GPS Multipath and Its Relation to Near-Surface Soil Moisture Content

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

doi:10.1109/jstars.2009.2033612

Cited by 234 publications

(172 citation statements)

References 21 publications

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“…SNR data are distinct from typical GPS ranging data in that they tell you nothing about the distance between the transmitting satellite and receiving antenna. However, they have the advantage that fluctuations in SNR levels caused by reflected signals can be easily observed for natural surfaces, such as soil, water, snow, and ice (Larson et al 2008(Larson et al , 2009. Unlike ranging data, where sophisticated models are needed for orbits, satellite and receiver clocks, relativity, and atmospheric delays, the background model for SNR data is a low-order polynomial.…”

Section: Past Workmentioning

confidence: 99%

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A 10-Year Comparison of Water Levels Measured with a Geodetic GPS Receiver versus a Conventional Tide Gauge

Larson

Ray

Williams

2017

Journal of Atmospheric and Oceanic Technology

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118

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A standard geodetic GPS receiver and a conventional Aquatrak tide gauge, collocated at Friday Harbor, Washington, are used to assess the quality of 10 years of water levels estimated from GPS sea surface reflections. The GPS results are improved by accounting for (tidal) motion of the reflecting sea surface and for signal propagation delay by the troposphere. The RMS error of individual GPS water level estimates is about 12 cm. Lower water levels are measured slightly more accurately than higher water levels. Forming daily mean sea levels reduces the RMS difference with the tide gauge data to approximately 2 cm. For monthly means, the RMS difference is 1.3 cm. The GPS elevations, of course, can be automatically placed into a well-defined terrestrial reference frame. Ocean tide coefficients, determined from both the GPS and tide gauge data, are in good agreement, with absolute differences below 1 cm for all constituents save K 1 and S 1 . The latter constituent is especially anomalous, probably owing to daily temperature-induced errors in the Aquatrak tide gauge.

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Section: Past Workmentioning

confidence: 99%

“…Their retrieved heights were accurate only to a few meters. The first GPS tidal reflection study using SNR data from an upright COTS unit was presented by Larson et al (2013a). Comparisons were made for 3 months of data from Onsala, Sweden, and Friday Harbor.…”

Section: Past Workmentioning

confidence: 99%

A 10-Year Comparison of Water Levels Measured with a Geodetic GPS Receiver versus a Conventional Tide Gauge

Larson

Ray

Williams

2017

Journal of Atmospheric and Oceanic Technology

Self Cite

118

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“…Remarkably, relevant geophysical properties of the surface (e.g., soil moisture, water-body roughness and/or salinity retrieval, snow/ice cover determination, etc.) can potentially be retrieved by this approach [17,91,92].…”

Section: Gnss-reflectometry (Gnss-r)mentioning

confidence: 99%

“…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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“…In practice, the L band signal can interact with the first 10 cm, depending on the soil moisture level and incidence direction [28,29]. In particular, in the case of almost dry soil, the penetration depth of active systems like GPS or a SAR was found to be around 10 cm [30] or 7 cm [31] respectively. Accordingly to [29], for passive L band remote sensing, the penetration depth varies from 10 cm to 1 m depending on whether the soil is wet or dry.…”

Section: Introductionmentioning

confidence: 99%

Detection of buried objects using reflected GNSS signals

Notarpietro

Mattia

Campanella

et al. 2014

EURASIP J. Adv. Signal Process.

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The use of reflected Global Navigation Satellite System (GNSS) signals for sensing the Earth has been growing rapidly in recent years. This technique is founded on the basic principle of detecting GNSS signals after they have been reflected off the Earth's surface and using them to determine the properties of the reflecting surface remotely. This is the so-called GNSS reflectometry (GNSS-R) technique. In this paper, a new application regarding the detection of metallic buried objects is analyzed and it is validated through several experimental campaigns. Although the penetration depth of GNSS signals into the ground is not optimal and depends on the soil moisture, GNSS signals can likely interact approximately with the first 10 cm of the ground and therefore can be reflected back by any metallic object buried on the first terrain layer. A very light and low-cost GNSS receiver prototype based on a software-defined radio approach was developed. This receiver can be used as a payload on board small drones or unmanned aerial systems to detect metallic objects (mines or other explosive devices). A signal processing tool based on an open-loop GNSS signal acquisition strategy was developed. The results of two experiments which show the possibility of using GNSS-R signals to detect buried metallic objects and to provide an estimate of their dimensions are discussed.

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GPS Multipath and Its Relation to Near-Surface Soil Moisture Content

Cited by 234 publications

References 21 publications

A 10-Year Comparison of Water Levels Measured with a Geodetic GPS Receiver versus a Conventional Tide Gauge

A 10-Year Comparison of Water Levels Measured with a Geodetic GPS Receiver versus a Conventional Tide Gauge

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

Detection of buried objects using reflected GNSS signals

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