Gravimetry
The precise measurement of spatial and temporal variations in Earth's gravitational acceleration field.
Governing formula
g_observed = g_theoretical + Δg_FreeAir - Δg_Bouguer + Δg_Terrain
SI unit
mGal (Milligals = 10⁻⁵ m/s²)
In depth
Geophysicists measure local gravity anomalies (Δg in mGal) to map subsurface rock density variations. Positive gravity anomalies indicate dense subsurface ore bodies or basalt, while negative anomalies indicate oil reservoirs or salt domes.
Examples in the real world
NASA's GRACE satellite mission measuring gravity changes to track global groundwater depletion and polar ice sheet loss.