Geoscience Reference
In-Depth Information
Fig. 6
Time series of displacement at ARAU, KUKP, MUKH, RANA and SARA stations
4 Implication of the Geocentric Datum Shift
The consequences of not updating the geocentric datum to the latest epoch (e.g.
2013), and the present reference frame (ITRF2008) have resulted in a number of
implications, which are discussed in the following sub-sections.
4.1 Inconsistent Satellite Orbit and Coordinate Bias
The GNSS reference system for instance, the WGS84 (G1674) for GPS, Para-
metrop Zemp 1990 (PZ-90) for Globalnaya Navigatsionnaya Sputnikovaya
Sistema (GLONASS), China Geodetic Coordinate System 2000 (CGCS2000) for
BeiDou, Galileo Terrestrial Reference Frame (GTRF) for Galileo and Japan
satellite navigation Geodetic System (JGS) for Quasi-Zenith Satellite System
(QZSS) have been designed to be compatible with the global datum, i.e. ITRF. The
GNSS reference system is mainly used for satellite orbit determination. Hence, the
position of a satellite (ephemeris and especially precise orbit) is corresponding to
the ITRF. Therefore, if the national network is contaminated with displacement,
the national geocentric datum will no longer be compatible with the ITRF. This
can lead to inconsistency in the satellite orbit interpretation. Furthermore, it would
introduce coordinate bias, especially in relative positioning, that can be considered
in a similar manner as the satellite orbit bias. Figure
7
illustrates the coordinate
bias at a reference station; this gives a wrong estimated rover's position in relative
positioning.
