Notes on verification

Confirmed by IGN's own geodesy documentation and corroborated by multiple independent governmental (SHOM), academic, and specialist sources, all consistent with no contradictions. [cascade flags: wikipedia_dropped_other_sources_exist | tier=bronze indep_score=0.525 clusters=3 claim_tier=notable | framework convergence=partial (upstreams: Institut national de l'information géographique et forestière (IGN), Service Hydrographique et Océanographique de la Marine (SHOM)/Refmar, SONEL (Système d'observation du niveau des eaux littorales)) — publishers independent, evidence may not be | kind=empirical eligibility=high]