[G06-5] GNSS reflectometry

[G06-5-02] IAG/GGOS inter-comparison campaign on SNR-based GNSS reflectometry for sea level monitoring

Felipe Geremia-Nievinski¹, Thomas Hobiger², Karen Boniface³, Ruediger Haas², Wei Liu⁴, Nicolas Roussel⁵, Joakim Strandberg², Sajad Tabibi⁶, Sibylle Vey⁴, ^○Jens Wickert⁴, Simon Williams⁷ (1.Federal University of Rio Grande do Sul, Brazil, 2.Chalmers University of Technology, Sweden, 3.Geosciences Environnement Toulouse, University of Toulouse, France, 4.GFZ Potsdam, Germany, 5.University of Toulouse, France, 6.University of Luxembourg, Luxembourg, 7.National Oceanography Centre, UK)

invited

A joint working group (JWG 4.3.9) on GNSS reflectometry (GNSS-R) was established at the end of 2015
under the auspices of the International Association of Geodesy (IAG) and the Global Geodetic Observing
System (GGOS). Its goal is to foster the adoption of GNSS-R corrections (e.g., hydrological loading) in
geodetic positioning as well as the generation of environmental parameters (e.g., soil moisture and coastal
sea level) based on GNSS-R using conventional geodetic instrumentation. Of particular interest are sea
level estimates using existing GNSS networks by means of signal-to-noise ratio (SNR) analysis. This
application has the potential to become a GGOS data product and an IAG data service in the near future.
JWG 4.3.9 initiated an inter-comparison campaign on SNR-based GNSS-R for sea level monitoring at the
end of 2016. Its purpose is to assess retrieval solutions from independent research groups under
comparable conditions. One year of RINEX files with GNSS measurements collected at the Onsala Space
Observatory, Sweden, were made available to JWG 4.3.9 members. More than half participated submitting
single-signal solutions (GPS L1 C/A) as well as a dual-frequency (L1/L2) and dual-constellation
(GPS/GLONASS) multi-signal solutions. In general, we found good agreement between the co-located tide
gauge record and SNR-based GNSS-R retrievals from different groups. Most correlation coefficients exceed
0.9 and standard deviations are at sub-decimeter level, with some solutions approaching 0.99 and few-cm,
respectively. Systematic effects and/or dependency on meteorological conditions have been revealed and
are subject of further discussion within JWG 4.3.9.