Acceleration of gravity
Barometric corrections

The acceleration of gravity g varies mainly with latitude, but also with altitude and even locally with the presence of major obstacles in the immediate vicinity (concrete blocks, for example) or at a distance (mountains). These variations from one place to another are large enough to need to be taken into account. Thus, g varies roughly from the south to the north of France between 9.800 and 9.810 m/s², corresponding to a relative variation of 0.1%.

Cartographic records are available giving g values at a number of points throughout France [6]. These values are measured using relative gravimeters calibrated by comparison with an international reference located at the Bureau International des Poids et Mesures (BIPM) in Sèvres (point A):