40 CFR 1065.630: Local acceleration of gravity.

(a) The acceleration of Earth's gravity, ag, varies depending on the test location. Determine ag at your location by entering latitude, longitude, and elevation data into the U.S. National Oceanographic and Atmospheric Administration's surface gravity prediction website at https://geodesy.noaa.gov/cgi-bin/grav_pdx.prl.

(b) If the website specified in paragraph (a) of this section is unavailable, or the test location is outside of the continental United States, you may calculate ag for your latitude as follows:

Where:

u = Degrees north or south latitude.

Example:

u = 45°

ag = 9.7803267715 · (1 + 5.2790414 · 10−3 · sin 2 (45) + 2.32718 · 10−5 · sin 4 (45) + 1.262 · 10−7 · sin 6 (45) + 7 · 10−10 · sin 8 (45)

ag = 9.8061992026 m/s 2