Discrepancy Between OpenGV Calibration Results and Expected Accuracy

[byungs2]

Hello @puzzlepaint .
I hope this message finds you well. I am writing to bring to your attention a concern regarding the calibration results obtained using the code provided.

Upon conducting calibration using the provided code, the maximum reprojection error was calculated to be 0.21, with a median value of 0.03. Additionally, the error histogram closely matched the exemplary case you provided, suggesting a successful calibration process.

However, when applying the OpenGV calibration, an unexpected discrepancy emerged. Specifically, the world coordinate-based positions of the camera in the x, y, and z dimensions exhibited a significant difference of approximately 30 cm compared to the anticipated values.
I additionally implemented the undistort code left in the Issue and performed Calibration using OpenCV after undistorting. The results were consistent with the previous outcome.

To address this matter, I would appreciate any insights or guidance you can offer on potential reasons for this discrepancy. It is crucial for me to understand the possible sources of error to ensure accurate calibration results and reliable camera pose estimation.

And I am currently working with a camera that has a resolution of 1920x1080 pixels and a focal length of 2.8 inches. I am planning to use a cell size of 40 for the calibration process. Could you kindly provide guidance on the approximate amount of data I should collect for an effective calibration?

Additionally, I would appreciate any insights on precautions or considerations to keep in mind during the data collection process. Ensuring the accuracy of the calibration is crucial for my project, and I want to be thorough in gathering the necessary data.

Thank you in advance for your assistance. Your expertise will be immensely valuable in ensuring a successful calibration process.

"""
About ENV
Camera resoultion : 1920 * 1080
Camera focal length : fixed 2.8 inch
Used camera model : central_generic
Cell size : 40
Half window : 15
Used pattern : pattern_resolution_17x24_segments_16_apriltag_0
"""