Interference mitigation: impact on GNSS timing

AbstractWhile interference mitigation techniques can significantly improve the performance of a Global Navigation Satellite System (GNSS) receiver in the presence of jamming, they can also introduce distortions, biases and delays on the GNSS measurements and on the final receiver solution. We analyze the impact of five interference mitigation techniques on the solution provided by a GNSS timing receiver that operates in a known location and under static conditions. In this configuration, the receiver only estimates its clock bias and drift, which can be potentially affected by interference mitigation. The analysis has been performed considering a multiconstellation case, including GPS L1 Coarse Acquisition (C/A), Galileo E1b/c and Beidou B1c signals. Tests were also conducted on the wideband Galileo E5b modulation. In all cases, real jammers were used to challenge GNSS signal reception. The techniques analyzed are four Robust Interference Mitigation (RIM) approaches and the Adaptive Notch Filter (ANF). From the analysis, it emerges that RIM techniques do not affect the receiver clock bias and drift. On the other hand, the ANF introduces a modulation-dependent delay on the clock bias. This delay is difficult to predict and is common to signals adopting modulations with similar spectral characteristics. In this respect, interoperable signals such as the Galileo E1b/c and Beidou B1c components are affected in the same way by the ANF, which leaves the Galileo–Beidou intersystem bias unaltered. Stability analysis has also been performed: interference mitigation does not significantly increase the short-term characteristics of the estimated clock bias and drift for low jamming levels.

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Impact of Element Pattern on the Performance of GNSS Power-Inversion Adaptive Arrays

Electronics ◽

10.3390/electronics8101120 ◽

2019 ◽

Vol 8 (10) ◽

pp. 1120

Author(s):

Liu ◽

Li ◽

Lv ◽

Chen ◽

Keyword(s):

Interference Mitigation ◽

Satellite System ◽

Antenna Element ◽

Radiation Patterns ◽

Adaptive Arrays ◽

Reference Element ◽

Element Pattern ◽

Power Inversion ◽

Global Navigation Satellite ◽

The Impact

Power-inversion (PI) adaptive arrays are widely used in Global Navigation Satellite System (GNSS) receivers for interference mitigation. The effects of element patterns on the performance of PI adaptive arrays are investigated in this paper. To this end, the performance of adaptive arrays is investigated by Monte Carlo simulations, using CST Microwave Studio (Dassault Systems, Vélizy-Villacoublay, France) to calculate the radiation patterns of circular microstrip elements which are used to compute the adaptive weight and the adaptive array gain. It is shown that the performance of PI adaptive arrays is mainly dependent on the gain pattern of the reference antenna element rather than the non-reference elements because the algorithm essentially pushes the elements into an unequal position. Furthermore, the results show that the impact of mutual coupling on the performance of the antenna array can be associated with the radiation patterns of the reference element, which is helpful in selecting the optimum reference element without increasing computational complexity, especially for small GNSS arrays.

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Multi-Layer Defences for Robust GNSS Timing Retrieval

Sensors ◽

10.3390/s21237787 ◽

2021 ◽

Vol 21 (23) ◽

pp. 7787

Author(s):

Ciro Gioia ◽

Daniele Borio

Keyword(s):

Global Navigation Satellite System ◽

Interference Mitigation ◽

Satellite System ◽

Navigation Satellite ◽

Integrity Monitoring ◽

Gnss Receivers ◽

Mitigation Techniques ◽

Receiver Autonomous Integrity Monitoring ◽

Global Navigation Satellite

A multi-layered interference mitigation approach can significantly improve the performance of Global Navigation Satellite System (GNSS) receivers in the presence of jamming. In this work, three levels of defence are considered including: pre-correlation interference mitigation techniques, post-correlation measurement screening and FDE at the Position, Velocity, and Time (PVT) level. The performance and interaction of these receiver defences are analysed with specific focus on Robust Interference Mitigation (RIM), measurement screening through Lock Indicator (LIs) and Receiver Autonomous Integrity Monitoring (RAIM). The case of timing receivers with a known user position and using Galileo signals from different frequencies has been studied with Time-Receiver Autonomous Integrity Monitoring (T-RAIM) based on the Backward-Forward method. From the experimental analysis it emerges that RIM improves the quality of the measurements reducing the number of exclusions performed by T-RAIM. Effective measurements screening is also fundamental to obtain unbiased timing solutions: in this respect T-RAIM can provide the required level of reliability.

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Inventory of Locations of Old Mining Works Using LiDAR Data: A Case Study in Slovakia

Sustainability ◽

10.3390/su13126981 ◽

2021 ◽

Vol 13 (12) ◽

pp. 6981

Author(s):

Marcela Bindzarova Gergelova ◽

Slavomir Labant ◽

Jozef Mizak ◽

Pavel Sustek ◽

Lubomir Leicher

Keyword(s):

Satellite System ◽

Precise Determination ◽

Lidar Data ◽

Positional Accuracy ◽

Current Form ◽

Mining History ◽

Mining Works ◽

Gnss Measurements ◽

Global Navigation Satellite

The concept of further sustainable development in the area of administration of the register of old mining works and recent mining works in Slovakia requires precise determination of the locations of the objects that constitute it. The objects in this register have their uniqueness linked with the history of mining in Slovakia. The state of positional accuracy in the registration of objects in its current form is unsatisfactory. Different database sources containing the locations of the old mining works are insufficient and show significant locational deviations. For this reason, it is necessary to precisely locate old mining works using modern measuring technologies. The most effective approach to solving this problem is the use of LiDAR data, which at the same time allow determining the position and above-ground shape of old mining works. Two localities with significant mining history were selected for this case study. Positional deviations in the location of old mining works among the selected data were determined from the register of old mining works in Slovakia, global navigation satellite system (GNSS) measurements, multidirectional hill-shading using LiDAR, and accessible data from the open street map. To compare the positions of identical old mining works from the selected database sources, we established differences in the coordinates (ΔX, ΔY) and calculated the positional deviations of the same objects. The average positional deviation in the total count of nineteen objects comparing documents, LiDAR data, and the register was 33.6 m. Comparing the locations of twelve old mining works between the LiDAR data and the open street map, the average positional deviation was 16.3 m. Between the data sources from GNSS and the registry of old mining works, the average positional deviation of four selected objects was 39.17 m.

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Sea Topography of the Ionian and Adriatic Seas Using Repeated GNSS Measurements

Water ◽

10.3390/w13060812 ◽

2021 ◽

Vol 13 (6) ◽

pp. 812

Author(s):

Sotiris Lycourghiotis

Keyword(s):

Satellite System ◽

Geoid Model ◽

Sea Surface Topography ◽

Mean Sea Surface ◽

The Mean ◽

A New Technique ◽

Gnss Measurements ◽

Global Navigation Satellite ◽

Constant Slope ◽

Ionian And Adriatic Seas

The mean sea surface topography of the Ionian and Adriatic Seas has been determined. This was based on six-months of Global Navigation Satellite System (GNSS) measurements which were performed on the Ionian Queen (a ship). The measurements were analyzed following a double-path methodology based on differential GNSS (D-GNSS) and precise point positioning (PPP) analysis. Numerical filtering techniques, multi-parametric accuracy analysis and a new technique for removing the meteorological tide factors were also used. Results were compared with the EGM96 geoid model. The calculated differences ranged between 0 and 48 cm. The error of the results was estimated to fall within 3.31 cm. The 3D image of the marine topography in the region shows a nearly constant slope of 4 cm/km in the N–S direction. Thus, the effectiveness of the approach “repeated GNSS measurements on the same route of a ship” developed in the context of “GNSS methods on floating means” has been demonstrated. The application of this approach using systematic multi-track recordings on conventional liner ships is very promising, as it may open possibilities for widespread use of the methodology across the world.

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Measurement of the Sea Surface Height with Airborne GNSS Reflectometry and Delay Bias Calibration

Remote Sensing ◽

10.3390/rs13153014 ◽

2021 ◽

Vol 13 (15) ◽

pp. 3014

Author(s):

Feng Wang ◽

Dongkai Yang ◽

Guodong Zhang ◽

Jin Xing ◽

Bo Zhang ◽

...

Keyword(s):

Wind Speed ◽

Arrival Time ◽

Elevation Angle ◽

Satellite System ◽

Sea Surface Height ◽

Antenna Pattern ◽

Sea Surface ◽

Observation Method ◽

Global Navigation Satellite ◽

The Impact

Sea surface height can be measured with the delay between reflected and direct global navigation satellite system (GNSS) signals. The arrival time of a feature point, such as the waveform peak, the peak of the derivative waveform, and the fraction of the peak waveform is not the true arrival time of the specular signal; there is a bias between them. This paper aims to analyze and calibrate the bias to improve the accuracy of sea surface height measured by using the reflected signals of GPS CA, Galileo E1b and BeiDou B1I. First, the influencing factors of the delay bias, including the elevation angle, receiver height, wind speed, pseudorandom noise (PRN) code of GPS CA, Galileo E1b and BeiDou B1I, and the down-looking antenna pattern are explored based on the Z-V model. The results show that (1) with increasing elevation angle, receiver height, and wind speed, the delay bias tends to decrease; (2) the impact of the PRN code is uncoupled from the elevation angle, receiver height, and wind speed, so the delay biases of Galileo E1b and BeiDou B1I can be derived from that of GPS CA by multiplication by the constants 0.32 and 0.54, respectively; and (3) the influence of the down-looking antenna pattern on the delay bias is lower than 1 m, which is less than that of other factors; hence, the effect of the down-looking antenna pattern is ignored in this paper. Second, an analytical model and a neural network are proposed based on the assumption that the influence of all factors on the delay bias are uncoupled and coupled, respectively, to calibrate the delay bias. The results of the simulation and experiment show that compared to the meter-level bias before the calibration, the calibrated bias decreases the decimeter level. Based on the fact that the specular points of several satellites are visible to the down-looking antenna, the multi-observation method is proposed to calibrate the bias for the case of unknown wind speed, and the same calibration results can be obtained when the proper combination of satellites is selected.

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Present-day orogenic processes in the western Kalpin nappe explored by interseismic GNSS measurements and coseismic InSAR observations of the 2020 Mw 6.1 Kalpin event

Geophysical Journal International ◽

10.1093/gji/ggab097 ◽

2021 ◽

Author(s):

Ping He ◽

Yangmao Wen ◽

Shuiping Li ◽

Kaihua Ding ◽

Zhicai Li ◽

...

Keyword(s):

Source Parameters ◽

Satellite System ◽

Tien Shan ◽

Dislocation Model ◽

Maximum Displacement ◽

Finite Fault ◽

Instantaneous Deformation ◽

Gnss Measurements ◽

Global Navigation Satellite ◽

Finite Fault Model

Summary As the largest and most active intracontinental orogenic belt on Earth, the Tien Shan (TS) is a natural laboratory for understanding the Cenozoic orogenic processes driven by the India-Asia collision. On 19 January 2020, a Mw 6.1 event stuck the Kalpin region, where the southern frontal TS interacts with the Tarim basin. To probe the local ongoing orogenic processes and potential seismic hazard in the Kalpin region, both interseismic and instantaneous deformation derived from geodetic observations are employed in this study. With the constraint of interseismic global navigation satellite system (GNSS) velocities, we estimate the décollement plane parameters of the western Kalpin nappe based on a two-dimensional dislocation model, and the results suggest that the décollement plane is nearly subhorizontal with a dip of ∼3° at a depth of 24 km. Then, we collect both Sentinel-1 and ALOS-2 satellite images to capture the coseismic displacements caused by the 2020 Kalpin event, and the interferometric synthetic aperture radar (InSAR) images show a maximum displacement of 7 cm in the line of sight near the epicentral region. With these coseismic displacement measurements, we invert the source parameters of this event using a finite-fault model. We determine the optimal source mechanism in which the fault geometry is dominated by thrust faulting with an E–W strike of 275° and a northward dip of 11.2°, and the main rupture slip is concentrated within an area 28.0 km in length and${\rm{\,\,}}$10.3 km in width, with a maximum slip of 0.3 m at a depth of 6–8 km. The total released moment of our preferred distributed slip model yields a geodetic moment of 1.59 × 1018 N$\cdot $m, equivalent to Mw 6.1. The contrast of the décollement plane depth from interseismic GNSS and the rupture depth from coseismic InSAR suggests that a compression still exists in the Kalpin nappe forefront, which is prone to frequent moderate events and may be at risk of a much more dangerous earthquake.

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GNSS-Assisted Integrated Sensor Orientation with Sensor Pre-Calibration for Accurate Corridor Mapping

Sensors ◽

10.3390/s18092783 ◽

2018 ◽

Vol 18 (9) ◽

pp. 2783 ◽

Cited By ~ 12

Author(s):

Yilin Zhou ◽

Ewelina Rupnik ◽

Paul-Henri Faure ◽

Marc Pierrot-Deseilligny

Keyword(s):

Satellite System ◽

Sensor Calibration ◽

Image Block ◽

Integrated Sensor ◽

Physical Constraints ◽

Pose Determination ◽

Sensor Orientation ◽

Global Navigation Satellite ◽

Oblique Images ◽

The Impact

With the development of unmanned aerial vehicles (UAVs) and global navigation satellite system (GNSS), the accurate camera positions at exposure can be known and the GNSS-assisted bundle block adjustment (BBA) approach is possible for integrated sensor orientation (ISO). This study employed ISO approach for camera pose determination with the objective of investigating the impact of a good sensor pre-calibration on a poor acquisition geometry. Within the presented works, several flights were conducted on a dike by a small UAV embedded with a metric camera and a GNSS receiver. The multi-lever-arm estimation within the BBA procedure makes it possible to merge image blocks of different configurations such as nadir and oblique images without physical constraints on camera and GNSS antenna positions. The merged image block achieves a better accuracy and the sensor self-calibrated well. The issued sensor calibration is then applied to a less preferable acquisition configuration and the accuracy is significantly improved. For a corridor acquisition scene of about 600 m , a centimetric accuracy is reached with one GCP. With the provided sensor pre-calibration, an accuracy of 3.9 c m is achieved without any GCP.

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Georeferencing of Laser Scanner-Based Kinematic Multi-Sensor Systems in the Context of Iterated Extended Kalman Filters Using Geometrical Constraints

Sensors ◽

10.3390/s19102280 ◽

2019 ◽

Vol 19 (10) ◽

pp. 2280 ◽

Cited By ~ 3

Author(s):

Sören Vogel ◽

Hamza Alkhatib ◽

Johannes Bureick ◽

Rozhin Moftizadeh ◽

Ingo Neumann

Keyword(s):

State Constraints ◽

Laser Scanner ◽

Measurement Data ◽

Satellite System ◽

Sensor Systems ◽

Measurement Models ◽

Non Linear ◽

Geometrical Constraints ◽

Global Navigation Satellite ◽

The Impact

Georeferencing is an indispensable necessity regarding operating with kinematic multi-sensor systems (MSS) in various indoor and outdoor areas. Information from object space combined with various types of prior information (e.g., geometrical constraints) are beneficial especially in challenging environments where common solutions for pose estimation (e.g., global navigation satellite system or external tracking by a total station) are inapplicable, unreliable or inaccurate. Consequently, an iterated extended Kalman filter is used and a general georeferencing approach by means of recursive state estimation is introduced. This approach is open to several types of observation inputs and can deal with (non)linear systems and measurement models. The capability of using both explicit and implicit formulations of the relation between states and observations, and the consideration of (non)linear equality and inequality state constraints is a special feature. The framework presented is evaluated by an indoor kinematic MSS based on a terrestrial laser scanner. The focus here is on the impact of several different combinations of applied state constraints and the dependencies of two classes of inertial measurement units (IMU). The results presented are based on real measurement data combined with simulated IMU measurements.

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Testing the Positioning Accuracy of GNSS Solutions during the Tramway Track Mobile Satellite Measurements in Diverse Urban Signal Reception Conditions

Energies ◽

10.3390/en13143646 ◽

2020 ◽

Vol 13 (14) ◽

pp. 3646 ◽

Cited By ~ 6

Author(s):

Mariusz Specht ◽

Cezary Specht ◽

Andrzej Wilk ◽

Władysław Koc ◽

Leszek Smolarek ◽

...

Keyword(s):

Global Navigation Satellite System ◽

Geodetic Network ◽

Satellite System ◽

Railway Vehicle ◽

Navigation Satellite ◽

Design Work ◽

System Solution ◽

Global Navigation ◽

Global Navigation Satellite ◽

The Impact

Mobile Global Navigation Satellite System (GNSS) measurements carried out on the railway consist of using satellite navigation systems to determine the track geometry of a moving railway vehicle on a given route. Their purposes include diagnostics, stocktaking, and design work in railways. The greatest advantage of this method is the ability to perform measurements in a unified and coherent spatial reference system, which effectively enables the combining of design and construction works, as well as their implementation by engineering teams of diverse specialties. In the article, we attempted to assess the impact of using three types of work mode for a GNSS geodetic network [Global Positioning System (GPS), GPS/Global Navigation Satellite System (GLONASS) and GPS/GLONASS/Galileo] on positioning availability at three accuracy levels: 1 cm, 3 cm and 10 cm. This paper presents a mathematical model that enables the calculation of positioning availability at these levels. This model was also applied to the results of the measurement campaign performed by five GNSS geodetic receivers, made by a leading company in the field. Measurements with simultaneous position recording and accuracy assessment were taken separately on the same route for three types of receiver settings: GPS, GPS/GLONASS and GPS/GLONASS/Galileo in an urban area typical of a medium-sized city. The study has shown that applying a two-system solution (GPS/GLONASS) considerably increases the availability of high-precision coordinates compared to a single-system solution (GPS), whereas the measurements with three systems (GPS/GLONASS/Galileo) negligibly increase the availability compared to a two-system solution (GPS/GLONASS).

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Impact of ECOM Solar Radiation Pressure Models on Multi-GNSS Ultra-Rapid Orbit Determination

Remote Sensing ◽

10.3390/rs11243024 ◽

2019 ◽

Vol 11 (24) ◽

pp. 3024

Author(s):

Yang Liu ◽

Yanxiong Liu ◽

Ziwen Tian ◽

Xiaolei Dai ◽

Yun Qing ◽

...

Keyword(s):

Solar Radiation ◽

Real Time ◽

Radiation Pressure ◽

Orbit Determination ◽

Precise Orbit Determination ◽

Solar Radiation Pressure ◽

Satellite System ◽

Ambiguity Fixing ◽

Global Navigation Satellite ◽

The Impact

The Global Navigation Satellite System (GNSS) ultra-rapid precise orbits are crucial for global and wide-area real-time high-precision applications. The solar radiation pressure (SRP) model is an important factor in precise orbit determination. The real-time orbit determination is generally less accurate than the post-processed one and may amplify the instability and mismodeling of SRP models. Also, the impact of different SRP models on multi-GNSS real-time predicted orbits demands investigations. We analyzed the impact of the ECOM 1 and ECOM 2 models on multi-GNSS ultra-rapid orbit determination in terms of ambiguity resolution performance, real-time predicted orbit overlap precision, and satellite laser ranging (SLR) validation. The multi-GNSS observed orbital arc and predicted orbital arcs of 1, 3, 6, and 24 h are compared. The simulated real-time experiment shows that for GLONASS and Galileo ultra-rapid orbits, compared to ECOM 1, ECOM 2 increased the ambiguity fixing rate to 89.3% and 83.1%, respectively, and improves the predicted orbit accuracy by 9.2% and 27.7%, respectively. For GPS ultra-rapid orbits, ECOM 2 obtains a similar ambiguity fixing rate as ECOM 1 but slightly better orbit overlap precision. For BDS GEO ultra-rapid orbits, ECOM 2 obtains better overlap precision and SLR residuals, while for BDS IGSO and MEO ultra-rapid orbits, ECOM 1 obtains better orbit overlap precision and SLR residuals.

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