Question about calibration

[Gatsby23]

Dear professor: Hello, I'm a freshman to the omni-based system. Recently, I have read your paper 《Autonomous aerial robot using dual‐fisheye cameras》. It's a wonderful idea to use the dual fisheye to improve the SLAM robustness and accuracy. However, there's one thing troubles me a lot: how to calibrate the omni-based cameras ? I use the kalibr [https://github.com/ethz-asl/kalibr] system to calibrate our device: like insta-360 or the Go-Pro. However, the reprojection error is large, always converged at 1 pixel above and when I use it in the SLAM system, it always failed. I'm confused is there some tricks about how to calibrate this kind of sensor or do I need some special movement to improve the calibration result？ I'm looking forward for your advices. Thank you very much.

Yours