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 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.

scholarly journals Assessment of Empirical Troposphere Model GPT3 Based on NGL’s Global Troposphere Products

Sensors ◽  
2020 ◽  
Vol 20 (13) ◽  
pp. 3631
Author(s):  
Junsheng Ding ◽  
Junping Chen
Keyword(s):  
Global Navigation Satellite Systems ◽  
Tropospheric Delay ◽  
Strongly Correlated ◽  
International Gnss Service ◽  
Total Delay ◽  
Average Deviation ◽  
Satellite Systems ◽  
Global Average ◽  
The North ◽  
Global Navigation Satellite

Tropospheric delay is one of the major error sources in GNSS (Global Navigation Satellite Systems) positioning. Over the years, many approaches have been devised which aim at accurately modeling tropospheric delays, so-called troposphere models. Using the troposphere data of over 16,000 global stations in the last 10 years, as calculated by the Nevada Geodetic Laboratory (NGL), this paper evaluates the performance of the empirical troposphere model GPT3, which is the latest version of the GPT (Global Pressure and Temperature) series model. Owing to the large station number, long time-span and diverse station distribution, the spatiotemporal properties of the empirical model were analyzed using the average deviation (BIAS) and root mean square (RMS) error as indicators. The experimental results demonstrate that: (1) the troposphere products of NGL have the same accuracy as the IGS (International GNSS Service) products and can be used as a reference for evaluating general troposphere models. (2) The global average BIAS of the ZTD (zenith total delay) estimated by GPT3 is −0.99 cm and the global average RMS is 4.41 cm. The accuracy of the model is strongly correlated with latitude and ellipsoidal height, showing obviously seasonal variations. (3) The global average RMS of the north gradient and east gradient estimated by GPT3 is 0.77 mm and 0.73 mm, respectively, which are strongly correlated with each other, with values increasing from the equator to lower latitudes and decreasing from lower to higher latitudes.

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).

scholarly journals The contribution of engineering surveys by means of GPS to the determination of crustal movements in Istanbul

2011 ◽  
Vol 11 (6) ◽  
pp. 1705-1713 ◽  
Author(s):  
M. Özyaşar ◽  
M. T. Özlüdemir
Keyword(s):  
Positional Information ◽  
Global Navigation Satellite Systems ◽  
Marmara Region ◽  
Satellite Systems ◽  
Geodetic Networks ◽  
The North ◽  
Richter Scale ◽  
Tectonically Active ◽  
Vertical Displacements ◽  
Global Navigation Satellite

Abstract. Global Navigation Satellite Systems (GNSS) are space based positioning techniques and widely used in geodetic applications. Geodetic networking accomplished by engineering surveys constitutes one of these tasks. Geodetic networks are used as the base of all kinds of geodetic implementations, Co from the cadastral plans to the relevant surveying processes during the realization of engineering applications. Geodetic networks consist of control points positioned in a defined reference frame. In fact, such positional information could be useful for other studies as well. One of such fields is geodynamic studies that use the changes of positions of control stations within a network in a certain time period to understand the characteristics of tectonic movements. In Turkey, which is located in tectonically active zones and struck by major earthquakes quite frequently, the positional information obtained in engineering surveys could be very useful for earthquake related studies. For this purpose, a GPS (Global Positioning System) network of 650 stations distributed over Istanbul (Istanbul GPS Triangulation Network; abbreviated IGNA) covering the northern part of the North Anatolian Fault Zone (NAFZ) was established in 1997 and measured in 1999. From 1998 to 2004, the IGNA network was extended to 1888 stations covering an area of about 6000 km2, the whole administration area of Istanbul. All 1888 stations within the IGNA network were remeasured in 2005. In these two campaigns there existed 452 common points, and between these two campaigns two major earthquakes took place, on 17 August and 12 November 1999 with a Richter scale magnitude of 7.4 and 7.2, respectively. Several studies conducted for estimating the horizontal and vertical displacements as a result of these earthquakes on NAFZ are discussed in this paper. In geodynamic projects carried out before the earthquakes in 1999, an annual average velocity of 2–2.5 cm for the stations along the NAFZ were estimated. Studies carried out using GPS observations in the same area after these earthquakes indicated that point displacements vary depending on their distance to the epicentres of the earthquakes. But the directions of point displacements are similar. The results obtained through the analysis of the IGNA network also show that there is a common trend in the directions of point displacements in the study area. In this paper, the past studies about the tectonics of Marmara region are summarised and the results of the displacement analysis on the IGNA network are discussed.

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.

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.

Slip Complementarity and Triggering between the Foreshock, Mainshock, and Afterslip of the 2019 Ridgecrest Rupture Sequence

2020 ◽  
Vol 110 (4) ◽  
pp. 1701-1715 ◽  
Author(s):  
Qiang Qiu ◽  
Sylvain Barbot ◽  
Teng Wang ◽  
Shengji Wei
Keyword(s):  
Joint Inversion ◽  
Stress Transfer ◽  
Strong Motion ◽  
Global Navigation Satellite Systems ◽  
Fault System ◽  
Coseismic Slip ◽  
Satellite Systems ◽  
The North ◽  
Global Navigation Satellite ◽  
Lower Crustal

ABSTRACT We investigate the deformation processes during the 2019 Ridgecrest earthquake sequence by combining Global Navigation Satellite Systems, strong-motion, and Interferometric Synthetic Aperture Radar datasets in a joint inversion. The spatial complementarity of slip between the Mw 6.4 foreshock, Mw 7.1 mainshock, and afterslip suggests the importance of static stress transfer as a triggering mechanism during the rupture sequence. The coseismic slip of the foreshock concentrates mainly on the east-northeast–west-southwest fault above the hypocenter at depths of 2–8 km. The slip distribution of the mainshock straddles the region above the hypocenter with two isolated patches located to the north-northwest and south-southeast, respectively. The geodetically determined moment magnitudes of the foreshock and mainshock are equivalent to moment magnitudes Mw 6.4 and 7.0, assuming a rigidity of 30 GPa. We find a significant shallow slip deficit (>60%) in the Ridgecrest ruptures, likely resulting from the immature fault system in which the sequence occurred. Rapid afterslip concentrates at depths of 2–6 km, surrounding the rupture areas of the foreshock and mainshock. The ruptures also accelerated viscoelastic flow at lower-crustal depths. The Garlock fault was loaded at several locations, begging the question of possible delayed triggering.

Migrating from ATS77 to NAD83(CSRS) in Nova Scotia

GEOMATICA ◽  
2017 ◽  
Vol 71 (2) ◽  
pp. 75-87
Author(s):  
Jason Bond
Keyword(s):  
Nova Scotia ◽  
Global Navigation Satellite Systems ◽  
Transformation Model ◽  
Mapping Data ◽  
Satellite Systems ◽  
Spatial Reference ◽  
The North ◽  
Coordinate Control ◽  
Original Size ◽  
Global Navigation Satellite

Since the late 1970s, the foundation for all survey work in Nova Scotia has been the Nova Scotia Coordinate Control System (NSCCS), which is based upon the Average Terrestrial System of 1977 (ATS77). In the early 2000s, some provincial mapping layers were migrated to the North American Datum of 1983 (based upon the Canadian Spatial Reference System (NAD83(CSRS)), but many still utilize ATS77. In 2012, the province began modernizing its Coordinate Referencing program using Global Navigation Satellite Systems (GNSS) and imple menting Active Control Stations (ACSs). The installation of 40 ACSs across the province between 2012 and 2015 enables the surveying community in Nova Scotia to migrate to NAD83(CSRS) by addressing ongoing accuracy and accessibility needs. The tech nology has allowed the passive, NAD83(CSRS)-based, Nova Scotia High Precision Network to expand to more than five times its original size. This densification effort has also allowed the transformation model between the two datums to be enhanced. With the geodetic infrastructure in place, the current primary need is for knowledge and methodologies to facilitate the transition. Two options are presented to aid surveyors and mappers in migrating data from ATS77 to NAD83(CSRS). The first approach utilizes a newly developed grid shift file intended for transforming mapping data and aiding surveyors in relocating boundary evidence, so that it can then be remeasured in NAD83(CSRS). A detailed discussion is provided on the development of grid shift file. The second approach is based upon the derivation of a set of local transformation parameters using a one-to-one sampling of the control monuments used in the historic survey.

scholarly journals Identifying 2010 Xynthia Storm Signature in GNSS-R-Based Tide Records

2019 ◽  
Vol 11 (7) ◽  
pp. 782 ◽  
Author(s):  
Phuong Lan Vu ◽  
Minh Cuong Ha ◽  
Frédéric Frappart ◽  
José Darrozes ◽  
Guillaume Ramillien ◽  
...  
Keyword(s):  
Atmospheric Pressure ◽  
Tide Gauge ◽  
Signal To Noise Ratio ◽  
Atlantic Coast ◽  
Singular Spectrum Analysis ◽  
Global Navigation Satellite Systems ◽  
Blind Separation ◽  
Tide Gauge Records ◽  
Satellite Systems ◽  
Global Navigation Satellite

In this study, three months of records (January–March 2010) that were acquired by a geodetic Global Navigation Satellite Systems (GNSS) station from the permanent network of RGP (Réseau GNSS Permanent), which was deployed by the French Geographic Institute (IGNF), located in Socoa, in the south of the Bay of Biscay, were used to determine the tide components and identify the signature of storms on the signal to noise ratio (SNR) during winter 2010. The Xynthia storm hit the French Atlantic coast on the 28th of February 2010, causing large floods and damages from the Gironde to the Loire estuaries. Blind separation of the tide components and of the storm signature was achieved while using both a singular spectrum analysis (SSA) and a continuous wavelet transform (CWT). A correlation of 0.98/0.97 and root mean square error (RMSE) of 0.21/0.28 m between the tide gauge records of Socoa and our estimates of the sea surface height (SSH) using the SSA and the CWT, respectively, were found. Correlations of 0.76 and 0.7 were also obtained between one of the modes from the SSA and atmospheric pressure from a meteorological station and a mode of the SSA. Particularly, a correlation reaches to 0.76 when using both the tide residual that is associated to surges and atmospheric pressure variation.

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