Integrated Positioning System Research Articles

Monitoring Water Levels and Currents Using Reflected GPS Carrier Doppler Measurements and Coordinate Rotation Model

This paper describes the development and application of a highly integrated Global Positioning System (GPS) receiver that employs reflected GPS signals to measure the floodwater levels, sea levels, and soil moisture of riverbeds. Both right- and left-hand circular polarization antennas are employed to simultaneously obtain direct and reflected signals. The objective of this paper is to use the carrier-phase Doppler shifts reflectivity of L1 and L2 band reflected signals and direct signals to determine the floodwater and sea levels in riverbeds, as well as to distinguish wet soil from bare soil. In monitoring coastal tidal currents, water levels, and floodwater levels, the reflection heights of this system are accurate to within 29 ~ 31 cm. Furthermore, the currents at reflection points are estimated using differential carrier Doppler shifts and a coordinate rotation correction model, which provide velocity vectors for flows speed of approximately 5 ~ 265 cm/s.

An integrated localization system for robots in underground environments

PurposeThe purpose of this paper is to design an integrated localization system for mobile robots in underground environments for exploring and rescuing tasks after incidents and detection of hazard gas in tunnels before ingress.Design/methodology/approachAn integrated localization system mainly based on a strap‐down inertial measurement unit and a digital compass is designed for exploring and rescuing task in coal mines and tunnels. After a system model was founded, a filtering algorithm combining a wavelet‐based pre‐filter with unscented Kalman filters was developed for reckoning tracks of robots and localizing it.FindingsBased on this research, an integrated localization system for robots in underground environments can be developed to explore some regions and rescue people. Although errors of localization exist, performance of the integrated system should be improved if some sensors and landmarks or maps of tunnels are introduced.Originality/valueWhat is proposed in this paper is an integrated localization system used in underground environments. In this research, property of environments has been taken into account as an important disturbance when filtering thresholds were set.

A low-cost integrated positioning system for autonomous off-highway vehicles

This article reports a method for integrating a low-cost positioning system, constructed using a Garmin N17 global positioning system (GPS) and an integrated inertial sensor unit, consisting of three single-axis microelectromechanical system (MEMS) gyros and one triaxial MEMS accelerometer, for autonomous off-highway vehicle use. Based on a vehicle position—velocity—attitude (PVA) model, a data fusion algorithm was formulated to extract more accurate and reliable positioning information from the raw data sensed by the GPS and inertial sensor unit. The developed integrated positioning system (IPS) was evaluated on an agricultural utility vehicle on three different sites. A real-time kinematic (RTK) differential GPS unit, capable of providing 2–3cm dynamic positioning accuracy while the position dilution of precision is low enough, was installed on the test vehicle to provide accurate positioning references in those evaluation tests. Results obtained from those tests showed that, when the vehicle was travelling on paved roads near buildings and/or under the trees, the maximum positioning error of the developed IPS was 0.50m, and that this maximum error level was reduced to 0.30m when the vehicle was travelling in open fields. The IPS could provide a position update rate at 50Hz; even the GPS could provide only a 1Hz update rate. Test results also revealed that this system could continuously provide accurate position signals when the GPS signal is lost for up to 30s. This research verified that a low-cost IPS could provide satisfactory position information for autonomous off-highway vehicle uses.

Sistema de Posicionamiento para Vehículos Autónomos

Uno de los objetivos más importantes de los Sistemas Inteligentes de Transporte (ITS) es evitar la pérdida de precisión en el posicionamiento y guiado del vehículo, debido a la disminución en la calidad de la señal del Sistema de Posicionamiento Global (GPS). En este artículo, se presenta un sistema de posicionamiento formado por la combinación de un GPS con una unidad de medida inercial ayudada por los sensores embarcados en el coche para realizar el guiado. En función de la precisión proporcionada por el GPS, el sistema discrimina entre tres posibles comportamientos: 1) Si la precisión es centimétrica, el GPS se encarga en solitario del guiado. 2) Si no se recibe la señal GPS, el control lo toma la unidad inercial. 3) Si la precisión de la señal del GPS no es centimétrica, la posición del vehículo se calcula mediante una combinación de ambas medidas. El sistema se ha instalado en un Citroën C3 Pluriel. Los resultados muestran un correcto comportamiento del vehículo en diferentes situaciones y prueban la necesidad de integrar la información sensorial para realizar un control de navegación óptimo.

Adaptive neuro-fuzzy module for inertial navigation system/global positioning system integration utilising position and velocity updates with real-time cross-validation

Recently, methods based on artificial intelligence (AI) have been suggested to provide reliable positioning information for different land vehicle navigation applications. The majority of these applications utilise both the global positioning system (GPS) and the inertial navigation system (INS). These AI modules were trained to mimic the latest vehicle dynamics so that, in case of GPS outages, the system relies on INS and the recently updated AI module to provide the vehicle position. Several neural networks and neuro-fuzzy techniques were implemented in real-time in a de-centralised fashion and provided acceptable accuracy for short GPS outages. It was reported that these methods provided poor positioning accuracy during relatively long GPS outages. In order to prevail over this limitation, this study optimises the AI-based INS/GPS integration schemes utilising adaptive neuro-fuzzy inference system with performing, in real-time, both GPS position and velocity updates. In addition, a holdout cross validation method during the update procedure was utilised in order to ensure generalisation of the model. The proposed system is tested using differential GPS and both navigational and tactical grades INS field test data obtained from a land vehicle experiment. The results showed that the effectiveness of the proposed system over both the existing AI-based and the conventional INS/GPS integration techniques, especially during long GPS outages. This method may have one limitation related to the unusual significant changes of the vehicle dynamics between the update and the prediction stages of operation which may influence the overall positioning accuracy.

Integrated System for Robust 6-DOF Positioning Utilizing New Closed-Form Visual Motion Estimation Methods in Planar Terrains

Estimating the relative positions and (or) trajectory of a camera from video images is a fundamental problem in motion vision. Of special relevance is the closed-form solution for planar scenes, for processing fly-over imagery from airborne and underwater robotics platforms, automated airplane landing utilizing runway landmarks, photomosaicing, etc. However, the method's robustness can break down in certain scenarios, e.g., due to inherent translation-rotation ambiguity of visual motion with short baselines and narrow field of view. The robustness can be improved by devising methods that compute a smaller set of motion parameters, utilizing other sensors to measure the remaining components. This paper addressed key issues in six degrees of freedom positioning from fly-over imagery by integrating vision with rotational angle sensors. First, we propose and utilize robust closed-form solutions for estimating the motion and orientation of a planar surface from the image flow variations up to first order, given measurements of pitch and roll motions. We also describe a calibration technique to enable the integration of angle sensor and visual measurements. Next, an error analysis enables us to evaluate the impact of inaccurate pitch and roll measurements on the estimates from the new closed-form solutions. Finally, the performance of our new methods and the integrated positioning system are evaluated in various experiments with synthetic and real data

An Integrated Position and Attitude Determination System to Support Real-Time, Mobile, Augmented Reality Applications

Augmented reality (AR) technologies enable digitally stored information (virtual objects) to be overlaid graphically on views of the real world. As such, they are able to significantly enhance decision-making and operational efficiency in complex environments. AR technologies typically comprise a fusion of positioning and attitude sensors with visualisation capability and an information processing system. The decreasing size and cost of visualisation and positioning hardware and the increasing portable processing power of laptop and handheld computers now offer enormous potential for the development of intelligent solutions based around realtime, mobile AR technologies. For any application built around AR technologies, its effectiveness lies in the accuracy to which the virtual objects can be aligned with views of the real world. For many of these applications, this is directly a function of the accuracy to which the position and orientation of the operation platform can be determined. This paper presents an integrated positioning system that combines an array of dual frequency GPS receivers, a fibre optic gyroscope and vehicle odometer within a centralized Kalman filter. It assesses the accuracy of the filter outputs of position and attitude as appropriate to supporting realtime, mobile AR applications. The design and testing of an AR prototype that combines the Kalman filter state with real-time imagery containing augmented objects will also be presented. Finally, approaches adopted to tune the filter and reduce inherent sensor noise, as well as results from a case study undertaken within the land mobile environment will be described.

Inertial Navigation System/Global Positioning System Fusion Algorithm Design in a Fast Prototyping Environment: Towards a Real-Time Implementation

In previous communications, the authors have high-lighted the advantages of using a fast-prototyping approach in the development of low-cost inertial navigation integration algorithms. More specifically, they have addressed two fundamental aspects of inertial navigation integration algorithm design: the validation of a Simulink simulator and the performance evaluation of the integration algorithms provided within Simulink for inertial data integration.This paper addresses the next step in the development sequence of Inertial Navigation System/Global Positioning System integration algorithm development: the inclusion of an extended Kalman filter in the Simulink fast-prototyping environment, the evaluation of the computation load of the different parts of the algorithm, and the experimental assessment of the entire fusion algorithm. As a general conclusion, the rapid-prototyping approach chosen in the implementation has permitted the design of the algorithms and data acquisition scheme in an efficient manner and in a short development time period.

Detecting Global Positioning Satellite Orbit Errors Using Short-Baseline Carrier-Phase Measurements

Asystem to detectorbit errorsaffecting differential global positioning system integrity isdescribed.Themethod isbased on the use of carrier-phase ranging measurements madeby two or more ground-based referencereceivers separated by short baselines. A dual-frequency, geometry-free widelane approach is used to resolve cycle ambigu- ities present in the carrier-phase measurements. The performance of the proposed integrity monitor is evaluated relative to existing integrity requirements for aircraft landing navigation applications. The results show that real- time protection is achievable against all types of ephemeris errors that can ine uence aircraft precision approach and landing navigation. LTHOUGH initially developed to support military applica- tions, the global positioning system (GPS) has quickly grown into an important and versatile civil navigation utility. The differ- ential GPS (DGPS) technique, in particular, has provided improve- ments in positioning accuracy sufe cient for many demanding ap- plications, including aircraft navigation during precision approach andlandingphasesofe ight.However,forsuchdife cultapplications, highaccuracyisgenerallynotsufe cient.Thenavigationsystemmust also provide a means to ensure its own integrity by reliably detect- ing navigation system failures or anomalies. In this work, detailed consideration is given to the real-time detection of a specie c type of navigation failure: incorrect knowledge of a GPS satellite orbit. Each GPS satellite broadcasts orbit ephemerides so users can compute satellite locations at any time of interest. The satellite lo- cations, together with ranging measurements also obtained from the satellite signals, are used to compute user position. An error in knowledge of satellite position will, therefore, cause a resulting error in the computed user position. Nominally, these errors are negligibly small for DGPS users, but integrity considerations for aircraft precision landing navigation dictate that anomalous con- ditions must be quickly detected. Furthermore, the effects of orbit anomalies differ from those of other navigation failures, for exam- ple, GPS receiver failures, in that orbit errors ultimately cause nav- igation errors that are dependent on the time-varying displacement between the aircraft and ground-based DGPS reference receiver. Therefore, the impact of undetectable orbit errors on navigation must ultimately be assessed separately by each individual aircraft within the DGPS service volume. In this regard, the Federal Avia- tion Administration (FAA), RTCA, Inc., and the International Civil Aviation Organization (ICAO) are developing specie c ephemeris integrity performance standards for DGPS-based aircraft precision landing. The FAA' s local-area augmentation system (LAAS) will serve as the baseline DGPS architecture considered in this paper. Whenever the GPSdata broadcast by the satellites do not contain the correct satellite orbit parameters, an ephemeris anomaly is said to exist. Although there may be a variety of potential causes for such anomalies, for example, unscheduled maneuvers, incorrect or- bit uploads, and faulted data decoding in the receiver, all ephemeris

GPS based IPS for ERP vehicles

GPS is an innovative technique for an electronic road pricing (ERP) system. By using GPS technology, ERP systems will be extremely efficient and cost-effective. This paper describes the next generation of ERP in Singapore and proposes a GPS based multisensor positioning system for ERP vehicles. Multisensor fusion algorithms are presented for the integration system. The integrated positioning system (IPS) developed in this paper makes it possible to realize GPS based ERP with a simple composition and low cost.

A Rigorous Positioning Equation and It’s Error Analysis and Precision Evaluation for Integrated Positioning System of Airborne GPS, INS and Laser Scanning Ranging

A Rigorous Positioning Equation and It’s Error Analysis and Precision Evaluation for Integrated Positioning System of Airborne GPS, INS and Laser Scanning Ranging

Integration of the global positioning system and geographical information systems for traffic congestion studies

The Transport Systems Centre (TSC) has developed an integrated Global Positioning System (GPS) – Geographical Information System (GIS) for collecting on-road traffic data from a probe vehicle. This system has been further integrated with the engine management system of a vehicle to provide time-tagged data on GPS position and speed, distance travelled, acceleration, fuel consumption, engine performance, and air pollutant emissions on a second-by-second basis. These data are handled within a GIS and can be processed and queried during the data collection (from a notebook PC in the vehicle) or saved to a file for later analysis. The database so generated provides a rich source of information for studies of travel times and delays, congestion levels, and energy and emissions. A case study application of the system is described focusing on studies of congestion levels on two parallel routes in a major arterial corridor in metropolitan Adelaide, South Australia. As part of these investigations, a discussion of the nature of traffic congestion is given. This provides both a general definition of traffic congestion and the discussion of a number of parametric measures of congestion. The computation of these parameters for the study corridor on the basis of data collected from the integrated GPS–GIS system is described. The GIS provides a database management platform for the integration, display, and analysis of the data collected from GPS and the in-vehicle instrumentation.

Advanced Transport Telematics Positioning Requirements: An Assessment of GPS Performance in Greater London

This paper presents the results of a study carried out in the Greater London area to assess and characterise the performance of the Global Positioning System (GPS) for vehicle positioning in urban areas. The performance assessment addresses, in varying levels of detail, the issues of service coverage, positioning accuracy, integrity and availability of service. The project was supported by Racal Survey Limited and is part of the wider research at Imperial College in the area of architectural design and testing of Advanced Transport Telematics (ATT) systems. The results highlight the shortcomings of GPS as the sole means for in-car navigation in urban areas and details the temporal and spatial considerations to be taken into account in the process of designing an integrated positioning system capable of meeting navigation requirements placed on ATT systems.

Ultrasonic Levitation and Positioning of Samples

Several problems on the levitation and contact-free position control of samples using ultrasonic energy were studied in development of an integrated positioning system for space processing. A method which employed a single ring-type radiator was proposed for multiaxial positioning with free access. Positioning in the standing wave field of a cylindrical tube was also studied. Finite element simulation was conducted to evaluate the magnitude and stability of the positioning force acting on a sample in a tube.