jgg     2014 34 (1):  78-83    ISSN: 0412-1961  CN: 21-1139/TG INSTANTANEOUS AMBIGUITY RESOLUTION FOR PPP-RTK USING  REGIONAL GROUND-BASED AUGMENTATION INFORMATION GNSS Research Center, Wuhan University, Wuhan 430079 Received: 2013-07-13  Revised: null  Online: 2014-01-23 Supporting info