jgg     2014 34 (1):  165-168    ISSN: 0412-1961  CN: 21-1139/TG STUDY ON PRECISION OF ELEVATION DIFFERENCE MEASUREMENT  BASED ON VRS TECHNIQUE 1)China University of Geosciences Great Wall College，Baoding 071000 2)College of Geoscience and Surveying Engineering, China University of Mining and Technology, Beijing 100083 3)College of Geoscience and Resource, China University of Geosciences, Beijing 100083 Received: 2013-09-21  Revised: null  Online: 2014-01-23 Supporting info