{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,6]],"date-time":"2026-07-06T15:01:40Z","timestamp":1783350100753,"version":"3.54.6"},"reference-count":23,"publisher":"MDPI AG","issue":"1","license":[{"start":{"date-parts":[[2016,1,20]],"date-time":"2016-01-20T00:00:00Z","timestamp":1453248000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001809","name":"National Natural Science Foundation of China","doi-asserted-by":"publisher","award":["41231174"],"award-info":[{"award-number":["41231174"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001809","name":"National Natural Science Foundation of China","doi-asserted-by":"publisher","award":["41274039"],"award-info":[{"award-number":["41274039"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"publisher"}]},{"name":"research grant of Hong Kong Research Grants Council (RGC)","award":["PolyU 5325\/12E, F-PP0F"],"award-info":[{"award-number":["PolyU 5325\/12E, F-PP0F"]}]},{"name":"China Postdoctoral Science Foundation funded project","award":["2014M562063"],"award-info":[{"award-number":["2014M562063"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>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 \u201cV\u201d 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 \u22122.0 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\u2019 time series of some GEO satellites might vary according to their relative geometries with the sun.<\/jats:p>","DOI":"10.3390\/s16010123","type":"journal-article","created":{"date-parts":[[2016,1,20]],"date-time":"2016-01-20T11:19:41Z","timestamp":1453288781000},"page":"123","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":50,"title":["Analysis of BeiDou Satellite Measurements with Code Multipath and Geometry-Free Ionosphere-Free Combinations"],"prefix":"10.3390","volume":"16","author":[{"given":"Qile","family":"Zhao","sequence":"first","affiliation":[{"name":"GNSS Research Center, Wuhan University, No.129 Luoyu Road, Wuhan 430079, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Guangxing","family":"Wang","sequence":"additional","affiliation":[{"name":"GNSS Research Center, Wuhan University, No.129 Luoyu Road, Wuhan 430079, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Zhizhao","family":"Liu","sequence":"additional","affiliation":[{"name":"Department of Land Surveying &amp; Geo-Informatics (LSGI), The Hong Kong Polytechnic University (PolyU), 181 Chatham Road South, Hung Hom, Kowloon, Hong Kong, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Zhigang","family":"Hu","sequence":"additional","affiliation":[{"name":"GNSS Research Center, Wuhan University, No.129 Luoyu Road, Wuhan 430079, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Zhiqiang","family":"Dai","sequence":"additional","affiliation":[{"name":"School of Geodesy and Geomatics, Wuhan University, No.129 Luoyu Road, Wuhan 430079, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Jingnan","family":"Liu","sequence":"additional","affiliation":[{"name":"GNSS Research Center, Wuhan University, No.129 Luoyu Road, Wuhan 430079, China"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2016,1,20]]},"reference":[{"key":"ref_1","unstructured":"CSNO BeiDou Navigation Satellite System Signal in Space Interface Control Document-Open Service Signal, Version 2.0, Available online: http:\/\/www.beidou.gov.cn\/attach\/2013\/12\/26\/20131226b8a6182fa73a4ab3a5f107f762283712.pdf."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"927","DOI":"10.3390\/s140100927","article-title":"Precise Point Positioning with the BeiDou Navigation Satellite System","volume":"14","author":"Li","year":"2014","journal-title":"Sensors"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"251","DOI":"10.1007\/978-3-642-54740-9_23","article-title":"Modeling and Performance Analysis of GPS\/GLONASS\/BDS Precise Point Positioning","volume":"Volume 305","author":"Sun","year":"2014","journal-title":"China Satellite Navigation Conference (CSNC) 2014 Proceedings: Volume III"},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"411","DOI":"10.1007\/978-3-642-54737-9_36","article-title":"Analysis of Characteristics of BDS Observable Combinations for Wide-Lane Integer Ambiguity Resolution","volume":"Volume 303","author":"Sun","year":"2014","journal-title":"China Satellite Navigation Conference (CSNC) 2014 Proceedings: Volume I"},{"key":"ref_5","doi-asserted-by":"crossref","unstructured":"Zhang, X., and He, X. 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