A potentiometer and a method for adjusting an impedance. The plant has a semi-erect growth habit and medium branching. One or more optical detectors analyze the light transmitted through and reflected back from the tissue and a processor utilizes this information to control the delivery of electrosurgical energy from the electrosurgical generator to the tissue. Responsive to an event at a later time, the system generally calculates, at the terminal, the satellite position at the later time based only on the satellite positioning data for the at least one specified time period.