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).
Sources
- Les réseaux de nivellement français - Géodésie (geodesie.ign.fr)
- https://www.aftopo.org/lexique/nivellement-general-la-france-reseau-du/ (aftopo.org)
- https://bofip.impots.gouv.fr/bofip/5101-PGP.html/identifiant=BOI-CAD-TOPO-10-20120912 (bofip.impots.gouv.fr)
- https://bofip-archives.impots.gouv.fr/bofip/31037-AIDA.html/identifiant=11A4112-19900920 (bofip-archives.impots.gouv.fr)