Vehicle Lidar Calibration

Calibration Process:

1. Calibrate List Page:

Click on ‘New Calibration’ on the calibration list page.

2. Calibration type selection:

Click on Vehicle-LiDAR calibration, to start it.

3. Calibration welcome page:

A welcome page with the set of instructions is shown at the beginning, just click on ‘Get started’ to go forward.

4. Vehicle configuration page:

Enter the calibration configuration along with the calibration name. Following are the vehicle configurations.

  • Wheelbase: Distance between left/right front wheel center and left/right rear wheel center in meters. If asked for a Wheelbase without left/right, measure either the left or right wheelbase. If the wheelbase is the same on both left and right, the right wheelbase is optional.

  • Track: Distance between front/rear left wheel center and front/rear right wheel center in meters. If asked for just Track without front/rear, measure either the front or rear track.

  • Diameter: Distance between bottom of the front/rear wheel to the top of the front/rear wheel (wheel height) in meters. Note: wheel diameter must include tires as well.

  • Overhang: Distance between center of the front/rear wheel to the front/rear bumper of the vehicle in meters.

5. Setup Lidar Details:

Enter the name of the lidar and the distance of the board from the vehicle. Also enter the lidar height if measured. This is an optional field. Steps will change depending on whether the value has been given or not. As discussed in the data collection, rear view data collection is optional. One can enter the values if they want to include the rear view as well.

Distance from LiDAR to ground: This configuration is required only when there are no ground points visible in the lidar. In such cases, the accurately measured distance from the lidar to the ground along the line perpendicular to the ground can be entered to proceed with the calibration process.

6. File Upload for front-view:

User needs to upload a pcd file which has a calibration target on the front side of the vehicle.

7. Detecting the ground plane and board plane for front-view:

  • When lidar-height is provided: When lidar-height is provided, only the board plane needs to be detected. So just mark some board points and click on detect plane to detect the board plane.

  • When lidar-height is not provided:When lidar-height is not provided, both the ground and the board plane are to be detected. If the ground points are more, then most probably the ground points get auto-detected or else mark the ground points to be detected by the ground plane. Similarly, board points should be marked to detect the board plane.

After ground plane detection

After board plane detection

Use the Add Sample/ Erase Sample option to add/erase the ground points, which are used in ground plane detection. Painted points are denoted in the green color.

Use the Add Marker/ Remove Marker option to add/erase the ground points, which are used in board plane detection.Painted points are denoted in the red color.

8. File Upload for left-view:

Similarly upload a file for left-view.

9. Detecting ground plane and board plane for left-view:

Similarly detect ground plane and the board plane for left-view.

10. File Upload for right-view:

Similarly, upload a file for right-view.

11. Detecting ground plane and board plane for right-view:

Similarly, detect the ground plane and the board plane for right-view.

12. Run calibration:

This step has the run calibration button. On clicking, calibration runs. This usually gets finished in 1 or 2 mins.

The extrinsic parameters can be viewed to the right.

Visualization:

Visualization shows the planes which are detected and also the lidar and the vehicle coordinates. This also shows the vehicle corners on the ground. The planes can be deselected. Also the fused point cloud can be deselected, to just look at the vehicle and the lidar axes and the vehicle body.

Error statistics:

Plane distance error is the mean of the distance between the plane lidar points to the respective planes.

Export:

Extrinsic parameters can be exported to a json file using the button at the top right corner.

Extrinsic Calibration Output:

  • roll, pitch, yaw, px, py, pz are the extrinsic parameters downloaded from the calibration tool.

  • vehiclePoint3D is the 3d coordinates of a point in the vehicle coordinate system.

  • lidarPoint3D is the 3d coordinates of a point in the lidar coordinate system.