As we entered the 21st century, with the development and integration of global information technology and industrialization, internet of things and cloud computing came into being, human society enters into the big data era. Since the 1990s, with the advent of worldwide information revolution and the development of internet, geospatial information science have also come of age, which pushed forward the building of digital Earth and cyber city. The combined PPP accuracy of “multiple parameters” method is comparable with that of traditional “single parameter” method and almost unaffected by freedom reduction of the function model. The PPP results demonstrate that the new algorithm can significantly accelerate the convergence of combined PPP by compensating the GLONASS code IFBs efficiently. It is worth to note that GLONASS code IFBs could be quite different with two receivers even if their receiver types, firmware versions and antenna types are all the same. GLONASS code IFBs with the same receiver manufacturer mostly show similar characteristics, however, abnormal behaviors are also found in some receivers. It seems to be difficult to provide a priori code IFB precisely with simple function model. The results show that the GLONASS code IFBs could be several meters and a significant correlation exists between code IFB and signal frequency. GPS/GLONASS observation data from 30 IGS sites which involves 6 different GNSS receiver manufacturers is processed with the proposed algorithm. In the meantime, the GLONASS code IFBs can be estimated precisely based on a single station. Multiple independent inter-system and inter-frequency bias (ISFB) parameters are introduced to the observation equations which could compensate the GLONASS code IFBs in the function model. A new algorithm of combined PPP and code IFBs estimation based on “multiple parameters” is proposed where inter-system bias parameter is merged with code IFB. The disadvantages of ignoring GLONASS receiver code inter-frequency biases(IFBs) in GPS/GLONASS combined precise point positioning (PPP) are analysed in this contribution. 3 ns for leveled carrier phase ionospheric observables, thus facilitate the precise study of ionosphere. 1 ns can be found for PPP-based ionospheric observables in comparison of 0. 2009), all the satellites' DCB are solved and compared with the products published by Centre for Orbit Determination in Europe (CODE), a discrepancy of no more than 0. Furthermore, by choosing a total of 4 days' observations from 8 global-distributed international GNSS service (IGS) tracking stations (i. With a short-baseline experiment, the sTEC determined with both kinds of ionospheric observations from one receiver were used to correct the corresponding observations of another receiver and single frequency PPP was implemented, the positioning results indicated a better reliability of sTEC calibrated with PPP-based ionospheric observables. In this contribution, an approach of calibrating sTEC and satellite-receiver's DCB with ionospheric observables estimated with uncombined precise point positioning (PPP) is proposed. However, the "leveled carrier phase ionospheric observable" is prone to be influenced by the arc length for leveling and receiver-dependent errors. The ionospheric observables can be determined by combining dual-frequency observations of GPS through carrier-to-code leveling process, which mainly include the slant total electron content (sTEC), satellite-receiver's differential code bias (DCB) and can be applied for ionosphere related research.
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