jgg     2015 35 (3):  406-411    ISSN: 0412-1961  CN: 21-1139/TG Study of Cycle-slip Detection Using BDS Triple-Frequency  Geometry-Free and Ionosphere-Free Combination 1 School of Geography Spatial Information, Information Engineering University, 62 Kexue Road,Zhengzhou 450001,China 2 Institute of Mechanical and Electrical Engineering, Zhengzhou University of Light Industry, 5 Dongfeng Road,Zhengzhou 450002,China Received: 2014-04-25  Revised: null  Online: 2015-06-02 Supporting info