GNSS

There has been an increasing role played by Global Navigation Satellite Systems (GNSS) in Intelligent Transportation System (ITS) applications in recent decades. In particular, cen-timeter/decimetre positioning accuracy is required for some safety related applications, such as lane control, collision avoidance, and intelligent speed assistance. Lane-level Anomalous driving detection underpins these safety-related ITS applications. The two major issues associated with such detection are (1) accessing high accuracy vehicle positioning and dynamic parameters; and (2) extraction of irregular driving patterns from such information. This paper introduces a new integrated framework for detecting lane-level anomalous driving, by combining Global Positioning Systems (GPS), BeiDou, and Inertial Measurement Unit (IMU) with advanced algorithms. Specifically, we use Unscented Particle Filter (UPF) to perform data fusion with different positioning sources. The detection of different types of Anomalous driving is achieved based on the application of a Fuzzy Inference System (FIS) with a newly introduced velocity-based indicator. The framework proposed in this paper yield significantly improved accuracy in terms of positioning and Anomalous driving detection compared to state-of-the-art, while offering an economically viable solution for performing these tasks.

Розглянуто досвід використання GNSS методів збору інформації для побудови цифрових моделей рельєфу. Показано, що точність GNSS методів
(статика, кінематика, RTK, «Stop and Go») співмірна з даними, отриманими класичними методами.

USE GPS - AREA MAINTENANCE AT DEFINITION OF THE SQUARE OF THE GROUND AREAS.

The experience of the use of GNSS data collection methods for the construction of digital elevation models. It is shown that the accuracy of GNSS techniques (static, kinematic, RTK, «Stop and Go») commensurate with those obtained by classical methods.

Keskin M, M Akkamis, YE Sekerli. 2018. An Overview of GNSS and GPS based Velocity Measurement in Comparison to Other Techniques. International Conference on Energy Research (ENRES2018), 1-2 November 2018, Alanya, Turkey, Proceedings Book, pp.392-404.  ......... .......... .............. ........... ............ ............ .......... ............ ............ ..........
Abstract: GNSS-based speed sensing have some advantages over other methods with no moving parts, not affected by tire properties, dust, ground ruggedness, tall vegetation, suitability for measuring human speed, etc. However, GNSS receiver manufacturers do not provide detailed data on the accuracy of their products in velocity measurement under different conditions. Hence, studies are conducted to assess the speed accuracy of the GNSS receivers. This paper overviewed studies on the accuracy of GNSS receivers for speed measurement and basic knowledge on other methods was also included. Studies revealed key findings: GNSS units determine the speed based on three methods (travel distance/time, Doppler shift and time-differenced carrier phase, TDCP) and the TDCP method can offer better accuracy than the other two methods. GNSS receivers with higher update frequencies give more accurate speed data as compared to the lower ones, especially in varying speed conditions (acceleration and deceleration). High correlation exists between GPS velocity error and acceleration and deceleration (R2>0.70) in variable speeds meaning that the error rises in higher acceleration and decelerations. GPS units underestimate the speed as compared to the actual speeds. The accuracy of speed with DGPS was improved as compared to non-differential GPS. Adding GLONASS to GPS does not improve the performance considerably. HDOP might be used as a quality indicator for speed data reliability. Also, caution should be exercised for GNSS speed measurement under challenging environments (overpass, forest, urban area, etc.). ............ ............ ............ ............ ............ .......... ........... ............ ............ ........... ........... .......... ............. .......... ............
Özet: GNSS esaslı hız ölçümü tekniği diğer yöntemlere göre bazı avantajlara sahiptir: hareketli parça bulunmaması, teker ve lastik özelliklerinden, tozlanmadan, zemin yüzeyinin düz olmamasından, zeminde yüksek boylu bitki örtüsü olmasından etkilenmemesi ve insan hızını ölçmeye uygun olması. Ancak, GNSS alıcısı üreten firmalar, ürünlerinin farklı koşullardaki hız ölçümü doğruluğu konusunda yeterli bilgi sunmamaktadır. Bu nedenle, GNSS alıcılarının hız ölçüm doğruluğunu değerlendirmek için çalışmalar yürütülmektedir. Bu makalede, GNSS alıcılarının ve kıyaslamalı olarak diğer yöntemlerin hız ölçümündeki doğruluğu konusunda yapılan çalışmalar özetlenmiştir. Bu konuda yapılan çalışmalar, önemli bulgular ortaya koymuştur: GNSS alıcıları hızı üç yöntemle belirleyebilmektedir (Alınan yol/zaman, Doppler frekans kayması ve TDCP). TDCP yöntemi hız ölçümünde diğer iki yöntemden daha iyi doğruluk sağlayabilmektedir. Yüksek veri güncelleme frekansına sahip GNSS alıcıları, özellikle değişen hız koşullarında (hızlanma ve yavaşlama), düşük frekanslı olanlara kıyasla daha doğru hız verisi sağlamaktadır. Değişken hızlarda GPS hız ölçümü hatası ile hızlanma ve yavaşlama ivmesi arasında yüksek korelasyon (R2>0.70) bulunmaktadır, bu, hata değerinin yüksek ivmeli hareket durumunda arttığı anlamına gelmektedir. GPS alıcıları, gerçek hızı az miktarda daha düşük değerlerde tahmin etmektedir. Diferansiyel GPS (DGPS) ile ölçülen hızın doğruluğu, diferansiyel olmayan GPS ile karşılaştırıldığında artmaktadır. GPS'e ek olarak GLONASS uydularının kullanımı performansı önemli ölçüde etkilememektedir. HDOP, hız ölçümünün güvenilirliği için kalite göstergesi olarak kullanılabilir. Ayrıca, olumsuz ortam koşullarında (üst geçit, orman, kentsel alan vb.) GNSS hız ölçümü doğruluğu konusunda dikkatli olunmalıdır.

Nile Delta, one of the most populated deltas around the world, is suffering from subsidence due to the natural compaction of its sediment. Land subsidence has a great impact on the infrastructure, economic, and social. This study investigatesthe evaluation of the land subsidence in Nile Delta using GNSS measurements. Eight stations of GNSS points through period 2013-2015 distributed around Nile Delta and the Northern part of Egypt are utilized using differential GPS with nine IGS stations by GAMIT/GLOBK V. 10.61. The main objective is to monitor the spatiotemporal variations of land surface within the Nile Delta by time series analysis of the ellipsoidal height. The northern part of Egypt can be divided into three major parts; the western part shows subsidence rate of 2 mm/year downward; Nile Deltaof 2.5 to 10 mm/year downward from west to east and the eastern part shows an uplift.

Precisión y exactitud del método GNSS en modo estático para redes topográficas utilizadas en ingeniería civil ABSTRACT A field check was implemented for calibrating surveying equipment. It was geo-referenced with a Total Station Theodolite and by implementing procedures concerning repeatability and reproducibility. We carried out GNSS (Global Navigation Satellite System) static positioning with double frequency equipment, sensitizing occupation times, day times, uncorrected coordinates subjected to a differential correction procedure and type of coordinates obtained. This facilitated an evaluation of precision and accuracy for the GNSS positioning with the static method, which gave a global RMSE (root mean square error) of 1 cm for conditions with no multi-path effect and 4 cm for field calibration points close to buildings. Additionally, optimal results for occupation times of 30 minutes were found, and the need to use planar Cartesian coordinates to ensure compatibility with the surveys using electronic measurement of distances, which allows the use of the static GNSS positioning for geo-referencing precise surveying networks, and can be used in different applications in Civil Engineering.

In an era of significant air traffic expansion characterised by a rising congestion of the radiofrequency spectrum and a widespread introduction of Unmanned Aircraft Systems (UAS), Global Navigation Satellite Systems (GNSS) are being exposed to a variety of threats including signal interferences, adverse propagation effects and challenging platform-satellite relative dynamics. Thus, there is a need to characterize GNSS signal degradations and assess the effects of interfering sources on the performance of avionics GNSS receivers and augmentation systems used for an increasing number of mission-essential and safety-critical aviation tasks (e.g., experimental flight testing, flight inspection/certification of ground-based radio navigation aids, wide area navigation and precision approach). GNSS signal deteriorations typically occur due to antenna obscuration caused by natural and man-made obstructions present in the environment (e.g., elevated terrain and tall buildings when flying at low altitude) or by the aircraft itself during manoeuvring (e.g., aircraft wings and empennage masking the on-board GNSS antenna), ionospheric scintillation, Doppler shift, multipath, jamming and spurious satellite transmissions. Anyone of these phenomena can result in partial to total loss of tracking and possible tracking errors, depending on the severity of the effect and the receiver characteristics. After describing GNSS performance threats, the various augmentation strategies adopted in the Communication, Navigation, Surveillance/Air Traffic Management and Avionics (CNS+A) context are addressed in detail. GNSS augmentation can take many forms but all strategies share the same fundamental principle of providing supplementary information whose objective is improving the performance and/or trustworthiness of the system. Hence it is of paramount importance to consider the synergies offered by different augmentation strategies including Space Based Augmentation System (SBAS), Ground Based Augmentation System (GBAS), Aircraft Based Augmentation System (ABAS) and Receiver Autonomous Integrity Monitoring (RAIM). Furthermore, by employing multi-GNSS constellations and multi-sensor data fusion techniques, improvements in availability and continuity can be obtained. SBAS is designed to improve GNSS system integrity and accuracy for aircraft navigation and landing, while an alternative approach to GNSS augmentation is to transmit integrity and differential correction messages from ground-based augmentation systems (GBAS). In addition to existing space and ground based augmentation systems, GNSS augmentation may take the form of additional information being provided by other on-board avionics systems, such as in ABAS. As these on-board systems normally operate via separate principles than GNSS, they are not subject to the same sources of error or interference. Using suitable data link and data processing technologies on the ground, a certified ABAS capability could be a core element of a future GNSS Space-Ground-Aircraft Augmentation Network (SGAAN). Although current augmentation systems can provide significant improvement of GNSS navigation performance, a properly designed and flight-certified SGAAN could play a key role in trusted autonomous system and cyber-physical system applications such as UAS Sense-and-Avoid (SAA).

Modern Remotely Piloted Aircraft Systems (RPAS) employ a variety of sensors and multi-sensor data fusion techniques to provide advanced functionalities and trusted autonomy in a wide range of mission-essential and safety-critical tasks. In particular, Navigation and Guidance Systems (NGS) for small RPAS require a typical combination of lightweight, compact and inexpensive sensors to satisfy the Required Navigation Performance (RNP) in all flight phases. In this paper, the synergies attainable by the combination of Global Navigation Satellite System (GNSS), Micro-Electromechanical System based Inertial Measurement Unit (MEMS-IMU) and Vision-Based Navigation (VBN) sensors are explored. In case of VBN, an appearance-based navigation technique is adopted and feature extraction/optical flow methods are employed to estimate the navigation parameters during precision approach and landing phases. A key novelty of the proposed approach is the employment of Aircraft Dynamics Models (ADM) augmentation to compensate for the shortcomings of VBN and MEMS-IMU sensors in high-dynamics attitude determination tasks. To obtain the best estimates of Position, Velocity and Attitude (PVA), different sensor combinations are analysed and dynamic Boolean Decision Logics (BDL) are implemented for data selection before the centralised data fusion is accomplished. Various alternatives for data fusion are investigated including a traditional Extended Kalman Filter (EKF) and a more advanced Unscented Kalman Filter (UKF). A novel hybrid controller employing fuzzy logic and Proportional-Integral-Derivative (PID) techniques is implemented to provide effective stabilization and control of pitch and roll angles. After introducing the key mathematical models describing the three NGS architectures: EKF based VBN-IMU-GNSS (VIG) and VBN-IMU-GNSS-ADM (VIGA) and UKF based Enhanced VIGA (EVIGA), the system performances are compared in a small RPAS integration scheme (i.e., AEROSONDE RPAS platform) exploring a representative cross-section of the aircraft operational flight envelope. A dedicated ADM processor (i.e., a local pre-filter) is adopted in the EVIGA architecture to account for the RPAS maneuvering envelope in different flight phases (assisted by a maneuver identification algorithm), in order to extend the ADM validity time across all segments of the RPAS trajectory. Simulation results show that the VIG, VIGA and EVIGA systems are compliant with ICAO requirements for precision approach down to CAT-II. In all other flight phases, the VIGA system shows improvement in PVA data output with respect to the VIG system. The EVIGA system shows the best performance in terms of attitude data accuracy and a significant extension of the ADM validity time is achieved in this configuration.

Se estudian los servicios de posicionamiento en línea y se toman como primer paso del postproceso de observaciones. Sus resultados, un par de coordenadas ITRF08 para la época de las observaciones procesadas, son los valores de ingreso para una aplicación web, llamada Calculadora ITRF08 → POSGAR07, que se desarrolla con el fin de referir dichas coordenadas al Marco de Referencia oficial de la Argentina y, en particular, de la provincia de Santa Fe: POSGAR07, época 2006.632.

Se describen las operaciones que la mencionada aplicación web realiza sobre las coordenadas
ITRF08 para transformarlas a POSGAR07, que se apoyan en los modelos de velocidades calculados por SIRGAS y los valores de los desplazamientos ocasionados por dos eventos especiales: el terremoto ocurrido la madrugada del 27 de febrero de 2010, con epicentro en el mar chileno a 150 km de Concepción; y otro de mucha menor envergadura, como fue el cambio de marco de referencia en el cual se expresan las coordenadas de SIRGAS.

Por último, se realizan pruebas automatizadas de exactitud del resultado de dichas operaciones, para comparar las coordenadas verdaderas u oficiales POSGAR07 de EP distribuidas en todo el país con coordenadas de las mismas EP, surgidas de los recálculos de la red SIRGAS-CON y transformadas a POSGAR07 con la Calculadora. Como conclusión se obtienen valores de desvíos estándar que reflejan para qué zonas del país es conveniente utilizar la aplicación web.

This paper describes the 4-Dimensional Trajectory (4DT) optimisation algorithm implemented to avoid a variety of Global Navigation Satellite System (GNSS) signal degradations predicted by an Avionics Based Integrity Augmentation system (ABIA). The paper focusses on descent and initial curved GNSS approach phases in a dense Terminal Manoeuvring Area (TMA) scenario, with multiple aircraft converging on the same short and curved final GNSS approach leg. The reference platform for this study is the Javelin Remotely Piloted Aircraft System (RPAS). The 4DT optimisation algorithm implements three degrees-of-freedom aircraft dynamics models as well as suitable GNSS satellite visibility models based on Global Positioning System (GPS) constellation ephemeris data. Direct transcription methods of the global orthogonal (pseudospectral) collocation family are implemented, generating optimal high-integrity trajectories for curved GNSS approaches in real-time. The optimal trajectories calculated by the pseudospectral method are subsequently processed by control input smoothing and manoeuvre identification algorithms to translate the mathematical optimum into a pilot-/autopilot-flyable and concisely described 4DT intent. The characteristics of the proposed 4DT optimisation algorithm are evaluated in representative simulation case studies targeting short and curved GNSS approaches in dense TMA conditions, showing very satisfactory performance.

In this paper, adaptive and robust non Gaussian sensor fusion INS/GNSS is proposed to solve specific problem of non linear time variant state space estimation with measurement outliers, different algorithms are proposed to solve this specific problem generally occurs in intentional and non intentional interferences caused by other radio navigation sources, or by the GNSS receivers deterioration. Non linear approximation techniques such as Extended Kalman filter EKF and modern Cubature based Kalman Filters are computed to estimate the navigation states for UAV flight control. Several comparisons are conduced and analyzed in order to compare the accuracy and the convergence of different approaches usually applied in navigation data fusion purposes. The modern non linear filter algorithm called Cubature Kalman Filter CKF which provides more accurate estimation with more stability in Tracking data fusion application is compared with conventional non linear filters. In this work, CKF is compared with EKF in ideal conditions and during GNSS impulsive interferences modeled as non Gaussian noises "Sum of Gaussian" supposed to occur during specific interval of time, during the same interval, we assume additional denied environment which consists in the variation of the Gaussian sum noise covariance, then, innovation based adaptive fading approach is selected and used to modify the covariance calculation of the parallel non linear filters performed in this work. Interesting results are observed, discussed with real perspectives in navigation data fusion for real time applications under multiple denied environment parameters.

Global Navigation Satellite Systems (GNSS) can support the development of low-cost and high performance navigation and guidance architectures for Unmanned Aircraft Systems (UAS) and, in conjunction with suitable data link technologies, the provision of Automated Dependent Surveillance (ADS) functionalities for cooperative Sense-and-Avoid (SAA). In non-cooperative SAA, the adoption of GNSS can also provide the key positioning and, in some cases, attitude data (using multiple antennas) required for automated collision avoidance. A key limitation of GNSS for both cooperative (ADS) and non-cooperative applications is represented by the achievable levels of integrity. Therefore, an Avionics Based Integrity Augmentation (ABIA) solution is proposed to support the development of an Integrity-Augmented SAA (IAS) architecture suitable for both cooperative and non-cooperative scenarios. The performances of this IAS architecture were investigated in representative simulation case studies by testing the ability of the SAA system to exploit the predictive (caution) and reactive (warning) integrity flags generated by ABIA. Additionally, the ABIA False Alarm Rate (FAR) and Detection Probability (DP) performances were examined and an initial evaluation of the complementarity with Space-Based and Ground-Based Augmentation Systems (SBAS/GBAS) was accomplished. Simulation results show that the proposed IAS architecture is capable of performing high-integrity conflict detection and resolution when GNSS is used as the primary source of navigation data and there is a clear synergy with state-ofthe art SBAS/GBAS in all applicable flight phases.

Global Navigation Satellite Systems (GNSS) have revolutionised positioning, navigation, and timing, becoming a common part of our everyday life. Aside from these well-known civilian and commercial applications, GNSS is now an established atmospheric observing system, which can accurately sense water vapour, the most abundant greenhouse gas, accounting for 60-70 % of atmospheric warming. In Europe, the application of GNSS in meteorology started roughly two decades ago and today it is a well-established research field. This review covers the state-of-the-art in GNSS meteorology in Europe. Discussed 5 are the advances in GNSS processing for derivation of tropospheric products, application of GNSS tropospheric products in operational weather prediction and application of GNSS tropospheric products for climate monitoring. Reviewed are the GNSS processing techniques and tropospheric products. Given is a summary of the use of the products for validation and impact studies with operational Numerical Weather Prediction (NWP) models as well as very short weather prediction (nowcasting) case studies. Climate research with GNSS is an emerging field of research, the studies so far have been limited to comparison with 10 the climate models and derivation of trends. More than 15 years of GNSS meteorology in Europe has already achieved outstanding cooperation between the atmospheric and geodetic communities. It is now feasible to develop next-generation GNSS tropospheric products and applications that can enhance the quality of weather forecasts and climate monitoring. This work is carried out within COST Action ES1206 "Advanced Global Navigation Satellite Systems tropospheric products for monitoring Severe Weather Events and Climate" 15 (GNSS4SWEC, http://gnss4swec.knmi.nl).

This paper presents new efficient guidance algorithms allowing Unmanned Aircraft Systems (UAS) to avoid a variety of Global Navigation Satellite System (GNSS) continuity and integrity performance threats detected by an Aircraft Based Augmentation System (ABAS). In particular, the UAS guidance problem is formulated as an optimal control-based Multi-Objective Trajectory Optimization (MOTO) problem subject to suitable dynamic and geometric constraints. Direct transcription methods of the global orthogonal collocation (pseudospectral) family are exploited for the solution of the MOTO problem, generating optimal trajectories for curved GNSS approaches in real-time. Three degrees-of-freedom aircraft dynamics models and suitable GNSS satellite visibility models based on Global Positioning System (GPS) constellation ephemeris data are utilised in the MOTO solution algorithm. The performance of the proposed MOTO algorithm is evaluated in representative simulation case studies adopting the JAVELIN UAS as the reference platform. The paper focusses on descent and initial curved GNSS approach phases in a Terminal Maneuvering Area (TMA) scenario, where multiple manned/unmanned aircraft converge on the same short and curved final GNSS approach leg. The results show that the adoption of MOTO based on pseudospectral methods allows an efficient exploitation of ABAS model-predictive augmentation features in online GNSS guidance tasks, supporting the calculation of suitable arrival trajectories in 7 to 16 s using a normal PC.