sentence: In practice the velocity calculation equation is Equation ( 23 ) : ( 23 ) v˙en = Cbnfb − ( 2 ω ien + ω enn ) × ven + γ nThe position calculation is given here [ 17 ] and the calculation of height is not considered here , because the vertical channel of INS is divergent [ 18 ] , and λ denotes the longitude of INS : ( 24 ) L˙ = 1RM + hvN ( 25 ) λ ˙