Hi Micha,

Thank you so much, this is exactly the kind of concrete, verifiable criterion I was looking for. The post-fit residual / redundancy contribution check, together with the standardized test statistics (T_prio/T_post), gives me a clear and practical way to validate whether a σ is actually acting as a proper quasi-fixed constraint, instead of relying on an arbitrary epsilon. And the laser-tracker/tape-measure analogy is a great way to put it, it really clarified the underlying logic for me.

Regarding the third point, please don't worry at all, I completely understand and I don't take it as brushing me off in the slightest. You've been extremely generous with your time and thoroughness throughout this thread. The remaining question is a domain/instrumentation matter to resolve by myself, not something left unsolved in JAG3D's model.

Thank you again for taking the time to think through all of this in such dept.

All the best,
Jan