[1][2] The acceleration of a body near the surface of the Earth is due to the combined effects of gravity and centrifugal acceleration from the rotation of the Earth (but the latter is small enough to be negligible for most purposes); the total (the apparent gravity) is about 0.5% greater at the poles than at the Equator.
Although the actual acceleration of free fall on Earth varies according to location, the above standard figure is always used for metrological purposes.
Already in the early days of its existence, the International Committee for Weights and Measures (CIPM) proceeded to define a standard thermometric scale, using the boiling point of water.
The 1887 CIPM meeting decided as follows: The value of this standard acceleration due to gravity is equal to the acceleration due to gravity at the International Bureau (alongside the Pavillon de Breteuil) divided by 1.0003322, the theoretical coefficient required to convert to a latitude of 45° at sea level.
[5]All that was needed to obtain a numerical value for standard gravity was now to measure the gravitational strength at the International Bureau.