  We discuss the method for the measurement of the gravity acceleration g by
means of Bloch oscillations of an accelerated BEC in an optical lattice. This
method has a theoretical critical point due to the fact that the period of the
Bloch oscillations depends, in principle, on the initial shape of the BEC
wavepacket. Here, by making use of the nearest-neighbor model for the numerical
analysis of the BEC wavefunction, we show that in real experiments the period
of the Bloch oscillations does not really depend on the shape of the initial
wavepacket and that the relative uncertainty, due to the fact that the initial
shape of the wavepacket may be asymmetrical, is smaller than the one due to
experimental errors. Furthermore, we also show that the relation between the
oscillation period and the scattering length of the BEC's atoms is linear; this
fact suggest us a new experimental procedure for the measurement of the
scattering length of atoms.
