Absolute measurements
Measuring the Earth's gravity field

An absolute measurement of gravity must give the value of the acceleration of gravity from measurements of time and distance.

The first measurements were made using pendulums. Indeed, the oscillation period T of a simple pendulum of length $\mathcal{l}$ is : $T=2\text{π}\sqrt{\frac{\mathcal{l}}{g}}$

For example, measurements made in Potsdam (Germany) in 1906 by Messrs. Kühnen and Furtwangler were used to establish the main basis of a long-used Potsdam system. The value found of 981,274.0 mGal has since been recognized to be in error by almost 14...