Showing papers on "GNSS augmentation published in 2004"

A system and method for provinding assistance data within a location network

Abstract: A system and method for providing assistance to a position receiver in a location network consisting of a Global Navigation Satellite System (GNSS) and a synchronized network of positioning-unit devices is disclosed. A positioning-unit device observes the time and frequency of received Global Navigation Satellite System (GNSS) signals relative to the synchronized network of positioning-unit devices. These time and frequency observations are modulated, as assistance data, onto the positioning signals that are broadcast by the positioning-unit devices. A position receiver demodulates the assistance data and analyzes the positioning signals. The position receiver then searches for Global Navigation Satellite System (GNSS) signals in a range responsive to the assistance data and the analysis of the received positioning signals.

Overbounding SBAS and GBAS Error Distributions with Excess-Mass Functions

Abstract: Safety-of-life GNSS augmentation systems must provide bounds on the probability with which hazardous navigation errors occur. This paper develops conservative bounding methods both for space-based augmentation systems (SBAS) and for ground-based augmentation systems (GBAS) by using excess-mass functions. The excess-mass concept, which employs conservative bounding functions with integrated density greater than unity, is applied to develop two new bounding strategies, of which the first focuses on probability density functions (EMP overbounding) and the second on cumulative distribution functions (EMC overbounding). These strategies can bound arbitrary error distributions, even those that are asymmetric, multimodal, or non-zero mean. To compare the two strategies to each other, and to existing methods such as paired-CDF overbounding and moment overbounding, a set of metrics are introduced to evaluate overbound performance given anomalies in the actual error distribution. These performance metrics provide a basis for application-specific trade studies that would balance the availability benefits of various overbounding methods against required modifications to the broadcast signal and protection limits. In the generic case, assuming identical error sources for all satellites and neglecting broadcast-message bandwidth constraints, the performance metrics favour the EMC approach, which tightly bounds unknown biases and heavy-tailed errors. The major drawback of the EMC approach is its sensitivity to outliers in sampled error distributions.

GNSS Signal Reliability Testing in Urban and Indoor Environments

Abstract: The availability of two GNSS (Global Navigation Satellite System), GPS and Galileo, will offer in future new possibilities to provide integrity and reliability information to the user both at signal and user levels due to increased redundancy. User-level reliability monitoring schemes, namely Receiver Autonomous Integrity Monitoring (RAIM), consist of statistically testing least- squares residuals of the observations on an epoch-by- epoch basis aiming towards reliable navigation fault detection and exclusion (FDE). Classic RAIM and FDE techniques are based on only GPS characteristics, so in this paper, methods will be discussed also suitable for a combined GPS/Galileo system with the focus on personal location in degraded signal environments. This paper concentrates on analyzing different navigation quality and reliability assessment procedures based on testing the GNSS least-squares residuals on an epoch-by- epoch basis. The focus will be on reliability testing schemes for degraded GNSS signals in urban conditions in order to obtain an acceptable position estimate, and analyzing the urban GNSS navigation accuracy conditions. The reliability testing schemes for integrated GPS/Galileo to be discussed include applying a global test for detecting an inconsistent location situation, a local test for localizing and eliminating measurement errors recursively and, in addition, certain measurement subset testing. The proposed FDE schemes are examined with simulated GPS/Galileo data and real-life urban GPS tests. Furthermore, some external reliability measures, Mean Radial Spherical Error and Distance Root Mean Squared estimates approximating the effect measurement errors have on the accuracy will be analyzed. This paper will provide an insight into user-level integrity and reliability monitoring and FDE schemes eligible for a future GNSS system particularly for degraded signal environments, where the conventional assumption of normally distributed errors does not necessarily hold. The aim is to improve solution reliability and provide additional accuracy information to the user in terms of approximated position error estimates.

Performance Evaluation of the Wide Area Augmentation System for Ionospheric Storm Events

Abstract: One of the greatest challenges in developing accurate and reliable satellite-based augmentation systems (SBAS) is modeling of ionospheric effects. Wide area GPS networks are generally sparse (station spacings of 500-1000 km), and ionosphere models can suffer degraded performance in regions where large spatial gradients in total electron content (TEC) exist. Of particular concern for Wide Area Augmentation System (WAAS) users is the feature called storm enhanced density, which is associated with large TEC gradients at mid-latitudes. This effect is a significant source of error in the WAAS correction models. The Canadian GPS Network for Ionosphere Monitoring (CANGIM) consists of three GPS reference stations in western Canada, augmented by two additional sites in the northern United States. In addition to measures of ionospheric activity, WAAS messages are collected continuously at these sites and decoded (post-mission) at University of Calgary. Localization schemes have been developed to compute WAAS ionosphere corrections for any location in North America. In this paper, performance of the broadcast WAAS ionosphere model is quantified through comparison with truth data from over 400 GPS reference stations in North America. WAAS ionosphere model accuracies throughout North America are evaluated for intense storm events, and compared with WAAS Grid Ionosphere Vertical Error (GIVE) bounds. Limitations in the WAAS ionosphere model are identified for enhanced ionospheric activity and, in particular, the storm enhanced density phenomenon.

A Method of Over Bounding Ground-Based Augmentation System (GBAS) Heavy Tail Error Distributions

Abstract: The purpose of this paper is to describe a statistical method of modeling and accounting for the heavy tail fault-free error distributions that have been encountered in the Local Area Augmentation System (LAAS), the FAA’s version of a ground-based augmentation system (GBAS) for GPS. The method uses the Normal Inverse Gaussian (NIG) family of distributions to describe a heaviest tail distribution, and to select a suitable NIG family member as a model distribution based upon a statistical observability criterion applied to the FAA’s LAAS prototype error data. Since the independent sample size of the data is limited to several thousand and the tail probability of interest is of the order of 10-9, there is a chance of mismodeling. A position domain monitor (PDM) is shown to provide significant mitigation of mismodeling, even for the heaviest tail that could be encountered, if it can meet certain stringent accuracy and threshold requirements. Aside from its application to GBAS, this paper should be of general interest because it describes a different approach to navigation error modeling and introduces the application of the NIG distribution to navigation error analysis.

A performance analysis of future global navigation satellite systems

Abstract: For an increasing number of applications, the performance characteristics of current generation Global Navigation Satellite Systems (GNSS) cannot meet full availability, accuracy, reliability, integrity and vulnerability requirements. It is anticipated however that around 2010 the next generation of GNSS will offer around one hundred satellites for positioning and navigation. This includes constellations from the US modernised Global Positioning System, the Russian Glonass, the European Galileo, the Japanese Quasi- Zenith Satellite System and the Chinese Beidou. It is predicted that the performance characteristics of GNSS will be significantly improved. To maximise the potential utility offered by this integrated infrastructure, this paper presents an approach adopted in Australia to quantify the performance improvements that will be available in the future. It presents the design of a GNSS simulation toolkit developed in Australia and the performance expectations of future GNSS for a number of important applications within the Asia Pacific region. In quantifying the improvement in performance realised by combined systems, this paper proposes a practical approach to facilitate the development of innovative applications based on future GNSS.

The Ionospheric Impact of the October 2003 Storm Event on WAAS

Abstract: The United States Federal Aviation Administration's (FAA) Wide Area Augmentation System (WAAS) for civil aircraft navigation is focused primarily on the Conterminous United States (CONUS). Other Satellite- Based Augmentation Systems (SBAS) include the European Geostationary Navigation Overlay Service (EGNOS) and the Japanese Global Navigation Satellite System (MSAS). Navigation using WAAS requires accurate calibration of ionospheric delays. to provide delay corrections for single frequency GPS users, the wide area differential GPS systems depend upon accurate determination of ionospheric total electron content (TEC) along radio links. Dual frequency transmissions from GPS satellites have been used for many years to measure and map ionospheric TEX on regional and global scales.

Virtual differential GPS based on SBAS signal

Abstract: In order to access the satellite-based augmentation system (SBAS) service, the end user needs access to the corresponding geostationary earth orbit (GEO) satellites that broadcast the augmentation information for the region. This is normally not a problem for aviation and maritime applications, because an open sky is typically available for such applications. However, it is difficult to access the GEO satellites directly at high latitudes for land applications because of the low elevation angles to the GEO satellites (e.g., 4–22° in Finland to the European geostationary navigation overlay services [EGNOS] GEO satellites). Results from a driving test of 6,100 km in Finland show that the EGNOS GEO satellites can be accessed in only 51.8% of the driving routes. Furthermore, it is also difficult to access the GEO satellites from city canyons, because the high buildings block the GEO signals. This article presents a solution to solve this problem by creating virtual differential GPS (DGPS) reference stations using the SBAS signal in space (SIS). The basic concept is to convert the SBAS signal to Radio Technical Commission for Maritime Services (RTCM) signals, and broadcast the converted RTCM signals over the wireless Internet using the Internet radio technology. Therefore, access to the SBAS service will not be limited by low elevation angles to the GEO satellites because the converted RTCM data streams are disseminated over the wireless Internet. Furthermore, the SBAS service can then be accessed via a legacy DGPS receiver. Two test cases have been carried out with the prototype system developed by the Finnish Geodetic Institute. The test results showed that the positioning accuracy of the virtual DGPS solution was about 1–2 m at 95%, which was similar to that of the standard WAAS/EGNOS solution. The positioning accuracy was not degraded, compared to that of the standard wide area augmentation system–European geostationary navigation overlay services (WAAS/EGNOS) solution, as long as the distance between the rover receiver and the virtual DGPS reference station was less than 150 km. A preliminary driving test of 400 km carried out in southern Finland showed that the availability of the virtual DGPS solutions was 98.6% along the driving route.

Procedure for guiding an aircraft in the approach phase and corresponding ground beacon

Abstract: The invention relates to a procedure for guiding an aircraft in the approach phase comprising of receiving information on a predefined approach path, this information being contained in a message M 4 originating from a ground beacon transmitting on the same transmission channel as that of a beacon of a GBAS type positioning accuracy augmentation system, receiving differential positioning radio satellite signals, and correction information from these satellite radio signals in the form of a message M 1 ′ originating from a ground central station of an SBAS type positioning accuracy augmentation system, via geostationary satellites of this augmentation system, calculating a corrected position based on the positioning signals and correction information, calculating an elevation and horizontal guidance deviation of the aircraft relative to the predefined approach path, based on the corrected position and information on the predefined approach path.

An Investigation of Tropospheric Errors On Differential GNSS Accuracy and Integrity

Abstract: This paper provides an in-depth analysis of the effects of the troposphere on satellite-based differential augmentations for aircraft precision approach and landing applications. The results of this effort are applicable to both the Space and Ground Based Augmentations Systems (GBAS/SBAS), including the Wide and Local Area Augmentation Systems (WAAS/LAAS) using GPS and/or Galileo. It is widely recognized that the dominant, non-common error sources in differential GNSS for aviation are noise, multipath, the ionosphere, and the troposphere. Of these errors, the troposphere is perhaps the least studied and least quantified error source within the aviation community. To fill this information void, the current models used to estimate the tropospheric corrections in the WAAS and LAAS Category I aircraft precision system are analyzed and compared. The potential for erroneous tropo corrections is illustrated by comparing models over a range of input parameters, including temperature, pressure, relative humidity, refractivity index (and uncertainty), as well as the tropospheric scale height. While the LAAS troposphere model primarily address the differential vertical tropospheric gradient between the LAAS ground station and approaching aircraft as a function of the altitude difference, it is also important to account for the tropo errors due to lateral separation. For operations at large airports, the LAAS ground station may be separated by distances up to three miles from the approach-end of the runway. At this distance during clear, stable weather conditions, errors due to lateral separation are often considered negligible. However, under severe weather conditions, localized weather behavior may cause the differential tropospheric corrections to exceed their budgeted values, especially for low-elevation satellites. Furthermore, the LAAS tropo corrections must be valid over the entire 23-nautical mile LAAS service volume to ensure safe terminal-area operations. Clearly, over this distance, lateral tropo gradients may become significant. Analogous to the strict error budgets developed for multipath and ionospheric errors, tropospheric errors must also be carefully considered and properly accounted for. To address this issue, several case studies are shown using weather information obtained from the Ohio University Scalia Laboratory for Atmospheric Analysis. The results of this research are of particular importance to WAAS and LAAS development because, if and when the aviation community adopts a multi-frequency, multiconstellation architecture to meet the most stringent requirements of Category II/III aircraft precision approach and landing operations, tropospheric anomalies will remain as a key error source that must be well understood and modeled in this aviation safety-of-life application.

Satellite Navigation vs. the Ionosphere: Where Are We, and Where Are We Going?

Abstract: This paper will address the recent results of the WAAS in the US and prototype SBAS and GBAS installations being testing in Rio de Janeiro. The focus of the paper is on the negative effects of the ionosphere, and describes some of the recent data and analysis that examine whether SBAS or GBAS can be made to operate during severe ionospheric conditions. The paper then concludes with the observation that many of these current problems will fade away when dual civilian frequency satellite constellations are available, but that some concerns related to scintillation will remain. In order to focus the research on the most pertinent problems, the future global mix of satellite navigation services for aviation need to be defined, at least in a broad level of detail.

Space based augmentation system with hierarchy for determining geographical corrections source

Abstract: Systems, devices and methods are provided for determining the appropriate or desired geographical correction source for SBAS corrections. One aspect provided herein is a method. According to one method embodiment, a Space Based Augmentation System (SBAS) correction message is received from a selected SBAS satellite. It is determined whether at least one criterion is satisfied for using the selected SBAS satellite as a correction source and then processing the correction message received therefrom. A second SBAS satellite is selected from which to receive SBAS correction messages upon determining that at least one criterion is not satisfied for using the selected SBAS satellite as a correction source. One example of SBAS is the Wide Area Augmentation System (WAAS) used in North America. Other aspects and embodiments are provided herein.

An integrity navigation system based on GNSS/INS for remote services implementation in terrestrial vehicles

Abstract: Nowadays, one of the most important applications of the navigation systems is the remote services. Applications such as the electronic-fee-collection, truck fleet control or antitheft devices imply millions of users through the roads of the whole world. Particularly in Europe, the development of the GALILEO system and the efforts of the European Parliament in prioritizing the toll collecting systems based on GNSS and cellular networks (GNSS/CN), enlarge highly the European market of potential users. In that million users market, no particular exceptions can be treated by a realistic solution. Most of the actual navigation systems rely mainly on the satellite navigation. Problems such as the deficit of precision, the lack of coverage or the service interruptions due to disturbances on the satellite network arouse the implementation of a more reliable solution combining GNSS and autonomous navigation systems. This paper is to present how a GNSS/INS integrated system offers the accuracy and quality assurance required in remote services. Both practical and theoretical researches about the possibilities of a single GPS receiver, the EGNOS-SISNeT/SBAS position correction improvements, the incoming GALILEO-GPS constellation and the use of a multisensor GNSS/INS integrated solution as a reliable navigation system for remote services applications are presented.

Ionospheric Threats to Space-Based Augmentation System Development

Abstract: The ionosphere contributes the largest and most unpredictable error to single frequency GPS users’ range measurements. The goal of a Space-Based Augmentation System (SBAS) in mitigating these ionospheric errors is two-fold. First, the SBAS broadcasts error corrections to its users for improved positioning accuracy. Moreover, the SBAS provides a service that GPS alone cannot: ensuring position estimate integrity, which is crucial to safety-of-life applications. The International Civil Aviation Organization (ICAO) has adopted a set of Standards and Recommended Practices (SARPs) for SBASs being developed worldwide. The SARPs are based on the Minimum Operational Performance Standards (MOPS) of the Wide Area Augmentation System (WAAS) currently operational in the United States. This paper surveys a range of ionospheric issues that an SBAS must consider if it is to comply with the ICAO SARPs. By examining observed ionospheric phenomena at a high level in a visually intuitive way, the author hopes to provide some insight as to why the SARPs are developed as they are and what additional issues are introduced by the constraints of the SARPs. This paper makes use of the following data: “supertruth” data collected from the WAAS network of receivers during several ionospheric storms as well as a nominal period for comparison; raw data from an individual WAAS network receiver during the 29-31 October 2003 ionospheric storm; and data from the same storm collected from nearly 400 stations in the Continuously Operating Reference Stations (CORS) and International GPS Service (IGS) networks and processed by the Jet Propulsion Laboratory (JPL). With these data sets the author illustrates the large absolute values of total electron content (TEC), to which GPS range errors are proportional, that may be seen during ionospheric storms. Large spatial and temporal gradients that have been observed are also shown. We discuss potential routes in bounding or mitigating the effect of these highly irregular periods of ionospheric activity by considering the approach WAAS has employed. In addition to bounding dangerous behavior that is not predicted by the SBAS choice of ionospheric model, the SBAS must also bound estimation and interpolation errors that exist both during nominal and stormy conditions. Such errors are introduced by modeling the ionosphere as a two-dimensional, infinitely thin shell. This error arises from the loss of altitudinal information in the collapse of the three spatial dimensions of the true ionosphere into a two-dimensional surface representation that can be easily broadcast. Finally, with an ionospheric model based on measurement and estimation of the real-time ionosphere, the SBAS runs a risk of undersampling the ionosphere over a geographic region for which it is providing service, as will be illustrated. When high spatial and temporal gradients are also highly localized, it is possible for them to remain undetected by the SBAS. For this reason bounding possible errors due to undersampling is crucial.

Satellite propagation path model along a railway track for GNSS applications

Abstract: The applications of GNSS (Global Navigation Satellite System) services are continuously growing in the field of transport. However, the choice of the system for a given application is directly guided by its availability and the availability of most satellite-based localization processes of terrestrial mobiles is considerably degraded in transport environments because of significant masking effects. In these environments, the availability of positioning information is not always guaranteed. We present the results of a railway study using both experimental measurements and the PREDISSAT simulation tool that we have developed. We follow a Markovian approach with three states corresponding to the three states of reception of the signal (direct, multipath and blocked). The probability of occurrence of each state characterizes the GNSS propagation channel in a railway environment.

A Study of the Ionospheric Effect on GBAS (Ground-Based Augmentation System) Using the Nation-Wide GPS Network Data in Japan

Abstract: This paper presents an investigation of spatial gradient of ionospheric delay that has a possibility of affecting GBAS (Ground-Based Augmentation System) using the nationwide and dense GPS network in Japan (GEONET; GPS earth observation network). GBAS is a system based on a differential GPS technique for aircraft precision approach near an airport using C/A pseudorange. In general, ionospheric delay will be removable using correction data set that is generating and transmitting from a ground segment of GBAS. However, a large spatial gradient of ionospheric delay between ground GPS monitoring station and aircraft will be a risk to integrity of GBAS. Therefore, our purpose is to exactly estimate local-scale variation of ionospheric delay. Because Japan is located in lower geomagnetic latitude than geographic latitude, ‘Equatorial anomaly’ phenomenon is especially remarkable for generating a variation of ionospheric delay gradient in the North-South direction. GEONET is consists of about 1,000 GPS stations using dual-frequency receiver and a typical distance between neighbor stations is about 20 km. We used Total Electron Content (TEC) data of GEONET with a correction of inter-frequency bias that provided from TEC database of Kyoto University, Japan. Firstly, we investigated general characteristic of spatial gradient of ionospheric delay over Japan using TEC data with rough grid and time resolutions. In distribution analysis of the number of times for each magnitude of gradient in the S-N direction, the results were consistent with the matter that growth of equatorial anomaly produced large TEC gradient toward south.

Pseudolite navigation system

Abstract: The pseudolite includes a communication (COM) satellite receiver for receiving a communication satellite specific RF signal from a communication satellite and providing communication satellite navigation and position data. A GNSS receiver receives a GNSS signal from a GNSS satellite and provides GNSS timing information. A pseudolite transmitter receives the communication satellite navigation and position data and the GNSS timing information. The pseudolite transmitter includes at least one digital signal generator for utilizing the communication satellite navigation and position data and the GNSS timing information for providing a digital signal generator output having an intermediate frequency and navigation message data which are suitable for up-conversion to a desired communication channel RF frequency. At least one communication satellite RF module of the pseudolite transmitter receives the digital signal generator intermediate frequency output from an associated signal generator and converts the intermediate frequency output to a communication satellite transmit RF signal having the desired communication channel RF frequency. The communication channel RF frequency is preferably adjustable and may cover a range of potential communication frequencies.

GNSS Augmentation Systems in the Maritime Sector

Abstract: The provision of differential global positioning system (DGPS) corrections, together with integrity information, using non-directional medium frequency (MF) marine radiobeacons is well established and has proved successful. However, the new signals to be available from GPS (L2C and L5) together with those transmitted from Galileo (E5a and E5b) will undoubtedly impact on the DGPS service, necessitating modification to enable augmentations to be provided for the new frequencies, as well as that provided for the L1 signal. In addition, there are a number of emerging systems, such as space-based augmentation systems (SBAS), terrestrial regional augmentation systems (RAS), on-board systems and proposed Galileo services that will be available in the near future. These new systems could either complement or compete with the maritime DGPS service and may well provide additional capability to enable new applications. Furthermore, maritime requirements have evolved considerably since the design of the DGPS service. These requirements not only cover general navigation by conventional craft but now also include high speed craft (HSC), fast manoeuvrable craft (FMC) and the plethora of other applications that need position, velocity and time inputs. The current snapshot of these requirements has been promulgated by the International Maritime Organization in Resolution A.915(22). However, these requirements will evolve as new applications develop and system capabilities are enhanced. In response to these changes, the General Lighthouse Authorities (GLAs) of the UK and Ireland have launched a major study to support the development of future radionavigation systems policy. The study has assessed future performance of the global components of GNSS (GPS, and Galileo) in the maritime context. The study is also assessing the contribution that can be made by the various augmentation systems (regional, local and autonomous) to meet unfulfilled requirements and, therefore, enable additional applications. The results generated to date suggest that, in order for the basic global requirement for general ocean, coastal and port approach navigation to be met, a combined GPSGalileo system will be required, operating on multiple frequencies. Current augmentations, notably the IALA DGPS system and the EGNOS service, will meet this requirement but do not give the global coverage that is needed. The more stringent requirements of port navigation and other operations, needing regional and local coverage, can only be met through local augmentation systems and may require the current IALA DGPS system to be upgraded to operate on multiple frequencies. The most stringent requirements for special operations would then require implementation of carrier phase systems which would have to be designed and located to support specific applications. The utility of integrated inertial sensors will be investigated as well as the capabilities of additional augmentation systems, such as Eurofix and the potential for using ranging signals from marine radiobeacons as well as LORAN-C stations. Future phases of the study will then assess the opportunity to integrate maritime and non-maritime systems to enable mutual benefits, as well as determining the value, pros and cons of potential future system mixes using cost-benefit and risk analysis in a scenario driven methodology.

Differential positioning system

Abstract: PROBLEM TO BE SOLVED: To enable differential positioning from immediately after power-on, on the basis of error correction information broadcast from an SBAS satellite, and realize miniaturization and cost reduction SOLUTION: Mobile stations 41, 42 receive, from the SBAS satellite 20, error correction data concerning positioning signals of a plurality of GPS satellites 11-14, and correction information containing a PRN mask showing correction data about which GPS satellite, store the PRN mask contained in the correction information, and perform the differential positioning from immediately after positioning is started, by using the PRN mask Ionosphere delay correction data are stored only about a range where an ionosphere penetrating point exists which radio wave from the GPS satellites 11-14 accessible from the mobile stations passes COPYRIGHT: (C)2004,JPO

Technology character analysis and application about Bei-Dou satellite navigation system

Abstract: The development course of double satellite navigation system is given and the construction and component of BeiDou satellite navigation system are pointed out too. Their function and location theory were analyzed through contrasting GPS, including the technology character of BeiDou satellite navigation system. Then, the application model of BeiDou satellite navigation system are analyzed in civilian, especially in economy benefit. Finally, the development future of satellite navigation system is prospect.

Requirements for enhancing trust, security and integrity of GNSS location services

Abstract: The paper describes a number of requirements for enhancing the trust of location acquisition from Satellite Navigation Systems, particularly for those applications where the location is monitored through a remote GNSS receiver. We discuss how the trust of a location acquisition could be propagated to an application through the use of a proposed tamper-resistant GNSS receiver which quantifies the trust of a location solution from the signaling used (ie. P(Y) code, Galileo SOL, PRS, CS) and provides a cryptographic proof of this to a remote application. The tamper-resistance state of the receiver is also included in this cryptographic proof.

Benefits of a Reconfigurable Software GNSS Receiver in Multipath Environment

Abstract: The increased interest for applications based on both navigation and communication systems, represents an important driver for the design and implementation of innovative receivers architectures. The realization of civil GPS applications, the advent of the European navigation system Galileo, and the integration of localization services in communication network make the reconfigurability an indispensable requirement for the development of innovative Global Navigation Satellite Systems (GNSS) platforms. In addition, it must be pointed out that several problem as indoor positioning and multipath recovery, are pushing the research activity in order to provide users of flexible devices able to adapt their functionalities according to the environment. Considering this complex scenario, the Software Defined Radio (SDR) approach constitutes an interesting perspective to develop modular architectures. In this paper, the implementation of a reconfigurable user terminal integrating both navigation and communication capabilities will be discussed. The work will be presented focusing the attention on software-designed functionalities and the Navigation Unit will be analyzed and tested. An example of adaptability of the receiver to the operating environment will be presented. The reconfigurable module for multipath mitigation in the tracking phase will be described with particular attention to the implementation aspect, and some simulation results will be presented.

Validation of novel navigation signal structures for future GNSS systems

Abstract: Prior to the design and development phase of the European Galileo programme, the European Space Agency (ESA) undertook several pre-development projects to reduce the overall programme risk. Navigation signal bandwidth was determined to be one key risk area. This paper describes the development and use of a highly flexible signal validation facility designed to generate and receive novel, band-limited GNSS signals. The GNSS signal validation facility consists of a fully functioned real-time GNSS constellation simulator and signal generator; a dedicated receiver, a navigation processing unit and a performance analysis software suite. The constellation simulator, receiver and navigation processing unit are capable of operating in real-time with 12 satellites in view and three frequencies per satellite. The GNSS signal validation facility itself is extremely flexible to allow performance comparisons of different satellite constellations, signal designs, code lengths, data rates and frequencies. The GNSS signal validation facility has been used in an extensive test campaign to evaluate the performance of the novel band-limited GNSS signals under realistic user conditions with a representative Galileo satellite constellation. A strong focus of the signal validation test campaign was the performance of three-carrier differential navigation algorithms. This paper briefly describes the operation of the GNSS signal validation facility and provides an overview of the main test campaign performance results. This paper contains the first published results from the GNSS signal validation facility. A major result from the test campaign is that the novel band-limited GNSS signals provide robust and accurate positioning capability with navigation data rates of up to 3000 s/s. The receiver was shown to receive 24 MHz band-limited signals with a loss of less than 1 dB for a spreading code of 15.345 Mc/s and a sampling frequency of 56 MHz.

GPS-Aided Inertial Navigation Avionics (GAIA) Integrated with MSAS and Maritime DGPS Beacon

Abstract: The JAXA (changed from the National Aerospace Laboratory of Japan) has developed a GPS Aided Inertial navigation Avionics (GAIA) for over 10 years. GAIA utilizes a carrier phase DGPS/INS (CDGPS/INS) algorithm and its accuracy is better than 1m for each axis. In UAV program called the High Speed Flight Demonstration (HSFD), a demonstrator made auto landing using GAIA in 2002. To promote the flight safety of general aviation, navigation system with high accuracy and reliability must be supplied in low cost. Also, small size, light weight and low power consumption are also important items for small aircrafts and UAV. The GAIA equipment for HSFD was expensive and heavy as ordinary INS. To reduce cost and weight, we changed the ring laser gyro built into GAIA equipment from Kearfott T-24 (0.8 n.m./h class) to small and low cost T-16B (20 n.m./h class). The new GAIA equipment weights 6 kg, significantly smaller than 9.8 kg of the former model. Despite the lower grade gyro, we achieved to maintain the navigation performance by the following methods. (1) The error dynamics of T-16B gyro such as random walk was identified precisely. (2) Through the sensitivity analysis of the error estimation filter, we defined the filter parameters to minimize the effect of random walk error. Ashtech DG16 made by Thales Navigation is used for the build-in GPS, SBAS and maritime DGPS beacon receiver. DG16 can receive MSAS, a SBAS by Japan. To add the maritime beacon DGPS function, we expanded the mode switching algorithm of GAIA navigation processor. In a ground test in stable condition for 14 hours, we found 95% position error of the beacon DGPS/INS integrated navigation showed a good result, 0.76m for latitude, 0.63m for longitude and 1.57m for altitude. A dynamic test result using an automobile was also good. We are planning flight tests as a next step. Through the development, we established the design method to tune the filter parameters and bring out the maximum navigation performance even with the middleclass gyro.

Synchronization for "beidou" satellite terrestrial improvement radio navigation system

Abstract: Absfract The feasible scheme to improve the ‘Beidou” dual satellite positioning by building terrestrial radio navigation systems was discussed. The principles and architecture of “Beidou” system were introduced briefly in this paper, the scheme of time transfer in one-way or in double way was emphasized respectively and the structure of a complete time transfer message frame was analyzed. The synchronization of terr&&d radio aavigatioa statha with tke “3ekbu” satellite was analyzed and designed. The formula of time gap between the user’s time and center control system’s was given out. This paper will be a guide to designing the synchroniization of terrestrial radio navigation system.

Precise Engineering Applications of Pseudolites Augmented GNSS

Abstract: SUMMARY In satellite based positioning and navigation, the number and spatial distribution of the observed GNSS satellites are a function of the observation site. Insufficient number of satellites, poor geometry and weak signal in space (SIS) due to the obstructions of the surroundings are serious constraints to the various precise engineering applications. Resulting positioning solutions with this solo system cannot meet the precision requirements of these applications. This paper discusses how ground-based pseudolite transmitters are used to strengthen GNSS geometry and signal availability for reliable bridge deformation and deflection monitoring. The main content of the paper includes an introduction to the system configuration, algorithms for integrating GNSS and pseudolite data, field trials, and deformation information extraction. As two of the major factors affecting positioning precision, time invariant multipath mitigation techniques and optimal locations of pseudolites according to particular observation site are discussed as specific topics. The results from an actual bridge trial are compared with those from a GNSS/pseudolite simulator to validate the feasibility of this augmented system for highly precise deformation monitoring. The data processing proves that it is possible to achieve millimetre positioning precision in three dimensions.

Analysis of Potential CW Interference Effects Caused by UWB Devices on GNSS Receivers

Abstract: Ultra Wide Band (UWB) signal transmission has been around since late 1950´s. Thanks to rapid advance in recent years and cost effective enabling technologies, UWB is now envisaged for a variety of applications from localization up to high data rate wireless communication, through wall imaging or ground penetrating radars. Regulation is a main issue for the success of UWB development in the next years. UWB regulation activities are well advanced in the USA and ongoing in Asia as well as in Europe. The FCC was the first to introduce such a regulation. Mainly motivated by interferences studies between GPS and UWB emitters, the FCC strongly limited the power density authorised for each UWB device transmitting on the 960-1600 MHz, with a specific mention for power density measured in each kHz. UWB appears generally as a noise floor increase factor, degrading the positioning accuracy. However, several documents reporting test highlighted the CW-like effect on GPS C/A receivers caused by UWB interferers with specific Pulse Repetition Frequency (PRF). As an example, UWB waveforms with a PRF of 19.94 MHz caused the GPS receiver to lose lock with a minimal addition of UWB power. This paper details the CW interference effects experienced by any GNSS receiver and bring an analytical derivation of the CW impact within the GNSS receiver at each stage of signal processing. Based on an analytical description of correlation process and on simulations of carrier and code tracking loops, the influence of each parameter impacting the loss of lock on the pure navigation signal is analyzed. It leads to a formulation of the probability of occurrence of this event, explaining how it can conduct to non integrity or discontinuity risks. Specificities of SBAS signals are analysed in order to evaluate their robustness to CW in comparison with GPS and finally the vulnerability of envisaged Galileo codes and signals structures are discussed.

Concerning information configuration of integrated navigation system

Abstract: The integrated navigation adopts multi-navigation-sensor to recompose the measure result by using information amalgamation technique.The information configuration of integrated navigation is mainly discussed in this paper,according to the background of sub-sonic aerocraft,through researching the configuration of integrated navigation system entropy.From the result,it is shown that the optimization controlling rule of integrated navigation system is equivalent to the most entropy principle of navigation system.

The Effect Analysis of Observation Errors and Satellite Geometry to Ambiguity Validation Test of Carrier Phase-Based GNSS

Abstract: In carrier phase-based GNSS(Global Navigation Satellite System) positioning, the determination of correct integer ambiguities is the key issue to get high precision positioning results. Therefore, much effort has been made to develop a vital quality control procedure, which can effectively validate the ambiguity resolution results. Such a quality control procedure has been traditionally based on a so-called F-ratio. A major shortcoming for this F-ratio is that its probability distribution is still unknown. Recently, a W-ratio test has been proposed to provide a more rigorous quality control procedure. This paper presents a series of sensitivity analysis for the two validation tests. The analysis will cover the performance analyses of both of the F and W-ratio with respect to undetected gross errors, un-modelled (reminding) systematic errors, and various specifications in the stochastic models, as well as geometry strengths relating to a variety of satellite constellation, such as GPS, GPS/pseudolites and GPS/Galileo integration.