Transfer mechanism behind region-disjoint imputation failure

Isolate the cause of the region-disjoint transfer failure observed for the MGFormer-inspired imputation system and the compact local-offset encoder on the held-out geographic region.

Background

The region-disjoint split causes both imputation systems to perform substantially worse on the held-out side of the longitude cut, whereas their validation performance on the training side remains near the vessel-disjoint level. The authors interpret this as a transfer failure rather than leakage.

Unlike the prediction-side collapse of the absolute-position tokenized models, the specific mechanism of the imputation systems’ region-transfer degradation is not isolated in the paper.

References

Like the prediction-side result, this is a transfer failure, not leakage, and we have not isolated its cause.

— Protocol before progress: leakage-aware evaluation of AIS trajectory prediction  (2609.25827 - Raisi et al., 22 Sep 2026) in Section 5, subsection “A published imputation system, and a leakage channel no split manifest closes”