jgg     2013 33 (6):  150-154    ISSN: 0412-1961  CN: 21-1139/TG CONTRAST STUDY ON VARIOUS METHODS EXTRACTING TREND  EXTRACTION  BASED ON NON-STATIONARY TIME SERIES Department of Surveying and Mapping Science and Engineering, Hohai University, Nanjing〓210098 Received: 2013-07-07  Revised: null  Online: 2013-12-13 Supporting info