1065.630—1980 international gravity formula.
         The acceleration of Earth's gravity, a
            g, varies depending on your location. Calculate a
            g at your latitude, as follows:
    
    Where:
        θ = Degrees north or south latitude.
        Example:
        θ = 45°
        ag = 9.7803267715 · (1 
        5.2790414 · 10−3 · sin2 (45)  
        2.32718 · 10−5 ·sin 4 (45)  
        1.262 · 10−7 ·sin 6 (45)  
        7 · 10−10 ·sin 8 (45)
        ag = 9.8178291229 m/s2