Thanks for your work, I have a question about how to konw degradation ahout ndt?

[tust13018211]

I made an attempt to use the Hessian matrix to detect degradation, But I find the ndt Hessian matrix cann`t point out the Direction of degradation. but I I see the parper LiTAMIN2: Ultra Light LiDAR-based SLAM using Geometric Approximation applied with KL-Divergence, it say the PCA can point the Direction of degradation, So, I want to know is there anything I
misunderstanding?

[koide3]

Maybe papers like the following one would help you:
https://link.springer.com/article/10.1007/s10846-021-01362-w