Showing papers on "GNSS augmentation published in 2003"
TL;DR: In this paper, the effects of scintillation on the availability of GPS and satellite-based augmentation system (SBAS) for L1 C/A and L2 semicodeless receivers are estimated in terms of loss of lock and degradation of accuracy.
Abstract: [1] Ionospheric scintillation is a rapid change in the phase and/or amplitude of a radio signal as it passes through small-scale plasma density irregularities in the ionosphere. These scintillations not only can reduce the accuracy of GPS/Satellite-Based Augmentation System (SBAS) receiver pseudorange and carrier phase measurements but also can result in a complete loss of lock on a satellite. In a worst case scenario, loss of lock on enough satellites could result in lost positioning service. Scintillation has not had a major effect on midlatitude regions (e.g., the continental United States) since most severe scintillation occurs in a band approximately 20° on either side of the magnetic equator and to a lesser extent in the polar and auroral regions. Most scintillation occurs for a few hours after sunset during the peak years of the solar cycle. Typical delay locked loop/phase locked loop designs of GPS/SBAS receivers enable them to handle moderate amounts of scintillation. Consequently, any attempt to determine the effects of scintillation on GPS/SBAS must consider both predictions of scintillation activity in the ionosphere and the residual effect of this activity after processing by a receiver. This paper estimates the effects of scintillation on the availability of GPS and SBAS for L1 C/A and L2 semicodeless receivers. These effects are described in terms of loss of lock and degradation of accuracy and are related to different times, ionospheric conditions, and positions on the Earth. Sample results are presented using WAAS in the western hemisphere.
239 citations
Patent•
09 May 2003TL;DR: In this article, an inertial augmentation assembly is used to compensate global positioning system based navigation information such as position, course, and track spacing for errors caused by variation of ground vehicle attitude (i.e., roll and yaw) over non-level terrain.
Abstract: A global positioning system based navigation system for a ground vehicle, in particular an agricultural ground vehicle such as a tractor, combine, sprayer, or the like, includes an inertial compensation assembly that provides inertial augmentation to compensate global positioning system based navigation information such as position, course, and track spacing for errors caused by variation of ground vehicle attitude (i.e., roll and yaw) over non-level terrain.
71 citations
Patent•
28 Jul 2003
TL;DR: In this article, the authors present a technique for unifying navigation hierarchies from different application sources, and providing a unified navigation area based on the united navigation hierarchy, which is used to provide an interface to information sources.
Abstract: Systems and techniques to provide a unifying navigation model with a navigation service that provides an interface to information sources. In general, in one implementation, the technique includes: uniting navigation hierarchies from different application sources, and providing a unified navigation area based on the united navigation hierarchy. Uniting the navigation hierarchies can involve supplying a navigation service with a navigation object model that provides, to a presentation layer, a homogeneous view of navigation information from the different application sources. Providing the unified navigation area can involve displaying a navigation window in a portal presentation, the navigation window including navigation links to resources of the different application sources, and the navigation links being organized according to the united navigation hierarchy.
39 citations
Patent•
31 Oct 2003TL;DR: In this paper, a hybrid system integrating a network of ground-based augmentation systems (GBAS) with a satellite based augmentation system (SBAS), permitting the high integrity features of the GBAS to be utilized with the much broader coverage area of the SBAS system without requiring significant expenditures that would be required for upgrading either of the systems independently.
Abstract: An arrangement and appertaining method utilizing the arrangement provides a cost effective way to implement an accurate and cost effective satellite positioning differential augmentation system This hybrid system integrates a network of Ground Based Augmentation Systems (GBAS) with a Satellite Based Augmentation System (SBAS), permitting the high integrity features of the GBAS to be utilized with the much broader coverage area of the SBAS system without requiring significant expenditures that would be required for upgrading either of the systems independently.
37 citations
DOI•
01 Jan 2003
TL;DR: A system and the algorithms for Pedestrian Navigation using a combination of sensors based on the Dead Reckoning technique coupled with GNSS is introduced and the feasibility of the use of a single gyro, in the context of pedestrian navigation, is demonstrated.
Abstract: This research has been sponsored by the Centre Suisse d'Electronique et de Microtechnique (CSEM) in Neuchâtel, Switzerland. It introduces a system and the algorithms for Pedestrian Navigation using a combination of sensors. The main objective is to localise a pedestrian anywhere and at any moment. The equipments utilised to fulfill this requirement are a Global Navigation Satellite System (GNSS) receiver and inertial sensors, which are attached to the person and as such need to be portable. An overview of Pedestrian Navigation constitutes the first part of the document. This new domain is examined from four different views: applications, tools (or sensors), architecture of the system and finally environment in which the pedestrian is travelling. As part of this process, the "state of the art" situation is presented. The approach followed in order to aid pedestrian to navigate is based on the Dead Reckoning technique coupled with GNSS. Consequently, the resolution of the travelled "distance" is separated from the resolution of the orientation of the walk. For the computation of the distance, a new technique based upon accelerometers and GNSS has been developed and demonstrated. The accelerometers are not used as a classical pedometer (counter of the number of steps) and the technique is not based on the double integration to obtain successively speed and distance. Instead, signal processing allows, considering individual parameters, the walking speed to be obtained directly from the signal of the accelerometers. This process, as well as the manner to determine the individual parameters, is presented in detail. The development of the algorithms is based on research performed in both the navigation and the medical domains (mainly in physiology). The computation of the orientation is more classical. It is based on the measurements made by a gyroscope and a GNSS receiver. The particularity of this study is the use of a single gyroscope to determine the orientation of the walk instead of three for the classical technique of inertial navigation. The influence of body movement on the gyroscope output has been deeply examined to determine the most appropriate way to process the signal of the gyroscope. The feasibility of the use of a single gyro, in the context of pedestrian navigation, is demonstrated. The potential added value for introducing a magnetic compass in the system is also evaluated. Finally a centralised Kalman filter has been designed and tested to merge all the sensors outputs, to combine the distance and the orientation, to integrate the Dead Reckoning solution and the GNSS solutions and to estimate all the parameters in a close to real-time process. The efficiency of this filter is demonstrated through different tests.
19 citations
12 Sep 2003
TL;DR: The Indian SBAS when operationalised is expected to fill the gap between the European EGNOS and the Japanese MSAS to provide seamless navigation to civilian aircrafts.
Abstract: The Indian Space Based Augmentation System (SBAS) known as GAGAN (GPS And GEO Augmented Navigation) system is a Proof of Concept system for introducing satellite-based CNS/ATM services in India. The Indian Space Research Organisation (ISRO) is implementing GAGAN for the Airports Authority of India (AAI). This paper describes the Indian Plan for satellite-based navigation system for civil aviation. The ground segment consists of eight Indian Reference Stations (INRESs), an Indian Master Control Centre (INMCC), an Indian Land Uplink Station (INLUS) and necessary communication links. Grid based Iono-tropo model for low latitude regions will be developed through deployment of a large number of Total Electron Content (TEC) receivers over the Indian sub-continent and analyzing the data collected. An Indian GEO stationary satellite will carry a navigation bent pipe transponder with CxC , CxL1 and CxL5 links. The helical array antennas for L1 & L5 downlinks are powered by 40 Watt RF amplifiers to achieve the required Equivalent Isotropically Radiated Power (EIRP), Preliminary analysis indicates that L1 & L5 downlink EIRPs would be in the vicinity of 33 dBW over the Indian Airspace. This increased EIRP is necessary to incorporate higher baud rates (upto 1 K baud) for L5 downlink and addition of a Q-channel for L1 downlink. Necessary link calculations for the Indian Nav. Payload are presented. Short term clock and carrier coherence is achieved through a highly stable Master oscillator on-board generating all local oscillator frequencies and with closed loop control with the INLUS. The Indian SBAS when operationalised is expected to fill the gap between the European EGNOS and the Japanese MSAS to provide seamless navigation to civilian aircrafts.
14 citations
TL;DR: The motivation for Global Navigation Satellite System (GNSS) software receivers is outlined, and features of traditional and software-based GNSS receiver architectures are highlighted and compared, focusing on the advantages of the software design.
Abstract: This paper outlines the motivation for Global Navigation Satellite System (GNSS) software receivers. Features of traditional and software-based GNSS receiver architectures are highlighted and compared, focusing on the advantages of the software design. The choice of which architecture is advantageous, particular in the case of embedded systems, is present along with design criteria—both for the current environment as well as what can be expected in the future.
13 citations
09 Sep 2003
TL;DR: In this paper, the authors used GPS measurements of geomagnetic storm days to perform a quantitative assessment of WAAS-type ionospheric correction algorithms in other parts of the world such as the low-latitude Brazil and midlatitude Europe.
Abstract: The Ionospheric correction algorithms have been characterized extensively for the mid-latitude region of the ionosphere where benign conditions usually exist. 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). Researchers are facing a more serious challenge in addressing the ionospheric impact on navigation using SBAS in other parts of the world such as the South American region on India. At equatorial latitudes, geophysical conditions lead to the so-called Appleton-Hartree (equatorial) anomaly phenomenon, which results in significantly larger ionospheric range delays and range delay spatial gradients than is observed in the CONUS or European sectors. In this paper, we use GPS measurements of geomagnetic storm days to perform a quantitative assessment of WAAS-type ionospheric correction algorithms in other parts of the world such as the low-latitude Brazil and mid-latitude Europe. For the study, we access a world-wide network of 400+ dual frequency GPS receivers.
8 citations
TL;DR: In this article, the authors show that severe scintillations in the equatorial zone disrupt geostationary satellite links even at the L-band frequency, and the minimum longitudinal separation required for reliable operation of satellite-based augmentation systems has been estimated, from the cumulative distribution of scintillation patch duration, to be 57° in the Indian longitude zone.
Abstract: In Satellite-Based Augmentation Systems (SBAS), the correction messages are transmitted to the users' receivers via geostationary communication satellites (GEOS) at GPS L1 (1575·42 MHz) frequency. Severe scintillations in the equatorial zone disrupt geostationary satellite links even at L-band. Observations of scintillations at 1·5 GHz from Calcutta (22·58°N, 88·38°E geographic, 32°N magnetic dip), located near the crest of the equatorial anomaly in the Indian zone, show that scintillations occur in patches of duration varying from a few minutes to several hours. During the solar maximum years 1998–2000, severe scintillations (Scintillation Index [ges ]15 dB) were recorded for 48 hr 55 min (1·27%) out of the total observation time of 3868 hr 9 min in the local time interval 19 to 00 hrs. In order to have a fail-safe system, it is suggested that more than one geostationary satellite be used in SBAS so that, if one link is disrupted, the other can be used for transmission of correction messages to the GPS users. The minimum longitudinal separation between two GEOS required for reliable operation of SBAS has been estimated, from the cumulative distribution of scintillation patch duration, to be 57° in the Indian longitude zone.
8 citations
25 Jun 2003
TL;DR: The main goal of this paper is to present the overall SDR receiver architecture, focusing attention on reconfigurability and flexibility issues which are guaranteed by the use of reprogrammable high-speed hardware (FPGA–Field Programmable Gate Array and DSP–Digital Signal Processor).
Abstract: The growth of innovative positioning-related services and applications within the wireless mass-market, and the green light for the development and modernization of Global Navigation Satellite Systems (GNSS) catalyze the research activity in the navigation field both at the system and user levels. In addition, different government institutions are working toward the definition of navigation plans and regulations which will require accurate locations of mobile users in case of emergency (US E-911 law and the European E-112 directive). From the technical standpoint, within every navigation/positioning system which will be available in the near future, the user terminal will play a central role. In fact, if navigation signals from different sources are available, the unique possibility to obtain the best navigation performance from the user perspective will be the employment of enhanced smart receivers able to fuse different data. With this aim, the Software Defined Radio (SDR) technology can be successfully employed for the design of innovative navigation receivers. The main goal of this paper is to present the overall SDR receiver architecture, focusing attention on reconfigurability and flexibility issues which are guaranteed by the use of reprogrammable high-speed hardware (FPGA–Field Programmable Gate Array and DSP–Digital Signal Processor). The direct benefit of such an implementation is the possibility to obtain a deep integration at the raw signal level between GPS and the future Galileo; the interoperability issue among different systems is then solved at the receiver level.
12 Sep 2003
TL;DR: In this paper, a series of flight tests conducted during March 2003 and July 2003 on the Ohio University DC-3 flying laboratory were conducted to investigate and characterize the nature of the biases induced on the code-phase measurements.
Abstract: It is well-recognized that GPS multipath is the dominant non-correctable error source in local-area differential GNSS systems such as the ground-based augmentation system (GBAS) for aircraft precision approach. Errors due to multipath also contribute to the overall system performance degradation of space-based augmentation systems (SBAS) such as the Wide Area Augmentation System (WAAS). To control, reduce, and limit multipath from GPS receivers employed at the ground reference station, the Federal Aviation Administration's GBAS, the Local Area Augmentation System (LAAS), employs a network of multi-element integrated multipath limiting antennas (IMLA). These ground-based antennas perform remarkably well, with their performance being studied extensively and well documented. Unfortunately, due to the construction and large physical size of the IMLA, they cannot be employed on the aircraft. Thus, standard patch-type airborne antennas must continue to be used on the aircraft for the reception of the GPS/GNSS signals. To fully understand the impact of multipath on key system performance parameters such as accuracy, integrity, and continuity (and the resulting availability of these functions), the properties and origin of airborne multipath and other errors/anomalies must be investigated. This paper presents results from a series of flight tests conducted during March 2003 and July 2003 on the Ohio University DC-3 flying laboratory. The primary goal of the flight tests was to investigate and characterize the nature of the biases induced on the code-phase measurements as the aircraft performed a series of tactical maneuvers. The relationship between the satellite azimuth and elevation relative to the aircraft is investigated. Signal distortions originating from different aircraft features such as the wings, fuselage, and tail are investigated. Code-minus-carrier processing techniques are employed to isolate the ranging biases on a per satellite basis. For the airborne sensor, NovAtel OEM4 GPS receivers were used, representing the state-of-art in receiver design. Repeatability of the airborne satellite tracking errors is also considered. Finally, the results of the investigation are interpreted in light of their implications on the vertical protection level (VPL) equations used to insure system integrity for operations such as Category III aircraft precision approach.
01 Jan 2003
TL;DR: The flight test combined with the RT-DGPS technique has qualitatively demonstrated that the GPS-determined attitude is feasible and quantitatively proved the pseudo-roll and pseudo-heading angles are especially reliable.
Abstract: Owing to the maturity of satellite technology and Global Positioning System (GPS), the new generation of Air Traffic Management (ATM) technique is designated to utilize the navigation information provided by the Global Navigation Satellite System (GNSS). For precision landing and take-off of an aircraft, the Local Area Augmentation System (LAAS) is needed to enhance the navigation accuracy, integrity, reliability and availability. Present study simulates the concept of LAAS and has established a ground-based Real-Time DGPS (RT-DGPS) reference station. This base station provides 0.5-meter RMS error and 0.2-meter correction for static horizontal navigation and 1.1-meter RMS error and 2-meter correction for dynamic horizontal navigation. The verification of pseudo-attitude in flight is also accomplished in an ultralight vehicle. The flight test combined with the RT-DGPS technique has qualitatively demonstrated that the GPS-determined attitude is feasible and quantitatively proved the pseudo-roll and pseudo-heading angles are especially reliable.
25 Jun 2003
TL;DR: The third civil GPS signal, L5, includes a dataless component that is allocated 50 percent of the total L5 signal power as discussed by the authors, which is optimized for a 50 Hz navigation data rate.
Abstract: The third civil GPS signal, L5, includes a data-less component that is allocated 50 percent of the total L5 signal power. This power allocation was optimized for a 50 Hz navigation data rate. Several Satellite-based Augmentation Systems (SBAS) are planning to provide a future signal at the L5 frequency (as they currently do on the GPS L1 frequency). Since the SBAS L5 signals will provide data at higher rate (250 or 500 bps), equally splitting power between an inphase (I) data channel and a quadraphase (Q) data-less channel as is done with the GPS L5 signals, may well not be optimal. Several SBAS L5 signal design options are considered in this paper, including various allocations of power between the data and data-less signal components. Both 250 bps and 500 bps data rates are considered in this paper. Future options for the SBAS L1 signals will also be presented that maintain the legacy signal design in one component (the I channel) and a second data stream in an independent Q channel to provide the possibility of higher data rates on L1 to accommodate future navigation systems such as Galileo. Legacy GPS and SBAS receivers would not be affected.
12 Sep 2003
TL;DR: In this paper, the performance of satellite-based augmentation system (SBAS) ionospheric estimation algorithms in equatorial regions was analyzed using recorded Brazilian GPS data, and the results of the analysis confirm those of a previous analysis that was based on data generated with an ionosphere model.
Abstract: The performance of Satellite-Based Augmentation System (SBAS) ionospheric estimation algorithms in equatorial regions was analyzed using recorded Brazilian GPS data. Algorithms similar in design to those employed by the U.S. Wide Area Augmentation System (WAAS) were used. The results of the analysis confirm those of a previous analysis that was based on data generated with an ionospheric model. The structure of the equatorial ionosphere, which causes GPS ionospheric range delays to vary from one point in space and time to another, is much more complex than the mid-latitude ionosphere and presents a difficult challenge to the development of a single-frequency SBAS capable of supporting a high availability of vertically guided approaches. The combined effects of the equatorial slant-to-vertical conversion errors, spatial and temporal decorrelation errors, modeling and estimation errors, and the demanding integrity requirements imposed on the error bounds broadcast by an SBAS, result in large error bounds that will severely limit the availability of vertically guided approach procedures during the local evening hours near the peak of the solar cycle.
TL;DR: Several architectures are described that are suitable for the autonomous assessment and provision to users of Local Integrity, and subelement functionalities are developed to support this.
Abstract: This article presents a number of Local Integrity concepts for augmentation of the Galileo satellite navigation system. Several architectures are described that are suitable for the autonomous assessment and provision to users of Local Integrity, and subelement functionalities are developed to support this. Performance results are presented from simulations conducted as part of the work
12 Sep 2003
TL;DR: In this article, the authors report results of a study designed to determine how one would safely reduce bounds on ionospheric errors so that a Space Based Augmentation System (SBAS) would be able to provide single frequency precision approach SBAS service in the presence of the ionosphere effects common to the equatorial region.
Abstract: We report results of a study designed to determine how one would safely reduce bounds on ionospheric errors so that a Space Based Augmentation System (SBAS) would be able to provide single frequency precision approach SBAS service in the presence of the ionospheric effects common to the equatorial region We work under the restrictions of the ICAO Standards And Recommended Practices for GNSS (SARPs) [1], which specifies a 5-by-5 degree grid of Ionospheric Grid Points, a thin shell model of the ionosphere with a shell height of 350 km, and an ionospheric message structure commensurate with that used by the Wide Area Augmentation System (WAAS) First, we study the applicability of WAAS algorithms suitably modified to account for larger spatial variability and enhanced using techniques recently developed to improve WAAS ionospheric storm day performance This exercise allows us to demonstrate the importance of tailoring SBAS ionospheric algorithms to the prevailing environmental conditions This is followed by a discussion of techniques that might allow integrity proofs to be completed for users in the presence of the types of ionospheric irregularities regularly encountered in the equatorial region In conclusion we assess the prospects for providing single frequency precision approach SBAS service in equatorial regions without any changes to the SARPs We list outstanding challenges to providing such service, and discuss the assumptions behind our assessment Finally, we entertain the possibility that techniques developed for dealing with equatorial ionospheric threats might be applied to WAAS in order to improve WAAS threat models and the way that WAAS deals with significant ionospheric irregularities
Book•
01 Jan 2003
TL;DR: In this article, the authors discuss the future of the GPS Local Area Augmentation System (LAAS) and the integration of EGNOS and Galileo in the European Air Navigation System.
Abstract: A Brief Summary of Four Keynote Addresses.- Galileo: Status and Way Forward.- At the Crossroads: Civil and Security Issues Concerning Navigation Satellites in Japan.- The Future of the GPS Local Area Augmentation System (LAAS).- Complement and Augmentation of GPS from a Quasi-Zenith Orbit.- A GNSS Literature Review and a Navigation System for Future Space Vehicles.- Galileo System Architecture - Status and Concepts.- Europe's Challenges in Developing its Own Satellite Navigation System.- Cislunar Navigation.- Compatibility and Interoperability of GPS and Galileo: A Continuum of Time, Geodesy, and Signal Structure Options for Civil GNSS Services.- Galileo - The Essentials of Interoperability.- Inmarsat: An Approach for Integration of EGNOS and Galileo.- A Software Perspective on GNSS Receiver Integration and Operation.- GNSS Safety of Life Services: Towards a Safer and More Effective Use of European Transport Networks.- Testing the Dubai Virtual Reference System (DVRS) National GPS-RTK Network.- Network-based RTK-GPS for Nationwide High-accuracy Positioning and Navigation in Japan.- Measuring Galileo's Channel - The Pedestrian Satellite Channel.- A Challenging Navigation Environment - Indoor Applications.- Evaluation of EGNOS (GNSS-1) for Application in a Vehicle Driving Support System.- The Use of Global Navigation Systems in the Aviation Industry.- The Advent of Galileo in the European Air Navigation System.- The Need for, and Benefits of, Galileo Local Services.- ISAGNSS: Infrastructure for Spanish GNSS Activities.- Session 6 Discussion Groups.- A Combined Localisation/Communications System for Mountain Rescue Applications.- Automatic Guidance of Farm Vehicles.- Algorithms of a Complex Inertial and Satellite Navigation System for Aircraft.- GPS-based Clock Synchronization for Precision Time Management for LEO Remote Sensing Satellites.- Space Radiation Environment and its Effects on Satellite Navigation Systems.- Navigation Support through Intelligent Agents.- A Novel Signal Processing Scheme for a Next Generation GNSS Receiver.- Damage Caused by GNSS Signals in the Light of the Liability Convention of 1972.- Galileo System Test Bed Validation Algorithms.- Potential Criteria for the Assessment of a Future Public-Private Partnership for Galileo.- Qualification of EGNOS for Routine Operation.- Solutions to Increasing the Availability of GPS and Future Upgrades of the Satellite Navigation System.- Symposium Summary.
12 Sep 2003
TL;DR: The Galileo global integrity concepts are compared with a regional approach using different concepts and IF algorithms but also different ground architectures.
Abstract: GPS and Galileo are expected to serve as navigation sources for a variety of applications. The most stringent performance requirements are derived from safety critical applications including aviation APV-II respectively CAT-I precision operations. The Galileo baseline architecture specifies a global integrity concept. This means e.g. that besides the accuracy, availability and continuity the specified integrity performance must be achieved on a global level. However Civil Aviation Authorities outside Europe, might wish due to sovereignty reasons as well as due to performance reasons to determine the System Integrity of Galileo independently. One concept would be to adapt the different Augmentation approaches for GPS (SBAS, GBAS, GRAS) for the Galileo case. However, the Galileo baseline already foresees to include a multi-regional integrity concept where regions can install own integrity determination architecture while Galileo will provide the interfaces from regions to the Galileo satellites for disseminating of the regionally determined integrity. The basic approach of the Galileo integrity concept hereby is the task split of the Galileo integrity monitoring between the System (providing the GNSS Integrity Channel) and the User (providing Receiver Autonomous Integrity Monitoring techniques). The system performance has to be achieved in terms of the specified accuracy, availability and continuity figures. In addition the integrity monitoring has to detect Hazardously Misleading Information (HMI) of the navigation system and to alert the users within the specified Time To Alert (TTA). The Galileo System shall provide timely warning if the errors caused by satellite, clock, signal and / or navigation message are larger than predicted via a combination of a Signal In Space Accuracy (SISA) and Integrity Flag (IF). The SISA is a quantitative estimation of the orbit and clock prediction of the Galileo Control Centre which is updated with every clock update - in a fault free case. If an error occurs in the satellites, clocks, signal, navigation message or in the processing itself, then it has to be detected by the Integrity Processing Facility (IPF) in real-time and a warning flag IF has to be sent to the user within the necessary Time-to-Alert. As the check in the IPF has to be performed nearly instantaneous (fraction of the Time to Alert), there has to be a sufficient number of Sensor Stations to get a statistically significant test, which allows even to identify and to exclude Sensor Stations with local disturbances in the observations. The main design driver of the Galileo architecture is the IF performance. This paper compares the Galileo global integrity concepts with a regional approach using different concepts and IF algorithms but also different ground architectures.
01 Jan 2003
TL;DR: This paper focuses on the GPS, the European Galileo and especially the methods used worldwide for the enhancement of satellite position fixes, and examines the large-scale Satellite-Based Augmentation Systems (SBAS) alternatives, namely WAAS and EGNOS.
Abstract: Precision farming is a management process, that involves the development and adaptation of knowledge – based technical management systems with the main goal of optimizing profit. Precision farming can be best understood as a cyclic optimization process, with control elements that measure both quantity and quality. This paper focuses on the GPS, the European Galileo and especially the methods used worldwide for the enhancement of satellite position fixes. To this end we examine the large-scale Satellite-Based Augmentation Systems (SBAS) alternatives, namely WAAS and EGNOS. The specific potential of augmentation systems in precision farming is evaluated against complexity and cost. The paper concludes with the assessment of alternative infrastructures for provision of differential corrections.
Patent•
01 May 2003
TL;DR: In this article, the authors describe a process, a satellite navigation system and a user terminal for furnishing and transmitting navigation data in a navigation system by transmitting several navigation data blocks from a navigation data transmission unit to navigation terminals.
Abstract: A process, a satellite navigation system and a user terminal for furnishing and transmitting navigation data in a navigation system by transmitting several navigation data blocks from a navigation data transmission unit to navigation terminals. Before transmitting the navigation data to the navigation device, an interleaving of at least two navigation data blocks takes place.
Patent•
29 Sep 2003
TL;DR: In this paper, a system for determining estimated navigation signal error information is proposed, where several error models are used by the evaluation unit, and, as a function of at least one defined selection standard, one of the error models is selected.
Abstract: A system for determining estimated navigation signal error information. Several error models are used by the evaluation unit, and, as a function of at least one defined selection standard, one of the several error models is selected. In determining the estimated navigation signal error information, the selected error model is applied to the received navigation signals, and the determined error information is transmitted to the radio navigation system and/or to user terminals.
TL;DR: The implemented integrity monitoring system and algorithms used in the tests are introduced and the scenarios of satellite failure are described.
Abstract: In recent years, many countries are developing aircraft navigation systems using GNSS(Global Navigation Satellite System), because GNSS has many technical and economic benefits. International organizations as ICAO(International Civil Aviation Organization) and RTCA(Radio Technical Commission for Aeronautics) set up international standards of GBAS(Ground Based Augmentation System) using GNSS and recommend countries to develop GBAS that is based on the standards. To go with the international stream, Korea Airport Cooperation has also developed GBAS. For evaluating the system, KAC and Seoul National University have performed flight tests of the developed GBAS several times and have concluded that the system has good accuracy enough to be used in aircrafts. At that time, the purpose of tests was focused on accuracy of GBAS. But integrity of the system which is important for safety of aircrafts was not tested sufficiently, because it is impossible to make erroneous situations of real GPS signals. So, at this time, we used GPS simulator which can generate GPS signals with satellite failure scenarios. The GPS simulator used in this test generates GPS signals by the scenarios organized in advance. The scenarios can include pseudorange and carrier phase error, parity error and etc. So we organized several scenarios which can includes potential errors of GPS signals and many possible cases for testing the system effectively and accurately. And we tested integrity function of the GBAS system by using GPS signals generated by the simulator. This paper introduces the implemented integrity monitoring system and algorithms used in the tests. And it describes the scenarios of satellite failure. Finally, this paper shows the results of tests.
12 Sep 2003
TL;DR: RTCM SC-104 as discussed by the authors is a public standard for differential and real-time kinematic (RTK) GNSS operations, which is designed to be highly efficient in terms of broadcast bandwidth, in order to accommodate the needs of RTK operations.
Abstract: RTCM SC-104 has developed a new public standard, called Version 3, for differential and real-time kinematic (RTK) GNSS operations. It is designed to be highly efficient in terms of broadcast bandwidth, in order to accommodate the needs of RTK operations. It is also highly flexible, supporting conventional RTK, networked RTK, low bandwidth RTK, as well as all differential GNSS legacy applications. Now that Selective Availability has been set to zero, the new standard will enable existing low-bandwidth broadcast services to accommodate RTK operations, or add other services in addition to differential GNSS. The paper discusses the numerous applications of the standard, the transport layer format, and the presentation layer messages that have been developed to date. The transport layer includes a byte count and a 24-bit cyclic redundancy check (CRC). The messages are laid out in a data base format which is believed to be clearer than the previous standard, and which makes it easy to build new messages on top of old ones, for example, to readily accommodate SBAS signals. The initial version of the standard provides for real-time kinematic operation of GNSS, and includes a number of auxiliary messages which describe the antennas used by the reference stations, the antenna reference point, and system information that includes the messages processed by the reference station. A second supporting document defines the next group of messages currently in preparation for subsequent incorporation into the standard in future releases. The Committee has a process for establishing both completeness and interoperability. Each participating vendor checks the standard to ensure that the data fields, and their range and resolution, are adequate to support their intended applications. Then, each one develops reference station files that are distributed to the others to establish interoperability of the data. Finally, the vendors bring prototype equipment to a test site and perform interoperability tests in real time. In this way problems are dealt with prior to publication of the standard.
01 Feb 2003
TL;DR: In this paper, different test methods to analyze the ionospheric corrections performance are presented, including the TEC TOPEX comparison test and the STEC variations test, and two very accurate analyses based on large baseline ambiguity resolution techniques giving comparisons for absolute STEC and double differenced STEC determinations.
Abstract: Satellite Based Augmentation systems (SBAS) provide to Global Navigation Satellite Systems (GNSS) users with an extra set of information, in order to enhance accuracy and integrity levels of GNSS stand alone positioning. In this context, different test methods to analyze the ionospheric corrections performance are presented. The first set of tests involves two of the ionospheric calculations that are applied daily to the Global Ionospheric Maps (GIM), computed by the IGS Associate Analysis Centers: a TEC TOPEX comparison test and the STEC variations test. The second family of tests provides two very accurate analyses based on large-baselines ambiguity resolution techniques giving comparisons for absolute STEC and double differenced STEC determinations. Those four analyses have been applied using EGNOS System Test Bed (ESTB) data showing some satellite dependent biases.
Journal Article•
TL;DR: In this article, how to design a net of altitude-damper, how to determine the parameters in the net and how to deal with the net in Kalman Filter of the integrated navigation system are discussed respectively by adopting the method of Monter-Carlo emulation to imitate the strapped-down navigation system and INS / GNSS integrated navigation systems.
Abstract: In inertial navigation system, the error accumulation of altitude is unsteady, so the outside information sources such as barometric altimeter, etc. should be used to damp the accumulation. In this paper, how to design a net of altitude-damper, how to determine the parameters in the net and how to deal with the net in Kalman Filter of the integrated navigation system are discussed respectively by adopting the method of Monter-Carlo emulation to imitate the strapped-down navigation system and INS / GNSS integrated navigation system. And finally the actual result of the emulation is given.
12 Sep 2003
TL;DR: In this paper, the effects of signal Doppler on short code spectral lines, data and symbol modulation effects, signal power versus elevation angle, and, more importantly, critical signals are evaluated.
Abstract: Intersystem interference is defined as interference from signals from one satellite navigation system to/from another such as between Galileo and GPS, though also extended to Satellite Based Augmentation Systems (SBAS). To date, the assessment of these interference effects has generally been overly conservative for the sake of simplicity in performing the analyses. This situation is further compounded by the fact that some of the signals, such as the GPS C/A code signals, are coded with relatively short repeating codes. Over the course of the last few years, a more complete interference analysis methodology has been developed to support RTCA SC159 Working Group 6, the working group that evaluates and defines interference to satellite navigation signals used for aviation navigation equipment requirements. This methodology evaluates the effects of signal Doppler on short code spectral lines, data and symbol modulation effects, signal power versus elevation angle, and, more importantly, critical signals. The methodology accounts for the fact that the codes are modulated with navigation data and error correction codes that spread the inherent spectral line structure over the symbol bandwidth. Representative satellite and user equipment antenna patterns are used to vary received signal power as a function of elevation angle. Lastly, only interference effects on critical signals are evaluated since only critical signals are absolutely required to perform the navigation function. This is the crux of the paradigm because weak signals need not be included unless they are critical signals. In most scenarios, critical signals are those at higher elevation angles, or there are no critical weak signals at all. This methodology was applied to GPS intrasystem interference effects, including the effects to/from SBAS signals, by the RTCA Working Group 6 and reported in a recent RTCA publication (DO-235A). It is now extended to GPS/Galileo intersystem interference effects. This paper will present the results of the extended methodology.
Journal Article•
TL;DR: A closed loop feedback cascade SINS/GNSS integrated navigation system is designed that can give the best estimation for the errors of position, velocity, and platform which are caused by the algorithm of SINS and the errors which are brought by the inertial measurement unit.
Abstract: The output of Kalman filter for SINS/GNSS integrated navigation system cannot be feedback to the algorithm of strapdown inertial navigation system and can not restrain the accumulation of the errors caused by the platform and inertial measurement unit, so the navigation accuracy will decrease. In this paper, a closed loop feedback cascade SINS/GNSS integrated navigation system is designed. The system can give the best estimation for the errors of position, velocity, and platform which are caused by the algorithm of SINS and the errors which are brought by the inertial measurement unit, then it can feedback to the SINS by itself. The system is demonstrated by simulation to have such characters as high accuracy and the ability of motion alignment, so it can keep the stability of long time navigation.
12 Sep 2003
TL;DR: Naoki Fujii is the leader of Ground Based Augmentation System (GBAS) research group and a Principle Researcher of Electronic Navigation Research Institute (ENRI) working in field of the development of Ground-Based Augmentation Systems for GNSS.
Abstract: GPS is widely used in many applications now. Safety-critical applications such as aircraft navigation require position information not only with high accuracy but also high integrity. To meet these two difficult requirements, Signal Quality Monitoring (SQM) is necessary for both the GBAS and the Space Based Augmentation System (SBAS). SQM must detect the distortion of the correlation-curve caused by satellite anomalies, such as "evil waveform". Electric Navigation Research Institute in Japan (ENRI) and Furuno Electric Co., Ltd.(FURUNO) have jointly developed a new GPS/SBAS receiver with real-time correlation-curve monitoring capability. This is the first prototype of the GPS/SBAS receiver with SQM in Japan. The receiver has 16 channels including 3 SBAS dedicated channels for L1 C/A signal tracking and 2 SQM channels. Each SQM channel has 127 correlation points distributed evenly at 0.025575 chip step. The width of the correlation monitoring range is about 3.2 chips. It can be allocated at any part of 1023-chip width by user selection. Each correlation point outputs both In-phase and Quadrature at 5 Hz. This receiver also supports Time-Divided-Multi-Signal Monitoring (TDMSM) mode, which changes monitoring satellite and/or monitoring range by time-sharing method. Using TDMSM, the receiver can produce up to 10 different satellites´ correlation-curves at 1 Hz update rate. That means most of the time, the receiver monitors all visible satellites in real-time. In addition to the SQM capability, the receiver can output up to 5 different position-fixes, such as GPS, DGPS, SBAS#1, SBAS#2, and SBAS#3. Raw observation data, such as accumulated carrier phase, pseudorange, carrier-to-noise ratio, Doppler-shift, and time-tag are also outputted at 5 Hz. The receiver is equipped with Ethernet. It allows us fast data output via network environment. We also developed data recorder program on the personal computer (PC). This paper introduces the detail specification of the SQM receiver and presents data collected in three different environments; (1) using parabolic antenna; (2) usual fixed-point observation; (3) multipath by GPS/SBAS simulator;