  The large angular and momentum acceptance magnetic spectrometer VAMOS++, at
GANIL, France, is frequently used for nuclear structure and reaction dynamics
studies. It provides an event-by-event identification of heavy ions produced in
nuclear reactions at beam energies around the Coulomb barrier. The highly
non-linear ion optics of VAMOS++ requires the use of the heavy ion trajectory
reconstruction methods in the spectrometer to obtain the high-resolution
definition of the measured atomic mass number. Three different trajectory
reconstruction methods, developed and used for VAMOS++, are presented in this
work. The performances obtained, in terms of resolution of reconstructed atomic
mass number, are demonstrated and discussed using a single data-set of fission
fragments detected in the spectrometer.
