In mathematics, the running angle is the angle of consecutive vectors ( X t , Y t ) {\displaystyle (Xt,Yt)} with respect to the base line, i.e.

ϕ ( t ) = arctan ⁡ ( Δ Y t Δ X t ) . {\displaystyle \phi (t)=\arctan \left({\frac {\Delta Yt}{\Delta Xt}}\right).}

Usually, it is more informative to compute it using a four-quadrant version of the arctan function in a mathematical software library.