scholarly journals A Spatial-Temporal Approach Based on Antenna Array for GNSS Anti-Spoofing

Sensors ◽  
2021 ◽  
Vol 21 (3) ◽  
pp. 929
Author(s):  
Yuqing Zhao ◽  
Feng Shen ◽  
Guanghui Xu ◽  
Guochen Wang
Keyword(s):  
Antenna Array ◽  
Doa Estimation ◽  
Satellite System ◽  
Oblique Projection ◽  
Power Comparison ◽  
Signal Model ◽  
Baseband Signal ◽  
Gnss Receivers ◽  
Navigation Signals ◽  
Global Navigation Satellite

The presence of spoofing signals poses a significant threat to global navigation satellite system (GNSS)-based positioning applications, as it could cause a malfunction of the positioning service. Therefore, the main objective of this paper is to present a spatial-temporal technique that enables GNSS receivers to reliably detect and suppress spoofing. The technique, which is based on antenna array, can be divided into two consecutive stages. In the first stage, an improved eigen space spectrum is constructed for direction of arrival (DOA) estimation. To this end, a signal preprocessing scheme is provided to solve the signal model mismatch in the DOA estimation for navigation signals. In the second stage, we design an optimization problem for power estimation with the estimated DOA as support information. After that, the spoofing detection is achieved by combining power comparison and cross-correlation monitoring. Finally, we enhance the genuine signals by beamforming while the subspace oblique projection is used to suppress spoofing. The proposed technique does not depend on external hardware and can be readily implemented on raw digital baseband signal before the despreading of GNSS receivers. Crucially, the low-power spoofing attack and multipath can be distinguished and mitigated by this technique. The estimated DOA and power are both beneficial for subsequent spoofing localization. The simulation results demonstrate the effectiveness of our method.

scholarly journals The Unbiased Characteristic of Doppler Frequency in GNSS Antenna Array Processing

2019 ◽  
Vol 2019 ◽  
pp. 1-10
Author(s):  
Yuchen Xie ◽  
Zhengrong Li ◽  
Feiqiang Chen ◽  
Huaming Chen ◽  
Feixue Wang
Keyword(s):  
Antenna Array ◽  
Carrier Phase ◽  
Array Processing ◽  
Doppler Frequency ◽  
Low Complexity ◽  
Satellite System ◽  
Accurate Estimation ◽  
Array Technology ◽  
Gnss Receivers ◽  
Global Navigation Satellite

The antenna array technology, especially the spaced-time array processing (STAP), is one of the effective methods used in Global Navigation Satellite System (GNSS) receivers to refrain the power of jamming and enhance the performance of receivers in the circumstance of interference. However, biases induced to the receiver because of many reasons, including characteristic of antennas, front-end channel electronics, and space-time filtering, are extremely harmful to the high precise positioning of receivers. Although plenty of works have been done to calibrate the antenna and to mitigate these biases, achieving a good performance of antijamming, high accuracy, and low complexity at the same time still remains challenging. Different from existing works, this paper leverages the characteristic of GNSS signal’s Doppler frequency in STAP, which is proven to remain unbiased to solve the problem, even when the nonideal antennas are used and the interference circumstance changes. Since the integration of frequency is carrier phase, the unbiased Doppler frequency leads to an accurate estimation of carrier phase which can be used to calibrate the antenna array without extra apparatus or complicating algorithms. Therefore, a simple Doppler-aid strategy may be developed in the future to solve the difficulty of STAP bias mitigation.

scholarly journals GNSS Multipath Detection Using Continuous Time-Series C/N0

Sensors ◽  
2020 ◽  
Vol 20 (14) ◽  
pp. 4059
Author(s):  
Nobuaki Kubo ◽  
Kaito Kobayashi ◽  
Rei Furukawa
Keyword(s):  
Time Series ◽  
Continuous Time ◽  
Urban Areas ◽  
Satellite System ◽  
Line Of Sight ◽  
Static Tests ◽  
Gnss Receivers ◽  
Multipath Detection ◽  
Global Navigation Satellite ◽  
Multipath Errors

The reduction of multipath errors is a significant challenge in the Global Navigation Satellite System (GNSS), especially when receiving non-line-of-sight (NLOS) signals. However, selecting line-of-sight (LOS) satellites correctly is still a difficult task in dense urban areas, even with the latest GNSS receivers. This study demonstrates a new method of utilization of C/N0 of the GNSS to detect NLOS signals. The elevation-dependent threshold of the C/N0 setting may be effective in mitigating multipath errors. However, the C/N0 fluctuation affected by NLOS signals is quite large. If the C/N0 is over the threshold, the satellite is used for positioning even if it is still affected by the NLOS signal, which causes the positioning error to jump easily. To overcome this issue, we focused on the value of continuous time-series C/N0 for a certain period. If the C/N0 of the satellite was less than the determined threshold, the satellite was not used for positioning for a certain period, even if the C/N0 recovered over the threshold. Three static tests were conducted at challenging locations near high-rise buildings in Tokyo. The results proved that our method could substantially mitigate multipath errors in differential GNSS by appropriately removing the NLOS signals. Therefore, the performance of real-time kinematic GNSS was significantly improved.

scholarly journals Application of Least Squares with Conditional Equations Method for Railway Track Inventory Using GNSS Observations

Sensors ◽  
2020 ◽  
Vol 20 (17) ◽  
pp. 4948
Author(s):  
Krzysztof Czaplewski ◽  
Zbigniew Wisniewski ◽  
Cezary Specht ◽  
Andrzej Wilk ◽  
Wladyslaw Koc ◽  
...  
Keyword(s):  
Measurement Data ◽  
Satellite System ◽  
Theoretical Description ◽  
Railway Track ◽  
Land Surveying ◽  
Gnss Receivers ◽  
Mobile Satellite ◽  
Global Navigation Satellite ◽  
Gnss Observations ◽  
Observation Results

Satellite geodetic networks are commonly used in surveying tasks, but they can also be used in mobile surveys. Mobile satellite surveys can be used for trackage inventory, diagnostics and design. The combination of modern technological solutions with the adaptation of research methods known in other fields of science offers an opportunity to acquire highly accurate solutions for railway track inventory. This article presents the effects of work carried out using a mobile surveying platform on which Global Navigation Satellite System (GNSS) receivers were mounted. The satellite observations (surveys) obtained were aligned using one of the methods known from classical land surveying. The records obtained during the surveying campaign on a 246th km railway track section were subjected to alignment. This article provides a description of the surveying campaign necessary to obtain measurement data and a theoretical description of the method employed to align observation results as well as their visualisation.

scholarly journals Testing Multi-Frequency Low-Cost GNSS Receivers for Geodetic Monitoring Purposes

Sensors ◽  
2020 ◽  
Vol 20 (16) ◽  
pp. 4375
Author(s):  
Veton Hamza ◽  
Bojan Stopar ◽  
Tomaž Ambrožič ◽  
Goran Turk ◽  
Oskar Sterle
Keyword(s):  
Low Cost ◽  
Base Point ◽  
Satellite System ◽  
Gnss Receivers ◽  
The Difference ◽  
Short Baselines ◽  
Height Component ◽  
Global Navigation Satellite ◽  
High Level ◽  
Positional Precision

Global Navigation Satellite System (GNSS) technology is widely used for geodetic monitoring purposes. However, in cases where a higher risk of receiver damage is expected, geodetic GNSS receivers may be considered too expensive to be used. As an alternative, low-cost GNSS receivers that are cheap, light, and prove to be of adequate quality over short baselines, are considered. The main goal of this research is to evaluate the positional precision of a multi-frequency low-cost instrument, namely, ZED-F9P with u-blox ANN-MB-00 antenna, and to investigate its potential for displacement detection. We determined the positional precision within static survey, and the displacement detection within dynamic survey. In both cases, two baselines were set, with the same rover point equipped with a low-cost GNSS instrument. The base point of the first baseline was observed with a geodetic GNSS instrument, whereas the second baseline was observed with a low-cost GNSS instrument. The results from static survey for both baselines showed comparable results for horizontal components; the precision was on a level of 2 mm or better. For the height component, the results show a better performance of low-cost instruments. This may be a consequence of unknown antenna calibration parameters for low-cost GNSS antenna, while statistically significant coordinates of rover points were obtained from both baselines. The difference was again more significant in the height component. For the displacement detection, a device was used that imposes controlled movements with sub-millimeter accuracy. Results, obtained on a basis of 30-min sessions, show that low-cost GNSS instruments can detect displacements from 10 mm upwards with a high level of reliability. On the other hand, low-cost instruments performed slightly worse as far as accuracy is concerned.

scholarly journals CORS ARCHITECTURE AND EVALUATION OF POSITIONING BY LOW-COST GNSS RECEIVER

2018 ◽  
Vol 44 (2) ◽  
pp. 36-44 ◽  
Author(s):  
Massimiliano Pepe
Keyword(s):  
Low Cost ◽  
Satellite System ◽  
Ease Of Use ◽  
Quality Data ◽  
Gnss Receiver ◽  
Stop And Go ◽  
Gnss Receivers ◽  
Spatial Positioning ◽  
Global Navigation Satellite

In recent years, the use of low cost GNSS receivers is becoming widespread due to their increasing performance in the spatial positioning, flexibility, ease of use and really interesting price. In addition, a recent technique of Global Navigation Satellite System (GNSS) survey, called Network Real Time Kinematic (NRTK), allows to obtain to rapid and accurate positioning measurements. The main feature of this approach is to use the raw measurements obtained and stored from a network of Continuously Operating Reference Stations (CORS) in order to generate more reliable error models that can mitigate the distance-dependent errors within the area covered by the CORS. Also, considering the huge potential of this GNSS positioning system, the purpose of this paper is to analyze and investigate the performance of the NTRK approach using a low cost GNSS receiver, in stop-and-go kinematic technique. By several case studies it was shown that, using a low cost RTK board for Arduino environment, a smartphone with open source application for Android and the availability of data correction from CORS service, a quick and accurate positioning can be obtained. Because the measures obtained in this way are quite noisy and, more in general, increasing with the baseline, by a simple and suitable statistic treatment, it was possible to increase the quality of the measure. In this way, this low cost architecture could be applied in many geomatics fields. In addition to presenting the main aspects of the NTRK infrastructure and a review of several types of correction, a general workflow in order to obtain quality data in NRTK mode, regardless of the type of GNSS receiver (multi constellations, single or many frequencies, etc.) is discussed.

scholarly journals GEOMATIC METHODS APPLIED TO THE CHANGE STUDY OF THE LA PAÚL ROCK GLACIER, SPANISH PYRENEES

2019 ◽  
Vol XLII-2/W13 ◽  
pp. 1771-1775
Author(s):  
A. Martínez-Fernández ◽  
E. Serrano ◽  
J. J. Sanjosé ◽  
M. Gómez-Lende ◽  
A. Pisabarro ◽  
...  
Keyword(s):  
Laser Scanning ◽  
Satellite System ◽  
Ice Age ◽  
Rock Glacier ◽  
Glacier Surface ◽  
The North ◽  
Spanish Pyrenees ◽  
Gnss Receivers ◽  
Rock Glaciers ◽  
Global Navigation Satellite

<p><strong>Abstract.</strong> Rock glaciers are one of the most important features of the mountain permafrost in the Pyrenees. La Paúl is an active rock glacier located in the north face of the Posets massif in the La Paúl glacier cirque (Spanish Pyrenees). This study presents the preliminary results of the La Paúl rock glacier monitoring works carried out through two geomatic technologies since 2013: Global Navigation Satellite System (GNSS) receivers and Terrestrial Laser Scanning (TLS) devices. Displacements measured on the rock glacier surface have demonstrated both the activity of the rock glacier and the utility of this equipment for the rock glaciers dynamic analysis. The glacier has exhibited the fastest displacements on its west side (over 35&amp;thinsp;cm&amp;thinsp;yr<sup>&amp;minus;1</sup>), affected by the Little Ice Age, and frontal area (over 25&amp;thinsp;cm&amp;thinsp;yr<sup>&amp;minus;1</sup>). As an indicator of permafrost in marginal environments and its peculiar morphology, La Paúl rock glacier encourages a more prolonged study and to the application of more geomatic techniques for its detailed analysis.</p>

scholarly journals RECEPTORES DE SINAIS DO SISTEMA GLOBAL DE NAVEGAÇÃO POR SATÉLITE SUBMETIDOS A INTERFERÊNCIAS FÍSICAS

2020 ◽  
Vol 35 (1) ◽  
pp. 115-125
Author(s):  
João Luiz Jacintho ◽  
Gabriel Araújo e Silva Ferraz ◽  
Lucas Santos Santana ◽  
Patrícia Ferreira Ponciano Ferraz
Keyword(s):  
Minimal Medium ◽  
Satellite System ◽  
Control Points ◽  
Satellite Navigation System ◽  
Accuracy And Precision ◽  
Agricultural Applications ◽  
Gnss Receivers ◽  
Survey Accuracy ◽  
Global Navigation Satellite ◽  
Interference Minimum

RECEPTORES DE SINAIS DO SISTEMA GLOBAL DE NAVEGAÇÃO POR SATÉLITE SUBMETIDOS A INTERFERÊNCIAS FÍSICAS   JOÃO LUIZ JACINTHO1, GABRIEL ARAÚJO E SILVA FERRAZ2, LUCAS SANTOS SANTANA3, PATRÍCIA FERREIRA PONCIANO FERRAZ4   1 Instituto Federal do Norte de Minas Gerais - IFNMG, Campus Araçuaí BR 367, km 278, s/n - Zona Rural, 39600-000, Araçuaí - MG, Brasil. [email protected]. 2 Departamento de Engenharia Agrícola, Universidade Federal de Lavras – UFLA, Aquenta Sol, 3037, 37200900, Lavras - MG, Brasil. [email protected]. 3Departamento de Engenharia Agrícola, Universidade Federal de Lavras – UFLA, Aquenta Sol, 3037, 37200900, Lavras - MG, Brasil. [email protected]. 4 Departamento de Engenharia Agrícola, Universidade Federal de Lavras – UFLA, Aquenta Sol, 3037, 37200900, Lavras - MG, Brasil. [email protected].   RESUMO: Incertezas são encontradas em trabalhos com receptores do Sistemas Global de Navegação por Satélite GNSS. Diante disso, objetivou-se com este estudo investigar a influência de obstáculos físicos nos erros de acurácia e precisão em levantamentos com receptores GNSS e suas aplicações agrícolas. Foram implantados quatros pontos de controle rastreados no modo estático (base) e oito pontos de estudos rastreados no modo cinemático em tempo real (RTK) e Estático Rápido (ER), utilizando um par de receptores GNSS e um par de receptores GNSS-RTK. Os níveis de acurácia e precisão foram avaliados em oito pontos obtidos por rastreios do tipo ER e RTK. Combinados com quatro bases fixas, alocados de três formas: mínima, média e alta interferência física. Pontos provenientes do levantamento RTK, apresentaram diferenças na ordem de milímetros a centímetros, quando comparados às coordenadas obtidas do levantamento (ER). Para os níveis de obstrução, a mínima interferência apresentou erro dentro dos limites estipulados pelo equipamento, a máxima interferência apresentou menor acurácia. O efeito do multipercurso do sinal foi o fator mais determinante para a redução da acurácia das coordenadas dos pontos. Recomenda-se a aplicação do levantamento RTK para trabalhos onde a precisão das coordenadas seja mais relevante que a acurácia.   Palavras-chaves: Geodésia, levantamento planialtimétrico, acurácia, precisão.   GLOBAL SATELLITE NAVIGATION SYSTEM RECEIVERS SUBMITTED TO PHYSICAL INTERFERENCES   ABSTRACT: Uncertainties are found in works with Global Navigation Satellite System receivers (GNSS). Therefore, this study aimed to investigate influence physical obstacles on accuracy and precision errors in surveys with GNSS receivers and their agricultural applications. Four control points tracked in static (base) mode and eight study points tracked in a kinematic mode in real-time (RTK) and Fast Static (ER) were implemented, using a pair of GNSS receivers and pair of GNSS-RTK receivers. Accuracy levels and precision were evaluated at eight points obtained by ER and RTK, combined with four fixed bases, allocated in three ways: minimal, medium and high physical interference. RTK survey points showed differences order millimeters to centimeters when compared to the survey (ER) coordinates. The obstruction levels, interference minimum, had an error within limits stipulated by equipment, interference maximum showed low accuracy. RTK survey is recommended for jobs where the coordinate precision is more relevant than accuracy.   Keywords: Geodesy, planialtimetric survey, accuracy, precision.

scholarly journals Towards Automatic UAS-Based Snow-Field Monitoring for Microclimate Research

Sensors ◽  
2019 ◽  
Vol 19 (8) ◽  
pp. 1945 ◽  
Author(s):  
Petr Gabrlik ◽  
Premysl Janata ◽  
Ludek Zalud ◽  
Josef Harcarik
Keyword(s):  
Rapid Development ◽  
Field Work ◽  
Satellite System ◽  
Mountain Range ◽  
Ground Control Points ◽  
Snow Covered Area ◽  
Covered Area ◽  
Gnss Receivers ◽  
Global Navigation Satellite ◽  
Optimum Solution

This article presents unmanned aerial system (UAS)-based photogrammetry as an efficient method for the estimation of snow-field parameters, including snow depth, volume, and snow-covered area. Unlike similar studies employing UASs, this method benefits from the rapid development of compact, high-accuracy global navigation satellite system (GNSS) receivers. Our custom-built, multi-sensor system for UAS photogrammetry facilitates attaining centimeter- to decimeter-level object accuracy without deploying ground control points; this technique is generally known as direct georeferencing. The method was demonstrated at Mapa Republiky, a snow field located in the Krkonose, a mountain range in the Czech Republic. The location has attracted the interest of scientists due to its specific characteristics; multiple approaches to snow-field parameter estimation have thus been employed in that area to date. According to the results achieved within this study, the proposed method can be considered the optimum solution since it not only attains superior density and spatial object accuracy (approximately one decimeter) but also significantly reduces the data collection time and, above all, eliminates field work to markedly reduce the health risks associated with avalanches.

scholarly journals Experimental Evaluation of the Impact of Different Types of Jamming Signals on Commercial GNSS Receivers

2020 ◽  
Vol 10 (12) ◽  
pp. 4240 ◽  
Author(s):  
Haidy Elghamrawy ◽  
Malek Karaim ◽  
Mohamed Tamazin ◽  
Aboelmaged Noureldin
Keyword(s):  
Satellite System ◽  
Signal Interference ◽  
Interference Signal ◽  
Long Distance ◽  
Wideband Signals ◽  
Global Positioning ◽  
Gnss Receivers ◽  
Propagation Medium ◽  
Global Navigation Satellite ◽  
The Impact

The received global navigation satellite system (GNSS) signal has a very low power due to traveling a very long distance and to the nature of the signal’s propagation medium. Thus, GNSS signals are easily susceptible to signal interference. Signal interference can cause severe degradation or interruption in GNSS position, navigation, and timing (PNT) services which could be very critical, especially in safety-critical applications. The objective of this paper is to evaluate the impact of the presence of jamming signals on a high-end GNSS receiver and investigate the benefits of using a multi-constellation system under such circumstances. Several jamming signals are considered in this research, including narrowband and wideband signals that are located on GPS L1 or GLONASS L1 frequency bands. Quasi-real dynamic trajectories are generated using the Spirent™ GSS6700 GNSS signal simulator combined with an interference signal generator through a Spirent™ GSS8366 unit. The performance evaluation was carried out using several evaluation metrics, including signal power degradation, navigation solution availability, dilution of precision (DOP), and positioning accuracy. The multi-constellation system presented better performance over the global positioning system (GPS)-only constellation in most cases. Moreover, jamming the GPS band caused more critical effects than jamming the GLONASS band.

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