search for a reference point to precisely adjust the initial phase
which is usually referred to as autofocusing. The paper presents two improved autofocusing techniques called weighted multiple scatterer algorithrn (WMSA)and improved scatter centroid tracking (ISCT). They are analyzed and compared with the dominant scatterer algorithm (DSA). Finally
the outdoor measured ISAR data of aircrafts are processed and the imaging results are compared with each other.