Additionally,
the outward centrifugal force produced by Earth's rotation is larger than at polar latitudes. This counteracts the Earth's gravity to a small degree – up to a maximum of 0.3% at the Equator – and reduces the apparent downward acceleration of falling objects.
The gravity field of Earth has been measured recently with a variety of satellites (GRACE, CHAMP, GOCE). The resulting data can be used to generate global geoids such as EGM96 (geoid calculator). Gravitational anomalies can be extracted by calculating differences with respect to the geoid. The range of variations is of order ±300 $mGal$ (±0.003 $m/s^2$).
Other factors have a small effect on gravity, such as the gravitational force from the Moon and the Sun that causes the tides. The fluctuations associated with these effects are of order 0.2 $mGal$ (2 $µm/s^2$).