Abstract
Coastal Global Navigation Satellite System Reflectometry (GNSS-R) can be used as a valuable supplement for conventional tide gauges, which can be applied for marine environment monitoring and disaster warning. Incidentally, an important problem in dual-antenna GNSS-R altimetry is the crosstalk effect, which means that the direct signal leaks into the down-looking antenna dedicated to the reflected signals. When the path delay between the direct and reflected signals is less than one chip length, the delay waveform of the reflected signal is distorted, and the code-level altimetry precision decreases consequently. To solve this problem, the author deduced the influence of signal crosstalk on the reflected signal structure as the same as the multipath effect. Then, a simulation and a coastal experiment are performed to analyze the crosstalk effect on code delay measurements. The L5 signal transmitted by the Quasi-Zenith Satellite System (QZSS) from a geosynchronous equatorial orbit (GEO) satellite is used to avoid the signal power variations with the elevation, so that high-precision GNSS-R code altimetry measurements are achieved in the experiment. Theoretically and experimentally, we found there exists a bias in proportion to the power of the crosstalk signals and a high-frequency term related to the phase delay between the direct and reflected signals. After weakening the crosstalk by correcting the delay waveform, the results show that the RMSE between 23-h sea level height (SSH) measurements and the in-situ observations is about 9.5 cm.
Highlights
The tide gauges (TG) located along continental coastlines and islands are crucial for providing global sea surface height (SSH) variation
In the Global Navigation Satellite System Reflectometry (GNSS-R) receiver, the reflected GNSS signal power waveform is the cross-correlation of the reflected signals and local signals at different time delay τ under specific Doppler frequency shift f 0 as below [32]: Y (τ, t0 ) =
The L5 signal from Quasi-Zenith Satellite System (QZSS) geosynchronous equatorial orbit (GEO) satellites is adopted in the experiment
Summary
The tide gauges (TG) located along continental coastlines and islands are crucial for providing global sea surface height (SSH) variation. The. Global Navigation Satellite System Reflectometry (GNSS-R) was proposed to retrieve SSH by using the signals of opportunity transmitted by the GNSS satellites [4]. Three different approaches are used to process GNSS reflected signals: the GNSS interferometric reflectometry (GNSS-IR), the interferometric GNSS-R (iGNSS-R), and the conventional GNSS-R (cGNSS-R). GNSS-IR takes advantage of the interference phenomenon, known as the multipath effect when the direct signal and the reflected signal enter the same geodetic antenna at low elevation angles [5,6,7,8]. The temporal resolution is low because the sampling rate is fundamentally limited by the number of satellite overflights and elevation angle spans [10].
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
