29 Aug 2022
29 Aug 2022
Status: this preprint is currently under review for the journal AMT.

Validation of tropospheric ties at the test setup GNSS co-location site in Potsdam

Chaiyaporn Kitpracha1,2, Robert Heinkelmann2, Markus Ramatschi2, Kyriakos Balidakis3, Benjamin Männel2, and Harald Schuh1,2 Chaiyaporn Kitpracha et al.
  • 1Technische Universität Berlin, Chair of Satellite Geodesy, Kaiserin-Augusta-Allee 104-106, 10553 Berlin, Germany
  • 2GFZ German Research Centre for Geosciences, Space Geodetic Techniques, Telegrafenberg, 14473 Potsdam, Germany
  • 3GFZ German Research Centre for Geosciences, Earth System Modelling, Telegrafenberg, 14473 Potsdam, Germany

Abstract. Atmospheric ties are the differences of atmospheric parameters between antennas or stations at the same site and meteorological conditions. However, there is often a discrepancy between the expected zenith delay differences and those estimated from geodetic analysis, potentially degrading a combined solution employing atmospheric ties to constrain atmospheric delay differences. To investigate the possible effects on GNSS atmospheric delay, this study set up an experiment with four co-located GNSS stations of the same type, both antenna and receiver. Specific height differences for each antenna w.r.t. one reference antenna have been measured. One antenna was equipped with a radome of the same height and type as an antenna close to the ground. Additionally, a meteorological sensor was used for meteorological data recording. The results show that tropospheric ties from the analytical equation based on meteorological data from Global Pressure and Temperature 3 (GPT3) model, Numerical Weather Models, in-situ measurements, and ray-traced tropospheric ties, reduced the bias of zenith delay roughly by 72 %. However, the in-situ tropospheric ties yielded the best precision in this study. These results demonstrate that the instrument effects on GNSS zenith delays were mitigated using the same instrument. In contrast, although the effects of the radome on atmospheric delays are well known, the magnitude of the effects determined in this study is unexpectedly large. Additionally, multipath effects at low-elevation observations degraded the tropospheric gradients. To extract the instrument effect, we set up another experiment with three GNSS stations and four different antennas. The height differences between the three stations were on one centimeter level. One of the three stations could be adjusted in height to control the height displacement after changing antenna. We succeeded in keeping the shift in the GNSS zenith delays within 2 mm level. The bias on GNSS zenith delays and tropospheric gradients agrees with the result of the previous experiment in this study. Moreover, we successfully detected the antenna-dependent effect on both the GNSS zenith delays and gradients from this experiment.

Chaiyaporn Kitpracha et al.

Status: open (until 18 Oct 2022)

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Chaiyaporn Kitpracha et al.

Chaiyaporn Kitpracha et al.


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Short summary
In this study, we expected to learn what are the potential effects of GNSS atmospheric delays from this unique experiment. The results show that the instrument effects on GNSS zenith delays were mitigated by using the same instrument. The radome causes unexpected bias of GNSS zenith delays in this study. In order to calibrate the instrumental effects, we set up the GNSS co-location site experiment to demonstrate calibrating GNSS instrumental effects.