Precise point positioning (PPP) and real-time kinematic techniques are interesting in several sectors, especially for autonomous applications. These users have high accuracy needs coupled with stringent requirements on continuity, availability, integrity, and convergence time, whose satisfaction can be challenging in harsh environments. Galileo launched on January 2023 the initial high accuracy service (HAS), a European free-of-charge PPP service with a worldwide coverage transmitted on E6 signals and provided through an internet connection. This paper characterizes the Galileo HAS product performance, including orbital errors, clock errors, code biases, and overall signal in space error (SISE), with live signals transmitted since HAS service declaration. The paper also presents the behavior of HAS SIS in the case of four satellite anomalies between September 2021 and August 2022, occurring for Galileo and GPS. Finally, the paper presents the results of HAS performance in both static open sky and road scenarios, showing a few-decimeter accuracy even in environments with degraded visibility. The paper shows the improvements in terms of robustness to satellite anomaly thanks to the Galileo HAS characteristics.

Strong ionospheric electron content gradients may lead to fast and unpredictable fluctuations in the phase and amplitude of the signals from Global Navigation Satellite Systems (GNSS). This phenomenon, known as ionospheric scintillation, is capable of deteriorating the tracking performance of a GNSS receiver, leading to increased phase and Doppler errors, cycle slips and also to complete losses of signal lock. In order to mitigate scintillation effects at receiver level, the robustness of the carrier tracking loop, the receiver weakest link under scintillation, must be enhanced. Kalman filter (KF)-based tracking algorithms are particularly suitable to cope with the variable working conditions imposed by scintillation. However, the effectiveness of this tracking approach strongly depends on the accuracy of the assumed dynamic model, which can quickly become inaccurate under randomly variable situations. This study first shows how inaccurate dynamic models can lead to a KF suboptimum solution or divergence, when both strong phase and amplitude scintillation are present. Then, to overcome this issue, it proposes two self-tuning KF-based carrier tracking algorithms, which self-tune their dynamic models by exploiting the knowledge about scintillation that can be achieved through scintillation monitoring. The algorithms have been assessed with live equatorial data affected by strong scintillation. Results show that the algorithms are able to maintain the signal lock and provide reliable scintillation indices when classical architectures and commercial ionospheric scintillation monitoring receivers fail.

The former Galileo Commercial Service (CS) will provide a High Accuracy Service (HAS) and a Commercial Authentication Service (CAS). The first will disseminate free Precise Point Positioning (PPP) corrections through the E6‐B signal whereas the second will provide authentication capabilities through the E6‐C pilot component that will be encrypted. For this reason, improved processing strategies for data‐only processing need to be investigated. The combined use of Kalman filtering and noncoherent integrations is analyzed in this work. A Software Defined Radio (SDR) receiver has been developed and used for the analysis. Different scenarios were considered including simulated data with decreasing Carrier‐to‐Noise Power Spectral Density Ratio (C/N0) levels and live static and dynamic data collected under harsh environments. It emerges that the use of Kalman filtering with extended noncoherent integrations is an effective approach to improve the performance of data‐only processing.

The Galileo High Accuracy Service (HAS) is currently in its testing phase, in which actual corrections are transmitted along with standard dummy messages. The dissemination of Precise Point Positioning (PPP) corrections is performed using an innovative scheme based on a Reed–Solomon code, which allows the reconstruction of the original navigation message from a subset of received pages. This approach introduces robustness to the reception process and aims at reducing the Time-to-Retrieve Data (TTRD); that is, the time to retrieve the HAS message. This study investigated the HAS demodulation performance considering Galileo signals collected at high latitudes. In particular, a Galileo E6-capable receiver was mounted on a vessel sailing from Bergen to Kirkenes, Norway, and reaching up to 71 degrees North. The trajectory of the vessel was at the border of the Galileo HAS service area and high-latitudes impact reception conditions, potentially leading to poor satellite geometries. Three months of data from January to March 2021 were analyzed, considering several metrics including Bit Error Rate (BER), Page Error Rate (PER), and TTRD. The analysis shows that the Reed–Solomon scheme adopted for data dissemination is also effective at high-latitudes, with daily PER below one percent and mean TTRD in the order of eight seconds when three satellites are broadcasting valid HAS corrections. Lower values of the TTRD are achieved with an increased number of satellites. These values are significantly lower than the update rate of the corrections broadcast by the Galileo HAS.

As the peak of Solar Cycle 25 approaches, space weather events such as Equatorial Plasma Bubble (EPBs) and geomagnetic storms are expected to become more frequent. While EPBs are a primary source of scintillation, geomagnetic storms can either enhance or suppress this activity depending on storm timing, intensity, and induced electric field effects, thereby causing significant ionospheric disturbances that degrade Global Navigation Satellite System (GNSS) signal reception performance. This study presents a novel, systematic evaluation of GPS + Galileo Precise Point Positioning (PPP) performance under intense ionospheric scintillation during the rising phase of Solar Cycle 25 using datasets from globally distributed stations. More than twenty months of data have been systematically analysed, with a focus on stations located in equatorial regions, which are the most affected by strong scintillation. PPP processing was performed using final products from the European Space Agency (ESA) with Multi-GNSS Experiment (MGEX) products employed as backups when ESA data were unavailable. It is shown that under severe scintillation the accuracy of the final PPP solution is severely reduced, with errors more than doubled with respect to calm days. In this respect, frequent cycle slips and anomalies in the input observations are detected. A comparative analysis of GPS-only and GPS + Galileo PPP solutions confirms that integrating Galileo not only mitigates the impact of scintillation but also improves the reliability and accuracy of positioning in challenging space weather conditions.

Nowadays, several smartphones on the market provide multi-frequency multi-constellations GNSS measurements, including carrier phase ones, allowing the achievement of high-accuracy positioning by exploiting Real Time Kinematic (RTK) or Precise Point Positioning (PPP) techniques. This paper will showcase the effectiveness of using smartphone measurements for RTK under different scenarios and for different applications using baselines of different lengths. The impact of the smartphone’s antenna on the solution will also be analysed. The assessment will be performed by evaluating different key performance indicators, including the time to first fix and the horizontal/vertical accuracy. This paper shows that around a 99% fix position can be achieved even using the smartphones’ antennas for the static case under open sky conditions. Moreover, high percentages of fix solutions can also be achieved in kinematic mode by ad hoc tuning of the RTK algorithm.