Feat: position along group axis of movement

[robitalec]

Position along group's mean bearing as leadership order

Given the mean bearing of a group of animals, shifts the coordinate system to a new origin at the group centroid and rotates the coordinate system by the mean bearing. Returns the distance along the mean bearing as the front-back position in group.

(eg. Andrienko 2013, Kölzsch 2020, Kano 2021)