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How can I get the calibration data for camera and lidar data which I captured?

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I have recorded the point cloud data using velodyne - VLP-16 Puck sensor and captured the data using logitech C270 (Normal Webcam). Now, I need to process the data for sensor fusion based object detection concept. For that, I need calib.mat file. But, I need to know how to calculate or get that .mat file. Without use of calib.mat (Calibration Mat file) file, I cannot detect the object in both the images(Image and .pcd data) in sensor fusion code.
People who are working or excel in this domain, kindly assist me on this.
Note:
I tried to get the data using camera calibrator but few values are null (means '0'). With that data i couldn't process further. Also i have a doubt, if I created the calib.mat file using one image, is that fine for all images(image & pcd data)? No need to change for different location of captured data?
Thanks in advance.
  1 Comment
Ramya Sivanandham
Ramya Sivanandham on 21 Jun 2022
I have tried to explore the LidarCameraCalibrationExample using vlp16 sensor data which is available in the matlab intself, but it is throwing following error:
"Visualize the detected checkerboard by using the helperShowCheckerboardPlanes function.
helperShowCheckerboardPlanes(ptCloudFileNames,indices)"
due to index exceeds number of array elements.
After filtered the point cloud and image files that are not used for detection process, image and point cloud files are became null!
But it is working properly with HDL64 sensor! Kindly check and assist me on this!

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Accepted Answer

Kritika Bansal
Kritika Bansal on 23 Jun 2022
Hi,
In order to get the calibration between lidar and camera, you can use the lidarCameraCalibrator app. This is a good place to help you get started with the process of calibration. You can refer to the following page for more details on getting started with the app: Get Started with Lidar Camera Calibrator.
The following page can help you with the recommended guidelines for the data collection process: Calibration Guidelines
-Kritika
  10 Comments
Ramya Sivanandham
Ramya Sivanandham on 30 Jun 2022
Oh, oh, OK... I got it. Yeah, different names only, I'll change it..
Thank you so much!!!!!!!!!!
Sorry for the silly questions.. but I dont know.. I just started to explore the Lidar toolbox and calibration activities..
Ramya Sivanandham
Ramya Sivanandham on 11 Jul 2022
Edited: Ramya Sivanandham on 11 Jul 2022
Hi Kritika and others,
I have an issue with the calibration of camera and lidar. I would like to know whether the process which I have done is proper or not! But I followed your instructions (Mathworks), but still not getting the matched pair.
  1. with the help of checkerboard pattern, have captured the data from camera and lidar
  2. captured the data as a frames through mScript.
  3. Lidar data captured through the veloview, as a pcap file. From pcap file, pcd file has extracted with the help of matlab convertion. Here is the issue that number of frames in camera and pcd data are different. I couldn't find the similar frames to do the calibration.
  4. another issue is, when i upload the lidar data, there won't be the proper ROI to detect the checkerboard. when i tried to adjust the ROI, placing of the ROI box is not happened.
  5. Sometimes, 1 frame will get matched but it was detected the different region from the checkerboard pattern.
My obervation from this issues,
  1. Due to different frame rate of lidar pcd data extraction from the pcap file, number of frame pair count is varying.
  2. Due to the different frame rate issue, couldn't detect the detectected pair.
  3. Due to improper ROI, detection is not happened.
Guys, Please let me know what i have missed and where should I concentrate or do the changes!!!!
I would like to try with cropped pcd data, but I didn't know. If someone helps me to crop the particular region of the input pcd data, will be more helpful to do this analysis.
or
Is any way to capture the sensor data at specified angle? (am using VLP-16 sensor)
Kindly assist me on this...
Thanks in advance.

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