Abstract: A method for measuring attributes of a particle in motion comprises observing a region of interest with an event-based sensor oriented such that lines of a pixel array of the sensor lie across an expected trajectory of the particle (P) through the region of interest; defining two reference lines of pixels (R1, R2) separated by a spatial distance (D); sampling a first group of events produced by a first of the two reference lines; sampling a second group of events produced by the second of the two reference lines; determining a temporal distance (T) between the second and first groups of events; and providing a longitudinal speed factor (vy) of the particle based on the spatial distance and the temporal distance.