Although GNSS can be used in smartphones and in-car navigation with an accuracy of a few meters, it can provide much more accurate positioning, of the order of centimetres in real time. Currently, there are two specific candidate GNSS techniques that can meet this real-time demand, namely PPP (Precise Point Positioning) and RTK (Real Time Kinematic), which are today mainly based on GPS and GLONASS, the only two fully operational systems. These two techniques, corresponding algorithms, error modelling and their implementation are at the core of the research training in TREASURE, which will incorporate the potential contribution of the other GNSS systems that are under development, such as Beidou and in particular Galileo, the European GNSS (EGNSS).
Crucially, two leading providers of high accuracy positioning in the areas of PPP for offshore operations and RTK for onshore applications (such as in precision agriculture), namely Fugro and Geo++, respectively, are TREASURE’s beneficiaries and will take a central role in the programme by supporting the integration of the new algorithms to be developed in the project into their systems for performance evaluation.
The project will concentrate on research that will pave the way for the development of a service that can ensure the enhanced real-time high accuracy positioning that is desperately needed by markets such the Agri-Tech market and potentially many others that will become apparent as the project evolves and results are disseminated. The research challenges to achieve this goal will be tackled through dedicated WPs (Work Packages).
TREASURE Work Packages
RESEARCH Work Package Title
WP1 Ionospheric models and data assimilation
WP2 Tropospheric models and real-time orbits
WP3 Ionospheric scintillation and interference mitigation models and tools
WP4 Real time PPP and NRTK algorithms
WP5 Conceptual prototype and marketing
NON-RESEARCH WP6 Training and Dissemination
TREASURE’s Work Packages are designed to achieve the following research objectives:
- Development of new ionospheric modelling and forecast, including scintillation (WP1), data assimilation for real-time applications (WP1), tropospheric modelling and forecast (WP2), real-time precise orbits, in particular for Galileo (WP2), carrier phase software defined radio receiver (WP3), interference mitigation techniques (WP3) and models for atmospheric effects mitigation, including scintillation (WP3) that are all suitable to support PPP and RTK and lead to real-time positioning accuracy of a few centimetres anywhere in the world.
- Development and integration of the above into new real-time PPP and RTK algorithms for offshore and inland applications (WP4).
- Development of new system integration approaches for the envisaged service prototype exploiting all the above, as well as research and strategies for market introduction of this service at prototype level (WP5).
The research will be carried out by the individual ESRs (Early Stage Researchers), who will enroll in PhD study to tackle the varied interconnected research challenges. TREASURE’s working methodology is shown schematically below in the project’s work plan. The diagram describes how the individual ESR PhD research projects interact, collaborate and are integrated through research WPs 1 to 5 to achieve the final goal of the project’s research training, while supported by the solid Training & Dissemination activities (covered by WP6) and the expert management of WP7.
The research methodology can be summarised by:
WP1 deals with ionospheric phenomena that need to be modelled and predicted to support the mitigation of their effects on (which is part of the task of WP3), as well as the development of real-time algorithms for (task of WP4) PPP and NRTK.
WP2 deals with models to estimate and correct the effects of the troposphere on PPP and NRTK, as well as the development of real-time precise orbits, in particular for Galileo, which are required especially for PPP.
WP3 exploits a software defined radio receiver to develop mitigation techniques for anthropogenic interference and ionospheric scintillation, which also limit the performance of real-time PPP and NRTK.
WP4 cooperates with and takes full advantage of WPs 1, 2 and 3 to develop and implement the sought after high accuracy real-time PPP and NRTK algorithms. WP4 cannot succeed without a successful and strongly harmonised collaboration with the previous WPs. All WPs will prioritise the exploitation of Galileo (EGNSS).
WP5 will investigate the suitable and interoperable ICT infrastructure for the exploitation of TREASURE’s innovative tools and its ultimate real-time high accuracy EGNSS solution. A dedicated task in WP5 will scientifically research the strategy for introduction of this solution to the market.
RTK enables improved GNSS positioning accuracy and reliability through the aid of fixed reference stations operating high-grade GNSS receivers at carefully surveyed reference locations. RTK uses the GNSS signal carriers and most RTK services adopt a maximum separation of less than 20km (or 50-70 km if a reference network is used, as in Network RTK, known as ‘NRTK’) between user and reference station in order to deliver sub-decimetre level accuracy. However, where atmospheric variations are strong, shorter distances and consequently a greater number of references stations may be necessary, rendering the technique not very cost-effective or even unreliable. This is the case for instance where gradients in the Total Electron Content (TEC) of the ionosphere (the ionised upper part of the atmosphere) are present, as often observed in equatorial and high latitude regions, which are also prone to the occurrence of scintillation affecting the satellites signals propagation, or for instance if the lower, neutral atmosphere (the troposphere) presents a complex and rapidly changing behaviour. It is, therefore, crucial to model and accurately predicts the state of the atmosphere in order to mitigate its effects and achieve highly accurate positioning with RTK.
PPP also uses the GNSS signal carriers, but without differencing the measurements (or ‘observables’) between the user and a known reference station. This is possible by incorporating external information in the solution, typically highly accurate (satellites clock and orbit) products derived from global networks. However, the accurate prediction of the state of the atmosphere, also crucial for PPP, is not normally available from these networks. Therefore, similarly to RTK, modelling and prediction of the atmosphere are necessary to mitigate its effects and are also at the top of the current PPP research agenda.
Furthermore, both in RTK and PPP not only natural but also anthropogenic (i.e. originating from human activity) interference can degrade positioning accuracy. The application of signal processing techniques tailored to the features of the interfering signals can improve the quality of the measurements that are then used to generate both PPP and RTK solutions. Additionally, receivers designed according to the software-defined radio (SDR) paradigm represent a low-cost alternative to commercial solutions for atmospheric monitoring, in particular, ionospheric TEC estimation and scintillation detection.
GNSS is currently being ‘modernized’, through measures to facilitate interoperation between systems (GPS, GLONASS, Beidou, Galileo), as well as the broadcast of new signals. This availability/interoperability of different signals/systems increases the number of observables, allowing better accuracy and reliability, also improving the ability to monitor and model the atmosphere, as well as other sources of interference.
High accuracy RTK and PPP require also the reliable resolution of the signal carrier phase ambiguity (the integer number of cycles necessary to unambiguously represent the distance between satellite and receiver), which is an unknown parameter in the position estimation process.
A disturbed atmosphere, the presence of interference or indeed any other errors, can impair carrier phase ambiguity resolution (AR), in particular by extending the time needed for the solution to converge, disrupting real-time operation. The main research aim of the project, therefore, is to achieve real-time AR in RTK and PPP through the integration of all available GNSS systems and signals, which together with enhanced interference detection and atmospheric modelling can lead to instantaneous positioning accuracies at the level of centimetres. In addition, the project will also develop new real-time precise orbit and clock products, in particular for Galileo, which will assist AR and are essential for EGNSS based high accuracy positioning.
The quality, innovation and credibility of this research programme are ensured by world-leading capabilities existing within the consortium, developed over the last ten years by the lead industrialists and researchers that will train the Fellows. Clearly, the research training in this project could not be accomplished by any of its beneficiaries individually. The step-change in GNSS real-time positioning proposed in this project will be its main research output – an output that will bring much-needed benefits to current industries such as agri-tech and offshore, and one which once fully proven and utilised in these industries will inspire its use by others. And as this real-time high accuracy becomes more easily available it is envisaged that it could become the new norm even in mass market applications.
The project is concentrating on research that will pave the way for the development of a service that can ensure the enhanced real-time high accuracy positioning that is desperately needed by markets such the Agri-Tech market and potentially many others that will become apparent as the project evolves and results are disseminated.
TREASURE is providing coordinated multi-sectoral and multi-disciplinary cutting-edge research that will address this through an integrated programme of academic and industrial training.