  Three-dimensional tracking of animal systems is the key to the comprehension
of collective behavior. Experimental data collected via a stereo camera system
allow the reconstruction of the 3d trajectories of each individual in the
group. Trajectories can then be used to compute some quantities of interest to
better understand collective motion, such as velocities, distances between
individuals and correlation functions. The reliability of the retrieved
trajectories is strictly related to the accuracy of the 3d reconstruction. In
this paper, we perform a careful analysis of the most significant errors
affecting 3d reconstruction, showing how the accuracy depends on the camera
system set-up and on the precision of the calibration parameters.
