This paper presents an end to end solution towards authenticated positioning using only Galileo E1B signal by utilizing the Open Service Navigation Message Authentication (OSNMA). One of the primary objectives of this work is to offer a complete OSNMA-based authenticated position solution by releasing FGI-GSRx-v2.1.0 (an open-source software-defined multi-constellation GNSS receiver) update. The idea is to bridge the gap between two open-source implementations by Finnish Geospatial Research Institute (FGI): FGI-GSRx and FGI-OSNMA (an open-source Python software package). FGI-GSRx-v2.1.0 utilizes FGI-OSNMA as an OSNMA computation engine to generate the authentication events with the information whether a tag is valid or not. FGI-GSRx compute the position authentication on the navigation layer for the Galileo signal that is OSNMA verified and have C/N_0 greater than 30 dB-Hz. OSNMA-based position authentication is presented through the findings from two real-world open sky use cases: a clean signal and a spoofed signal recorded during the Jammertest 2023 in Andøya, Norway. The results show the availability of authenticated position for 80.86% for clean signal and 10% for the spoofed scenario during the complete simulation interval. A comparison of authenticated versus non-authenticated position solutions presents high deviation of 3DRMS, mean and standard deviations of not authenticated solution which is indicative of change from the stationary true reference in case of a spoofing event in open sky.

Dilution of Precision (DOP) is routinely used in GNSS to assess the quality of the constellation geometry for the positioning algorithm. Those DOP factors are computed from the estimation covariance of a snapshot weighted least squares (WLS) estimate under certain hypotheses. This paper proposes to define DOP factors for GNSS solutions based on Factor Graph Optimization (FGO). Factor Graph solutions have become popular in the GNSS domain. They allow to easily model probabilistic contraints, called factors, over a large time window, by mixing observations and motion constraints accross consecutive epochs. The solution is solved by performing a batch WLS estimation for the states at all considered epochs, using all available factors. Due to the simple nature of the estimation algorithm - a WLS solution - it is possible to derive the theoretical estimation error covariance, which will indicate the accuracy of the computed solution. In this paper, a formula is proposed to approximate the DOP for the factor graph solution. Then, the formula is validated in various scenarios involving fixed or changing satellite visibility.

With the booming development of low earth orbit (LEO) satellite constellations, enhancing the global navigation satellite system (GNSS) performance based on LEO satellites is attracting more and more research attention. Compared with medium earth orbit (MEO) satellites, LEO satellites have faster motion speeds and more rapid geometric changes. When combined with GNSS, they can effectively shorten the required convergence time of precise point positioning (PPP), which is one of the main advantages of LEO navigation augmentation system. To achieve this goal, a dedicated LEO navigation augmentation signal needs to be broadcasted, and the signal needs to meet the following design requirements: (1) It can support high-precision carrier phase measurement to achieve PPP function (2) Can provide high data rate to meet the broadcasting needs of precise navigation messages (3). The signal frequency band should be within the GNSS frequency band to reduce the complexity and cost of GNSS/LEO receivers (4) the spectrum of LEO navigation augmentation signal should be separated from the GNSS signal spectrum as much as possible to reduce interference with the GNSS signal. This paper takes the GNSS L1 and L5 frequency bands as examples to conduct a preliminary design of LEO navigation augmentation signal. From the perspective of reducing interference to GNSS signals, the carrier frequency of the LEO navigation augmentation signal is selected, and the modulation type is designed. In order to meet the requirements of both high-precision measurement and high data rate broadcasting, it is proposed that the LEO navigation signal consists of a measurement component for modulating low-speed messages and a data component for modulating high-speed messages. These two signal components are combined into one signal using multiplexing code shift keying (MCSK) method. On this basis, compatibility assessment was conducted, and the impact of LEO navigation signals on GNSS signal was further analyzed.

Traditional Global Navigation Satellite Systems (GNSS) are subject to intentional or unintentional disturbances in the northern regions of Norway, leading to loss of critical infrastructure. The VHF Data Exchange System (VDES) has been suggested as an alternative source of positioning, navigation and timing (PNT), based on statistical estimates, for maritime applications. However, an empirical investigation into the feasibility of such a contingency-system has only recently become possible after the launch of the NorSat-TD satellite with purpose-designed VDES ranging downlink signal capabilities. This paper presents an analysis of the characteristics of empirical VDE-SAT range measurements and a system-level performance analysis of a GNSS-contingency system based on the empirical ranging data. Using the equated error level of the signal, the positioning performance of simulated autonomous systems of VDE-SAT PNT-sources is analysed, followed by an assessment of the combination of the empirical VDE-SAT range measurements and traditional GNSS measurements in a critical GNSS contingency scenario. In total, 236 VDE-SAT pseudorange observations obtained from eleven satellite passes recorded in July 2023 were used. Residual analysis shows that the range measurements have a standard deviation of 260.8 m. The previously neglected atmospheric propagation effects on a VDE-SAT range measurement are shown to be significant, and the largest effect is likely to be the time-delay due to the ionosphere. The system performance analysis shows that VDE-SAT as a PNT-source could be used as a possible future general navigation backup system, with a positioning accuracy within 1000 m. Finally, an important conclusion is that a contemporary GNSS-contingency system is possible with the measured signal performance, where NorSat-TD acting as a PNT-source can, under the correct geometric conditions, allow a positioning accuracy within 1000 m in combination with partial GNSS coverage at the user. This project was funded by the ESA NAVISP program.

The increasing complexity of lunar exploration missions necessitates stricter navigation requirements, especially when human life is involved. Extensive research is currently being conducted on various positioning systems suitable for the lunar environment. These include both the exploitation of terrestrial GNSS (Global Navigation Satellite System) signals and the deployment of a lunar-dedicated satellite system known as the Lunar Communication and Navigation Services (LCNS). In order to meet the demanding navigation requirements, the usage of one or more lunar beacons to enhance Positioning, Navigation, and Timing (PNT) performance for different assets is under investigation to complement LCNS system. This research aims to demonstrate the improvement of PNT accuracy by exploiting Differential LCNS (DLCNS) positioning techniques. Both Single Point Positioning (SPP) and DLCNS techniques processed with estimation algorithm such as Weighted Least Squares (WLS) and Extended Kalman Filter (EKF) were developed in a simulated lunar environment to assess their performances.

This paper addresses the implementation of an integrity monitor as part of a factor-graph-based absolute and relative position estimator for swarm navigation. Applications that use small Unmanned Aerial Vehicles (sUAV) are increasing in demand and complexity. Using multiple possibly dissimilarly equipped sUAVs to perform tasks such as infrastructure inspection or mapping may not only significantly reduce the time required to complete a task but also reduce the risk of threats to population and property due to the reduced complexity and weight, increased reliability, longer endurance of the smaller platforms, and, most importantly, the ability of the swarm to increase safety by exploiting the increase and reliability of knowledge in distributed cognition and swarm-wide collaboration.

In previous work, the authors introduced the use of factor graph optimization (FGO) for decentralized sUAV position estimation. In the proposed method, each of the swarm members gathered as much observations as possible either directly from its sensors (e.g., range-radios, GNSS, inertial, laser-range scanner, camera), or indirectly from other sUAVs via the swarm network (Figure 1). These observations are then used to setup a factor graph consisting of both measurement and motion model residuals. Finally, this factor graph is optimized to obtain the sUAV position estimate (either absolute or relative). Flight tests and simulation result have shown good estimation accuracy performance in partial GNSS-denied environments when the gathered observations provide sufficient constraints for the algorithm to converge.

In this paper, the authors address the integrity aspects of the proposed method. In particular, the detection of faults (off-nominal conditions) in the measurements (similarly to receiver autonomous integrity monitoring), a method to assess the observability of the estimator, and the selection of the best possible subset of observations if it is overdetermined. The paper will also include some preliminary flight test results with programmed sensor failures.

The aim of this work is to develop basic findings for a continuous Signal Quality Monitoring system based on a measurement campaign. Four Galileo satellites were repeatedly recorded and their metrics were analyzed. Due to the stable course, thresholds for the detection of threat models can be determined. These values were tested against simulated signals and the sensitivity of the detection was found to be satisfactory. Based on the convergence behavior of the data, a recommended measurement duration of 180-200 seconds can be recommended. Finally, the influence of the GPU and memory clock on the performance of predefined conditions close to the receiver was tested. The core clock of the GPU was identified as the bottleneck of the processing.

Global Navigation Satellite Systems are widely used in critical infrastructure and safety of life applications such as aviation, maritime and land transportations. With such widespread use, open signal descriptions, and a crowded RF spectrum, jamming and spoofing are well-known threats to GNSS. GNSS Resilience and Integrity Technology (GRIT) is a firmware suite developed for NovAtel OEM7 receivers to expand situational awareness and interference detection and mitigation tools across applications and environments to protect against GNSS threats including jamming and spoofing attacks. GRIT includes Interference toolkit (ITK) and spoofing detection toolkit (SK) to identify when a GNSS signal is under threat. Recently, open service navigation massage authentication (OSNMA) implementation joins the NovAtel’s multi-layer protection suite against malicious attack. OSNMA enhances the GNSS security by cryptologic protection by implementing on the newly developed Galileo E1B Open Service Navigation Message.

Norwegian jamming and spoofing test occurred during 18-22 of September 2023 in Bleik, Norway. During Jammer Test 2023, various methods were used to interfere and manipulate navigation systems to mislead the participant’s equipment. These tests included stationary meaconing on GPS L1 and L2 bands which involved retransmission of live sky signal. Furthermore, different methods of spoofing were tested on multiple constellations and frequencies including coherent and incoherent stationary spoofer using synthetic ephemeris where the transmitted satellite ephemerides are different from the live sky satellites. During each meaconing and spoofing tests, varying jamming scenarios were executed simultaneously depending on the test such as five minutes of jamming on all signals before spoofing begins or continuous jamming of non-spoofed signals during scenarios.
This article provides NovAtel receivers jamming and spoofing detection performance of actual data collected during the jammer test 2023. The jamming detection provides spectrum monitoring and jamming characterization on all GNSS bands. The effectiveness of the anti-jam and anti-spoofing technology is demonstrated using representative complex spoofing and jamming test cases during this event. OSNMA detection results for various scenarios will be provided and comparison of the benefits and limitations of OSNMA and receiver-based spoofing detection metrics will be discussed in detail.

Magnetic flux density (MFD) fingerprint map matching is a technique which can provide absolute position solutions by comparing a series of MFD measurements with a database [1–4]. The standard technique of fingerprint map matching relies on consistent measurement of the same physical phenomena during the survey (mapping) and the location phases [4]. However, fluctuations in MFD due to AC electricity, influenced by dynamic power requirements like the operation of a 3 KW kettle, challenge standard fingerprint map matching (Figure 1).

This paper addresses this challenge by employing spectral filtering to isolate MFD from AC sources in both the database creation and navigation phases. The resulting isolation of this temporal variable source enhances the base map's resilience to changes over time, ensuring its functionality regardless of the building's power status. This is particularly vital for applications such as firefighting operations, where the base map's effectiveness is crucial irrespective of the presence or absence of AC mains current.

The experimental environment for this paper is outdoors, which enables full control of the magnetic environment, in which a simulation of unshielded underfloor cables is used (Figure 2). The experiment involves a single AC source alongside multiple DC sources (Figure 3). This filtering technique should work anywhere and future work could bring this technique indoors. By using a variety of different magnetometers with different sampling rates the effectiveness of the filtering is analysed.

In conclusion, this study enhances MFD fingerprint map matching by effectively isolating AC-induced variability, setting the stage for increased robustness of this technique for future applications in indoor navigation.

References

1. Akai N, Ozaki K. 3D magnetic field mapping in large-scale indoor environment using measurement robot and Gaussian processes. In: 2017 International Conference on Indoor Positioning and Indoor Navigation, IPIN 2017 [Internet]. Sapporo, Japan: IEEE; 2017 [cited 2023 Apr 10]. p. 1–7. Available from: http://ieeexplore.ieee.org/document/8115960/
2. Ashraf I, Kang M, Hur S, Park Y. MINLOC: Magnetic Field Patterns-Based Indoor Localization Using Convolutional Neural Networks. IEEE Access [Internet]. 2020 [cited 2021 May 25];8:66213–27. Available from: https://ieeexplore.ieee.org/document/9056514/
3. Ashraf I, Zikria Y Bin, Hur S, Park Y. A Comprehensive Analysis of Magnetic Field Based Indoor Positioning with Smartphones: Opportunities, Challenges and Practical Limitations. IEEE Access [Internet]. 2020 [cited 2022 Sep 13];8:228548–71. Available from: https://ieeexplore.ieee.org/document/9301308/
4. Hanley D, Oliveira ASD de, Zhang X, Kim DH, Wei Y, Bretl T. The Impact of Height on Indoor Positioning With Magnetic Fields. IEEE Trans Instrum Meas [Internet]. 2021 [cited 2023 Mar 29];70:1–19. Available from: https://ieeexplore.ieee.org/document/9354181/
5. IET (Institution of Engineering and Technology). Requirements for Electrical Installations: IET Wiring Regulations (18th Edition) [Internet]. 18th ed. 2022. Available from: https://electrical.theiet.org/bs-7671/about-bs-7671/

Digitalization has revolutionized the maritime industry. Technological advancements in navigation and positioning system and tools, like Electronic Chart Display and Information System (ECDIS) have increased the information flow and processing need. The visual and mental complexity to handle these advanced systems can be overwhelming . What would be the impact of these advancements in navigation systems on the Situational Awareness of navigator while encountering complex navigation scenarios.
Training/ with simulator data provides an opportunity for the crew to familiarize themselves with the user interfaces of these complex navigation systems and prepare them to handle various complex navigation scenarios, respond and assess their responses for better preparedness and improved situational awareness (SA). However, it is also important to be able to understand how good the navigatror's situational awareness actually is.
We propose a SA Tool that establishes optimal conditions for evaluating situational awareness, with insights informing the development of intuitive systems and user-interfaces. In the domain of maritime safety, an inverse correlation exists between situational awareness and scenario and system complexity, emphasizing the need for effective training and assessments for improving situational awareness . The SAGAT method (Situational Awareness Global Assessment Technique, Endsley,2000), which is well established in other domains, is employed to calculate an individual’s SA score. The tool developed can evaluate participant’s situational awareness in different navigational scenarios on Ship Handling Simulators using the latest navigation tools. It employs a dynamic questionnaire with contextual maps to assess the SA of the participants and integrates a rule-based system, to evaluate the performance of the participants and calculate a situational awareness score, providing a dedicated interface for real-time evaluation and result storage. This tool offers numerous possibilities in the field of assessing the SA of navigators.