Showing papers on "GNSS augmentation published in 2002"

Apparatus and method for navigation of an aircraft

Abstract: In accordance with this invention, an apparatus and method for aircraft navigation are provided that utilize a blended architecture consisting of a global positioning system (GPS) and micro-electromechanical sensors (MEMS) for the primary navigation system and a laser gyroscope system for the secondary navigation system. The blended architecture of the present invention provides a navigation system that is at least as accurate, redundant and fault-tolerant as conventional navigation systems. In addition, the navigation system components may be distributed throughout the aircraft and may share computing resources with other avionics systems to process signals and provide data to the avionics systems. Overall, the navigation system of the present invention is significantly less expensive and easier to maintain, but equally or more precise and redundant, relative to conventional navigation systems.

An Assessment of the Current WAAS Ionospheric Correction Algorithm in the South American Region

Abstract: The Federal Aviation Administration’s (FAA) Wide Area Augmentation System (WAAS) for civil aircraft navigation is focused primarily on the Conterminous United States (CONUS). The ionospheric correction algorithms for WAAS have been characterized extensively for this mid-latitude region of the ionosphere where benign conditions usually exist. Researchers are facing a more formidable challenge in addressing the ionospheric impact on navigation using Satellite-Based Augmentation Systems (SBAS) in other parts of the world such as the South American region. 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 region. In this paper, we use data from the South American region to perform a preliminary quantitative assessment of the performance of WAAS correction algorithms in this region. For this study, we accessed a world-wide network of 230 dual-frequency GPS receivers. The network includes: 1) the Continuously Operating Reference Sites (CORS) in the United States; 2) stations in and near South America as part of the Brazilian Network of Continuous Monitoring of GPS (RBMC), operated by the Brazilian Institute of Geography and Statistics (IGBE); and (3) sites included in the International GPS Service (IGS) global network. Data sets have been selected to include both a quiet and geomagnetically disturbed day. To provide ground-truth and calibrate GPS receiver and transmitter inter-frequency biases, we processed the GPS data using Global Ionospheric Mapping (GIM) software developed at the NASA Jet Propulsion Laboratory to compute calibrated high resolution observations of ionospheric total electron content (TEC). We assessed the WAAS’s planar fit algorithm in the equatorial region where the spatial gradients and the absolute slant TEC are known to be the highest in the world. We found that in Brazil the dominant error source for the WAAS planar fit algorithm is the inherent spatial variability of the equatorial ionosphere with ionospheric slant range delay residuals as high as 15 meters and root- mean square residuals for the quiet day of 1.9 meters. This compares to a maximum residual of 2 meters in CONUS, and 0.5 meter RMS. We revealed that ionospheric gradients in Brazil are at the 2 meter over 100 km level. Contrary to results obtained for CONUS, we discovered that a major ionospheric storm had a small impact on the planar fit residuals in Brazil.

Assisted gps signal detection and processing system for indoor location determination

Abstract: An assisted GPS signal detection and processing system enables an end user to obtain position information from satellite navigation signals in indoor environments that have excess signal attenuation. The system includes a master navigation signal receiver having an antenna disposed with clear sky access to a plurality of navigation satellites. The master navigation signal receiver receives satellite navigation signals from the plurality of navigation satellites, and relays an assisted satellite navigation signal to a plurality of end user signal receivers via a medium. The assisted navigation signal includes at least one of satellite location information, clock correction information, and frequency discipline information. The end user signal receivers each have an antenna for receiving the satellite navigation signals directly. The end user signal receivers are also coupled to the medium to receive the assisted navigation signal from the master navigation signal receiver. The satellite navigation signals received by the end user signal receivers via the antennas may be at least partially attenuated due to passing through physical structures. The end user signal receivers are able to recover end user position information from the attenuated satellite navigation signals by use of the assisted navigation signal.

An intelligent navigation solution for land mobile location-based services

Abstract: In this research, the authors discuss how the integration of spatial information with real-time positioning sensors into a navigation solution can lead to a significant improvement in navigation results as well as prolonging successful navigation in areas were absolute positioning is unavailable. In order to reduce the inaccuracies associated with low-cost inertial sensor over time, the authors suggest integrating the measurements that are provided by navigation instruments with additional spatial information contained within a map database. It is shown that the information contained in a Geographic Information System (GIS) can be extracted and integrated into the navigational solution.

System and method for augmentation of satellite positioning systems

Abstract: A system and a method for augmentation of satellite positioning systems wherein a monitoring ground station (MGS) is connected to a computer center in charge of determining the level of error of a satellite (NS) broadcasting positioning signals and transmitting navigation correction data to a mobile user. Said transmission is performed using a digital satellite system using at least one digital satellite (DS)capable of broadcasting multiplexed data in down-link transmission to a user station (U). The user station (U) de-multiplexes and retrieves said navigation correction data from said digital satellite down-link transmission by means of a down-link frame adapter (7) connected to a satellite receiver (6). Specific data such as time or GNSS allmanacs are replicated under specific format and put into specific part of signaling channel to enable time broadcast to standard receivers of DS system, and to speed-up acquisition of GNSS satellite signal by standard GNSS receivers possibly in use in said U station. A method is also disclosed for broadcasting time with a reasonable accuracy.

System and method for computing navigation information in the presence of interference

Abstract: Navigation information for a first navigation system (110) is computed based on interference signals (120) and satellite signals. The first navigation system (110) comprises means for receiving N satellite signals capable of being processed and at least M interference signals (120), where M = K-N and K equals the minimum number of satellites required to be tracked for unambiguously determining navigation information for the first navigation system (110). Based the at least M interference signals (120) and the N satellite signals received and capable of being processed, the navigation system (110) computes navigation information for the first navigation system (110).

Ionospheric Effects on Low-Latitude Space Based Augmentation Systems

Abstract: The FAA´s Wide Area Augmentation System (WAAS) was primarily developed for use in the mid-latitude CONtiguous United States (CONUS), where the ionosphere is well studied and well behaved. In the low- latitude regions, the magnitudes of the absolute range delay values are much higher, and the equatorial anomaly produces large spatial gradients over latitude. In the CONUS region, scintillation effects are very rare, but strong amplitude fading and phase scintillation effects occur regularly in the equatorial anomaly regions. Associated with the irregularities that produce scintillation effects are large plasma depletions in ionospheric range delay that may severely limit Space Based Augmentation System (SBAS) Precision Approach (PA) availability in those regions during those times. The FAA´s WAAS system will likely be the first of several SBAS systems to operate in various parts of the world. SBAS technology is also being developed for operational use in Japan (MTSAT) and Europe (EGNOS). The FAA National Satellite Test Bed (NSTB) program, a prototype WAAS, is currently involved in joint test efforts with Chile, Singapore and Brazil for the purpose of determining the feasibility, limitations and benefits of SBAS technology in those countries. In data that the NSTB has collected and analyzed from these sites, scintillation and equatorial anomaly effects are apparent. In this paper, we will present the ionospheric phenomena that may challenge SBAS operation at low latitudes. This presentation will include statistical summaries of long- term scintillation activity in Brazil. In addition, we present data describing the effects of scintillation on GEO WAAS messages and on a WAAS dual-frequency receiver operating in Rio de Janeiro, Brazil since October 2001. This data will provide insight into low latitude ionospheric effects on Precision Approach capability in this most challenging ionospheric environment.

How will galileo improve positioning performance

Abstract: With the launch of Galileo, the European Union's new civilian-managed Global Navigation Satellite System (GNSS), civilian users will have more than double the GNSS signals when paired with those from the U.S. Global Positioning Satellite (GPS) system. Users obtain the best advantage when they combine both systems' signals and observable. Having more signals means they are more likely to be available in difficult terrain such as urban canyons and steep mountains. But the added signals will also improve the precision of location calculations and the detection of measurement noise and other distortions. The study shows how the calculations based on both sets of signals can estimate ionospheric effects and other distorting factors to reach unheard-of levels of ambiguity resolution.

Comparison of GEO and GPS Orbit Determination

Abstract: Geostationary Earth Orbit (GEO) satellites serve as relays to transmit messages for Space Based Augmentation Systems (SBASs), such as the Wide Area Augmentation System (WAAS), the European Geostationary Navigation Overlay Service (EGNOS), and the Multifunction Transport Satellite Based Augmentation System (MSAS). GEO satellites can act as ranging sources for SBAS users as well, adding to the availability and continuity of a number of SBAS services. Unfortunately, since the GEO is nearly stationary relative to the SBAS stations, separating the position and velocity errors from the clock errors is difficult and makes the GEO range errors much larger than GPS range errors. A technique has been proposed to decouple the clock errors in a bent-pipe GEO system and has been shown to drop the GEO range errors to levels comparable to those for GPS satellites [1]. This paper explores further the expected improvement in the GEO orbit determination using this clock error decoupling technique. WAAS field data are used in an extended Kalman filter based on the WAAS Corrections and Verifications (C&V) software to study the GEO range errors with a known clock. The GEO range errors with a known clock are found to be up to a factor of ~5 better than those for the fielded WAAS and to within 50% of the GPS range errors.

Dynamic Properties Of GNSS / INS Based Train Position Locator For Signalling Applications

Abstract: This paper deals with dynamic properties of global navigation satellite systems- (GNSS) and inertial navigation systems (INS)- based train position locators (TPL) intended for railway signaling applications. The focus is on cost-effective on-board train positioning and routing detection on a 'dark' track where GNSS SIS (signal-in-space) is temporarily unavailable. The route-map-matching technique is considered to be a key method to improve the accuracy and reliability of the entire locator system. The double heading differences fully compensating the drift of a gyro are introduced to estimate the reliability of the routing decision process by means of Bayes theorem. The sensor data validation process based on the route map is also discussed. On-board detection of the characteristic elements of the switch is proposed to achieve higher safety standards and reduce the cost of signaling.

A new scheme of vision based navigation for flying vehicles-concept study and experiment evaluation

Abstract: In this paper, a new scheme of vision based navigation was proposed for flying vehicles. In this navigation scheme, the main navigation tool is a camera, plus an altimeter. The feasibility of this navigation scheme was carefully studied both from theory and numerical analysis. Unlike most of vision based navigation approaches using feature trajectories to compute 3D-platform motion, we use the image geometrical transformation parameters between consecutive frames to infer3D displacement of camera. Due to this change, the navigation process can be conducted even if there is no salient features that can be extracted from in the image sequence, for example, in the case of flying over the sea. As a result, the long-range navigation becomes possible by use EO sensor. Moreover, the way of improvement navigation accuracy was also discussed in the paper. The experiment results demonstrated that the navigation accuracy of this system is compatible to GPS (Global Positioning system), much higher than all kinds of INS (Inertial Navigation System) in terms of position estimation. It is a good alternative choice when the GPS signal is not available.

Flight Testing of the D8PSK/TDMA Datalink Technology for the Ground-based Regional Augmentation System

Abstract: Since 2000, Airservices Australia’s Global Navigation Satellite Systems (GNSS) Program Office (GNSSPO) has been working with the International Civil Aviation Organisation (ICAO) GNSS Panel (GNSSP) on producing Standards and Recommended Practices (SARPs) for an alternate wide area augmentation system based on a Very High Frequency (VHF) data link This Ground-based Regional Augmentation System (GRAS) was proposed due the financial, legal and institutional issues which Australia had identified as limiting the applicability of the satellite based solutions being progressed by the USA and other large economic nations Following approval by ICAO’s Air Navigation Commission in 1999, the Differential Eight Phase Shift Keying (D8PSK)/Time Division Multiple Access (TDMA) data link technology, already accepted by ICAO for Ground Based Augmentation Systems (GBAS), was accepted as the basis for the GRAS data link Airservices Australia has operated a test-bed network using six ground reference stations and two D8PSK/TDMA VHF transmitter sites for the past two years This network has proven the viability of using a single VHF frequency to implement a GRAS over a large area such as Australia, using the TDMA properties of the technology to separate the signals from the various VHF transmitter sites Flight tests conducted over the past two years have shown the viability of GRAS providing navigation services to Approach with Vertical Guidance Level 1 (APV I) and potentially Level 2 (APV II) parameters as defined by ICAO GNSS SARPs The system has demonstrated the capability to support variable geometry approach paths such as curved final approach paths, different glidepath angles and variable touchdown points This paper provides the results of flight tests conducted in the first half of 2002 which support the use of the D8PSK/TDMA data link, and the concept of using a single VHF frequency to implement a GRAS These results will be used by the GNSSP to support validation of the GRAS SARPs, due for completion in 2003

Increasing the reliability and quality of information control systems by utilizing the latest scientific and technical achievements in satellite navigation technologies

Abstract: A presentation is given of the prospects for developing and maintaining the GLONASS satellite navigation system and ways of improving the quality, reliability, and effectiveness of solving various problems by utilizing satellite navigation technology.

Hybrid instrument landing systems for aircraft

Abstract: Disclosed are combinations of electronic navigation systems for aircraft landing approaches, enabling overall operating complexity (especially on the ground) of electronic aircraft guidance systems for precision approaches to be reduced significantly in relation to prior art and future GNSSS-assisted (Global Navigation Satellite Systems) approach methods, while at the same time increasing the number of regionally available systems in the case of failures of supraregional systems (e.g. GNSS). The aim of the invention is, leading on from the previous prevailing idea, to cover and meet all requirements with respect to flight guidance in the approach with the aid of essentially one system and to specially use optimised separate systems or system components for the final approach, making it no longer necessary to eradicate the weaknesses of an individual system (e.g. precision of altitude guidance and integrity problems with GNSS) by means of complex measures(e.g. GBAS for GNSS). According to the invention, the system combinations also diffuse problems related to integrity of the data base on board the aircraft occurring when area navigation systems (e.g.GNSS, LORAN-C) are used.

A network-type navigation system

Abstract: We have developed a new, network-type navigation system and put it on the market as an Alpine product starting 2002/06. The following features distinguish this system from existing ones: (1) Seamless navigation: smooth networking with mobile phones and PCs expands the scope of navigation to beyond simply the interior of the vehicle; (2) Easy search of up-to-date information: access to server-side databases provides the most up-to-date information, with the implementation of fuzzy searches greatly improving the ease of operation; and (3) Mobile navigation: the use of mobile phones enables navigation even after getting out of the vehicle (such as when walking or using Park & Ride). The car navigation system has continued to develop rapidly since its first appearance in the early 90s. The addition of new features such as voiced route guidance, D-GPS, VICS (Vehicle Information and Communication System), DVD-ROM, and voice recognition has greatly improved the operability, accuracy, and data capacity of such systems, enabling the support of a safer and more comfortable driving environment. The advance of IT (Information Technology) within the past few years has also brought significant changes in the mobile environment. The explosive spread of mobile phones, especially, has promoted the integration of the automobile within a communication network. Such trends provide new possibilities for further enhancing the driving experience.

Optimal Constellation Design for Satellite Based Augmentation System

Abstract: Global Positioning System (GPS) is widely utilized in daily life, for instance car navigation. Wide Area Augmentation System (WAAS) and Local Area Augmentation System (LAAS) are proposed so as to provide GPS better navigation accuracy and integrity capability. Satellite Based Augmentation System (SBAS) is a kind of WAAS and Multi-functional Transportation Satellite (MTSAT) has been developed in Japan. To improve navigation accuracy most efficiently, augmentation satellites should be so placed that minimize Geometric Dilution of Precision (GDOP) of constellation. In this paper the result of optimal constellation design for SBAS is shown.

Enhancing mobile applications by combination of GNSS and W-CDMA

Abstract: The location requirements for emergency callers outside urban areas can hardly be fulfilled without global navigation satellite systems (GNSS). Consequently, interest in positioning techniques based on use of a GNSS such as GPS or on the cellular network infrastructure itself is growing rapidly in the mobile-telephone community. Moreover, the increasing demand for commercial location-based services (LBS) has driven cellular-phone and network manufacturers to focus on positioning solutions which are even more accurate than the regulatory mandates for positioning of emergency callers. One example of these upcoming LBS is our PARAMOUNT project, which aims at improving user-friendly info-mobility services for hikers and mountaineers by combining wireless communications (GMTS), satellite navigation (GNSS) and geographic information systems (GIS), based on a mobile client/server architecture. The availability of mobile phones or PDAs with combined GNSS and cellular network-based wireless communication on a high integration level is one primary demand of such LBS applications. Based on this, we will give some initial answers to the question of whether mobile handset architecture synergies exist for the combination of GNSS with wireless location in CDMA cellular wireless networks. In order to identify synergies, we will outline similarities and differences between wireless communication and satellite navigation. In this respect, we pay particular attention to the so-called RAKE receiver architecture employed in mobile CDMA cellular handsets. Our initial investigations will show that the RAKE receiver architecture, on which mobile CDMA cellular handsets are based, will most likely be the one most suitable for achieving synergies between the two positioning techniques within the same mobile handset architecture. Consequently, several receiver components could be used to handle both types of signals (navigation and communications), resulting in a reduction of manufacturing costs and in a decrease in energy consumption.