GNSS Agency Research Articles

EGNOS Performance Along Finnish Coast

The purpose of this article is to demonstrate the benefits of EGNOS (European Geostationary Navigation Overlay Service / SBAS in Europe) for the community and inform about the activities that are ongoing for the provision of EGNOS L1 maritime service. EC (European Commission) and GSA (European GNSS Agency) are assessing an EGNOS L1 maritime service with the objective to complement the existing maritime radio-navigation systems (e.g. DGNSS). community is interested in using SBAS for ocean waters, coastal waters and harbour entrances/approaches considering operational needs (IMO Res. 1046), especially where there is no back-up infrastructure or in poorly covered environments. EGNOS L1 Service aims at providing pseudo-range corrections and alert information to the GPS L1 signals for maritime navigation, obtaining enhanced accuracy and ranging integrity information over Europe. In order to ensure a safe use of SBAS by all shipborne receivers, an IEC 61108 standard for SBAS receiver equipment should be published. IEC 61108 is a collection of IEC standards for Maritime navigation and radio-communication equipment and systems - Global navigation satellite systems (GNSS). In consequence, EC, GSA, ESA and ESSP are developing guidelines for manufacturers for the implementation of SBAS in shipborne receivers to be compliant with the operational requirements defined in International Organization (IMO) Resolution A.1046. These guidelines, together with a set of test specifications, intend to support the integration of SBAS in the standardisation process for maritime navigation and radio-communication equipment and systems within IEC framework. One GNSS campaign will be performed along the Finnish coast in order to analyse the EGNOS performance in the border of Northeast EGNOS coverage area. Different types of receivers configured to use SBAS will be on board the vessel to analyse the results. The set of receivers to be used would include maritime receivers, high-end receivers and also new receivers aligned with the future SBAS guidelines. On one side, the EGNOS navigation errors will be obtained with respect to a reference PPP post-processed trajectory. On the other side, the EGNOS availability will be obtained, taking especial attention at the border service coverage area. The EGNOS performance results will be compared with respect to the GPS standalone solution, to verify EGNOS provides an enhanced navigation position. The performance obtained with the receivers will be compared with the operational requirements defined in the IMO Resolution A.1046 (27) to assess the feasibility of EGNOS for some maritime applications. Finally, a deep performance analysis will be done in the Northeast border of EGNOS coverage area for ocean waters, coastal waters and harbour entrances/approaches. Based on the results obtained from a receiver, it will be shown a reliable EGNOS navigation solution with better accuracy than GPS standalone solution. The results aim at confirming that EGNOS L1 service is compliant with the operational requirements defined in the IMO Res. A.1046 (27) for ocean waters, coastal waters and harbour entrances/approaches, being beneficial for maritime community.

EDAS (EGNOS Data Access Service) Differential GNSS Corrections: A Reliable Free-of-Charge Alternative for Precision Farming in Europe

Abstract EDAS (EGNOS Data Access Service) is the EGNOS internet broadcast service, which provides free of charge access to the data collected and generated by the EGNOS infrastructure. EDAS disseminates over the Internet, both in real time and via an FTP archive, the raw data of the GPS, GLONASS (no commitment on GLONASS data is provided (1)) and EGNOS GEO satellites collected by the receivers located at the EGNOS reference stations, which are mainly distributed over Europe and North Africa. The EDAS services offer several types of GNSS data in various protocols and formats, such as DGNSS corrections. This paper reports on the results of some in-field tests conducted by ESSP and Topcon Agriculture to confirm the suitability of EDAS DGNSS corrections for precision farming in Europe. The European Commission (EC) is the owner of EGNOS system (including EDAS) and has delegated the exploitation of EGNOS to the European GNSS Agency (GSA). EDAS service provision is performed by ESSP, as EGNOS Services Provider, under contract with the GSA, the EGNOS program manager. In the ENC 2018 article “EDAS (EGNOS Data Access Service): Differential GPS corrections performance test with state-of-the-art precision agriculture system”, ESSP and Topcon Agriculture presented the results of the first in-field test conducted in a dynamic and real-life environment in the summer of 2017. The test results indicated that the EDAS DGNSS corrections could enable a reliable pass-to-pass accuracy performance for a wide range of precision agriculture applications and become an attractive solution for cereal farms, when the farm is located in the vicinity of an EGNOS reference station. In particular, Topcon Agriculture acknowledged that the observed performance was sufficient to support the following precision agriculture applications: spraying and spreading of any crop type, tilling and harvesting of cereal. Then, ESSP and Topcon Agriculture engaged in additional testing activities to further characterise the EDAS DGPS performance in different scenarios (i.e. at various European locations and with a variety of distances between the designated farm and the target EGNOS reference station). In each test, multiple runs with the rover tractors have been performed over the reference patterns predefined in the Topcon guidance systems. Data recorded during the tests has been analysed in detail, looking at the key performance indicators (e.g. cross track error and pass-to-pass performance) that characterize the EDAS DGPS performance for precision agriculture applications. Different techniques for the computation of the pass-to-pass accuracy performance have been used, including a procedure to measure live in the field and a post-processing alternative. The diversity of scenarios available allows drawing conclusions on the applicability of EDAS DGPS corrections (in terms of maximum distance from the target EGNOS station) for precision agriculture and also understanding the impact of operationally relevant aspects such as the quality of the mobile internet coverage (highly variable across Europe). The EDAS system and its architecture, the main types of data disseminated through EDAS services and the online information available to the EDAS users are introduced in this paper. In particular, the EDAS Ntrip service is described in detail, since it provides the differential corrections to the GPS and GLONASS satellites at the EGNOS reference stations in RTCM format, which are the basis for the present study. The article also reports on the results of the latest tests, which have been performed using Topcon receivers, vehicles and auto-steering systems. In all cases, two different Topcon guidance systems on board tractors were running simultaneously to assess the EDAS DGPS positioning performance with respect to a the reference provided by a top-performing RTK-based Topcon solution. The objective of this paper is to draw conclusions on the use of EDAS DGPS corrections as a reliable free-of-charge alternative for precision farming in Europe (especially for cereal farms), based on the available performance results from the testing campaign and the feedback from the involved precision agriculture experts.

Galileo Ionospheric Correction Algorithm: An Optimization Study of NeQuick‐G

AbstractAt present most low‐cost GNSS receivers operate one frequency in the L band. For them one of the largest error contributions is the delay of radio signals in the Ionosphere. NeQuick‐G is the official ionospheric correction algorithm (ICA), which has been adopted for Galileo, the European GNSS Programme. The NeQuick‐G implementation is complex when compared with other ICAs. It is also demanding in terms of computational resources. The Joint Research Centre completed a reference implementation of NeQuick‐G based on the official document “Ionospheric Correction Algorithm for Galileo Single Frequency Users” provided by the European Global Navigation Satellite Systems Agency. The rationale behind the JRC implementation of NeQuick‐G was the intent to write an independent source code from scratch, without using the pseudo‐codes from the reference document and solely relying on the physics descriptions. Using such implementation as baseline, this paper describes an optimization attempt of the official pseudo‐code from an algorithmic perspective. The objective was to reduce the computational load while not sacrificing the performance. The new proposed integration method is able to speed up calculations to 21% and 49% with respect the two official integration algorithms. The overall computational burden depends on the number of operations, which is eventually closely correlated to the number of calls of the ionospheric model. This underlines the quest to find an integration method reducing this number of calls. Moreover, based on the findings of this study, the authors strongly recommend revisiting the convergence control of the integration routines introduced in (European Commission, 2016, https://www.gsc‐europa.eu/sites/default/files/sites/all/files/Galileo_Ionospheric_Model.pdf).

Quality assessment of GPS, Galileo and BeiDou-2/3 satellite broadcast group delays

The quality of broadcast group delays (BGDs) transmitted in the navigation messages of the Global Positioning System (GPS), BeiDou-2/3 and Galileo is assessed by comparison with multi-GNSS differential code bias (DCB) products generated at the Chinese Academy of Sciences (CAS). An automatic DCB (AutoDCB) realignment procedure is presented to handle discontinuities within individual BGD/DCB series. The analysis is performed over a four-year period starting from January 2014. For GPS, the consistency between broadcast timing group delays (TGDs) and CAS MGEX DCBs is 0.25 ns, and the corresponding values are 0.05, 0.3 and 0.45 ns for L1C/A, L2C and L5Q inter-signal corrections (ISCs), respectively. The best agreement between GPS L2C ISCs and CAS MGEX C1W-C2L DCBs is emphasized. The inconsistency between broadcast and post-processed C2I-C6I DCBs (=TGD1) is found to decrease from 1.5 to 0.45 ns across the entire BeiDou-2 constellation since late July 2017, indicating a significant quality improvement of BeiDou-2 transmitted TGD1 parameters. A systematic offset of around 4.0 ns is found between TGD1 reference datums of BeiDou-3 and BeiDou-2 constellations, which needs to be removed in the combined BeiDou-2/3 B1I single-frequency or B1I+B3I dual-frequency standard positioning applications. Aside from the increasingly improved repeatability of broadcast E1-E5a/5b delays, an overall agreement at the level of 0.1–0.4 ns is achieved between Galileo transmitted value and DCB metadata from European GNSS Agency (GSA) for the in-orbit validation (IOV) satellites. In the comparison of Galileo BGDs and CAS MGEX DCBs, the consistency is at the level of 0.4 and 0.3 ns for IOV and full operation capability (FOC) satellites, respectively. The requirement of the routine assessment of broadcast group delays is also emphasized, in particular for newly launched satellites of new constellations.

ESTABLISHING NEW FOUNDATIONS FOR THE USE OF REMOTELY-PILOTED AIRCRAFT SYSTEMS FOR CIVILIAN APPLICATIONS

Abstract. Skyopener is a project funded by the EU through the European GNSS Agency (GSA) in the framework of the Horizon 2020 program. Skyopener’s goal is contributing to the roadmap for the integration of civil Remotely Piloted Aircraft Systems (RPAS) into nonsegregated airspace, by providing and testing enabling technologies, in particular with reference to European initiative U-Space, aimed at establishing regulations and infrastructure for integration of unmanned aviation into shared airspace. The main outcomes of the project include: implementing and testing a reliable and secure redundant air-ground communication link, based on satellite and 3G/4G networks; integrating the mission management system and ground station with a UTM (Unmanned aerial system Traffic Management) client, and experimenting UTM services being deployed by one of the partners; demonstrating technical and economic feasibility of long- range missions beyond visual line of sight (BVLOS) by executing corridor mapping on a high-voltage powerline, and airport area surveys (e-TOD: electronic-Terrain Obstacle Database).

Design, Implementation and Validation of a GNSS Measurement Exclusion and Weighting Function with a Dual Polarized Antenna.

Global Navigation Satellite Systems (GNSSs) have become a ubiquitous tool for our modern society to carry out vital tasks such as transportation, civil engineering or precision agriculture. This breath has reached the realm of safety-critical applications such as time management of critical infrastructures or autonomous vehicles, in which GNSS is an essential tool nowadays. Unfortunately, current GNSS performance is not enough to fulfill the requirements of these professional and critical applications. For this reason, the FANTASTIC project was launched to boost the adoption of these applications. The project was funded by the European GNSS agency (GSA) in order to enhance the robustness and accuracy of GNSS in harsh environments. This paper presents the part related to the development of a weighting and exclusion function with a dual circularly polarized antenna. The idea is to reduce the effects of multipath by weighting and/or excluding those measurements affected by multipath. The observables and other metrics obtained from a dual polarized antenna will be exploited to define an exclusion threshold and to provide the weights. Real-world experiments will show the improvement in the positioning solution, using all available constellations, obtained with the developed technique.

GRAIL-2: Enhanced Odometry based on GNSS

Following the introduction of the Satellite Navigation technology (GNSS) in the railway domain started with past European initiatives, the objective of GRAIL-2 is to define, develop and validate a GNSS application in high-speed railway lines, focusing at a concrete market and aiming at offering a product close to the customers within the European Rail Traffic Management System framework (ERTMS) paradigm. The proposed system is based on Enhanced Odometry.In the frame of the 7th Framework Programme, 2nd Call, the GRAIL-2 consortium has been granted with European funds to start rolling out the strategy, defined in the precedent project, GRAIL, for a smooth integration of GNSS into control and command applications and particularly within the European Train Control Systems (ETCS) framework. The GRAIL-2 Consortium is composed of 10 participants from 8 EC countries.A prototype is been developed and it will be tested to demonstrate the concept in a real environment. Details on the concept, activities performed and first results are presented in this paper.The GRAIL-2 project is managed by the European GNSS Agency (GSA) in the name of the European Commission.