{"id":21697,"date":"2026-07-14T09:38:23","date_gmt":"2026-07-14T07:38:23","guid":{"rendered":"https:\/\/ngi.be\/?page_id=21697"},"modified":"2026-08-06T14:15:36","modified_gmt":"2026-08-06T12:15:36","slug":"reference-altimetrique","status":"publish","type":"page","link":"https:\/\/ngi.be\/fr\/offre\/les-services\/services-geodesiques\/reference-altimetrique\/","title":{"rendered":"R\u00e9f\u00e9rence altim\u00e9trique"},"content":{"rendered":"<p>Les altitudes sont toujours exprim\u00e9es par rapport \u00e0 un niveau de r\u00e9f\u00e9rence (le \u00ab\u00a0niveau z\u00e9ro\u00a0\u00bb). En Belgique, ce niveau z\u00e9ro correspond au niveau moyen de la mer \u00e0 mar\u00e9e basse \u00e0 Ostende, mesur\u00e9 entre 1834 et 1853. Il a servi de base \u00e0 la d\u00e9termination des altitudes des rep\u00e8res altim\u00e9triques lors du Deuxi\u00e8me Nivellement G\u00e9n\u00e9ral (DNG). Ces rep\u00e8res, qui sont r\u00e9partis sur tout le territoire, permettent aux utilisateurs de d\u00e9terminer les altitudes avec pr\u00e9cision.<\/p>\n<p>Le DNG, ex\u00e9cut\u00e9 de 1947 \u00e0 1968, comporte quelque 17\u00a0000 rep\u00e8res diss\u00e9min\u00e9s dans tout le pays. Le renouvellement (c\u2019est-\u00e0-dire la nouvelle mesure et l\u2019ajustement) de ce r\u00e9seau a \u00e9t\u00e9 r\u00e9alis\u00e9 entre 1981 et 2000. Entre 2005 et 2017, des parties de ce r\u00e9seau ont \u00e9t\u00e9 mesur\u00e9es pour la troisi\u00e8me fois, toujours selon la technique topographique du nivellement optique.<\/p>\n<p>Tous les rep\u00e8res de nivellement ont \u00e9t\u00e9 recalcul\u00e9s en 2018. Vous pouvez consulter les r\u00e9sultats de cette op\u00e9ration dans la documentation g\u00e9od\u00e9sique <a href=\"https:\/\/gdoc.ngi.be\" target=\"_blank\" rel=\"noopener\">G-DOC<\/a>.<\/p>\n<p><strong>Point de r\u00e9f\u00e9rence du DNG<\/strong><\/p>\n<p>Un \u00ab\u00a0rep\u00e8re fondamental\u00a0\u00bb a \u00e9t\u00e9 choisi pour mat\u00e9rialiser le niveau z\u00e9ro. Il s\u2019agit du point GIKMN situ\u00e9 \u00e0 l\u2019Observatoire royal de Belgique \u00e0 Uccle. Ce rep\u00e8re faisait partie du Nivellement de Pr\u00e9cision (NP), un relev\u00e9 effectu\u00e9 \u00e0 la fin du 19e si\u00e8cle.<\/p>\n<p>\u00c0 partir du milieu du si\u00e8cle dernier, l\u2019altitude du point z\u00e9ro, soit 100,174\u00a0m\u00e8tres, a \u00e9t\u00e9 utilis\u00e9e comme valeur de r\u00e9f\u00e9rence pour tous les calculs du r\u00e9seau de nivellement. Cette altitude a \u00e9t\u00e9 calcul\u00e9e \u00e0 partir des niveaux moyens des basse eaux \u00e0 Ostende (altitude 0\u00a0m), mesur\u00e9s entre 1834 et 1853.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Les altitudes sont toujours exprim\u00e9es par rapport \u00e0 un niveau de r\u00e9f\u00e9rence (le \u00ab\u00a0niveau z\u00e9ro\u00a0\u00bb). En Belgique, ce niveau z\u00e9ro correspond au niveau moyen de la mer \u00e0 mar\u00e9e basse \u00e0 Ostende, mesur\u00e9 entre 1834 et 1853. Il a servi de base \u00e0 la d\u00e9termination des altitudes des rep\u00e8res altim\u00e9triques lors du Deuxi\u00e8me Nivellement G\u00e9n\u00e9ral&#8230;<\/p>\n","protected":false},"author":19,"featured_media":0,"parent":656,"menu_order":16,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_acf_changed":false,"footnotes":""},"class_list":["post-21697","page","type-page","status-publish","hentry"],"acf":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v28.5 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>R\u00e9f\u00e9rence altim\u00e9trique - IGN<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/ngi.be\/fr\/offre\/les-services\/services-geodesiques\/reference-altimetrique\/\" \/>\n<meta property=\"og:locale\" content=\"fr_FR\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"R\u00e9f\u00e9rence altim\u00e9trique - IGN\" \/>\n<meta property=\"og:description\" content=\"Les altitudes sont toujours exprim\u00e9es par rapport \u00e0 un niveau de r\u00e9f\u00e9rence (le \u00ab\u00a0niveau z\u00e9ro\u00a0\u00bb). 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