title: Analysis of BeiDou Satellite Measurements with Code Multipath and Geometry-Free Ionosphere-Free Combinations.
abstract: Using GNSS observable from some stations in the Asia-Pacific area, the carrier-to-noise ratio (CNR) and multipath combinations of BeiDou Navigation Satellite System (BDS), as well as their variations with time and/or elevation were investigated and compared with those of GPS and Galileo. Provided the same elevation, the CNR of B1 observables is the lowest among the three BDS frequencies, while B3 is the highest. The code multipath combinations of BDS inclined geosynchronous orbit (IGSO) and medium Earth orbit (MEO) satellites are remarkably correlated with elevation, and the systematic "V" shape trends could be eliminated through between-station-differencing or modeling correction. Daily periodicity was found in the geometry-free ionosphere-free (GFIF) combinations of both BDS geostationary Earth orbit (GEO) and IGSO satellites. The variation range of carrier phase GFIF combinations of GEO satellites is -2.0 to 2.0 cm. The periodicity of carrier phase GFIF combination could be significantly mitigated through between-station differencing. Carrier phase GFIF combinations of BDS GEO and IGSO satellites might also contain delays related to satellites. Cross-correlation suggests that the GFIF combinations' time series of some GEO satellites might vary according to their relative geometries with the sun.
authors.affiliation: GNSS Research Center, Wuhan University, No.129 Luoyu Road, Wuhan 430079, China. zhaoql@whu.edu.cn.
authors.forename: Qile
authors.initials: Q
authors.lastname: Zhao
authors.affiliation: GNSS Research Center, Wuhan University, No.129 Luoyu Road, Wuhan 430079, China. gxwang@whu.edu.cn.
authors.forename: Guangxing
authors.initials: G
authors.lastname: Wang
authors.affiliation: Department of Land Surveying &amp; Geo-Informatics (LSGI), The Hong Kong Polytechnic University (PolyU), 181 Chatham Road South, Hung Hom, Kowloon, Hong Kong, China. lszzliu@polyu.edu.hk.
authors.forename: Zhizhao
authors.initials: Z
authors.lastname: Liu
authors.affiliation: GNSS Research Center, Wuhan University, No.129 Luoyu Road, Wuhan 430079, China. zhigang.hu@whu.edu.cn.
authors.forename: Zhigang
authors.initials: Z
authors.lastname: Hu
authors.affiliation: School of Geodesy and Geomatics, Wuhan University, No.129 Luoyu Road, Wuhan 430079, China. dzq@whu.edu.cn.
authors.forename: Zhiqiang
authors.initials: Z
authors.lastname: Dai
authors.affiliation: GNSS Research Center, Wuhan University, No.129 Luoyu Road, Wuhan 430079, China. jnliu@whu.edu.cn.
authors.forename: Jingnan
authors.initials: J
authors.lastname: Liu
keywords: BDS; CNR; GFIF; GNSS; elevation; hardware delay; multipath