Safety arguments for next generation, location aware computing

Radio frequency signal compatibility is the basis of interoperability of the Satellite e-Based Augmentation System (SBAS). SBAS should abide by relative international radio regulations of International Telecommunication Union (ITU) and meet the compatibility requirements of radio frequency signal between the Global Navigation Satellite System (GNSS)/SBAS, in order to avoid negative mutual interference. According to ITU Proposal and related reference and assumptions, the paper made simulation of signal receiving maximum power in the BeiDou Satellite-Based Augmentation System (BDSBAS) global signal coverage. And then, interference of BDSBAS to Global Positioning System (GPS)/WAAS (Wide Area Augmentation System) on L1/L5 bands were calculated and analyzed, with equivalent carrier-to-noise ratio as the evaluation parameter. The result shows that the carrier-to-noise ratio decrease of GPS/WAAS caused by BDSBAS B1C and B2a signals are extremely lower than inter-system interference of GPS/WAAS, and thus can be ignored in practical applications. Therefore, BDSBAS will not cause the service performance degradation of GPS and WAAS.

An experiment to measure equatorial amplitude scintillations on the geostationary Wide Area Augmentation System (WAAS) Satellite Based Augmentation System (SBAS) signal was conducted in Cachoeira Paulista (22.70°S, 45.01°W geographic coordinates; −17.74°N, 21.74°E geomagnetic coordinates), Brazil from December 2003 through February 2004. The purpose of this paper is to estimate the scattering height of the irregularities using the WAAS signal scintillations as compared to nearby Global Positioning System (GPS) signal scintillations. Estimating the scattering height is important because the calculated zonal drift velocity of the irregularities using the measured scintillation pattern velocity on the ground is height dependent. Accurate height estimation is also required if one wishes to develop phase screen scintillation models. The difference in the pattern velocities is due to the different signal puncture point velocities with respect to the ionospheric drift. Two east‐west receivers are used to measure the scintillation pattern drift velocity and to compare the results of the geostationary WAAS satellite signal to that of a GPS satellite signal, which has a nonzero ionospheric signal puncture point velocity. By varying the assumed scattering height for the measurements from the nearby GPS signal, the zonal velocity measurements from the GPS scintillations can be matched to those of the WAAS scintillations, and a scattering height estimate can be made. When the puncture points have minimal separation, the inferred ionospheric irregularity zonal velocities should be equal. On the two nights for which data are available, scattering height estimates of 669 ± 209 km for the first night and 388 ± 139 km for the second night were obtained. On the second night, the reported mean hmF2 as calculated using a collocated Digisonde was 385 ± 17 km over the same period as the GPS/WAAS scattering height estimate. The geometry of this experiment was not optimal, but analysis demonstrates that future experiments could be substantially more accurate.

Three years ago, FAA started on an ambitious program to perform research, development and implementation of satellite navigation based on the approval and use of the DoD's Global Positioning System (GPS). One of the research and development (R&D) projects was to determine the capabilities and requirements for a GPS Wide-Area Augmentation System (WAAS), a ground-based GPS augmentation. The FAA's WAAS will consist of up to about 30 ground reference stations that will combine data to estimate separate corrections for clock and ephemeris for each monitored satellite, and also generate a correction term for ionospheric delays at lattice points on a grid formed by the intersection of lines of constant latitude and longitude. The corrections are relayed through geostationary satellites in order to reach all users in a wide geographic area. Since WAAS is expected to support Category I (CAT I) precision approaches, stringent integrity monitoring requirements will have to be satisfied. Existing single location navigation sources, such as ILSs, are monitored at a single location, whereas WAAS must be monitored at many locations and the information combined to produce a single integrity broadcast message suitable for a wide geographic area. In addition, the WAAS message includes separate differential correction components that can be individually monitored, but the integrity information must be correlated with an aircraft position error. The authors develop integrity monitoring requirements, starting with the instrument landing system (ILS), and extrapolating them for WAAS.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

This paper considers what the SNS (Satellite Navigation Systems), such as Global Positioning System (GPS), GLONASS, Galileo, and Compass; and SBAS (Satellite Based Navigation Systems) such as European Geostationary Navigation Overlay System (EGNOS), Wide Area Augmentation System (WAAS), Multi-functional Transport Satellite Based Augmentation System (MSAS) and GPS and Geo Augmented Navigation (GAGAN) services, might look like 10 years from now. All these systems, called GNSS (Global Satellite Navigation System), are undergoing construction or modernization (new satellites, new frequencies, new signals, new monitoring stations, etc.) and continuous improvement to increase accuracy, availability, integrity, and resistance to interference. The most significant events in SNS and SBAS over the last 10 years are presented. In addition, three possible scenarios for SNS in the years 2016 and 2021 (most probable, optimistic, and pessimistic), including the number of satellites, are presented.

Study on real-time construction quality monitoring of storehouse surfaces for RCC dams

Chapter 24 - Recent Geoeffective Space Weather Events and Technological System Impacts

\nWith the development of Global Navigation Satellite System (GNSS), multiple constellations broadcasting more signals in the same frequency bands will cause interference effects on the systems. At a minimum, all GNSS signals and services must be compatible. In this paper, a complete methodology for the signal interference assessment is presented. Real simulations accounting for the interference effects were carried out on the L1 band where GPS and Wide Area Augmentation System (WAAS) are sharing the same band. And the results show that the WASS can provide a sound basis for compatibility with GPS.\n

Purpose The purpose of this paper is to present the problem of implementation of the differential global navigation satellite system (DGNSS) differential technique for aircraft accuracy positioning. The paper particularly focuses on identification and an analysis of the accuracy of aircraft positioning for the DGNSS measuring technique. Design/methodology/approach The investigation uses the DGNSS method of positioning, which is based on using the model of single code differences for global navigation satellite system (GNSS) observations. In the research experiment, the authors used single-frequency code observations in the global positioning system (GPS)/global navigation satellite system (GLONASS) system from the on-board receiver Topcon HiperPro and the reference station REF1 (reference station for the airport military EPDE in Deblin in south-eastern Poland). The geodetic Topcon HiperPro receiver was installed in Cessna 172 plane in the aviation test. The paper presents the new methodology in the DGNSS solution in air navigation. The aircraft position was estimated using a “weighted mean” scheme for differential global positioning system and differential global navigation satellite system solution, respectively. The final resultant position of aircraft was compared with precise real-time kinematic – on the fly solution. Findings In the investigations it was specified that the average accuracy of positioning the aircraft Cessna 172 in the geocentric coordinates XYZ equals approximately: +0.03 ÷ +0.33 m along the x-axis, −0.02 ÷ +0.14 m along the y-axis and approximately +0.02 ÷ −0.15 m along the z-axis. Moreover, the root mean square errors determining the measure of the accuracy of positioning of the Cessna 172 for the DGNSS differential technique in the geocentric coordinates XYZ, are below 1.2 m. Research limitations/implications In research, the data from GNSS onboard receiver and also GNSS reference receiver are needed. In addition, the pseudo-range corrections from the base stations were applied in the observation model of the DGNSS solution. Practical implications The presented research method can be used in a ground based augmentation system (GBAS) augmentation system, whereas the GBAS system is still not applied in Polish aviation. Social implications The paper is destined for people who work in the area of aviation and air transport. Originality/value The study presents the DGNSS differential technique as a precise method for recovery of aircraft position in civil aviation and this method can be also used in the positioning of aircraft based on GPS and GLONASS code observations.

The localization system is the most important part of the overall drone navigation system. The Global Positioning System (GPS) or Global Navigation Satellite System (GNSS) is the main device commonly used in a drone. However, under certain conditions, GPS or GNSS may not function optimally, such as in situations of signal jamming or enclosed environments. This paper implemented a new approach to address this issue by combining GNSS data with Visual Odometry (VO) through Machine Learning (ML) methods. The followed process consists of three main stages. First, performing speed and orientation estimation using VO. Second, performing left and right feature separation on the images to generate a more stable and robust estimation of speed and rotation. Third, refining speed and orientation estimation by integrating GNSS data through ML-based data fusion. The proposed method strives to enhance drone localization accuracy, despite disruptions or unavailability of GNSS signals. The research results indicate that the introduced method significantly reduces Absolute Translation Error (ATE) compared to utilizing VO or GNSS separately. The average ATE produced reached 4.38 m and an orientation of 8.26°, indicating that this data fusion approach provides a significant improvement in drone localization accuracy, making it reliable in operational scenarios with limited GNSS signals.

Built-up city 'urban canyons' offer an environment which challenges the physical limitations of modem real-time GPS positioning systems and, yet, is perhaps the one environment where the successful application of GPS technology could benefit most users. With a view to the next generation of Real Time Kinematic (RTK) positioning systems, this paper highlights the limitations imposed on current RTK systems operating in the urban canyon using GPS visibility trials conducted in the urban canyon of the Perth Central Business District (CBD). Furthermore, following the recent release of receivers capable of integrating the Global Positioning System (GPS) and the Russian equivalent, the Global Navigation Satellite System (GLONASS), the advantages of integration of both GPS and GLONASS systems are demonstrated using GLONASS visibility simulations at selected points in the Perth CBD.

The Federal Aviation Administration has embarked on an historic task of modernizing and significantly improving the national air transportation system. One system that uses the Global Positioning System (GPS) to determine aircraft navigational information is called the Wide Area Augmentation System (WAAS). This paper describes a reliability assessment of one candidate system architecture for the WAAS. A unique aspect of this study regards the modeling and solution of a candidate system that allows a novel cold sparing scheme. The cold spare is a WAAS communications satellite that is fabricated and launched after a predetermined number of orbiting satellite failures have occurred and after some stochastic fabrication time transpires. Because these satellites are complex systems with redundant components, they exhibit an increasing failure rate with a Weibull time to failure distribution. Moreover, the cold spare satellite build-time is Weibull and upon launch is considered to be a good-as-new system with an increasing failure rate and a Weibull time to failure distribution as well. The reliability model for this system is nonMarkovian because three distinct system clocks are required: the time to failure of the orbiting satellites, the build time for the cold spare, and the time to failure for the launched spare satellite. A powerful dynamic fault tree modeling notation and Monte Carlo simulation technique with importance sampling are shown to arrive at a reliability prediction for a 10 year mission.

The potential for the use of smartphones in GNSSs (Global Navigation Satellite Systems) positioning has increased in recent years due to the emergence of the ability of Android-based devices used to process raw satellite data. This paper presents the results of a study on the use of SBAS data transmitted by the EGNOS (European Geostationary Navigation Overlay Service) system in GNSS positioning using a Xiaomi Mi8 smartphone. Raw data recorded at a fixed point were used in post-processing calculations in GPS/EGNOS positioning by determining the coordinates for every second of a session of about 5 h and comparing the results to those obtained with a Septentrio AsteRx2 GNSS receiver operating at the same time at a distance of about 3 m. The calculations were performed using the assumptions of the GNSS/SBAS positioning algorithms, which were modified with carrier-phase smoothed code observations and the content of the corrections transmitted by EGNOS.

This paper addresses topics concerning the development of future Unmanned Aerial Vehicles (UAV) so that they can operate safely within the community of the Federal Aviation Administration (FAA) and the International Civil Aviation Organization (ICAO). Studies by the Defense Science Board; the Office of Science and Technology; Government Accountability Office; and the Congressional Research Service: Library of Congress; have all emphasized that soon there will be a significant number of UAVs operating sideby- side with manned civil aircraft in the FAA’s National Airspace System (NAS). It is anticipated that future UAVs will start to perform many of the dull, dirty, and dangerous civilian missions. In 2006, about 600 UAVs are expected to be manufactured in the US alone. Therefore, there is an urgent need for developers of UAVs to understand safety certification for operations in the NAS, and that safety certification starts with the safety requirements; safety design; safe development process; safety verification; and safe operating procedures in the planned operational environment. This paper presents and discusses the experiences and lessons gained by the authors on the development of end-toend aviation safety; from the safety requirements to their final safety certification in the planned operational environment. The authors’ previous and ongoing works include the Global Navigation Satellite Systems (GNSS) systems such as the GPS; WAAS; LAAS; MSAS; GPS III; and different operational environments at different airports such as Incheon International Airport. The FAA started with the two traditional safety certifications processes: airborne system certification and ground system certification; governed mostly by Federal Aviation Regulations (FAR) and FAA’s Acquisition Management System (AMS), respectively. However, when FAA started to implement GNSS, the lines between airborne and ground systems became blurred, and as a result many current Communications, Navigation, Surveillance, and Air Traffic Management (CNS/ATM) systems have to follow both processes. We will also discuss the current Safety Management Systems being developed by both FAA and ICAO as an integrated, systematic, and harmonized approach and process to sort out the differing safety requirements from FAA, SAE-ARP, MIL-STD, RTCA, ASTM, ICAO, etc. to provide the eventual safe operations within the NAS. The discussion will then focus on the real world of institutional, operational, and technical issues for safety certification worldwide. Despite the numerous standards and guidance documents, many past safety analyses and studies were guided by best practices that had been used successfully in the past to streamline the process of providing all the required documentations and verifications. One such area is in the use of the “Integrity Panel of Experts” that had been used successful in the implementation of safety for the FAA’s Wide Area Augmentation System (WAAS) and Local Area Augmentation System (LAAS) programs. In many areas of the world, safety certification from a technical point of view is only the first step to achieving safety certification to fly in their national and sovereign airspace. Finally, we will show the first steps that UAV manufactures need to consider if they want their UAVs to be approved to fly safely in different national civilian airspace.

The Federal Aviation Administration (FAA) is investigating the feasibility of using the Global Positioning System (GPS), together with local augmentation as the primary navigation system for the Category II and III precision approach of aircraft. This augmented system would be known as a local area augmentation system (LAAS) because it would place subsystems on the ground at or near an airport to greatly enhance the performance of airborne GPS receivers approaching that airport. The LAAS would complement space-based augmentations of GPS, such as the wide area augmentation system. When complete, the integrated system will meet stringent requirements on accuracy, integrity, continuity, and availability. Indeed, the LAAS will improve the airborne accuracy from approximately 100 m for stand-alone GPS to better than 1 m. This high accuracy is required so that LAAS can guarantee the integrity and continuity of the aircraft guidance during the approach phase of flight. Integrity requires the LAAS to detect any situations which threaten the safety of the landing, and notify the aircraft within 2 s of such a threat. Continuity is a competing consideration-it requires that the total number of alarms, true plus false, sent to the aircraft is very small. High continuity guarantees that the total number of aborted approaches is manageably small. Finally, availability is the fraction of the time during which LAAS is operational-providing position fixes with the specified accuracy, integrity and continuity. This paper describes the LAAS which has been proposed by the FAA. It discusses the fundamental operation of the LAAS.

Since the beginning of the International Global Navigation Satellite System (GLONASS) Experiment, IGEX, in October 1998, the Center for Orbit Determination in Europe (CODE) has acted as an analysis center providing precise GLONASS orbits on a regular basis. In CODE's IGEX routine analysis the Global Positioning System (GPS) orbits and Earth rotation parameters are introduced as known quantities into the GLONASS processing. A new approach is studied, where data from the IGEX network are combined with GPS observations from the International GPS Service (IGS) network and all parameters (GPS and GLONASS orbits, Earth rotation parameters, and site coordinates) are estimated in one processing step. The influence of different solar radiation pressure parameterizations on the GLONASS orbits is studied using different parameter subsets of the extended CODE orbit model. Parameterization with three constant terms in the three orthogonal directions, D, Y, and X (D = direction satellite–Sun, Y = direction of the satellite's solar panel axis), and two periodic terms in the X-direction, proves to be adequate for GLONASS satellites. As a result of the processing it is found that the solar radiation pressure effect for the GLONASS satellites is significantly different in the Y-direction from that for the GPS satellites, and an extensive analysis is carried out to investigate the effect in detail. SLR observations from the ILRS network are used as an independent check on the quality of the GLONASS orbital solutions. Both processing aspects, combining the two networks and changing the orbit parameterization, significantly improve the quality of the determined GLONASS orbits compared to the orbits stemming from CODE's IGEX routine processing.