gal
Accelerationexact by definition
The gal is exactly 1 cm/s², 0.01 m/s². It is the unit of gravimetry and of strong-motion seismology: Earth's surface gravity is about 980 gal, and peak ground acceleration in an earthquake record is reported in gal or in fractions of g.
Watch out: It is not the gallon, and the symbol is capitalised Gal to keep them apart. Note also that gravity anomalies are almost never quoted in gal itself; the practical unit is the milligal, and the microgal for absolute gravimeters.
| 1 Gal | 0.01 m/s² |
Named for Galileo, who established that bodies fall with constant acceleration. It is a CGS unit that survived the move to SI purely because the numbers come out conveniently sized for the field, and because everything ever published in geodesy uses it.