1. An analysis system for enabling determination of the velocities of migrating objects, comprising: a space-time map generator for generating a space-time map of points representative of the signal peaks of signals detected at a plurality of spaced positions; and a vertex finder for identifying at least one vertex from the space-time map, with a single vertex being identified for each group of objects having a common constraint and the velocities of the objects being determinable from the sets of points in the space-time map corresponding to the respective objects as fitted to the respective vertex.