ZGOUBI USERS' GUIDE - HEP

82 4 DESCRIPTION OF THE AVAILABLE PROCEDURESExtrapolation Off Median PlaneThe vector field ¡ and its derivatives in the median plane are calculated by means of a second or fourth order polynomialinterpolation, depending on the value of the parameter IORDRE (IORDRE=2, 25 or 4, see section 1.4.2). The transformationfrom polar to Cartesian coordinates is performed following eqs (1.4.9 or 1.4.10). Extrapolation off median planeis then performed by means of Taylor expansions, following the procedure described in section 1.3.2.