Same as QSUSTR (14.1.1) : Replace ``track'' by ``vertex'' and ``QVEC'' by ``QVRT''.
Utility routines can be called with user tracks as arguments. For these tracks, only the basic attributes (columns 1 to 7) are modified : QX,QY,QZ,QE,QP,QM,QCH. All other columns are left unchanged (and NOT set to 0!).