This paper introduces a new approach for determining azimuth‐ and elevation‐dependent phase center biases through a field measurement in an absolute sense. It gives particular attention to multipath effects. The model, the conditions for the field procedure, and preliminary analysis of the results are presented. The absolute antenna phase center calibration procedure is implemented in the GPS processing package GEONAP.
The reference frame of a global terrestrial network is defined by the origin, the orientation and the scale. The origin of the ITRF2014 is defined by the ILRS long-term solution, the orientation by no-net rotation conditions w.r.t. the previous reference frame (ITRF2008), and the scale by the mean values from global VLBI and SLR solution series (Altamimi et al. in J Geophys Res Solid Earth 121:6109–6131, 2016). With the release of the Galileo satellite antenna phase center offsets (PCO) w.r.t. the satellites center of mass (GSA in Galileo IOV and FOC satellite metadata, 2019) and the availability of new ground antenna calibrations for GNSS receivers, based on anechoic chamber measurements or on robot calibrations, GNSS global network solutions qualify to contribute to the scale determination of terrestrial networks, as well. Our analysis is based on global multi-GNSS solutions of the years 2017 and 2018 and may be seen as “proof of concept” for the contribution of GNSS data to the scale determination of the terrestrial reference frame. In a first step, the currently used Galileo PCO estimations (Steigenberger et al. in J Geod 90:773–785, 2016) are compared to the released PCO values, which show discrepancies on the decimeter-level. Eventually, the published Galileo PCOs are used in an experimental solution as known values. GNSS-specific PCOs are estimated, as well, for GPS and GLONASS, together with the “standard” parameters set up in global GNSS solutions. From the estimated network coordinates, a time series of daily scale parameters of the terrestrial network is extracted, which shows an offset of the order of 1 ppb (parts per billion, corresponding to a height difference of 6.4 mm on the Earth’s surface) w.r.t. to the ITRF2014 network and an annual variation with an amplitude of about 0.3 ppb.
Abstract. The Real-Time Working Group (RTWG) of the International GNSS Service (IGS) is
dedicated to providing high-quality data and high-accuracy products for Global
Navigation Satellite System (GNSS) positioning, navigation, timing and Earth
observations. As one part of real-time products, the IGS combined Real-Time
Global Ionosphere Map (RT-GIM) has been generated by the real-time weighting
of the RT-GIMs from IGS real-time ionosphere centers including the Chinese
Academy of Sciences (CAS), Centre National d'Etudes Spatiales (CNES),
Universitat Politècnica de Catalunya (UPC) and Wuhan University
(WHU). The performance of global vertical total electron content (VTEC)
representation in all of the RT-GIMs has been assessed by VTEC from
Jason-3 altimeter for 3 months over oceans and dSTEC-GPS technique with
2 d observations over continental regions. According to the
Jason-3 VTEC and dSTEC-GPS assessment, the real-time weighting technique is
sensitive to the accuracy of RT-GIMs. Compared with the performance of
post-processed rapid global ionosphere maps (GIMs) and IGS combined final GIM
(igsg) during the testing period, the accuracy of UPC RT-GIM (after the
improvement of the interpolation technique) and IGS combined RT-GIM (IRTG) is
equivalent to the rapid GIMs and reaches around 2.7 and 3.0 TECU (TEC unit,
1016 el m−2) over
oceans and continental regions, respectively. The accuracy of CAS RT-GIM and
CNES RT-GIM is slightly worse than the rapid GIMs, while WHU RT-GIM requires a
further upgrade to obtain similar performance. In addition, a strong
response to the recent geomagnetic storms has been found in the global
electron content (GEC) of IGS RT-GIMs (especially UPC RT-GIM and IGS combined
RT-GIM). The IGS RT-GIMs turn out to be reliable sources of real-time global
VTEC information and have great potential for real-time applications including
range error correction for transionospheric radio signals, the monitoring of
space weather, and detection of natural hazards on a global scale. All the IGS
combined RT-GIMs generated and analyzed during the testing period are
available at https://doi.org/10.5281/zenodo.5042622 (Liu et al., 2021b).
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.