Offline calibration of BES II vertex chamber

An algorithm based on VCJULI to calibrate the BES II vertex chamber is described. The calibration includes the determination of global T-o, the subtraction of t(o) shift for each wire, the corrections of wire position itself and the position of the vertex chamber relative to the main drift chamber, the establishment of drift time to drift distance relation, etc. The main performance of the BES II vertex chamber is given accordingly: space resolution is better than 100 mum.