jgg     2013 33 (6):  28-30    ISSN: 0412-1961  CN: 21-1139/TG STUDY ON  A FAST ALGORITHM FOR MODEL GRAVITY  ANOMALIES IN LOCAL AREAS Information Engineering University，Institute of Geographic Spatial Information，Zhengzhou 450052 Received: 2013-04-23  Revised: null  Online: 2013-12-13 Supporting info