Timeline

Heritage classified

Key figures

Origin and history

The Marégraphe de Marseille, installed in 1883 at 174 de la Corniche, in the region of Calvo, was designed to establish a national altimeter reference. Between 1885 and 1897, its continuous measurements of the sea level allowed to define the zero of the General Levelling of France (NGF), adopted in 1897 as the reference altitude. This instrument, the result of a collaboration between the German engineer Heinrich Reitz and the Frenchman Charles Lallemand, incorporates a revolutionary totalizer system to automatically calculate the averages, avoiding heavy manual calculations.

The observatory consists of two buildings: a shelter for the aircraft and a house for the guard. Its location, chosen for the stability of the limestone rock and the absence of hydrological disturbances, also houses the fundamental marker (1.661 m above the NGF zero), sealed in the rock. The mechanical gauge, still functional although supplemented by digital tools since 1998, has produced an uninterrupted data set for 135 years, essential for studying sea level rise (approximately 1.2 mm/year since 1885).

Ranked a historic monument in 2002, the site is managed by IGN and SHOM, and participates in international networks such as GLOSS (UNESCO). His story is related to figures such as Paul-Adrien Bourdalouë, pioneer of French levelling, and Louis-Auguste Sébillotte, conductor of the Bridges and Chaussées who supervised his construction. Today, the association The friends of the Marégraphe de Marseille (created in 2021) work for its enhancement, highlighting its dual role: scientific heritage and key tool for monitoring climate change.

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