Fig 1B shows the histogram of fit parameter values obtained by fitting to each fish individually.  Note that since this model (Eq. \ref{eq:ptw-basic}) does not consider wall effects or social forces, the parameter values fit using the above described procedure do not form a well-defined comparison between different fish.  Instead, we use the following observations about the range of fit parameter values shown in Fig 1B  to make representative choices for our simulations.  First, ... (autocorr times).  Choose tau_s/tau_w = 10, and consider tau_s = 1 as setting time scale.  similarly, can set mu=1, to define length scale.  For noise, set sigma_omega = 0.4 (or 0.3?).  We will use different values of sigma_s:  0 (no noise), and 0.3.

** Fig 1B should express length in "body lengths"