

Choose scenarios with abundant spatial geometric characteristics for data collection as shown in the figure below.
Avoid scanning areas without spatial geometric features as well as point cloud interference between LiDAR sensors.

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Documents / Resources

| terra Livox Lidar Auto Extrinsics Calibration [pdf] User Guide
Livox Lidar Auto Extrinsics Calibration, Livox Lidar, Auto Extrinsics Calibration
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