European Geostationary Navigation Overlay Service Research Articles

Method of Evaluating the Positioning System Capability for Complying with the Minimum Accuracy Requirements for the International Hydrographic Organization Orders.

According to the IHO (International Hydrographic Organization) S-44 standard, hydrographic surveys can be carried out in four categories, the so-called orders—special, 1a, 1b, and 2—for which minimum accuracy requirements for the applied positioning system have been set out. These amount to, respectively: 2 m, 5 m, 5 m, and 20 m at a confidence level of 0.95. It is widely assumed that GNSS (Global Navigation Satellite System) network solutions with an accuracy of 2–5 cm (p = 0.95) and maritime DGPS (Differential Global Positioning System) systems with an error of 1–2 m (p = 0.95) are currently the two main positioning methods in hydrography. Other positioning systems whose positioning accuracy increases from year to year (and which may serve as alternative solutions) have been omitted. The article proposes a method that enables an assessment of any given navigation positioning system in terms of its compliance (or non-compliance) with the minimum accuracy requirements specified for hydrographic surveys. The method concerned clearly assesses whether a particular positioning system meets the accuracy requirements set out for a particular IHO order. The model was verified, taking into account both past and present research results (stationary and dynamic) derived from tests on the following systems: DGPS, EGNOS (European Geostationary Navigation Overlay Service), and multi-GNSS receivers (GPS/GLONASS/BDS/Galileo). The study confirmed that the DGPS system meets the requirements for all IHO orders and proved that the EGNOS system can currently be applied in measurements in the orders 1a, 1b, and 2. On the other hand, multi-GNSS receivers meet the requirements for order 2, while some of them meet the requirements for orders 1a and 1b as well.

Performance of EGNSS-Based Timing in Various Threat Conditions

Today’s society is highly reliant on time and frequency synchronization, e.g., in communications systems and financial networks. Precise timing is more and more derived from satellite navigation receivers that are unfortunately very susceptible to various signal threats. We studied the performance of global navigation satellite system (GNSS) timing under different operating conditions and tested the effectiveness of different techniques that improve timing receiver robustness. These features were tested under various threat scenarios related to specific vulnerabilities in GNSS-based timing, such as interference and navigation message errors, and their efficiency was analyzed against the corresponding scenarios. We found that interference or meaconing-type spoofing can threaten GNSS timing, but it can be detected by means of automatic gain control (AGC) and carrier-to-noise ratio-based methods. GNSS interruptions due to interference can be bridged by a local oscillator holdover technique based on a Kalman filter whose parameters are based on a GNSS time solution. Navigation message errors are mitigated by the European Geostationary Navigation Overlay Service (EGNOS), and constellation-wide timing errors can be detected by the use of a dual-constellation [global positioning system (GPS)-Galileo] cross-check. Dual-frequency operation for timing, in addition to mitigating first-order ionospheric effects, was found to be more robust to interference with the option to fall back to single frequency.

Peculiarities Regarding Satellite Navigation on the Territory of Romania

Abstract This paper describes the particularities of satellite navigation on the territory of Romania in search of solutions to improve the accuracy of these systems. The performance of a Global Navigation Satellite System (GNSS) is influenced by many factors, including distortion of the signal, the influence of the ionosphere and the troposphere, multipath propagation. Some of these factors depend on the geographical position and the environment in which the navigation system is used. Moreover, Romania is located at the border of coverage of two Satellite Based Augmentation Systems (SBAS) – European Geostationary Navigation Overlay Service (EGNOS) and System for Differential Corrections and Monitoring (SDCM) which leads to some peculiarities regarding satellite navigation.

Analysis of the EGNOS quality parameters during high ionosphere activity

Today, one of the key problems of global navigation satellite systems (GNSS) positioning with single-frequency receivers is the variability of the ionospheric delay. Satellite-based augmentation systems (SBAS) could overcome this problem since they generate the real time (updated every 5 min) ionospheric delay corrections but these can be unstable during space weather disturbances. The aim of this article is to present the quality of European Geostationary Navigation Overlay Service (EGNOS) positioning during two one-week observation periods in March 2015 and September 2017, in which the last two strongest geomagnetic storms took place. In order to perform a reliable analysis, the study was conducted at four IGS stations in different geographical latitudes located near the EGNOS availability border. The analyses and graphs of important navigation parameters were made using Septentrio Post Processing SDK and PEGASUS software which were developed in accordance with relevant aviation guidelines. The results showed an improvement in the quality of positioning in 2017, which could indicate positive impact of the new EGNOS software release. Nevertheless, even with the latest software, EGNOS positioning may still be unstable during geomagnetic storms, especially in the northern and southern borders of service coverage.

Evaluation of Orbit, Clock and Ionospheric Corrections from Five Currently Available SBAS L1 Services: Methodology and Analysis

To meet the demands of civil aviation and other precise navigation applications, several satellite-based augmentation systems (SBASs) have been developed around the world, such as the Wide Area Augmentation System (WAAS) for North America, the European Geostationary Navigation Overlay Service (EGNOS) for Europe, the Multi-functional Satellite Augmentation System (MSAS) for Japan, the GPS (Global Positioning System) Aided GEO Augmented Navigation (GAGAN) for India, and the System for Differential Corrections and Monitoring (SDCM) for Russia. The SBASs broadcast messages to correct satellite orbit, clock, and ionosphere errors to augment the GPS positioning performance. In this paper, SBAS orbit, clock and ionospheric corrections are evaluated. Specifically, the orbit, clock and ionospheric corrections derived from SBAS messages are comprehensively evaluated using data collected from the above mentioned systems over 181 consective days. The evaluation indicates that the EGNOS outperforms other systems with signal-in-space range error (SISRE) at 0.645 m and ionospheric correction accuracy at 0.491 m, respectively. Meanwhile, the accuracy of SDCM is comparable to EGNOS with SISRE of 0.650 m and ionospheric correction accuracy of 0.523 m. For WAAS, the SISRE is 0.954 m and the accuracy of ionospheric correction is 0.505 m. The accuracies of the SBAS corrections from the MSAS and GAGAN systems, however, are significantly worse than those of others. The SISREs are 1.931 and 1.325 m and the accuracies of ionospheric corrections are 0.795 and 0.858 m, for MSAS and GAGAN, respectively. At the same time, GPS broadcast orbit, clock and ionospheric corrections are also evaluated. The results show that there are no significant improvements in the SISRE of the broadcast navigation data by applying SBAS corrections. On the other hand, the accuracy of SBAS ionospheric corrections is still much better than GPS broadcast ionospheric corrections, which could still be beneficial for single-frequency users.

Estimation of Spatial Gradients and Temporal Variations of the Total Electron Content Using Ground‐Based GNSS Measurements

AbstractPrecision and safety of life applications of Global Navigation Satellite Systems require key information on space weather conditions in particular on the perturbation degree of the ionosphere. Such systems are particularly vulnerable against severe spatial gradients and rapid changes of the total electron content (TEC) measured along different satellite‐receiver links. To estimate spatial gradients and rapid temporal variations of ionospheric TEC, two approaches are discussed. The Gradient Ionosphere indeX (GIX) and the Sudden Ionospheric Disturbance indeX are able to estimate the perturbation degree of the ionosphere instantaneously without taking into account previous measurements. The capabilities and accuracy of the index approaches are demonstrated by simulations using a 3‐D electron density model of the ionosphere and plasmasphere in conjunction with realistic Global Navigation Satellite Signal constellations. Real data tests confirm the applicability of GIX and the related standard deviation GIX Sigma to monitor spatial gradients. Sudden Ionospheric Disturbance indeX is able to monitor rapid temporal variations of TEC as exemplified by using Global Navigation Satellite Signal measurements carried out during solar flare events. Both approaches could identify enhanced space weather impacts on precise point positioning and the European Geostationary Navigation Overlay Service. More comprehensive studies analyzing ionospheric storms in close dialogue with potential customers are needed to fully utilize the potential of these approaches to serve as objective ionospheric indices for scaling horizontal TEC gradients and rapid TEC variations in space weather services.

How to prevent loss of satellite navigation continuity caused by nimbostratus? Concept for Polish ATM

In 2018, the Polish project concerned on operational implementation of instrumental approach procedures for landing using satellite signal with the support of SBAS (Satellite Based Augmentation System) - EGNOS (European Geostationary Navigation Overlay Service) was completed. This made Poland one of a few countries in which such an approach procedures were applied at the majority of controlled airports occurring in FIR (Flight Information Region) Warsaw. In the adopted procedures, minima comparable to those from the precision landing approach ILS (Instrument Landing System) cat. I were used. Satellite systems and signals provided by them are therefore a key element of the strategy for the development of communication, navigation and surveillance systems in civil aviation. What is more, positioning in various branches of transport (rail, road, and air) is often carried out thanks to satellite navigation systems, and therefore their correct functioning has a significant impact on the safety of vehicle traffic. It cannot be overlooked that the limited operational use of satellite systems in air transport is caused by various errors that are inherent to the work of these systems. The satellite system, in all its complexity, can be treated as a measurement system. This is why the research problem of the article concerns on the use of information about atmospheric factors interfering with the satellite signal for forecasting the continuity value of this signal. The rationale for choosing this problem is, among others, the fact that failure to meet the requirements for signals prevents their operational use. A review of literature made for the purposes of this article points to a number of studies conducted in the field of modeling and prediction of signal parameters through artificial neural networks. However, no detailed research that would include the use of ionospheric & tropospheric factors, as well as historical data on the accuracy, continuity, availability and integrity of satellite signal forecasting in air transport navigation has been found so far. Their implementation will therefore have a significant impact on the development of science in this area.

Nequick2 Model Behaviour for Global Ionospheric Delay Mitigation During Solar Cycle-24

Abstract The ionospheric delay is the major current source of potential range delay for single-frequency GNSS users. Different ionospheric delay mitigation methods have been developed to mitigate the ionospheric delay effects for single-frequency users. The NeQuick is a quick-run ionospheric electron density model particularly designed for trans-ionospheric propagation applications developed at the Aeronomy and Radio propagation Laboratory of the Abdus Salam International Centre for Theoretical Physics (ICTP), Italy. NeQuick2 is the latest version of the NeQuick ionosphere electron density model. NeQuick model been used by the European Space Agency (ESA) European Geostationary Navigation Overlay Service (EGNOS) project for assessment analysis and has been adopted for single-frequency positioning applications in the frame work of the European satellite navigation system (Galileo). NeQuick2 model adopted modifications related to the modeling of the F1 layer peak electron density, height and thickness parameter. Also, a new formulation of the shape parameter k has been adopted. This paper presents a global study for the behavior of the modified NeQuick2 model. The zenith ionospheric range delay correction by the model has been assessed using the highly accurate IGS-Global Ionospheric Maps (IGS-GIMs) for two different-latitude stations (Aswan, Egypt) (low-latitude) (24.1o N) and (Helsinki, Finland) (high-latitude) (60.2o N). The study was carried out during current solar cycle-24 over three different months that each of them reflects a different state of solar activity. It can be concluded that NeQuick2 model globally presents overestimation for ionospheric delay for quiet and medium ionospheric activity states respectively, while the model presents underestimation for high activity state of the ionosphere layer.

Assessment of the Positioning Accuracy of DGPS and EGNOS Systems in the Bay of Gdansk using Maritime Dynamic Measurements

Differential Global Positioning Systems (DGPS) and the European Geostationary Navigation Overlay Service (EGNOS) are included in a group of supporting systems (Ground-Based Augmentation System (GBAS)/Space-Based Augmentation System (SBAS)) for the American GPS. Their main task is to ensure better positioning characteristics (accuracy, reliability, continuity and availability) compared to GPS. Therefore, they are widely applied wherever GPS failures affect human safety, mainly in aviation, land and marine navigation. The aim of this paper is to assess the predictable positioning accuracy of DGPS and EGNOS receivers using a vessel manoeuvring in the Bay of Gdansk. Two receivers were used in the study: a Simrad MXB5 (DGPS) and a Trimble GA530 (EGNOS), which were simultaneously recording their coordinates. The obtained values were compared with the trajectory computed using a geodetic Global Navigation Satellite System (GNSS) receiver (Trimble R10) connected to a GNSS network, ensuring an accuracy of 2–3 cm (p = 0·95). During a four-hour measurement session, the accuracy statistics of these systems were determined based on around 11,500 positionings. Studies have shown that both positioning systems ensure a similar level of accuracy of their positioning services (approximately 0·5–2 m) and they meet the accuracy requirements set in published standards.

Examination of Autonomous GPS and GPS/EGNOS Integrity and Accuracy for Aeronautical Applications

The Global Navigation Satellite System (GNSS) is increasinglyused in navigation and positioning in land, water and air applications.Although they are very useful and willingly employedin everyday live and commercial products, it must be stressedthat GNSS alone does not always provide adequate performance,particularly in demanding aeronautical applicationswhere high level of integrity is required. Integrity and accuracyof positioning are the key parameters in air navigation.The paper presents research on current values of GNSS accuracyand integrity in north-eastern Poland, the region whichuntil 2014 was out of official coverage of European GeostationaryNavigation Overlay Service (EGNOS) Open Service (OS).The integrity and accuracy of positioning of static point andflying aircraft was examined in order to check present usabilityof different GNSS techniques which can be deployed for enroute,approach and landing phase of a flight. Since the integritylevels in aviation are strictly dependent on the phase offlight and landing of an aircraft, the analyses were performedin two computational modes: positioning using GPS/EGNOSdata and using autonomous GPS. Both modes were calculatedin en-route variant and because with the use of EGNOS it ispossible to perform approach, GPS/EGNOS mode was alsoanalyzed in Precision Approach (PA) variant. Overall assessmentof the accuracy and integrity of positioning in the studiedvariants is at the satisfactory level, not exceeding the levelsdefined by official aviation regulations.

The comparison of EGNOS performance at the airports located in eastern Poland

The European Geostationary Navigation Overlay Service (EGNOS) is the first pan-European satellite navigation system. EGNOS makes GPS suitable for safety critical applications such as flying and landing an aircraft. To use EGNOS in aviation the system monitoring and validation in certain localization in needed, as well as official flight procedure design and certification. According to these rules, several GNSS/EGNOS stations located at Polish airfields are currently operational, permanently collecting EGNOS data. The newest monitoring station was established and put into operation at the Polish Air Force Academy in Dęblin in the beginning of 2016. Dęblin is situated in central-eastern part of Poland (south of Warsaw). Until recently this area was on the edge of official coverage of EGNOS services, especially Safety-of-Life (SoL) service. Latest official documents declare that theoretically the eastern part of Poland is currently fully covered with EGNOS SoL service, however this still needs to be practically confirmed. New station equipped with the newest Javad Delta-3 GNSS receiver will allow to evaluate practical quality of EGNOS in this area. The article presents preliminary results of EGNOS Safety of Life service performance in Dęblin in comparison to the results obtained in Olsztyn which is situated in north-eastern part of Poland (north of Warsaw). The main parameters characterizing navigational system i.e. accuracy, integrity, continuity and availability were analyzed in detail. The results can be the basis to assess the possibility of implementation of the EGNOS APV approach and landing procedures in Dęblin and Olsztyn.

SSIEGNOS: A New Asian Single Site Tropospheric Correction Model

This paper proposes a new Asian single site tropospheric correction model called the Single Site Improved European Geostationary Navigation Overlay Service model (SSIEGNOS) by refining the European Geostationary Navigation Overlay Service (EGNOS) model at a single site. The performance of the SSIEGNOS model is analyzed. The results show that (1) the bias and root mean square (RMS) error of zenith tropospheric delay (ZTD) calculated from the EGNOS model are 0.12 cm and 5.87 cm, respectively; whereas those of the SSIEGNOS model are 0 cm and 2.52 cm, respectively. (2) The bias and RMS error show seasonal variation in the EGNOS model; however, little seasonal variation is observed in the SSIEGNOS model. (3) The RMS error decreases with increasing altitude or latitude in the two models; however, no such relationships were found in the bias. In addition, the annual predicted bias and RMS error in Asia are −0.08 cm and 3.14 cm for the SSIEGNOS model, respectively; however, the EGNOS and UNB3m (University of New Brunswick) models show comparable predicted results. Relative to the EGNOS model, the annual predicted bias and RMS error decreased by 55% and 48%, respectively, for the SSIEGNOS model.

Identification of scintillation signatures on GPS signals originating from plasma structures detected with EISCAT incoherent scatter radar along the same line of sight.

Ionospheric scintillation originates from the scattering of electromagnetic waves through spatial gradients in the plasma density distribution, drifting across a given propagation direction. Ionospheric scintillation represents a disruptive manifestation of adverse space weather conditions through degradation of the reliability and continuity of satellite telecommunication and navigation systems and services (e.g., European Geostationary Navigation Overlay Service, EGNOS). The purpose of the experiment presented here was to determine the contribution of auroral ionization structures to GPS scintillation. European Incoherent Scatter (EISCAT) measurements were obtained along the same line of sight of a given GPS satellite observed from Tromso and followed by means of the EISCAT UHF radar to causally identify plasma structures that give rise to scintillation on the co‐aligned GPS radio link. Large‐scale structures associated with the poleward edge of the ionospheric trough, with auroral arcs in the nightside auroral oval and with particle precipitation at the onset of a substorm were indeed identified as responsible for enhanced phase scintillation at L band. For the first time it was observed that the observed large‐scale structures did not cascade into smaller‐scale structures, leading to enhanced phase scintillation without amplitude scintillation. More measurements and theory are necessary to understand the mechanism responsible for the inhibition of large‐scale to small‐scale energy cascade and to reproduce the observations. This aspect is fundamental to model the scattering of radio waves propagating through these ionization structures. New insights from this experiment allow a better characterization of the impact that space weather can have on satellite telecommunications and navigation services.

A Study of SBAS Position Domain Analysis Method: WAAS and EGNOS Performance Evaluation

A Satellite Based Augmentation System (SBAS) is a system that provides positioning information with high and accurate reliability to users who require ensuring high safety such as airplane taking off and landing. A continuous performance evaluation on navigation safety facilities shall be performed to determine whether developed systems meet the required performance before and after the operation. In this paper, SBAS position domain analysis is discussed in relation to analysis items for performance evaluation. The performance evaluation on the SBAS in the position domain shall conduct analysis on accuracy, integrity, continuity, and availability, which are items in the required navigation performance (RNP). In the paper, position domain analysis was conducted with regard to the Wide Area Augmentation System (WAAS) in the USA and the European Geostationary Navigation Overlay Service (EGNOS), which were developed already and now under operation. The analysis result showed that each of the systems satisfied the APV-I performance requirements recommended by the International Civil Aviation Organization (ICAO) with regard to daily data. It is necessary to verify using long-term data, whether the performance requirements in the RNP items are satisfied for system certification.

First observations of super plasma bubbles in Europe

AbstractIonospheric plasma bubbles of equatorial origin have never been registered at midlatitudes in Europe. During the 22–23 June 2015 geomagnetic storm the prompt penetration electric fields caused the occurrence of plasma bite‐outs in the postsunset sector over low latitudes of Western Africa and large‐scale plasma bubbles extended toward Europe. For the first time, using multisite GPS and Global Navigation Satellite System observations (~1500 stations), the super plasma bubble signatures were registered in Europe. They were observed more than 8 h (20–04 UT) and covered a broad area within 30°–40°N and 20°W–10°E. These unique results were confirmed by measurements on board Swarm and DMSP satellites and ground‐based absolute total electron content observations. Occurrence of the super plasma bubbles in Europe affected Global Navigation Satellite Systems measurements over a number of stations in Spain, Portugal, southern France, and Italy and led to performance degradation of the European Geostationary Navigation Overlay Service.

Study of EGNOS accuracy and integrity in eastern Poland

ABSTRACTThe ionosphere is one of the main factors affecting the accuracy and integrity of satellite-based augmentation system positioning systems. This paper presents the results of a 30-day study of the accuracy and integrity of the European Geostationary Navigation Overlay Service (EGNOS) conducted at the EPOD airport belonging to the Aeroclub of Warmia and Mazury in Olsztyn, in northeastern Poland (the area until recently considered as the edge of EGNOS coverage). Analyses of the parameters characterising the accuracy and integrity of positioning were performed in three calculation variants/modes: with the original EGNOS ionospheric correction, with correction determined by means of Klobuchar algorithm, and finally with modified ionospheric coefficients developed by the CODE. Studies have shown clearly that the original EGNOS ionospheric model gives the best integrity and accuracy results allowing to use EGNOS for approach with vertical guidance procedures, while the Center for Orbit Determination in Europe and Klobuchar models could only be used for non-precision approach operations.

European Pathways to Introduce EGNOS and Galileo for Dangerous Goods Transport

Every year the transport of dangerous goods amounts to more than 154 billion tonne-km on European roads, railways and inland waterways (source: Eurostat http://epp.eurostat.ec.europa.eu, year 2013). When speaking about dangerous goods movement, traceability and monitoring are not only a matter of an intelligent and efficient logistics. They also imply aspects related to security and safety, being a concern common to involved industries and authorities.For this reason, tracking & tracing the shipment of dangerous goods requires an efficient collection of timely and precise information about the various operations. Besides, reliability is a fundamental requirement, especially in the case of intermodal transport where different operators and modalities are involved. About 85% of the shrinkage in the overall supply chain occurs while materials, components or finished goods are in transit.In this respect, the satellite navigation technology is a key element, as it enables:•The continuous localization, control and monitoring of goods traffic during transport.•The collection of data to be further analysed for statistical reporting and incident prevention.Systems based on the use of satellite positioning are today widely adopted in the transport of dangerous goods operations. Tracking & tracing devices (installed on board of the asset transporting the goods) can also integrate sensors to enable the monitoring of the status of the goods and different telecommunication means (satellite and/or terrestrial) for positions/data transmission.Various past and on-going European initiatives are also introducing the use of the European satellite navigation (EGNSS, European Global Navigation Satellite System), starting from EGNOS (European Geostationary Navigation Overlay Service) and in view of Galileo.Among these initiatives, the project SCUTUM (SeCUring the EU GNSS adopTion in the dangeroUs Material transport, www.scutumgnss.eu) concluded in 2011, exhaustively and successfully demonstrated that EGNOS provides precise and reliable localization and tracking, and thus it is particularly suitable for monitoring the transport of dangerous goods. Today, thanks to SCUTUM, EGNOS is used to monitor around 1,200 road tankers transporting dangerous goods by road in Europe (Italy, France, Austria, Slovakia, Hungary, Romania, Czech Republic).Capitalizing on SCUTUM's achievements, the on-going project CORE, started in 2014 and with a duration of 4 years, is extending the use of EGNOS to the intermodal transport of dangerous goods, and analysing the advantages of the introduction of Galileo.As done in SCUTUM, also CORE is expected to launch an operational best practice in Europe. Moreover, similarly to SCUTUM, the project's results will feed the on-going UNECE OTIF WG (United Nations Economic Commission for Europe Organisation Intergouvernementale pour les Transports Internationaux Ferroviaires Working Group) on Telematics in relation to the use of telematics for the transport of dangerous goods, specifically for what the EGNSS is concerned.

Examination of GPS/EGNOS integrity in north‐eastern Poland

Integrity of positioning is one of the key aspects of satellite based augmentation systems. This paper presents a study carried out in north-eastern Poland, a region which is considered as a border of the operation of the European Geostationary Navigation Overlay Service (EGNOS) system. Detailed analyses concerning operational parameters of EGNOS were done during the 12-hour and 24-hour measurement sessions conducted at a fixed point. The study was focused on the role of ionospheric delays in the integrity model according to the Radio Technical Commission for Aeronautics guidelines. In determination of the accuracy and integrity of positioning, two variants of calculations were adopted: one based on a standard interpolation algorithm determining ionospheric delay by the EGNOS system, and the other based on the Klobuchar model. The research found that the first method is characterised by only slightly better accuracy results, while significant differences were obtained by examining the integrity of positioning. For both variants of the calculation design, the values of protection levels determined for the fixed point are much higher than the positioning accuracy, which meets the integrity requirements of the navigation system.

An Imaging Compensation Algorithm for Correcting the Impact of Tropospheric Delay on Spaceborne High-Resolution SAR

Atmospheric refraction in the troposphere causes the propagation speed of electromagnetic signals to be less than the light speed. This creates a difference between the actual propagation path delay and the distance of the geometrical straight-line path, i.e., a quantity known as the tropospheric delay. As classical imaging algorithms for spaceborne synthetic aperture radar (SAR) do not take the tropospheric delay into account, imaging filters are designed based on the assumption of rectilinear propagation with the light speed. Therefore, a residual phase exists in imaging results, which affects focusing quality under the condition of high resolution. In order to compensate for the impact of tropospheric delay on focusing performance, this paper modifies the spaceborne SAR echo model and then proposes an imaging compensation algorithm. The key to this algorithm is to fit a range delay coefficient based on the European Geostationary Navigation Overlay Service model of zenith delay and Niell mapping function, which projects the zenith delay onto the looking direction. After range compensation, classical imaging, and azimuth compensation, which compose the proposed algorithm, the processed results are well focused.

The evaluation of the positioning accuracy of the EGNOS and DGPS systems based on the long-term measurements in the years 2006–2014

Abstract The DGPS (Differential GPS) and EGNOS (European Geostationary Navigation Overlay Service) systems belong to a group of systems supporting the global satellite system GPS (Global Positioning System). These systems have significantly better navigation performance than GPS and, therefore, they are widely used in the maritime, civil and air navigation. The analysis of the positioning accuracy of GPS leads to the conclusion: from year to year the accuracy of the positioning determination increases. The effect of the permanent increasing of the GPS positioning accuracy is the parallel increasing of the positioning accuracies of all the supporting systems. In connection with the constant improvement of the precision characteristics of the above mentioned systems on one hand and the fact, that the users do not possess the current information about the actual status of these characteristics on the other hand, it is reasonable to conduct the periodical research in this area. For that purpose the long-term measurement campaigns were realized in the years 2006-2014; the values of measures, describing the positioning accuracies obtained by both systems, were determined on the basis of those campaigns.