scholarly journals Investigating GNSS multipath effects induced by co-located Radar Corner Reflectors

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Thomas Fuhrmann ◽  
Matthew C. Garthwaite ◽  
Simon McClusky
Keyword(s):  
Land Surface ◽  
Reference Frames ◽  
Surface Deformation ◽  
Signal To Noise Ratio ◽  
Ground Plane ◽  
Global Navigation Satellite Systems ◽  
Satellite Systems ◽  
Multipath Effects ◽  
Global Navigation Satellite ◽  
Relative Measurements

Abstract Radar Corner Reflectors (CR) are increasingly used as reference targets for land surface deformation measurements with the Interferometric Synthetic Aperture Radar (InSAR) technique. When co-located with ground-based Global Navigation Satellite Systems (GNSS) infrastructure, InSAR observations at CR can be used to integrate relative measurements of surface deformation into absolute reference frames defined by GNSS. However, CR are also a potential source of GNSS multipath effects and may therefore have a detrimental effect on the GNSS observations. In this study, we compare daily GNSS coordinate time series and 30-second signal-to-noise ratio (SNR) observations for periods before and after CR deployment at a GNSS site. We find that neither the site coordinates nor the SNR values are significantly affected by the CR deployment, with average changes being within 0.1 mm for site coordinates and within 1 % for SNR values. Furthermore, we generate empirical site models by spatially stacking GNSS observation residuals to visualise and compare the spatial pattern in the surroundings of GNSS sites. The resulting stacking maps indicate oscillating patterns at elevation angles above 60 degrees which can be attributed to the CR deployed at the analysed sites. The effect depends on the GNSS antenna used at a site with the magnitude of multipath patterns being around three times smaller for a high-quality choke ring antenna compared to a ground plane antenna without choke rings. In general, the CR-induced multipath is small compared to multipath effects at other GNSS sites located in a different environment (e. g. mounted on a building).

Bit Sign Transition Cancellation Method for GNSS Signal Acquisition

2011 ◽  
Vol 65 (1) ◽  
pp. 73-97 ◽  
Author(s):  
Kewen Sun ◽  
Letizia Lo Presti
Keyword(s):  
Doppler Shift ◽  
Signal To Noise Ratio ◽  
Search Space ◽  
Global Navigation Satellite Systems ◽  
Main Peak ◽  
Signal Acquisition ◽  
Satellite Systems ◽  
Gps Modernization ◽  
Improved Performance ◽  
Global Navigation Satellite

The next generation Global Navigation Satellite Systems (GNSS), such as Galileo and Global Positioning System (GPS) modernization, will use signals with equal code and bit periods, resulting in a potential bit sign transition in each primary code period of the received signal segments. A bit sign transition occurring within an integration period usually causes a splitting of the Cross Ambiguity Function (CAF) main peak into two smaller side lobes along the Doppler shift axis in the search space and it may lead to an incorrect Doppler shift estimate, which results in a serious performance degradation of the acquisition system. This paper proposes a novel two steps based bit sign transition cancellation method which can overcome the bit sign transition problem and remove or mitigate the CAF peak splitting impairments. The performance of the proposed technique has been comprehensively evaluated with Monte Carlo simulations in terms of detection and false alarm probabilities, which are presented by Receiver Operating Characteristic (ROC) and Signal-to-Noise-Ratio (SNR) curves. The test results show that the proposed acquisition technique can provide improved performance in comparison with the state-of-the-art acquisition approaches.

scholarly journals Estimating Wave Direction by Using Terrestrial GNSS Reflectometry

2019 ◽  
Author(s):  
Jörg Reinking ◽  
Ole Roggenbuck ◽  
Gilad Even-Tzur
Keyword(s):  
Correlation Length ◽  
Signal To Noise Ratio ◽  
Simulated Data ◽  
Global Navigation Satellite Systems ◽  
Wave Direction ◽  
Satellite Systems ◽  
The North ◽  
Scattered Power ◽  
Length Changes ◽  
Global Navigation Satellite

The signal-to-noise ratio (SNR) data is part of the global navigation satellite systems (GNSS) observables. In a marine environment, the oscillation of the SNR data can be used to derive reflector heights. Since the attenuation of the SNR oscillation is related to the roughness of the sea surface, the significant wave height (SWH) of the water surface can be calculated from the analysis of the attenuation. The attenuation depends additionally on the relation between the coherent and the incoherent part of the scattered power. The latter is a function of the correlation length of the surface waves. Because the correlation length changes with respect to the direction of the line of sight relative to the wave direction, the attenuation must show an anisotropic characteristic. In this work, we present a method to derive the wave direction from the anisotropy of the attenuation of the SNR data. The method is investigated based on simulated data as well by the analysis of experimental data from a GNSS station in the North Sea.

Earth Orientation Parameter Estimation by Integrating VLBI and GNSS on the Observation Level

2021 ◽  
Author(s):  
Jungang Wang ◽  
Kyriakos Balidakis ◽  
Maorong Ge ◽  
Robert Heinkelmann ◽  
Harald Schuh
Keyword(s):  
Polar Motion ◽  
Reference Frames ◽  
Global Navigation Satellite Systems ◽  
Satellite Systems ◽  
Earth Orientation ◽  
Long Baseline ◽  
Space Geodetic Techniques ◽  
Global Navigation Satellite ◽  
The Impact ◽  
Globally Distributed

<p>The terrestrial and celestial reference frames are linked by the Earth Orientation Parameters (EOP), which describe the irregularities of the Earth's rotation and are determined by the space geodetic techniques, namely, Very Long Baseline Interferometry (VLBI), Satellite Laser Ranging (SLR), Global Navigation Satellite Systems (GNSS), and Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS). The satellite geodetic techniques (SLR, GNSS, and DORIS) cannot determine the UT1-UTC or celestial pole offsets (CPO), rendering VLBI the only technique capable of determining full EOP set. On the other hand, the GNSS technique provides precise polar motion estimates due to the continuous observations from a globally distributed network. Integrating VLBI and GNSS provides the full set of EOP and guarantees a superior accuracy than any single-technique solution.</p><p>In this study we focus on the integrated estimation of the full EOP set from GNSS and VLBI. Using five VLBI continuous observing campaigns (CONT05–CONT17), the GNSS and VLBI observations are processed concurrently in a common least-squares estimator. The impact of applying global ties (EOP), local ties, and tropospheric ties, and combinations thereof is investigated. The polar motion estimates in integrated solution are dominated by the huge GNSS observations, and the accuracy in terms of weighted root mean squares (WRMS) is ~40 μas compared to the IERS 14 C04 product, which is much better than that of the VLBI-only solution. The UT1-UTC and CPO in the integrated solution also show slight improvement compared to the VLBI-only solution. Moreover, the CPO agreement between the two networks in CONT17, i.e., the VLBA and IVS networks, shows an improvement of 20% to 40% in the integrated solution with different types of ties applied.</p>

Seismic and Geodetic Analysis of Rupture Characteristics of the 2020 Mw 6.5 Monte Cristo Range, Nevada, Earthquake

2021 ◽  
Author(s):  
Chengli Liu ◽  
Thorne Lay ◽  
Fred F. Pollitz ◽  
Jiao Xu ◽  
Xiong Xiong
Keyword(s):  
Surface Deformation ◽  
Joint Inversion ◽  
Complex Surface ◽  
Global Navigation Satellite Systems ◽  
Fault System ◽  
Satellite Systems ◽  
Walker Lane ◽  
Global Navigation Satellite ◽  
Mina Deflection ◽  
East West

ABSTRACT The largest earthquake since 1954 to strike the state of Nevada, United States, ruptured on 15 May 2020 along the Monte Cristo range of west-central Nevada. The Mw 6.5 event involved predominantly left-lateral strike-slip faulting with minor normal components on three aligned east–west-trending faults that vary in strike by 23°. The kinematic rupture process is determined by joint inversion of Global Navigation Satellite Systems displacements, Interferometric Synthetic Aperture Radar (InSAR) data, regional strong motions, and teleseismic P and SH waves, with the three-fault geometry being constrained by InSAR surface deformation observations, surface ruptures, and relocated aftershock distributions. The average rupture velocity is 1.5  km/s, with a peak slip of ∼1.6  m and a ∼20  s rupture duration. The seismic moment is 6.9×1018  N·m. Complex surface deformation is observed near the fault junction, with a deep near-vertical fault and a southeast-dipping fault at shallow depth on the western segment, along which normal-faulting aftershocks are observed. There is a shallow slip deficit in the Nevada ruptures, probably due to the immature fault system. The causative faults had not been previously identified and are located near the transition from the Walker Lane belt to the Basin and Range province. The east–west geometry of the system is consistent with the eastward extension of the Mina Deflection of the Walker Lane north of the White Mountains.

Influence of GNSS Receivers on GPR Results

2018 ◽  
Vol 23 (3) ◽  
pp. 383-389
Author(s):  
Dariusz Tanajewski ◽  
Dariusz Popielarczyk ◽  
Adam Ciecko
Keyword(s):  
Mutual Influence ◽  
Signal To Noise Ratio ◽  
Reference Signal ◽  
Global Navigation Satellite Systems ◽  
Data Sets ◽  
Stability Parameters ◽  
Satellite Systems ◽  
Gnss Receiver ◽  
Satellite Positioning ◽  
Global Navigation Satellite

Even though satellite positioning has been used in ground penetrating radar (GPR) measurements for years, there are no studies ruling out the influence of modern satellite positioning receivers on the operation of GPR antennas. In order to rule out mutual influence between devices, a field study was carried out to determine the possible influence of a Global Navigation Satellite Systems (GNSS) receiver on the results obtained from GPR. To this end, several equipment combinations based on two receivers were compared. This was followed by a numerical analysis of selected samples from the recorded data sets. The following were calculated: average values of signal amplitudes, their standard deviations and the signal-to-noise ratio, coefficient of variation, and signal stability parameters. We also suggested using a modified standard deviation based on the properties of the reference signal. Based on the results, we concluded that there were rather significant changes between the data sets for various equipment combinations, which may indicate that a GNSS receiver affects GPR data in some way. However, the influence was not significant enough to result in the qualitative misinterpretation of data.

scholarly journals GNSS-Reflectometry and Remote Sensing of Soil Moisture: A Review of Measurement Techniques, Methods, and Applications

2020 ◽  
Vol 12 (4) ◽  
pp. 614 ◽  
Author(s):  
Komi Edokossi ◽  
Andres Calabia ◽  
Shuanggen Jin ◽  
Iñigo Molina
Keyword(s):  
Remote Sensing ◽  
Soil Moisture ◽  
Land Surface ◽  
Low Cost ◽  
Measurement Techniques ◽  
Passive Microwave ◽  
Global Navigation Satellite Systems ◽  
Ecological Processes ◽  
Satellite Systems ◽  
Global Navigation Satellite

The understanding of land surface-atmosphere energy exchange is extremely important for predicting climate change and weather impacts, particularly the influence of soil moisture content (SMC) on hydrometeorological and ecological processes, which are also linked to human activities. Unfortunately, traditional measurement methods are expensive and cumbersome over large areas, whereas measurements from satellite active and passive microwave sensors have shown advantages for SMC monitoring. Since the launch of the first passive microwave satellite in 1978, more and more progresses have been made in monitoring SMC from satellites, e.g., the Soil Moisture Active and Passive (SMAP) and Soil Moisture and Ocean Salinity (SMOS) missions in the last decade. Recently, new methods using signals of opportunity have been emerging, highlighting the Global Navigation Satellite Systems-Reflectometry (GNSS-R), which has wide applications in Earth’s surface remote sensing due to its numerous advantages (e.g., revisiting time, global coverage, low cost, all-weather measurements, and near real-time) when compared to the conventional observations. In this paper, a detailed review on the current SMC measurement techniques, retrieval approaches, products, and applications is presented, particularly the new and promising GNSS-R technique. Recent advances, future prospects and challenges are given and discussed.

scholarly journals Hybrid Data Fusion and Tracking for Positioning with GNSS and 3GPP-LTE

2010 ◽  
Vol 2010 ◽  
pp. 1-12 ◽  
Author(s):  
Christian Mensing ◽  
Stephan Sand ◽  
Armin Dammann
Keyword(s):  
Data Fusion ◽  
Global Navigation Satellite Systems ◽  
Optimum Conditions ◽  
Satellite Systems ◽  
3Gpp Lte ◽  
User Simulation ◽  
Multipath Effects ◽  
Hybrid Data ◽  
Global Navigation Satellite ◽  
Communications System

Global navigation satellite systems (GNSSs) can provide reliable positioning information under optimum conditions, where at least four satellites can be accessed with sufficient quality. In critical situations, for example, urban canyons or indoor, due to blocking of satellites by buildings and severe multipath effects, the GNSS performance can be decreased substantially. To overcome this limitation, we propose to exploit additionally information from communications systems for positioning purposes, for example, by using time difference of arrival (TDOA) information. To optimize the performance, hybrid data fusion and tracking algorithms can combine both types of sources and further exploit the mobility of the user. Simulation results for different filter types show the ability of this approach to compensate the lack of satellites by additional TDOA measurements from a future 3GPP-LTE communications system. This paper analyzes the performance in a fairly realistic manner by taking into account ray-tracing simulations to generate a coherent environment for GNSS and 3GPP-LTE.

scholarly journals Estimating Wave Direction Using Terrestrial GNSS Reflectometry

2019 ◽  
Vol 11 (9) ◽  
pp. 1027 ◽  
Author(s):  
Reinking ◽  
Roggenbuck ◽  
Even-Tzur
Keyword(s):  
Correlation Length ◽  
Signal To Noise Ratio ◽  
Simulated Data ◽  
Global Navigation Satellite Systems ◽  
Wave Direction ◽  
Satellite Systems ◽  
The North ◽  
Scattered Power ◽  
Length Changes ◽  
Global Navigation Satellite

The signal-to-noise ratio (SNR) data are part of the global navigation satellite systems (GNSS) observables. In a marine environment, the oscillation of the SNR data can be used to derive reflector heights. Since the attenuation of the SNR oscillation is related to the roughness of the sea surface, the significant wave height (SWH) of the water surface can be calculated from the analysis of the attenuation. The attenuation depends additionally on the relation between the coherent and the incoherent part of the scattered power. The latter is a function of the correlation length of the surface waves. Since the correlation length changes with respect to the direction of the line of sight relative to the wave direction, the attenuation must show an anisotropic characteristic. In this work, we present a method to derive the wave direction from the anisotropy of the attenuation of the SNR data. The method is investigated based on simulated data, as well by the analysis of experimental data from a GNSS station in the North Sea.

scholarly journals GPS Multipath Analysis Using Fresnel Zones

Sensors ◽  
2018 ◽  
Vol 19 (1) ◽  
pp. 25 ◽  
Author(s):  
Florian Zimmermann ◽  
Berit Schmitz ◽  
Lasse Klingbeil ◽  
Heiner Kuhlmann
Keyword(s):  
Fresnel Zone ◽  
Position Estimation ◽  
Global Navigation Satellite Systems ◽  
Limiting Factors ◽  
Systematic Effect ◽  
Satellite Systems ◽  
Multipath Effects ◽  
The Individual ◽  
Global Navigation Satellite ◽  
Fresnel Zones

GNSS (Global Navigation Satellite Systems) multipath has been subject to scientific research for decades and although numerous methods and techniques have already been developed to mitigate this effect, it is still one of the accuracy-limiting factors in many GNSS applications. Since multipath is highly dependent on the individual antenna environment, there is still a need for new methods and further investigations to increase the understanding of this systematic effect. In this paper, the concept of Fresnel zones is applied to two different aspects of multipath. First, Fresnel zones are determined for the line-of-sight transmission between satellite and receiver. By comparing the boundary of the Fresnel zones to an obstruction adaptive elevation mask, potentially diffracted signals can be identified and excluded from the position estimation process. Both the percentage of epochs with fixed ambiguities and the positioning accuracy can be increased by the proposed method. Second, Fresnel zones are used to analyze the multipath induced by a horizontal and spatially-limited reflector. The comparison of simulated and real signal-to-noise (SNR) observations reveals a relationship between the percentage of the overlap of the Fresnel zone and reflector and the occurrence of multipath. It is found that an overlap of 50% is sufficient to induce multipath effects. This is of special interest, since this does not confirm theoretical assumptions of the multipath theory.

scholarly journals Sensitivity of TDS-1 GNSS-R Reflectivity to Soil Moisture: Global and Regional Differences and Impact of Different Spatial Scales

2018 ◽  
Vol 10 (11) ◽  
pp. 1856 ◽  
Author(s):  
Adriano Camps ◽  
Mercedes Vall·llossera ◽  
Hyuk Park ◽  
Gerard Portal ◽  
Luciana Rossato
Keyword(s):  
Soil Moisture ◽  
Land Surface ◽  
Incidence Angle ◽  
Spatial Scales ◽  
Ground Truth ◽  
Global Navigation Satellite Systems ◽  
Satellite Systems ◽  
Left Hand ◽  
The Uk ◽  
Global Navigation Satellite

The potential of Global Navigation Satellite Systems-Reflectometry (GNSS-R) techniques to estimate land surface parameters such as soil moisture (SM) is experimentally studied using 2014–2017 global data from the UK TechDemoSat-1 (TDS-1) mission. The approach is based on the analysis of the sensitivity to SM of different observables extracted from the Delay Doppler Maps (DDM) computed by the Space GNSS Receiver–Remote Sensing Instrument (SGR-ReSI) instrument using the L1 (1575.42 MHz) left-hand circularly-polarized (LHCP) reflected signals emitted by the Global Positioning System (GPS) navigation satellites. The sensitivity of different GNSS-R observables to SM and its dependence on the incidence angle is analyzed. It is found that the sensitivity of the calibrated GNSS-R reflectivity to surface soil moisture is ~0.09 dB/% up to 30° incidence angle, and it decreases with increasing incidence angles, although differences are found depending on the spatial scale used for the ground-truth, and the region. The sensitivity to subsurface soil moisture has been also analyzed using a network of subsurface probes and hydrological models, apparently showing some dependence, but so far results are not conclusive.

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