In mathematics, the running angle is the angle of consecutive vectors <math>(Xt,Yt)</math> with respect to the base line, i.e.
- <math>\phi(t) = \arctan\left(\frac {\Delta Yt} {\Delta Xt} \right) .</math>
Usually, it is more informative to compute it using a four-quadrant version of the arctan function in a mathematical software library.