LiDAR ↔ LiDAR Calibration

LiDAR Circle Target

All of MetriCal's LiDAR calibrations require a circle target to be used in the object space.

LiDAR ↔ LiDAR Guidelines

Many of the tips for LiDAR ↔ LiDAR data capture are similar to Camera ↔ LiDAR capture. Below we've outlined best practices for capturing a dataset that will consistently produce a high-quality calibration between two LiDAR components.

Data Capture Best Practices

DO	DON'T
✅ Vary distance from sensors to target to capture a wider range of readings.	❌ Stand at a single distance from the sensors.
✅ Ensure good point density on the target for all LiDAR sensors.	❌ Only capture poses where the target does not have sufficient point density.
✅ Rotate the target on its planar axis to capture poses at different orientations.	❌ Keep the board in a single orientation for every pose.
✅ Maximize convergence angles by angling the target up/down and left/right during poses.	❌ Keep the target in a single orientation, minimizing convergence angles.
✅ Pause in between poses (1-2 seconds) to eliminate motion artifacts.	❌ Move the target constantly or rapidly during data capture.
✅ Achieve convergence angles of 35° or more on each axis when possible.

Key Considerations for Quality Calibration

Maximize Variation Across All 6 Degrees Of Freedom

When capturing the circular target with multiple LiDAR components, ensure that the target can be seen from a variety of poses by varying:

• Roll, pitch, and yaw rotations of the target relative to the LiDAR sensors
• X, Y, and Z translations between poses

MetriCal performs LiDAR-based calibrations best when the target can be seen from a range of different depths. Try moving forward and away from the target in addition to moving laterally relative to the sensors.

The field of view of a LiDAR component is often much greater than a camera, so be sure to capture data that fills this larger field of view.

Data Capture Process

When capturing data for LiDAR ↔ LiDAR calibration:

1. Position the LiDAR circle target within view of all LiDAR sensors being calibrated
2. Ensure good point cloud density on the target from each LiDAR
3. Move the target through various orientations and positions
4. Pause for 1-2 seconds at each position to eliminate motion artifacts
5. Repeat until you have covered a wide range of target positions and orientations

Troubleshooting

If you encounter errors during calibration, please refer to our Errors documentation.

Common issues with LiDAR ↔ LiDAR calibration include:

• No features detected (cal-calibrate-001)
• Too many component observations filtered (cal-calibrate-006)
• Compatible component type has no detections (cal-calibrate-008)

Remember that when working with multiple LiDAR sensors, it's important to ensure all sensors can clearly see the calibration target throughout the data capture process.