The General Levelling of France (''niveau général de la
France
France (), officially the French Republic ( ), is a country primarily located in Western Europe. It also comprises of overseas regions and territories in the Americas and the Atlantic, Pacific and Indian Oceans. Its metropolitan area ...
'' or ''NGF'')
forms a network of benchmarks in mainland France and
Corsica, now overseen by the
Institut Géographique National
An institute is an organisational body created for a certain purpose. They are often research organisations (research institutes) created to do research on specific topics, or can also be a professional body.
In some countries, institutes can ...
. It is now the official
levelling
Levelling or leveling (American English; see spelling differences) is a branch of surveying, the object of which is to establish or verify or measure the height of specified points relative to a datum. It is widely used in geodesy and cartogra ...
network in mainland France. It is made up of two networks:
* NGF - IGN69 for mainland France, with the 'zero level' determined by the
tide gauge
A tide gauge is a device for measuring the change in sea level relative to a vertical datum.
It its also known as mareograph, marigraph, sea-level recorder and limnimeter.
When applied to freshwater continental water bodies, the instrument ma ...
at
Marseille
Marseille ( , , ; also spelled in English as Marseilles; oc, Marselha ) is the prefecture of the French department of Bouches-du-Rhône and capital of the Provence-Alpes-Côte d'Azur region. Situated in the camargue region of southern Fra ...
* NGF - IGN78 for
Corsica, with the 'zero level' determined by the tide gauge at
Ajaccio
{{DEFAULTSORT:General Levelling Of France
Topography
Geography of France