jgg     2007 27 (3):  39-43    ISSN: 0412-1961  CN: 21-1139/TG NNR CONDITION,ITRF AND GLOBAL PLATE MOTION MODEL Zhang Xiguang; Lu Zhiping; and Zhao Dongqing Institute of Surveying and Mapping, Information Engineering University, Zhengzhou 450052 Received: 1900-01-01  Revised: 1900-01-01  Online: null Supporting info null