Lidar calibration with fixed intrinsic parameters

Hi, I have a calibration data which is,

Angle : LR, UD, Rot

-14.144831,-0.008000,0.000249

TranslationMatrix

-0.010000,-0.090000,-0.135700

intrinsicCameraParameter

1055.465497,1055.605856,969.483445,603.504962,-0.146335,0.063113,-0.001973,0.000488

and I wonder if there's a way that I can apply these parameters for lidar-camera calibration in MATLAB.

Answer 1

[Maneet Kaur Bagga]

Hi Seungryul Lee,

Please follow the steps provided below to apply these parameters for Lidar-Camera Calibration:

• Load the Calibration data in MATLAB by either reading the data from a file or directly assigning the values to the variables.
• You can create the "cameraIntrinsics" object using the provided Intrinsic Camera Parameter as shown in the code provided below.

focalLength = [1055.465497, 1055.605856]; 
principalPoint = [969.483445, 603.504962]; 
radialDistortion = [-0.146335, 0.063113]; 
tangentialDistortion = [-0.001973, 0.000488]; 
intrinsics = cameraIntrinsics(focalLength, principalPoint,'RadialDistortion', radialDistortion, ...
    'TangentialDistortion', tangentialDistortion);

• Create a transformation Matrix that represents the rotation and translation between the lidar, and the camera coordinate systems as shown in the code provided below.

rotationAngles = [-14.144831, -0.008000, 0.000249]; 
translationVector = [-0.010000, -0.090000, -0.135700];
rotationMatrix = eul2rotm(deg2rad(rotationAngles), 'XYZ'); 
translationMatrix = translationVector'; 
extrinsics = rigidtform3d(rotationMatrix, translationMatrix); 

Now you can apply the intrinsic and extrinsic calibration parameters to the lidar and camera data:

• For lidar data, you can transform the lidar points to the camera coordinate system using the "transformPointsForward" function as shown in the code provided below.

lidarPoints = ...  % Your lidar data, Nx3 matrix 
cameraPoints = transformPointsForward(extrinsics, lidarPoints); 

• For camera data, you can undistort the distorted image points using the “undistortPoints” function as shown in the code provided below.

distortedImagePoints = ...  % Your distorted image points, Nx2 matrix 
undistortedImagePoints = undistortPoints(distortedImagePoints, intrinsics); 

For better understanding please refer to the following MATLAB Documentations provided below:

cameraParameters

https://www.mathworks.com/help/vision/ref/cameraparameters.html

cameraIntrinsics

https://www.mathworks.com/help/vision/ref/cameraintrinsics.html

rigidtform3d

https://www.mathworks.com/help/images/ref/rigidtform3d.html

I hope this helps!

Thank You

Maneet Bagga