Experimental Evaluation of GNSS-Reflectometry Altimetric Precision Using the P(Y) and C/A Signals

Carreño-Luengo, Hugo; Camps, Adriano; Ramos-Perez, I.; Rius, A.

doi:10.1109/jstars.2014.2320298

Cited by 39 publications

(59 citation statements)

References 24 publications

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“…As can be seen, the wave profile as measured by the level sensor (Figure 10) is correlated with the one derived from PYCARO's observables obtained from the C/A code. (However, the amplitude estimated from PYCARO [14] is larger than that from the gauges. A similar behavior was observed in a field experiment over the Mediterranean Sea using the GPS C/A code, but not with the GPS P(Y) code [14].)…”

Section: Water Surface Height Measurementsmentioning

confidence: 73%

“…PYCARO is a closed-loop GNSS-R receiver with delay and Doppler tracking loops [13,14] that uses conventional GNSS-R (cGNSS-R) for the open GPS codes (C/A) and reconstructed GNSS-R (rGNSS-R) for the encrypted ones. The coherent component of the scattered signals is studied experimentally in the Canal d'Investigació i Experimentació Marí tima (CIEM)/UPC-BarcelonaTech wave channel [15].…”

Section: Introductionmentioning

confidence: 99%

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Empirical Results of a Surface-Level GNSS-R Experiment in a Wave Channel

Carreño-Luengo

Camps

2015

Remote Sensing

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Abstract:The scattering of GNSS signals over a water surface is studied when the receiver is at a low height, as in GNSS-R coastal altimetry. The precise determination of the local sea level and wave state from the coast will provide useful altimetry and wave information as "dry" tide and wave gauges. An experiment has been conducted at the Canal d'Investigació i Experimentació Marí tima (CIEM) wave channel for two simulated "sea" states. The GNSS-reflectometer used is the P(Y) and C/A ReflectOmeter (PYCARO) instrument, a closed-loop receiver with delay and Doppler tracking loops that uses the conventional GNSS-R technique for the GPS C/A code. After retracking of the scattered GPS signals, the coherent and incoherent components have been studied. To reproduce the transmitted GPS signals indoors, a Rohde and Schwarz signal generator is used. It is found that, despite the ratio of the coherent and incoherent components being ~1, the coherent component is strong enough that it can be tracked. The coherent component comes from clusters of points on the surface that approximately satisfy the specular reflection conditions ("roughed facet"). The Pearson's linear correlation coefficients of the derived "sea" surface height with the wave gauge data are: 0.78, 0.85 and 0.81 for a SWH = 36 cm and 0.34, 0.74, and 0.72 for a SWH = 64 cm, respectively, for transmitter elevation angles of θ e = 60°, 75° and 86°, respectively. Finally, the rms phase of the received signal before the retracking processing is used to estimate the effective rms surface height of the 'facets', where the waves get scattered. It is found to be between 2.5-and 4.1-times smaller than the theoretical values corresponding to the half of the coherent reflectivity decaying factor.

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Section: Water Surface Height Measurementsmentioning

confidence: 73%

Section: Introductionmentioning

confidence: 99%

Empirical Results of a Surface-Level GNSS-R Experiment in a Wave Channel

Carreño-Luengo

Camps

2015

Remote Sensing

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“…It is worth pointing out some considerations about the squaring losses of the P (Y) code correlation technique implemented in PYCARO (rGNSS-R). They have a non-linear dependence with the SNR of the received signal [8]: The lower the SNR, the larger the squaring losses [25]. Therefore, the polarimetric ratio as derived from the P (Y) code is higher because of the SNR of the collected RHCP signals is lower than the LHCP ones.…”

Section: Results Of a Stratospheric Balloon Experiments Over Boreal Fomentioning

confidence: 99%

“…The structure of these forests is quite homogeneous which allows the use of allometric equations to characterize the biomass. An updated version of the PYCARO reflectometer [8] including GLONASS and Galileo correlation channels was used. Additionally, both dual-band (L1, L2) and dual-polarization (RHCP, LHCP) zenith-looking antenna patch to collect the direct GNSS signals and nadir-looking antenna array to collect the Earth-reflected signals ( Figure 1) were installed in the gondola.…”

Section: Experimental Set-up and Scenariomentioning

confidence: 99%

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First Polarimetric GNSS-R Measurements from a Stratospheric Flight over Boreal Forests

et al. 2015

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Abstract:The first-ever dual-frequency multi-constellation Global Navigation Satellite Systems Reflectometry (GNSS-R) polarimetric measurements over boreal forests and lakes from the stratosphere are presented. Data were collected during the Swedish National Space Board (SNSB)/European Space Agency (ESA) sponsored Balloon Experiments for University Students (BEXUS) 19 stratospheric balloon experiment using the P(Y) and C/A ReflectOmeter (PYCARO) instrument operated in closed-loop mode. Maps of the polarimetric ratio for L1 and L2 Global Positioning System (GPS) and GLObal Navigation Satellite System (GLONASS), and for E1 Galileo signals are derived from the float phase at 27,000 m height, and the specular points are geolocalized on the Earth's surface. Polarimetric ratio (Γ /Γ ) maps over boreal forests are shown to be in the range 2-16 dB for the different GNSS codes. This result suggests that the scattering is taking place not only over the soil, but over the different forests elements as well. Additionally to the interpretation of the experimental results a theoretical investigation of the different contributions to the total reflectivity over boreal forests is performed using a bistatic scattering model. The simulated cross-(reflected Left Hand Circular Polarization LHCP) and co-polar (reflected Right Hand Circular Polarization RHCP) reflectivities are evaluated for the soil, the canopy, and the canopy-soil interactions for three different biomass densities: 725 trees/ha, 150 trees/ha and 72 trees/ha. For elevation angles larger than the Brewster angle, it is found that the cross-polar OPEN ACCESSRemote Sens. 2015, 7 13121 signal is dominant when just single reflections over the forests are evaluated, while in the case of multiple reflections the co-polar signal becomes the largest one.

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First spaceborne phase altimetry over sea ice using TechDemoSat‐1 GNSS‐R signals

Cardellach

Fabra

et al. 2017

Geophysical Research Letters

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165

127

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A track of sea ice reflected Global Navigation Satellite System (GNSS) signal collected by the TechDemoSat‐1 mission is processed to perform phase altimetry over sea ice. High‐precision carrier phase measurements are extracted from coherent GNSS reflections at a high angle of elevation (>57°). The altimetric results show good consistency with a mean sea surface (MSS) model, and the root‐mean‐square difference is 4.7 cm with an along‐track sampling distance of ∼140 m and a spatial resolution of ∼400 m. The difference observed between the altimetric results and the MSS shows good correlation with the colocated sea ice thickness data from Soil Moisture and Ocean Salinity. This is consistent with the reflecting surface aligned with the bottom of the ice‐water interface, due to the penetration of the GNSS signal into the sea ice. Therefore, these high‐precision altimetric results have potential to be used for determination of sea ice thickness.

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Experimental Evaluation of GNSS-Reflectometry Altimetric Precision Using the P(Y) and C/A Signals

Cited by 39 publications

References 24 publications

Empirical Results of a Surface-Level GNSS-R Experiment in a Wave Channel

Empirical Results of a Surface-Level GNSS-R Experiment in a Wave Channel

First Polarimetric GNSS-R Measurements from a Stratospheric Flight over Boreal Forests

First spaceborne phase altimetry over sea ice using TechDemoSat‐1 GNSS‐R signals

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