Satellite Navigation Receiver Research Articles

An Efficient Two-Fold Marginalized Bayesian Filter for Multipath Estimation in Satellite Navigation Receivers

Multipath is today still one of the most critical problems in satellite navigation, in particular in urban environments, where the received navigation signals can be affected by blockage, shadowing, and multipath reception. Latest multipath mitigation algorithms are based on the concept of sequential Bayesian estimation and improve the receiver performance by exploiting the temporal constraints of the channel dynamics. In this paper, we specifically address the problem of estimating and adjusting the number ofmultipath replicas that is considered by the receiver algorithm. An efficient implementation via a two-fold marginalized Bayesian filter is presented, in which a particle filter, grid-based filters, and Kalman filters are suitably combined in order to mitigate the multipath channel by efficiently estimating its time-variant parameters in a track-before-detect fashion. Results based on an experimentally derived set of channel data corresponding to a typical urban propagation environment are used to confirm the benefit of our novel approach.

Spreading code phase measurement technique for snapshot GNSS receiver

Driven by the expanding demand of location based services (LBS), the integration of satellite navigation receiver into mobile devices has received much attention in the last years. Snapshot positioning technique has turned out to be a very suitable candidate in LBS applications for its predominance of low cost and low power dissipation. However, the limited snapshot length is a major hurdle that limits the availability and accuracy of receivers. A code phase measurement technique is developed and used for snapshot receivers. By utilizing the features of the modernized global navigation satellite system (GNSS) signals and the characteristic of snapshot positioning, it uses a novel dual update-rate tracking loop with a non-causal smoothing estimator to obtain a relatively accurate estimation from a second or less snapshot data. Experiments with simulated data show that the proposed method has better estimation accuracy than the conventional code tracking loop in confined data length snapshot receivers.

Hybrid analytical resolution approach based on ambiguity function for attitude determination

When satellite navigation receivers are equipped with multiple antennas, they can deliver attitude information. In previous researches, carrier phase differencing measurement equations were built in the earth-centered, earth-fixed (ECEF) coordinate, and attitude angles could be obtained through the rotation matrix between the body frame (BF) and the local level frame (LLF). Different from the conventional methods, a hybrid algorithm is presented to resolve attitude parameters utilizing the single differencing (SD) carrier phase equations established in LLF. Assuming that the cycle integer ambiguity is known, the measurement equations have attitude analytical resolutions by using simultaneous single difference equations for two in-view satellites. In addition, the algorithm is capable of reducing the search integer space into countable 2D discrete points and the ambiguity function method (AFM) resolves the ambiguity function within the analytical solutions space. In the case of frequency division multiple access (FDMA) for the Russian Global Orbiting Navigation Satellite System (GLONASS), a receiver clock bias estimation is employed to evaluate its carrier phase. An evaluating variable and a weighted factor are introduced to assess the integer ambiguity initialization. By static and dynamic ground experiments, the results show that the proposed approach is effective, with enough accuracy and low computation. It can satisfy attitude determination in cases of GPS alone and combined with GLONASS.

An advanced dual-frequency positioning algorithm for satellite navigation receivers

With the development of the Ground Positioning System (GPS) modernization and the expectable implementation of Galileo, people pay more and more attention to civil applications on multi-frequency signals. This paper proposes a new and advanced positioning algorithm for the dual-frequency satellite navigation receivers, concerning the various influences of all the ranging error sources and taking advantage of the Klobuchar single-frequency ionospheric model. The paper also presents positioning precision provided by the new algorithm. Theoretical analysis and experimental results show that, the new dual-frequency positioning algorithm can achieve higher positioning accuracy than the single-frequency positioning algorithm and the traditional dual-frequency positioning algorithm.

Characterization of the aeronautical satellite navigation channel through high‐resolution measurement and physical optics simulation

AbstractIn this paper we discuss the results of a measurement campaign investigating the environment of satellite navigation receivers for aeronautical applications, where reflections on the plane as well as from the ground decrease the accuracy of the positioning. The focus is on the most critical flight phase—the final approach. For this scenario a wideband model is derived, which allows to investigate the performance of present and future global navigation satellite systems. The work was carried out under an European Space Agency contract (ESTEC Contract number 16059/02/NL/DS) entitled ‘Navigation signal measurement campaign for critical environments’, by Joanneum Research (Austria) with subcontracts to DLR (Germany) and the University of Vigo (Spain). Copyright © 2007 John Wiley & Sons, Ltd.

The integration of GPS, vegetation mapping and GIS in ecological and behavioural studies

Global Positioning System (GPS) satellite navigation receivers are increasingly being used in ecological and behavioural studies to track the movements of animals in relation to the environments in which they live and forage. Concurrent recording of the animal's foraging behaviour (e.g. from jaw movement recording) allows foraging locations to be determined. By combining the animal GPS movement and foraging data with habitat and vegetation maps using a Geographical Information System (GIS) it is possible to relate animal movement and foraging location to landscape and habitat features and vegetation types. This powerful approach is opening up new opportunities to study the spatial aspects of animal behaviour, especially foraging behaviour, with far greater precision and objectivity than before. Advances in GPS technology now mean that sub-metre precision systems can be used to track animals, extending the range of application of this technology from landscape and habitat scale to paddock and patch scale studies. As well as allowing ecological hypotheses to be empirically tested at the patch scale, the improvements in precision are also leading to the approach being increasing extended from large scale ecological studies to smaller (paddock) scale agricultural studies. The use of sub-metre systems brings both new scientific opportunities and new technological challenges. For example, fitting all of the animals in a group with sub-metre precision GPS receivers allows their relative inter-individual distances to be precisely calculated, and their relative orientations can be derived from data from a digital compass fitted to each receiver. These data, analyzed using GIS, could give new insights into the social behaviour of animals. However, the improvements in precision with which the animals are being tracked also needs equivalent improvements in the precision with which habitat and vegetation are mapped. This needs some degree of automation, as vegetation mapping at a fine spatial scale using the traditional manual approach is far too time consuming. This paper explores these issues, discussing new applications as well as approaches to overcoming some of the associated problems.

Vehicular remote tolling services using EGNOS

Future Global Navigation Satellite Systems (GNSS) will significantly improve the performance of current navigation systems, providing new and enhanced capabilities. This will enable the implementation of innovative and advanced services and applications closer to the user's needs. In this framework, the road sector is one of the major potential markets for GNSS applications and, therefore, it is very promising for future EGNOS and GALILEO related applications. Satellite navigation receivers are now commonly installed in cars as a key tool for proving new services to people on the move such as electronic charging, real-time traffic information, emergency calls, route guidance, fleet management, or advance driving assistance systems. Specifically, a very important commercial opportunity is represented by the tolling-related applications. This paper describes the Vehicular Remote Tolling (VeRT) Project sponsored by Galileo Joint Undertaking (GJU) and performed in the frame of the first GJU Call under the EC VI Framework Programme. The overall design of the service provision architecture is also presented in this paper, together with the main topics related to the following activities focused on the service prototype demonstrator development.

Information Dissemination in Self-Organizing Intervehicle Networks

Intervehicle communication (IVC) is an emerging topic in research and application that is getting increasing attention from all major car manufacturers. In this paper, a novel method for scalable information dissemination in highly mobile ad hoc networks is proposed: segment-oriented data abstraction and dissemination (SODAD). With SODAD, information can be distributed in an information range multiple orders of magnitude larger than the transmission range of the air interface, even if only 1%-3% of all vehicles are equipped with an IVC system, e.g., during market introduction. By restricting the method to the dissemination of map/position-based data, scalability is achieved. In the second half of this paper, an example application for the SODAD method is presented: a self-organizing traffic-information system (SOTIS). In SOTIS, a car is equipped with a satellite navigation receiver, an IVC system, and a digital map. Each individual vehicle collects traffic information for its local area. Using the digital map, the traffic information is analyzed based on road segments. By distributing the information in the ad hoc intervehicle network using the SODAD method, a decentralized traffic information system is created. The performance of the proposed methods is evaluated using network simulation with vehicular mobility models. Simulation results for typical scenarios are presented. Furthermore, a prototype implementation based on commercially available standard hardware demonstrates the feasibility of the proposed approach.

Adapting the Principle of Integrated Navigation Systems to Measuring the Motion of Rigid Multibody Systems

During the last years integrated navigation systems based on gyros,accelerometers, and satellite navigation receivers became powerful,favourably priced devices for the guidance of aircraft and ships.Comparable equipment using especially wheel sensors exists for cars. Thekernel of such systems is a Kalman filter estimating the relevantvehicle motion. The filter design in turn requires a kinematical modelto settle on the motion components considered and to describe themechanical meaning of the measurements employed. Up to now, usual modelsrepresent a single rigid body with two, three or six degrees of freedom.

Applying the principle of integrated navigation systems to estimating the motion of large vehicles

Combining inertial sensors and GPS has led to integrated navigation systems of a performance surpassing classical navigation requirements. A utilisation of this technology suggests itself which considers not only the classical movement of a small, rigid body but expands the application range also to large aircraft, space stations and suchlike. The signals generated on this basis are usable both for vehicle guidance and for structural control. The key element of such a generalisation is the kinematical model describing the vehicle motion: Until now, the mentioned restriction to rigid bodies is regular and considers only inertial sensors referring to a single vehicle point. A more general navigation system design considers, however, a specific model comprising additional degrees of freedom from structural distortions as well as spatially distributed sensors. This model is employed within an extended Kalman filter estimating the vehicle motion state of high resolution regarding time. In addition, the filter uses the signals of gyros, accelerometers, satellite navigation receivers, and structural sensors. For this purpose, the paper discusses firstly different variants of integrated navigation systems followed by a presentation of the advantage of spatially distributing satellite navigation antennas over the vehicle structure. Finally, the integrated system for a simple flexible aircraft structure is introduced.

Integrating satellite and inertial navigation—conventional and new fusion approaches

The backbone of aiding inertial navigation systems by satellite navigation receivers is the data fusion of the subsystem outputs. Its conventional mechanization emerged from the classical, necessary aiding of inertial navigation systems and is based on linearized error models. Recent approaches therefore use directly the nonlinear kinematical equations of the rigid body motion. These methods lead to a simpler system structure as well as to smaller estimation error variances. To verify this statement, the paper presents a systematization of the different fusion schemes and a comparison between results of postprocessed flight test data.

Attitude determination from single-antenna carrier-phase measurements

A model of carrier phase measurement (as carried out by a satellite navigation receiver) is formulated based on electromagnetic theory. The model shows that the phase of the open-circuit voltage induced in the receiver antenna with respect to a local oscillator (in the receiver) depends on the relative orientation of the receiving and transmitting antennas. The model shows that using a single receiving antenna, and making carrier phase measurements to seven satellites, the three-axis attitude of a user platform (in addition to its position and time) can be computed relative to an initial point. This measurement model can also be used to create high-fidelity satellite signal simulators that take into account the effect of platform rotation as well as translation.

Integrating Satellite and Inertial Navigation-Conventional and New Fusion Approaches

The backbone of aiding inertial navigation systems by satellite navigation receivers is the data fusion of the subsystem outputs. Its conventional mechanization emerged from the classical, necessary aiding of inertial navigation systems and is based on linearized error models. Recent approaches therefore use directly the nonlinear kinematical equations of the rigid body motion. These methods lead to a simpler system structure as well as to smaller estimation error variances. To verify this statement, the paper presents a systematization of the different fusion schemes and a comparison between results of postprocessed flight test data.

Development of Software Structure for Integrated Navigation Receivers in Shipping

Important issues for automation of shiphandling are accuracy, availability and reliability of position, velocity and time. In most cases there are satellite navigation receivers as the primary position fix system. Accuracy of satellite navigation receivers onboard ships can be affected by shadowing from obstructions, reflections, multipath, satellite changings, ship’s movements or ship’s maneuvering. Various means of increasing accuracy, availability and reliability are examined using integrated solutions with: (D)GPS/(D)GLONASS with ship dynamic identification or their combination with LORAN-C. A reliability check should be done using ranges to satellites or, better yet, by ranges to a terrestrial system. More accurate measurement of ship’s velocity (compared to electromagnetic or Doppler log) can be accomplished using GPS, DGPS or an integrated solution. Parameters that can be integrated into a position solution include: terrestrial navigation systems; a second satellite navigation system; ship parameters (rudder angle, propeller speed, gyro heading); and, environmental parameters (wind, current). These parameters lead to a more accurate prediction of position and ship dynamics.

Practical Rhumb Line Calculations on the Spheroid

About ten years ago this author wrote the software for a suite of navigation programmes which was resident in a small hand-held computer. In the course of this work it became apparent that the standard text books of navigation were perpetuating a flawed method of calculating rhumb lines on the Earth considered as an oblate spheroid. On further investigation it became apparent that these incorrect methods were being used in programming a number of calculator/computers and satellite navigation receivers. Although the discrepancies were not large, it was disquieting to compare the results of the same rhumb line calculations from a number of such devices and find variations of some miles when the output was given, and therefore purported to be accurate, to a tenth of a mile in distance and/or a tenth of a minute of arc in position. The problem has been highlighted in the past and the references at the end of this show that a number of methods have been proposed for the amelioration of this problem. This paper summarizes formulae that the author recommends should be used for accurate solutions. Most of these may be found in standard geodetic text books, such as, but also provided are new formulae and schemes of solution which are suitable for use with computers or tables. The latter also take into account situations when a near-indeterminate solution may arise. Some examples are provided in an appendix which demonstrate the methods. The data for these problems do not refer to actual terrestrial situations but have been selected for illustrative purposes only. Practising ships' navigators will find the methods described in detail in this paper to be directly applicable to their work and also they should find ready acceptance because they are similar to current practice. In none of the references cited at the end of this paper has the practical task of calculating, using either a computer or tabular techniques, been addressed.

A Fast Satellite Selection Algorithm for Combined GPS and GLONASS Receivers

This paper derives a fast satellite selection algorithm; that is, an algorithm to select the best subset of satellites to use for positioning in circumstances whereby a satellite navigation receiver is not capable of using all satellites in view. The algorithm adopts the weighting factor concept to determine the contribution of each satellite to the overall positioning accuracy. Selection by this algorithm is shown to be especially efficient when the number of available satellites is large, so it is likely to be particularly useful for receivers capable of making combined measurements to GPS and GLONASS satellites.

Electronics Instruments & Control for Oil Exploration

Various types of sophisticated electronic instruments and controls are used in the exploration for oil and natural gas.The rapid growth in the use of digital methods for the recording, processing, storing and retrieving of different sub-surface geophysical data, during the past few years stems from two very important reasons, namely (i) Availability of high speed digital devices, such as micro-processor, analog to digital converters, multichannel multiplexers, memory chips both RAM and ROM etc. and (ii) Availability of very fast digital computers and peripherals for processing the data obtained with these recording units. These high speed recorders are used for the real time conversion of 24 or more channels of seismic data, logging data etc in the digital form.The above data are processed by dedicated as well as general purpose digital computers for obtaining a clear picture of the sub-surface. Since all the sub-surface data obtained will have to be tested by carrying out actual drilling of the wells which cost several times more than for carrying out exploration from surface, the instruments used for collecting the data and the computers used for the processing the data obtained are required to be as accurate and sophisticated as possible. This is achieved by utilising the latest developments in the Electronic components, sub-assemblies and instruments in the geophysical equipment used for oil exploration.After the drilling is carried out, the well is Surveyed with the sophisticated electrical logging system utilising minicomputers, micro-processors etc., so as to obtain the data in the well regarding the quality and quantity of the hydrocarbons present in the well.In the same manner, the position location of the various surveys both onshore and offshore is carried out by utilising the integrated satellite navigation system which provides the means for accurate navigation in the marine surveys and which gives very good control and location of the survey points both onshore and offshore by utilising very accurate and sophisticated electronic controls and devices. The accuracy of such surveys can be within 30 meters or even less. In the offshore, the satellite system is integrated with Gyro-compass, four beam doeppler Sonar, satellite navigation receiver and a digital computer.Even the accuracy of measurements with the electrical magnetic and gravitational methods of surveys have considerably improved by utilising, sophisticated electronic equipment and the processing techniques. Because of the advancement in the electronics, surveys on land can be carried out by utilising the imagery received from various satellites sent up by agencies in U.S.A., U.S.S.R., etc. By using all the above advanced techniques, the risks inherent with the oil exploration has been reduced to a large extent.