Towards a plug&play solution for real-time precise positioning on mass-market devices

Despite pedestrian and vehicle navigation are the key applications enabled by the development of GNSS technology, the best approach to obtain accurate, reliable, continuous and robust PVT (Position-Velocity-Timing) solutions for this purpose has yet to be identified. The real limiting factor is the environment in which the users usually navigate: e.g. multipath effects and cycle slips in harsh urban environments strongly affect, respectively, pseudorange measurements and the continuity of carrier-phase observations. Therefore, positioning services relying on code-based algorithms cannot always meet the required accuracy - which varies depending on the targeted use case -; on the other hand, phase-based approaches as Real-Time Kinematic (RTK) and Precise Point Positioning (PPP) require strong effort to deal with the ambiguity term and its reinitialization when cycle slips occur. These problems are amplified when GNSS measurements from Android smartphone are considered due to the low-cost, linearly polarized and multi-purpose antenna which inevitably impacts on the quality of GNSS observables. This paper focuses on the performance analysis of GNSS POWER - an algorithm based on the loosely coupling between Single Point Positioning (SPP) solutions and variometric velocity - combined with IGS SSR corrections to increase the accuracy achievable in a real-time stand-alone solution. The integration of SSR corrections within GNSS POWER algorithm is validated in both static and kinematic scenarios using high-end GNSS receivers and Andorid smartphones. The results demonstrated the advantages of using SSR corrections on SPP and GNSS POWER solutions also on Android devices opening to new applications of real-time stand-alone positioning approaches on mass-market devices

Validation of performance of real-time kinematic PPP. A possible tool for deformation monitoring

Structural failures (bridge or building collapses) and geohazards (landslides, ground subsi- dence or earthquakes) are worldwide problems that often lead to significant economic and loss of life. Monitoring the deformation of both natural phenomena and man-made struc- tures is a major key to assessing structural dynamic responses. Actually, this monitoring process is under real-time demand for developing warning and alert systems. One of the most used techniques for real-time deformation monitoring is the Global Navigation Satellite System (GNSS) real-time procedure, where the relative positioning approach, using a well-known reference station, has been applied. This study was conducted to evaluate the actual quality of the real-time kinematic Precise Point Positioning (PPP) GNSS solution for deformation monitoring, where it can be concluded that a promise tool is under development and should be taken into account on actual and near future real-time deformation monitoring studies and applications.This research was supported by the Spanish Science and Innovation Directorate project number AYA2010-18706 and the Generalitat Valenciana Geronimo Forteza research program with project number FPA/2014/056.Martín Furones, ÁE.; Anquela Julián, AB.; Dimas Pagés, A.; Cos-Gayón López, FJ. (2015). Validation of performance of real-time kinematic PPP. A possible tool for deformation monitoring. Measurement. 69:95-108. https://doi.org/10.1016/j.measurement.2015.03.026S951086

Implementation of PPP as new GNSS Observation Type in the Geomonitoring System GOCA

[EN] Early detection of significant movements in both natural and artificial structures is crucial to prevent human, environmental and economic losses. For this reason, Geomonitoring in an active field. GNSS technics are also a filed in which lot of research and improvement have been made in recent years. Some studies have indicated the potential of GNSS technics in the field of Geomonitoring. The aim of this master thesis is developing a software that allows processing GNSS data with Precise Point Positioning technic in the context of the geomonitoring project GOCA. With this implementation, potential of PPP with low cost receiver (U-Blox ZED-F9P) using different products and settings is evaluated in this document. Based on a literature review, that includes the study of GOCA project and a summary of main PPP approaches, a C++ dialog-based software was design and developed, using RTKLIB and WaPPP as software engines. Besides that, two different observations were made (one 12 hours to post-processing and one real time) in order to test the developed software and evaluate the obtained results using different parameters or products. The obtained results reaffirm the potential of the PPP technique, even using low cost receiver. Even some differences between different software engines or IGS products were found, the results allow us to conclude that PPP is a technique with many advantages in the field of geomonitoring, since it avoids the use of several receivers and good accuracies are obtained. However, some aspects need further research in this context, as there is no common criterion for establishing convergence time and new methodologies and algorithms are being developed in the field of PPP processing.[ES] La detección temprana de movimientos significativos en estructuras naturales y artificiales es crucial para prevenir pérdidas humanas, ambientales y económicas. Por esta razón, Geomonitorización es un campo activo. Las técnicas de GNSS son también un campo en el que se han realizado muchas investigaciones y mejoras en los últimos años. Algunos estudios han indicado el potencial de las técnicas GNSS en el campo de la geomonitorización. El objetivo de esta tesis de máster es desarrollar un software que permita el procesamiento de datos GNSS con la técnica de posicionamiento de punto preciso en el contexto del proyecto de geomonitorización GOCA. Con esta implementación, el potencial del PPP con el receptor de bajo coste (U-Blox ZED-F9P) usando diversos productos y configuraciones se va a evalúar en este documento. Basado en una revisión de la literatura, que incluye el estudio del proyecto GOCA y un resumen de los principales enfoques PPP, se diseñó y desarrolló un software basado en diálogos C++, utilizando RTKLIB y WaPPP como motores de software. Además, se realizaron dos observaciones diferentes (una de 12 horas para el post-procesamiento y otra en tiempo real) con el fin de probar el software desarrollado y evaluar los resultados obtenidos utilizando diferentes parámetros o productos. Los resultados obtenidos reafirman el potencial de la técnica PPP, incluso utilizando un receptor de bajo coste. Incluso habiendo encontrado algunas diferencias entre diferentes motores de software o productos IGS, los resultados nos permiten concluir que PPP es una técnica con muchas ventajas en el campo de la geomonitorización, ya que evita el uso de varios receptores y se obtienen buenas precisiones. Sin embargo, algunos aspectos necesitan más investigación en este contexto, ya que no existe un criterio común para establecer el tiempo de convergencia y se están desarrollando nuevas metodologías y algoritmos en el campo del procesamiento PPP.Luján García Muñoz, R. (2020). Implementation of PPP as new GNSS Observation Type in the Geomonitoring System GOCA. http://hdl.handle.net/10251/139668TFG

Maintaining real-time precise point positioning during outages of orbit and clock corrections

The precise point positioning (PPP) is a popular positioning technique that is dependent on the use of precise orbits and clock corrections. One serious problem for real-time PPP applications such as natural hazard early warning systems and hydrographic surveying is when a sudden communication break takes place resulting in a discontinuity in receiving these orbit and clock corrections for a period that may extend from a few minutes to hours. A method is presented to maintain real-time PPP with 3D accuracy less than a decimeter when such a break takes place. We focus on the open-access International GNSS Service (IGS) real-time service (RTS) products and propose predicting the precise orbit and clock corrections as time series. For a short corrections outage of a few minutes, we predict the IGS-RTS orbits using a high-order polynomial, and for longer outages up to 3 h, the most recent IGS ultra-rapid orbits are used. The IGS-RTS clock corrections are predicted using a second-order polynomial and sinusoidal terms. The model parameters are estimated sequentially using a sliding time window such that they are available when needed. The prediction model of the clock correction is built based on the analysis of their properties, including their temporal behavior and stability. Evaluation of the proposed method in static and kinematic testing shows that positioning precision of less than 10 cm can be maintained for up to 2 h after the break. When PPP re-initialization is needed during the break, the solution convergence time increases; however, positioning precision remains less than a decimeter after convergence

A New Cooperative PPP-RTK System with Enhanced Reliability in Challenging Environments

Compared to the traditional PPP-RTK methods, cooperative PPP-RTK methods provide expandable service coverage and eliminate the need for a conventional expensive data processing center and the establishment and maintenance of a permanently deployed network of dense GNSS reference stations. However, current cooperative PPP-RTK methods suffer from some major limitations. First, they require a long initialization period before the augmentation service can be made available from the reference stations, which decreases their usability in practical applications. Second, the inter-reference station baseline ambiguity resolution (AR) and regional atmospheric model, as presented in current state-of-art PPP-RTK and network RTK (NRTK) methods, are not utilized to improve the accuracy and service coverage of the network augmentation. Third, the positioning performance of current PPP-RTK methods would be significantly degraded in challenging environments due to multipath effects, non-line-of-sight (NLOS) errors, poor satellite visibility and geometry caused by severe signal blockages. Finally, current position domain or ambiguity domain partial ambiguity resolution (PAR) methods suffer from high false alarm and miss detection, particularly in challenging environments with poor satellite geometry and observations contaminated by NLOS effect, gross errors, biases, and high observation noise. This thesis proposed a new cooperative PPP-RTK positioning system, which offers significant improvements to provide fast-initialization, scalable coverage, and decentralized real-time kinematic precise positioning with enhanced reliability in challenging environments. The system is composed of three major components. The first component is a new cooperative PPP-RTK framework in which a scalable chain of cooperative static or moving reference stations, generates single reference station-derived or reference station network-derived state-space-representation (SSR) corrections for fast ambiguity resolution at surrounding user stations with no need for a conventional expensive data processing center. The second component is a new multi-feature support vector machine (SVM) signal classifier based weight scheme for GNSS measurements to improve the kinematic GNSS positioning accuracy in urban environments. The weight scheme is based on the identification of important features in GNSS data in urban environments and intelligent classification of line-of-sight (LOS) and NLOS signals. The third component is a new PAR method based on machine learning, which employs the combination of two support vector machine (SVM) to effectively identify and exclude bias sources from PAR without relying on satellite geometry. The prototype of the new PPP-RTK system is developed and substantially tested using publically available real-time SSR products from International GNSS Service (IGS) Real-Time Service (RTS)

REAL TIME PPP APPLIED TO AIRPLANE FLIGTHT TESTS

The availability in real time of GNSS satellites orbits, clock corrections and code and phase biases provided the possibility of application of Real Time Precise Point Positioning (RTPPP). This paper presents the methodology concerning RTPPP and application to kinematic trajectories of airplane flight tests, but without using the carrier phase bias. So, it is PPP float solution. It requires RT positioning estimation, task that most of time presents certain difficulties due to loss of communication or of satellites during maneuvers of the airplane. However, if the corrections become unavailable for a certain period of time, the system starts using the ultra-rapid IGS orbits. The experiments were accomplished taking into account a case simulating RT and another in fact RT, but storing data and corrections for post processing. The PPP solutions obtained either simulating RT or in RT were compared against the PPP post processed solution that uses the final clock and orbit corrections. Then, statistics were generated to analyze the quality of both results. They were applied to kinematic trajectory that on average was 360 km/h, reaching about 600 km/h. The results provided accuracy better than the requisites for such cases which is of about 80 cm in height

Global RTK Corrections for Monitoring Displacements: Geo-Informatics

Developing solutions for real-time positioning is on high demand, conducted by autonomous technologies and IoT. The traditional RTK uses reference stations to correct the position in real-time, however this method has disadvantages, with the need of permanent stations nearby being the bigger one, as well as the lack of scalability. Methods of positioning in real-time using State Space Representation (SSR) messages solve the need of stations in the vicinity. The proposed method in this dissertation adopts SSR messages to correct the positioning, using an open source program package for GNSS positioning named RTKLIB. The main goal of this dissertation is to compute and analyze the final solutions and verify if it is possible to monitor stations in real-time using the proposed method.O posicionamento preciso em tempo-real utilizando Sistemas de Posicionamento baseado em satélites, conhecido vulgarmente por Global Navigation Satellite Systems (GNSS) ou Global Positioning System (GPS), é uma área intensiva de investigação, impulsionado principalmente por aplicações como condução autónoma ou a Internet of Things (IoT). Métodos de posicionamento em tempo-real tradicionais utilizam estações de referência para corrigir a posição dos receptores em seu redor. Porém, estes métodos apresentam várias desvantagens, em particular o facto da qualidade da correção ser dependente da distância à estação, o que obriga à existência de redes densas de estações de referência. Métodos de posicionamento baseados em correções globais resolvem este problema de proximidade. Estes métodos são baseados no conceito em que os erros que afetam o posicionamento são modelados sobre largas áreas em vez da correção direta a partir das observações da estação(ões) de referência(s) mais próximas. O objetivo desta dissertação é implementar um serviço que permita monitorizar a posição de estações permanentes de forma a que se possa detetar deslocamentos devido a causas humanas (e.g., deformação de um edifício) ou naturais (e.g., sismos ou vulcões) usando correções globais, permitindo assim a sua utilização em qualquer ponto da Terra

From RTK to PPP‑RTK: towards real‑time kinematic precise point positioning to support autonomous driving of inland waterway vessels

PPP-RTK is Precise Point Positioning (PPP) using corrections from a ground reference network, which enables single receiver users with integer ambiguity resolution thereby improving its performance. However, most of the PPP-RTK studies are investigated and evaluated in a static situation or a post-processing mode because of the complexity of implementation in real-time practical applications. Moreover, although PPP-RTK achieves a faster convergence than PPP, it typically needs 30 s or even longer to derive high-accuracy results. We have implemented a real-time PPP-RTK approach based on undifferenced observations and State-Space Representation corrections with a fast convergence of less than 30 s to support autonomous driving of inland waterway vessels. The PPP-RTK performances and their feasibility to support autonomous driving have been evaluated and validated in a real-time inland waterway navigation. It proves the PPP-RTK approach can realize a precise positioning of less than 10 cm in horizontal with a rapid convergence. The convergence time is within 10 s after a normal bridge passing and less than 30 s after a complicated bridge passing. Moreover, the PPP-RTK approach can be extended to outside of the GNSS station network. Even if the location is 100 km away from the border of the GNSS station network, the PPP-RTK convergence time after a bridge passing is also normally less than 30 s. We have realized the first automated entry into a waterway lock for a vessel supported by PPP-RTK and taken the first step toward autonomous driving of inland vessels based on PPP-RTK