Methods of measurement for the beam-based alignment system in HLS

The beam-based alignment system is given in HIS (Hefei Light Source), in which a switchable shunt resistor was installed on quadrupole to bypass a small percentage of the magnet current. The system can measure BPM-to-quadrupole offset which can be used to position the beam in the magnetic center of quadrupoles. In measurement, some methods ( linear fitting with single corrector, parabola fitting with single corrector, linear fitting with local bump, and parabola fitting with local bump ) are used. These measurement results are given, and compared among the methods mentioned above.