  We investigate the typical sizes and shapes of sets of points obtained by
irregularly tracking two-dimensional Brownian bridges. The tracking process
consists of observing the path location at the arrival times of a
non-homogeneous Poisson process on a finite time interval. The time varying
intensity of this observation process is the tracking strategy. By analysing
the gyration tensor of tracked points we prove two theorems which relate the
tracking strategy to the average gyration radius, and to the asphericity -- a
measure of how non-spherical the point set is. The act of tracking may be
interpreted either as a process of observation, or as process of depositing
time decaying "evidence" such as scent, environmental disturbance, or disease
particles. We present examples of different strategies, and explore by
simulation the effects of varying the total number of tracking points.
