Before revision: Given a trajectory T = \{P_1, P_2, P_3, ..., P_n\} is the 2D position at time t. For each pair of positions P_t and P_{t+1}, calculate the direction angle \theta (t, t+1), as the angle of the line with slope in equation equ:slope.
After revision: P1, P2, P3, ..., PnT =, where PtGiven a trajectory T = \{P_1, P_2, P_3, ..., P_n\} is the 2D position at time t. For each pair of positions P_t and P_{t+1}, calculate the direction angle \theta (t, t+1), as the angle of the line with slope in equation equ:slope.