Use of GPS receivers as a soil moisture network for water cycle studies

Larson, Kristine M.; Small, E. E.; Gutmann, E. D.; Bilich, Andria; Braun, John; Zavorotny, Valery U.

doi:10.1029/2008gl036013

Cited by 349 publications

(232 citation statements)

References 30 publications

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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

Tabibi

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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“…In addition, the multi-path from ground GPS networks is possibly related to the near-surface soil moisture. Larson et al (2008) found nearly consistent fluctuations in near-surface soil moisture from the ground-based observations of GPS multi-path. They found GPS estimates of soil moisture were comparable to estimates in the top 5 cm of soil measured from conventional sensors.…”

Section: Hydrologic Sensingmentioning

confidence: 72%

Observing and understanding the Earth system variations from space geodesy

Jin

Dam

Wdowinski

2013

Journal of Geodynamics

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a b s t r a c tThe interaction and coupling of the Earth system components that include the atmosphere, hydrosphere, cryosphere, lithosphere, and other fluids in Earth's interior, influence the Earth's shape, gravity field and its rotation (the three pillars of geodesy). The effects of global climate change, such as sea level rise, glacier melting, and geoharzards, also affect these observables. However, observations and models of Earth's system change have large uncertainties due to the lack of direct high temporal-spatial measurements. Nowadays, space geodetic techniques, particularly GNSS, VLBI, SLR, DORIS, InSAR, satellite gravimetry and altimetry provide a unique opportunity to monitor and, therefore, understand the processes and feedback mechanisms of the Earth system with high resolution and precision. In this paper, the status of current space geodetic techniques, some recent observations, and interpretations of those observations in terms of the Earth system are presented. These results include the role of space geodetic techniques, atmospheric-ionospheric sounding, ocean monitoring, hydrologic sensing, cryosphere mapping, crustal deformation and loading displacements, gravity field, geocenter motion, Earth's oblateness variations, Earth rotation and atmospheric-solid earth coupling, etc. The remaining questions and challenges regarding observing and understanding the Earth system are discussed.

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“…The interference technique has shown to be applicable also for geodetic antennas as shown by the University of Colorado, which is surprising since the aim of such antennas is to suppress multipath to minimize errors in positioning [92,106,107]. A high correlation between the estimates of the phase of the reflected signals and the height and the soil moisture content at the top centimeter has been shown, however it cannot represent the soil moisture content deeper because of the limited GPS signal penetration.…”

Section: Gnss-r For Soil Moisture Recoverymentioning

confidence: 99%

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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Use of GPS receivers as a soil moisture network for water cycle studies

Cited by 349 publications

References 30 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

Observing and understanding the Earth system variations from space geodesy

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

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