Land Geophysical Parameters Retrieval Using the Interference Pattern GNSS-R Technique

Rodriguez-Alvarez, Nereida; Camps, A.; Vall-llossera, M.; Bosch-Lluis, X.; Monerris, A.; Ramos-Perez, I.; Valencia, E.; Marchan-Hernandez, J.F.; Martínez-Fernández, J.; Baroncini-Turricchia, G.; Pérez-Gutiérrez, C.; Sánchez, Nilda

doi:10.1109/tgrs.2010.2049023

Cited by 198 publications

(142 citation statements)

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“…There is a type of GPS-R that relies on the multipath reception of simultaneously and coherently recorded directly and reflected signals. It employs signal-to-noise ratio (SNR) measurements for retrieving environmental parameters such as soil moisture (Kavak et al, 1998;Larson et al, 2008;RodriguezAlvarez et al, 2011;Chew et al, 2014;Alonso-Arroyo et al, 2014), snow depth (Jacobson, 2008;Larson et al, 2009;Rodriguez-Alvarez et al, 2012;Nievinski and Larson, 2014d;Jin and Najibi, 2014), vegetation growth Rodriguez-Alvarez et al, 2011;Wan et al, 2014), and sea level variations (Anderson, 2000;Lö fgren et al, 2014). The technique samples the environment over a sizable area, e.g., $1000 m 2 in the vicinity of a 2-m tall GPS antenna.…”

Section: Introductionmentioning

confidence: 99%

Assessment of modernized GPS L5 SNR for ground-based multipath reflectometry applications

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Geremia‐Nievinski

Dam

et al. 2015

Advances in Space Research

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Global Positioning System (GPS) signal-to-noise ratio (SNR) measurements can be employed to retrieve environmental variables in multipath reception conditions, whereby direct or line-of-sight transmission is received simultaneously with coherent reflections thereof. Previous GPS SNR multipath studies of soil moisture and snow depth have focused on the legacy GPS L1 and L2 bands. In the present paper, short-delay, near-grazing incidence multipath from the L5-band GPS SNR is assessed for its value in detecting soil moisture and snow depth. The L5 signal will become more important in the future because of compatibility and interoperability among the different global satellite navigation systems. The L5 results are compared with L2C estimates to determine whether the L2C-L5 differences (given their differing power budgets and their modulation properties) are significant. To address these questions, measurements and simulations were employed. A physically-based multipath simulator was enhanced to investigate the differences between parameter retrievals for the L2C and the L5 GPS signals. Parameter retrievals from synthetic observations for different scenarios were compared. Comparisons included varying reflector height, surface material, and surface roughness. Measurements from two GPS stations in Colorado, USA, were used to retrieve soil moisture and snow depth conditions. Over a 153-day period that encompassed the catastrophic 2013 Colorado flooding event, L2-derived volumetric soil moisture had an RMS difference of 0.042 cm 3 /cm 3 while the L5 RMS difference was 0.034 cm 3 / cm 3 with respect to in-situ data (values of volumetric soil moisture range between 0.04 and 0.34 cm 3 /cm 3 ). In a separate 483-day campaign, L5-derived snow depth estimates were compared to L2C-derived values and found strongly correlated, deviating from a one-toone relationship by only 0.00001 ± 0.0064 cm/cm. These results indicate the absence of any detectable biases in L5 as compared to L2C for retrieving soil moisture and snow depth from GPS SNR multipath observations.

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Section: Introductionmentioning

confidence: 99%

Assessment of modernized GPS L5 SNR for ground-based multipath reflectometry applications

Tabibi

Geremia‐Nievinski

Dam

et al. 2015

Advances in Space Research

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“…The co-polar component over soil-surface is dominant for low elevation angles up to θ ~ 30°, while the cross-polar is the highest component for larger elevation angles. Actually, this corresponds to the Brewster angle, which is a property of the reflector type and indicates the change of polarity of the vertical component of incident electromagnetic field after being reflected [36]. A common characteristic of the full ranges of biomass densities and elevation angles under study is the order of reflectivity levels.…”

Section: Discussionmentioning

confidence: 99%

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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“…The variation of phase between the two signals causes constructive and destructive interferences that can be exploited to measure the soil moisture. This concept, called Interference Pattern Technique (IPT), has been extensively used by the Universitat Politècnica de Catalunya [17,103,104]. They used a specific receiver for GNSS-R, using vertically and horizontally polarized antennae instead of RHCP only.…”

Section: Gnss-r For Soil Moisture Recoverymentioning

confidence: 99%

“…Moreover, a lot of research has been conducted with traditional GPS receivers that use a RHCP antenna. For the reflections, the polarization is affected by the properties of the soil, consequently, to process the signal reflections efficiently, both antenna polarizations should be used, either vertical and horizontal (as in [104]), or LHCP and RHCP. This, however, directly impacts the processing charge, as there are twice as many data to process.…”

Section: Gnss-r For Snow Cover Estimationmentioning

confidence: 99%

“…However, these improvements will come at the price of additional signal processing and research challenges. For example, the chipping rate of the signals at the L5/E5 band is 10 times higher than for the GPS L1 C/A signal, a chip representing a distance of 29.1 m instead of 291 m. This has a direct consequence for some of the proposed GNSS-R techniques, such as those relying on interference due to the carrier only where the direct and reflected codes are assumed aligned [19,104], which is not true anymore even for small extra paths (≤10 m). Therefore, when considering these signals, both the carrier phase and the code alignment have to be considered; otherwise the interference methods discussed previously may provide unreliable results or at least the possible range for the antenna height will be decreased [104].…”

Section: Future Options For the Gnss-rmentioning

confidence: 99%

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Soil Moisture & Snow Properties Determination with GNSS in Alpine Environments: Challenges, Status, and Perspectives

et al. 2013

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Moisture content in the soil and snow in the alpine environment is an important factor, not only for environmentally oriented research, but also for decision making in agriculture and hazard management. Current observation techniques quantifying soil moisture or characterizing a snow pack often require dedicated instrumentation that measures either at point scale or at very large (satellite pixel) scale. Given the heterogeneity of both snow cover and soil moisture in alpine terrain, observations of the spatial distribution of moisture and snow-cover are lacking at spatial scales relevant for alpine hydrometeorology. This paper provides an overview of the challenges and status of the determination of soil moisture and snow properties in alpine environments. Current measurement techniques and newly proposed ones, based on the reception of reflected Global Navigation Satellite Signals (i.e., GNSS Reflectometry or GNSS-R), or the use of laser scanning are reviewed, and the perspectives offered by these new techniques to fill the current gap in the instrumentation level are discussed. Some key enabling technologies OPEN ACCESSRemote Sens. 2013, 5 3517 including the availability of modernized GNSS signals and GNSS array beamforming techniques are also considered and discussed.

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Land Geophysical Parameters Retrieval Using the Interference Pattern GNSS-R Technique

Cited by 198 publications

References 25 publications

Assessment of modernized GPS L5 SNR for ground-based multipath reflectometry applications

Assessment of modernized GPS L5 SNR for ground-based multipath reflectometry applications

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

Soil Moisture & Snow Properties Determination with GNSS in Alpine Environments: Challenges, Status, and Perspectives

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