Symplectic mappings that describe the 3D betatronic motion in a magnet
ic lattice are considered. We define the dynamic aperture in terms of
the connected volume in phase space of initial conditions that are bou
nded for a given number of iterations. Different methods for a fast es
timate of this quantity are given; the analysis of the associated erro
rs and the optimization of the integration steps are outlined. A compa
rison of the accuracy of these methods is given for both simple models
and more realistic lattices.