1. A method of mapping movement of objects through a known space, the method comprising: determining a location parameter for each of a plurality of objects at a plurality of points in time and corresponding locations in the known space, the known space comprising a network of motion constrained pathways for the objects; generating a vector field over location and time across the known space using the location parameters, to specify, for each object, motion of that object through the known space over time; generating a motion path for each object using velocities from the vector field for that object, as the object moves through the known space over time; and outputting a mapping of the motion paths for the plurality of objects over the known space.