Retrieval of Significant Wave Height and Mean Sea Surface Level Using the GNSS-R Interference Pattern Technique: Results From a Three-Month Field Campaign

Abstract

Abstract-Since 1993, when the European Space Agency (ESA) proposed the use of GNSS reflected signals for sea mesoscale altimetry, a wide range of applications have appeared. This work focuses on the retrieval of Significant Wave Height (SWH) and the Mean Sea Surface Level (MSSL) from a ground-based experiment using the Interference Pattern Technique (IPT). Two different observables on the IPT are analyzed: the oscillation frequency, and the angle where coherency is lost. The point where coherency in the reflection process is lost can be related to the Rayleigh criterion for smooth surfaces and helps to determine the SWH. Spectral analysis on the interference pattern helps to determine the MSSL. A three-month field campaign was performed on the "Pont del Petroli" pier, Badalona, Spain, to see how the reflected GNSS signals were affected by coastal sea state, and check previous assumptions. Results from this field experiment are shown confirming that the SWH can be retrieved with an accuracy of 6 cm and the MSSL with 4 cm. Estimations of both parameters are obtained every 30 minutes approximately.

A Method Using GNSS Lh-Reflected Signals for Soil Roughness Estimation

“…It can be taken as a bistatic radar system that the transmitter and receiver are not co-located. Several applications of GNSS-R have been extensively explored including the soil moisture content (Egido, 2012;Jia, 2016;Katzberg 2006;Masters, 2004;Rodriguez-Alvarez, 2011;, vegetation biomass (Mironov, 2012;Ulaby, 1985), wave height (Alonso-Arroyo, 2015), snow depth (Jin, 2016;Larson, 2009), ice thickness (Yan, 2016) and so on (Garrison, 2014).…”

Vegetation Sensing Using GPS Interferometric Reflectometry: Experimental Results With a Horizontally Polarized Antenna

“…The frequency f m (and thus the antenna height H) can be estimated using the Lomb-Scargle Periodogram (LSP) that is similar to Discrete Time Fourier Transform but does not require evenly sampling. Some other frequency retrieval algorithms are discussed in [18]. The frequency derived antenna height is often referred to as effective reflector height H eff [22], [23] and it is not always equal to the geometrical antenna height-for a geodetic antenna, the nonnegligible LHCP gain and the layering effect of soil medium are the primary reasons for this discrepancy [11].…”

“…Among the passive microwave techniques, GPS Interferometric Reflectometry (GPS-IR) has proven its utility in various earth environmental sensing applications, including the measurements of snow depth [3]- [8], near-surface soil moisture [9]- [14], costal sea level [15]- [18], and vegetation biophysical to the horizon, H 0 is the apparent height of the GPS antenna above the reflecting surface. GPS-IR is essentially a bistatic radar system.…”

SNR Degradation in GNSS-R Measurements Under the Effects of Radio-Frequency Interference

“…One of these applications is GNSS-Reflectometry (GNSS-R), a promising technique in the field of remote sensing, that was first proposed in 1988 for scatterometry applications [6]. Later in 1993, GNSS-R was first suggested for mesoscale ocean altimetry [7], and since then, this technique has been used in the retrieval of many geophysical parameters such as measuring sea surface state [8], sea surface salinity [9], soil moisture [10], and ocean altimetry [11] among others.…”

“…(36e) Eventually, (8) has been obtained from the combination of (36a) and (36e), and omitting the dependence with ν and τ in the terms that it does not apply.…”