The metropolitan France leveling network (mainland and Corsica) is subdivided into 4 increasingly dense levels called 1st, 2nd, 3rd, and 4th order.
Notes on verification
Directly confirmed by IGN's own geodesy site and corroborated by independent French government and professional sources (BOFiP, AFT). [tier=silver indep_score=0.925 clusters=2 claim_tier=everyday | framework convergence=partial on IGN's official definition of the NGF/IGN69-IGN78 leveling network structure (upstreams: Institut Géographique National (IGN), Nivellement Général de la France (NGF) system, IGN 1969/1978 leveling network) — publishers independent, evidence may not be | kind=empirical eligibility=high]
Sources
- Les réseaux de nivellement français - Géodésie (seed:geography_and_travel)
- https://www.aftopo.org/lexique/nivellement-general-la-france-reseau-du/ (corroboration)
- https://bofip.impots.gouv.fr/bofip/5101-PGP.html/identifiant=BOI-CAD-TOPO-10-20120912 (corroboration)
- https://bofip-archives.impots.gouv.fr/bofip/31037-AIDA.html/identifiant=11A4112-19900920 (corroboration)