A MATLAB Toolset to Determine Strict Gaussian Bounding Distributions of a Sample Distribution

Nowadays one can use four global navigation satellite systems (GNSS). Two of them are complete constellations (GPS, Glonass) and two (Beidou, Galileo) are already usable and will be finish in the near future. Additionally satellite based augmentation systems (SBAS) like WAAS, EGNOS, GAGAN or QZSS complement the GNSS service. However, within all systems one can observe changes, modifications, and updates every year. This can be related to satellite renewables leading to signal property changes. Especially, for safety critical applications using GNSS, like advanced receiver autonomous integrity monitoring (ARAIM) or ground-based augmentation systems (GBAS) the new or changed signal properties are of high interest. With the help of detailed information about the signal deformation and the received signal power it is possible to calculate realistic error bounds and consequently realistic protection level for these kinds of safety critical applications. This paper presents an overview of the findings according new signals or signal configurations of GPS, Beidou and QZSS of the last two years. After a brief introduction of the measurement facility the paper will introduce basic analysis about the quality of the signal shape in spectral and modulation domain. Using our precise calibrated measurement facility, we will also present an analysis of the transmitted satellite signal power including estimates about the power sharing among individual signal components within each band. Considering the measured power in relation to the boresight angle of the satellite one can derive a cut through the antenna pattern of the satellite and can assess the antenna symmetry properties. Examples for different satellites will be presented. Finally, we will end with a conclusion regarding the considered signal developments and its impact on GNSS users.

As Global Navigation Satellite System continues to upgrade, the number of satellite increases and new signals in different frequencies are available. This offers users some benefits such as increased availability and improved diversity of signal. For safety-of-life users like aviation, higher availability of integrity is the key goal. A technology providing integrity with little or no ground infrastructure is receiver autonomous integrity monitoring (RAIM). As more satellites are visible to the receiver, the redundancies increase and RAIM availability for detecting faults improves. Moreover, the ionosphere delay could be eliminated through multi-frequency combination. The Advanced RAIM (ARAIM) uses multi-constellation and multi-frequency GNSS and hopes to provide vertical guidance for aircraft. For evaluating ARAIM in flight, an inexpensive flight is executed by an unmanned aircraft systems (UAS) with a developed ARAIM software receiver. The receiver supports civilian signals including GPS L1 C/A, L2C and GLONASS G1, G2. An efficient software architecture are proposed for the real-time purpose. Using the outputs from the receiver, a developed ARAIM toolbox computes the protection levels. Field test is conducted by flying the UAS on a live test campaign. The ARAIM performance during the flight shows that the vertical protection level achieves the target.

Two Receiver Autonomous Integrity Monitoring (RAIM) architectures, Advanced RAIM (A-RAIM) and Relative RAIM (R-RAIM), are compared with two different RAIM algorithms, the Classic method and the Multiple Hypothesis Solution Separation (MHSS) method. The difference between A-RAIM and R-RAIM is in the positioning methods that produce different error models and projection matrices for integrity monitoring. The difference between RAIM algorithms lies in the methods of risk distribution. The influences of different positioning methods on integrity results are analysed in this paper via a generalized RAIM framework. Simulation results for the LPV-200 service with worldwide coverage show that the R-RAIM position domain method has the best results, while the differences between these methods decrease with application of the optimization method.

With the growing availability of navigation satellite constellations from more than one service provider, emergence of multi-constellation Global Navigation Satellite System (GNSS) makes it possible to develop Receiver Autonomous Integrity Monitoring (RAIM) capability with improved range measurement redundancy and accuracy. An emerging concept for receiver avionics that leverages the availability of multiple constellations, called Advanced RAIM (ARAIM), is being developed with a vision of not only providing worldwide approaches with vertical guidance, (Localizer Performance with Vertical Guidance, LPV-200, in particular) but it would also significantly expand Required Navigation Precision (RNP) operations availability worldwide. In the design of ARAIM, this improved capability stems mainly from introduction of an Integrity Support Message (ISM). The ISM is a periodically updated set of parameters that represent the statistical characterization of the core navigation constellation performance. This ISM is received by and utilized in the user avionics as a priori information in the ARAIM user algorithm. One critical issue is that when the statistical characterization of the core constellation performance is not accurate, ARAIM integrity performance may degrade. In our previous paper, we analyzed the sensitivity of Vertical ARAIM (V-ARAIM) performance to the ISM parameter deviations, leading to very interesting and important findings regarding ISM sensitivity. In our analysis, the term “deviation” is used to refer to an increase in the ISM values representative of actual core constellation performance relative to the broadcast ISM parameter values. In this paper, we extend the earlier analysis to Horizontal ARAIM (H-ARAIM). H-ARAIM requires a fault exclusion capability to meet the stricter RNP continuity requirements. The purpose of this paper is to see how the sensitivity characteristics of ARAIM to ISM deviation from actual values differ between H-ARAIM and V-ARAIM. The analysis in this paper, along with the analysis done previously for V-ARAIM, will help develop procedures that could be applied consistently and systematically to determine a set of “close-to-optimal” ISM parameter values to broadcast. This will facilitate global acceptance of an ISM update process.

As an advanced algorithm for receiver autonomous integrity monitoring (RAIM), advanced RAIM (ARAIM) has gained considerable attention in the civil aviation sector and is gradually finding applications in other fields. However, with the increasing number of visible satellites, the number of fault subsets processed by the multiple hypothesis solution separation (MHSS) method grows exponentially, imposing a substantial computational burden on the receiver. Furthermore, ARAIM’s uniform distribution of integrity and continuity risks among fault subsets results in overly conservative protection levels (PLs). These challenges are often addressed as separate issues. However, this study proposes a novel PL optimization algorithm that incorporates a subset grouping method with a feedback structure to reduce the number of fault subsets, thereby decreasing detection time. In addition, an improved cuckoo search algorithm (ICSA) is developed to allocate integrity and continuity risks more effectively, optimizing the PLs. Experimental results demonstrate the effectiveness of the proposed method. Compared to ARAIM, without IMU, the protection level optimization of proposed algorithm improves by 34.38% and 35.06% in the vertical and horizontal directions, respectively; with IMU, the protection level optimization of proposed algorithm improves by 74.21% and 74.49% in the vertical and horizontal directions, respectively. In addition, due to the fault subsets reduction, the fault detection time is reduced by 54%, 47%, and 26% compared with ARAIM, FSPA, and Feedback ARAIM, respectively.

This paper evaluates the potential capacity of Receiver Autonomous Integrity Monitoring (RAIM) algorithms for Global Positioning System (GPS) and GPS Aided GEO Augmented Navigation (GAGAN) to support approach and landing phases of flight with vertical guidance. As the traditional RAIM does not support vertical guidance, Advanced RAIM (ARAIM) with potential to achieve worldwide coverage of vertical guidance, is used. These algorithms have focused on the Horizontal Protection Level (HPL) and Vertical Protection Level (VPL). User position is computed by detecting and excluding faults within the navigation solution and position accuracies are also provided. It is found that using RAIM, Position Dilution of Precision (PDOP) mean was good (1.5674) and Position Error (PE) was estimated to be 9.4042m with Fault Detection and Exclusion (FDE) implementation. While on the other hand, to increase horizontal and vertical accuracies, Advanced RAIM algorithm is implemented using GPS and GAGAN data. In case of GPS, Horizontal Protection Error (HPE) mean is 32.8541m and Vertical Protection Error (VPE) mean is 19.9901m. In case of GAGAN, HPE mean is 2.7190m and VPE mean is 3.3010m, thus achieving 95 percent accuracy requirement.

The Advanced Receiver Autonomous Integrity Monitoring (ARAIM) provides an Aircraft‐Based Augmentation System function for aircraft Global Navigation Satellite System equipment. Currently, the consideration of temporal correlations of test statistics is an important update to the ARAIM baseline algorithm. However, due to the tight budgets of integrity and continuity, the updated ARAIM Fault Detection and Exclusion (FDE) is not satisfactory in availability coverage. The baseline algorithm is based on equal allocation of integrity and continuity, which causes ARAIM to be susceptible to faults and satellite outages. An availability optimisation of ARAIM FDE based on dynamic budget allocation is proposed, aiming to make full use of the prior knowledge provided by the Integrity Support Message (ISM). The contribution of each solution separation test in the ARAIM FDE to the total continuity and integrity risks is estimated, and the continuity and integrity allocation constraints are obtained. The impacts of faults and satellite outages on availability are analysed, and a predictive Protection Level (PL) for ARAIM FDE is proposed for use as an objective function for optimising risk allocation. Then, a risk allocation method based on the multiplier penalty function method is proposed. The performances of the baseline algorithm and the proposed method under the maximum Number of Effective Samples are simulated. For dual‐constellation H‐ARAIM, the optimised Horizontal PL (HPL) is 40% lower than that of the baseline algorithm on average, and the average number of critical satellites supporting RNP 0.3 is less than 1 worldwide. For the three‐constellation V‐ARIAM, the optimised HPL is 27% lower than that of the baseline algorithm on average, and the optimised Vertical PL (VPL) is 18% lower. The proposed method has high availability coverage and can better respond to the requirements for high‐performance navigation services.

The Satellite Based Augmentation System (SBAS) can transmit a variety of correction information through satellite, such as ephemeris error, satellite clock error, ionospheric delay and integrity information, which will provide better navigation information for civil aviation aircrafts. Compared with the Instrument Landing System (ILS) commonly used in civil commercial aviation, the SBAS has the advantages of low environmental requirements and lower equipment cost. And the SBAS can provide lower-cost navigation services for civil aviation (including general aviation), so that the significant economic and social benefits will be produced. Based on SBAS satellite broadcast signals, using the navigation receiver with SBAS functions to get the broadcast correction information and integrity information from the Multi-Functional Satellite Augmentation System (MSAS) of Japan. The raspberry pi will receive the information through the USB interface and select them. Finally, the data will be Displayed on the external display. The user uses the display to input fixed instructions to select and compare whether to use SBAS positioning accuracy, which provides a visual demonstration platform for civil aviation teaching.

Global navigation satellite system (GNSS) plays a crucial role in many fields, such as aerospace and transportation. Integrity is the measure of trust used in GNSS positioning especially in safety-critical applications. Advanced receiver autonomous integrity monitoring (ARAIM), taking full advantage of multi-constellation GNSS, shows huge potential to provide vertical navigation in civil aviation en route navigation and terminal approaches. However, the multi-constellation ARAIM also greatly exposes computational complexity and potential performance hazards in fault modes determination and fault-tolerant positioning. From the perspective of integrity risk control, rather than the pursuit of better positioning accuracy blindly for safety-critical applications, the concept of constellation dynamic selection is proposed and implemented in ARAIM and the performance analysis is discussed in this paper. Only the best two constellations which have the best vertical geometry performance are involved in ARAIM calculation anytime anywhere. The proposed method shows superiority in both integrity availability and computational complexity in both simulations and actual GNSS signal experiments. While the computational complexity is less than 10% of that using four constellations, 100% availability under LPV-200 criteria can be achieved in worldwide coverage experiment. The proposed method also overcomes the shortcomings of ARAIM with two fixed constellations and shows good robustness under depleted scenarios. Furthermore, the statistics results from observation stations proved the applicability and generality of the proposed method under current developing GNSS constellations.

Civil aviation transportation equipment is more convenient and faster than other transportation tools and is an essential part of intelligent transportation. It is significant to study the reliability of positioning information and enhance traffic safety. Advanced receiver autonomous integrity monitoring (ARAIM) can provide vertical guidance during the different navigation stages in civil aviation fields. The traditional multiple hypothesis solution separation (MHSS) algorithm distributes the probability of hazardous misleading information (PHMI) and probability of false alarm (PFA) uniformly over all visible satellites resulting in reduced global availability of ARAIM. Aiming at this problem, we proposed an adaptive simulated annealing particle swarm optimization (ASAPSO) algorithm to redistribute integrity and continuity risks and establish a protection level optimization model. Based on the real BeiDou navigation satellite system/global positioning system (BDS/GPS) data, the experimental results show that the optimized algorithm can reduce the vertical protection level (VPL), and the ARAIM global availability of BDS/GPS is improved by 1.73%∼2.73%. The optimized algorithm can improve the availability of integrity monitoring at different stages of the navigation system and provide a basis for ensuring the reliability of the positioning results.

We provided an overview of various satellite-based augmentation systems (SBAS) options for augmented GNSS services in Australia, and potentially New Zealand, with the aim to tease out key similarities and differences in their augmentation capabilities. SBAS can technically be classified into two user categories, namely SBAS for aviation and "non-aviation" SBAS. Aviation SBAS is an International Civil Aviation Organization (ICAO) certified civil aviation safety-critical system providing wide-area GNSS augmentation by broadcasting augmentation information using geostationary satellites. The primary aim was to improve integrity, availability and accuracy of basic GNSS signals for aircraft navigation. On the other hand, "non-aviation" SBAS support numerous GNSS applications using positioning techniques such as wide-area differential-GNSS (DGNSS) and precise point positioning (PPP). These services mainly focus on delivering high-accuracy positioning solutions and guaranteed levels of availability, and integrity remains secondary considerations. Next-generation GNSS satellites capable of transmitting augmentation signals in the L1, L5 and L6 frequency bands will also be explored. These augmentation signals have the data capacity to deliver a range of augmentation services such as SBAS, wide-area DGNSS and PPP, to meet the demands of various industry sectors. In addition, there are well-developed plans to put in place next-generation dual-frequency multi-constellation SBAS for aviation. Multi-constellation GNSS increases robustness against potential degradation of core satellite constellations and extends the service coverage area. It is expected that next-generation SBAS and GNSS will improve accuracy, integrity, availability and continuity of GNSS performance.

The field of GNSS integrity comprises a plethora of integrity related algorithms, each featured with different characteristics. These algorithms use a priori information of some parameters in order to provide integrity information to the user. One type of these algorithms, RAIM, is extensively used in the maritime domain in order to provide an indication if the position calculated is likely to be outside of the requirements of maritime performance standards, as it is required by IMO regulation. The term “Classical RAIM” refers to fully autonomous algorithms which can implement only one, a combination or all the following capabilities: Fault Detection, Fault Exclusion and Protection Level computation. In order to provide this indication, a GNSS receiver shall incorporate RAIM using at least Fault Detection (FD) algorithms, or similar means to determine if accuracy is within the performance standards and provide an integrity indication. In order to harmonise and ensure the correct RAIM algorithms implementation, its usage is standardised by the standard IEC 61108, in particular 1 and 3 series for GPS and Galileo constellations. The current RAIM definition in standards does not constrain the specific RAIM algorithm implementation deliberately in order to let the manufactures implement the most suitable one for their applications. In addition, in order to prove that a receiver is compliant with the requirements specified in this standard, two simple tests are proposed. The first one intends to test the performance of the receiver under safe and caution states, and the other one tests the unsafe state. However, as it is recognised by IALA in the last workshop on the future of marine radiobeacons, “current implementations of Receiver Autonomous Integrity Monitoring (RAIM) are considered inadequate due to the current lack of maritime specific RAIM algorithms.” It has been observed some limitation of current RAIM implementations beyond a specific algorithm for maritime. First of all, the relaxed requirements, in terms of high probabilities of false alarms and of not detecting an error condition, might be justified due to the limitations expected from some implementations of RAIM algorithms. In addition, requirements for GPS and Galileo RAIM differs significantly. Secondly, they are based on some hypothesis as single-failure assumption, a priory estimation of error values components (too conservative in order to provide the integrity required for any user under any condition) or the no existence of biases in faultfree measurements that may not ensure the integrity required if these hypothesis are not met in maritime domain. Finally, considering the simplicity of the aforementioned tests, which do not provides a set of parameters for testing or even assess the probabilities of miss-detection or false alarm, there is no assurance that the RAIM algorithm implemented in the receiver correctly provides the integrity required. To ensure this, it would be necessary to improve the test method in order to characterize the value of the introduced error and add new tests to evaluate the complete set of requirements to the implemented integrity algorithm. The GSA (European GNSS Agency), under GSALOT3TRANS framework contract, analysed the implementation of EGNSS in the area of transport applications. In particular, the Specific Contract 7 (SC7) MarTech it is being assessed the potential use of SBAS combined with RAIM in maritime and inland waterways (IWW) domains. The industrial partners of this specific contract are VVA Brussels (prime) and GMV. Although is not contemplated in any of the aforementioned regulations, the use of SBAS on top of other GNSS technologies that use RAIM may imply some important advantages. The first advantage and the most obvious of the SBAS corrections usage on top of RAIM is the increased performances in terms of accuracy, availability and continuity. The use of SBAS integrity information may also overcome the limitation of some RAIM algorithms that are only able to detect one faulty satellite. SBAS integrity messages also contains valuable information about the estimation of error components that may be used by the RAIM algorithm on real time with enough level of integrity to improve the performance. The aim of this paper is to provide a summary of the activities developed so far as part of GSALOT3TRANS SC7 regarding the current RAIM limitations in the maritime domain and the potential use of SBAS in combination with it to overcome some of these limitations.

The aim of the paper is to analyse the distribution of update periods of Issue of Data (IOD) parameters in Galileo F/NAV and Navstar Global Positioning System (GPS) LNAV messages. For this purpose, a new method aiming at the reconstruction of IOD update periods reported by a network of monitoring stations is proposed. Over one year of Galileo F/NAV and over three years of GPS LNAV data is processed and consolidated using the proposed method. A reconstruction rate of 99.66% is achieved for the Galileo F/NAV messages. To extract the information on the consecutive update periods of IOD parameters, two metrics are proposed. It was observed that Galileo F/NAV messages can experience fast single and fast double updates. Double updates happen at worst over two subsequent Galileo F/NAV sub-frames. The obtained results suggest a possible impact on Satellite-Based Augmentation System (SBAS). In order to assess the impact on a drafted Dual Frequency Multi Constellation (DFMC) SBAS Standards And Recommended Practices (SARPs), a Galileo F/NAV IOD selector, whose task is to select a specific IOD for augmentation in SBAS, is proposed and implemented. The design of the Galileo F/NAV IOD selector takes into account the observed IOD update periods as well as relevant requirement defined in the drafted DFMC SBAS Minimum Operational Performance Standards (MOPS). The selector aims at maximising the minimum time that the SBAS user has to decode the navigation message identified by the IOD before it is selected for augmentation. In addition, the maximum time that the SBAS would be using IOD, which is no longer transmitted by the Satellite Vehicle (Sv), is also over bounded by the design. According to the analysed data, it is identified that an optimal time to trigger the selection of new IOD of Galileo F/NAV message for augmentation is 350s when maximising the minimum decoding time. The trigger time guarantees that the SBAS user would always have at least 200s available to decode the Galileo F/NAV message.

Integrity monitoring (IM) is essential if GNSS positioning technologies are to be fully trusted by future intelligent transport systems. A tighter and conservative stochastic model can shrink protection levels in the position domain and therefore enhance the user-level integrity. In this study, the stochastic models for vehicle-based GNSS positioning are refined in three respects: (1) Gaussian bounds of precise orbit and clock error products from the International GNSS Service are used; (2) a variable standard deviation to characterize the residual tropospheric delay after model correction is adopted; and (3) an elevation-dependent model describing the receiver-related errors is adaptively refined using least-squares variance component estimation. The refined stochastic models are used for positioning and IM under the Advanced Receiver Autonomous Integrity Monitoring (ARAIM) framework, which is considered the basis for multi-constellation GNSS navigation to support air navigation in the future. These refinements are assessed via global simulations and real data experiments. Different schemes are designed and tested to evaluate the corresponding enhancements on ARAIM availability for both aviation and ground vehicle-based positioning applications.

The shipping industry is moving towards an e-Navigation concept where a range of electronic and radio navigation technologies will provide harmonized, safe and reliable support for maritime navigation. Augmented GNSS is one of the supporting technologies for e-Navigation. Satellite Based Augmentation Systems (SBAS) could be used to improve accuracy and provide integrity to users. Vessels bound by the International Maritime Organization’s (IMO) Safety of Life as Sea convention (SOLAS) are required to use type approved receivers. Currently, there are neither standards nor regulations to define how the shipborne receiver has to process the SBAS signal from a safety perspective. Non-SOLAS vessels are free to use non-certified receivers and many receivers apply SBAS information, albeit with no guarantees. Shipborne receivers on board SOLAS ships will be able to use SBAS messages through the use of the Multi-system shipborne radionavigation receiver (MSR) standard [1]. SEASOLAS (EGNOS Dual-Frequency Dual Constellation Maritime Safety Service) project analysed a potential safety service with an integrity concept tailored for maritime and inland waterways users. EGNOS V3 Dual Frequency Multi-Constellation service will be available as of 2025. SEASOLAS project was fully financed by the European Commission under the Horizon 2020 program for research and innovation and has been developed by a consortium led by GMV with the European Satellite Service Provider (ESSP), General Lighthouse Authorities (GLA) of the United Kingdom and Ireland, VVA Brussels and Kongsberg Seatex as partners. SEASOLAS project developed a number of advanced solutions based on a receiver that processes EGNOS V3 data and implements autonomous integrity techniques to deal with local error sources whose behaviour is difficult to model and predict. The proposed solutions aim at, on one hand, providing integrity at user level (by bounding the position error with a high confidence level, i.e. the integrity risk); and on the other hand, fulfilling the required performance, at user level, of the SEASOLAS worst-case scenarios. This paper summarises the main outcomes of the activities developed in the frame of the project.