Client-server-based LBS architecture: A novel positioning module for improved positioning performance

Permission to distribute obtained from publisher.This work presents a new efficient positioning module that operates over client-server LBS architectures. The aim of the proposed module is to fulfil the position information requirements for LBS pedestrian applications by ensuring the availability of reliable, highly accurate and precise position solutions based on GPS single frequency (L1) positioning service. The positioning module operates at both LBS architecture sides; the client (mobile device), and the server (positioning server). At the server side, the positioning module is responsible for correcting user’s location information based on WADGPS corrections. In addition, at the mobile side, the positioning module is continually in charge for monitoring the integrity and available of the position solutions as well as managing the communication with the server. The integrity monitoring was based on EGNOS integrity methods. A prototype of the proposed module was developed and used in experimental trials to evaluate the efficiency of the module in terms of the achieved positioning performance. The positioning module was capable of achieving a horizontal accuracy of less than 2 meters with a 95% confidence level with integrity improvement of more than 30% from existing GPS/EGNOS services

Context-aware GPS Integrity Monitoring for Intelligent Transport Systems (ITS)

The integrity of positioning systems has become an increasingly important requirement for location-based Intelligent Transports Systems (ITS). The navigation systems, such as Global Positioning System (GPS), used in ITS cannot provide the high quality positioning information required by most services, due to the various type of errors from GPS sensor, such as signal outage, and atmospheric effects, all of which are difficult to measure, or from the map matching process. Consequently, an error in the positioning information or map matching process may lead to inaccurate determination of a vehicle’s location. Thus, the integrity is require when measuring both vehicle’s positioning and other related information such as speed, to locate the vehicle in the correct road segment, and avoid errors. The integrity algorithm for the navigation system should include a guarantee that the systems do not produce misleading or faulty information; as this may lead to a significant error arising in the ITS services. Hence, to achieve the integrity requirement a navigation system should have a robust mechanism, to notify the user of any potential errors in the navigation information. The main aim of this research is to develop a robust and reliable mechanism to support the positioning requirement of ITS services. This can be achieved by developing a high integrity GPS monitoring algorithm with the consideration of speed, based on the concept of context-awareness which can be applied with real time ITS services to adapt changes in the integrity status of the navigation system. Context-aware architecture is designed to collect contextual information about the vehicle, including location, speed and heading, reasoning about its integrity and reactions based on the information acquired. In this research, three phases of integrity checks are developed. These are, (i) positioning integrity, (ii) speed integrity, and (iii) map matching integrity. Each phase uses different techniques to examine the consistency of the GPS information. A receiver autonomous integrity monitoring (RAIM) algorithm is used to measure the quality of the GPS positioning data. GPS Doppler information is used to check the integrity of vehicle’s speed, adding a new layer of integrity and improving the performance of the map matching process. The final phase in the integrity algorithm is intended to verify the integrity of the map matching process. In this phase, fuzzy logic is also used to measure the integrity level, which guarantees the validity and integrity of the map matching results. This algorithm is implemented successfully, examined using real field data. In addition, a true reference vehicle is used to determine the reliability and validity of the output. The results show that the new integrity algorithm has the capability to support a various types of location-based ITS services.Saudi Arabia Cultural Burea

Weighted Least Squared Approach to Fault Detection and Isolation for GPS Integrity Monitoring

Reliability of a global navigation satellite system is one of great importance for global navigation purposes. Therefore, an integrity monitoring system is an inseparable part of aviation navigation system. Failures or faults due to malfunctions in the systems should be detected to keep the integrity of the system intact. In order to solve the problem that least squares method detects and isolates a satellite fault for GPS integrity monitoring, in this paper, a weighted least squares algorithm is proposed for satellite fault detection and isolation. The algorithm adopts the diagonal elements of the covariance matrix of GPS measurement equation as the weighted factor. Firstly, the weighted least squares approach for satellite fault detection establishes the test statistic by the sum of the squares of the pseudo-range residuals of each satellite for GPS. Then, the detection threshold is obtained by the false alarm rate of the fault detection, probability density function and visiable satellite number.The effectiveness of the proposed approach is illustrated in a problem of GPS (Global Positioning System) autonomous integrity monitoring system. Through the real raw measured GPS data，based on least squares RAIM method and the weighted least squares RAIM approach, the performance of the two algorithms is compared. The results show that the proposed RAIM approach is superior to the least squares RAIM algorithm in the sensitivity of fault detection and fault isolation performance for GPS integrity monitoring

A Positioning System in an Urban Vertical Heterogeneous Network (VHetNet)

Global navigation satellite systems (GNSSs) are essential in providing localization and navigation services to most of the world due to their superior coverage. However, due to high pathloss and inevitable atmospheric effect, the positioning performance of any standalone GNSS is still poor in urban areas. To improve the positioning performance of legacy GNSSs in urban areas, a positioning system, which utilizes high altitude platform station (HAPS) and 5G gNodeBs (gNBs), in a futuristic urban vertical heterogeneous network (VHetNet) is proposed. In this paper, we demonstrate the effectiveness of gNBs in improving the vertical positioning accuracy for both the GPS-only system and the HAPS-aided GPS system by analyzing the impact of the density of gNBs and the pseudorange error of gNB on the positioning performance of the gNB augmented positioning systems. We also demonstrate the effectiveness of receiver autonomous integrity monitoring (RAIM) algorithms on the HAPS and/or gNB aided GPS systems in urban areas

Bayesian Inference of GNSS Failures

International audienceThe probability of failure (failure rate) is a key input parameter to integrity monitoring systems used for safety, liability or mission critical applications. A standard approach in the design of Global Positioning System (GPS) integrity monitoring is to utilize the service commitment on the probability of major service failure, often by applying a conservative factor. This paper addresses the question of what factor is appropriate by applying Bayesian inference to real and hypothetical fault histories. Global Navigation Satellite System (GNSS) anomalies include clock or signal transmission type faults which are punctual (may occur at any time) and incorrect ephemeris data which are broadcast for a nominal two hours. These two types of anomaly, classified as continuous and discrete respectively are addressed. Bounds on the total probability of failure are obtained with given confidence levels subject to well defined hypotheses relating past to future performance. Factors for the GPS service commitment of 10-5 per hour per satellite are obtained within the range two to five with high confidence (up to 1-10-9)

High accuracy tightly-coupled integrity monitoring algorithm for map-matching

A map-matching algorithm employs data from Global Positioning System (GPS), a Geographic Information System (GIS)-based road map and other sensors to first identify the correct link on which a vehicle travels and then to determine the physical location of the vehicle on the link. Due to uncertainties associated with the raw measurements from GPS/other sensors, the road map and the related methods, it is essential to monitor the integrity of map-matching results, especially for safety and mission-critical intelligent transport systems such as positioning and navigation of autonomous and semi-autonomous vehicles. Current integrity methods for map-matching are inadequate and unreliable as they fail to satisfy the integrity requirement due mainly to incorrect treatment of all the related uncertainties simultaneously. The aim of this paper is therefore to develop a new tightly-coupled integrity monitoring method for map-matching by properly treating the uncertainties from all sources concurrently. In this method, the raw measurements from GPS, low-cost Dead-Reckoning (DR) sensors and Digital Elevation Model (DEM) are first integrated using an extended Kalman Filter to continuously obtain better position fixes. A weight-based topological map-matching process is then developed to map-match position fixes onto the road map. The accuracy of the map-matching process is enhanced by employing a range of network features such as grade separation, traffic flow directions and the geometry of road link. The Receiver Autonomous Integrity Monitoring (RAIM) technique, which has been successfully applied to monitor the integrity of aircraft navigation, is modified and enhanced so as to apply it to monitor the quality of map-matching. In the enhanced RAIM method, two modifications are made: (1) a variable false alarm rate (as opposed to a constant false alarm rate) is considered to improve the fault detection performance in selecting the links, especially near junctions. (2) a sigma inflation for a non-Gaussian distribution of measurement noises is applied for the purpose of satisfying the integrity risk requirement. The implementation and validation of the enhanced RAIM method is accomplished by utilising the required navigation performance parameters (in terms of accuracy, integrity and availability) of safety and mission-critical intelligent transport systems. The required data were collected from Nottingham and central London. In terms of map-matching, the results suggest that the developed map-matching method is capable of identifying at least 97.7% of the links correctly in the case of frequent GPS outages. In terms of integrity, the enhanced RAIM method provides better the fault detection performance relative to the traditional RAIM

DEFORMATION ANALYSIS OF OFFSHORE PLATFORM USING GPS TECHNIQUE AND ITS APPLICATION IN STRUCTURAL INTEGRITY ASSESSMENT

One of a major problem with offshore platform is the occurrence of deformation which can have serious and potentially fatal consequences. The implementing of a deformation monitoring system to maintain regular surveillance of the stability is a means to address both human safety and company profitability. The approach developed in this study uses a precise relative Global Positioning System (GPS) which is advantageous for deformation monitoring in terms of long-baseline data as offshore platforms are located hundreds of kilometres from shore. This research focused on customizing GPS data processing of offshore platform deformation and its implementation for structural integrity assessments. A preliminary investigation was performed on simulated GPS network to ensure tool reliability, processing method feasibility and enhanced precision of the processed data. Additionally, preventative steps were taken on the network simulation to ensure that the technique was capable of detecting any deformation. Commercial software was found to be inadequate for long-baseline processing and was substituted with GAMIT/GLOBK scientific software, capable of processing GPS data for offshore platforms. This case study refers a Jacket-type offshore platform using secondary three epochs GPS data to analyze deformation. The results of data processing revealed deformation magnitude in the form of three dimensional displacement, dx, dy and dz which was then used to assess platform’s structural integrity, focusing on four points of the main pile located on the upper deck. The structural integrity assessment identified that translation and rotation of all structural joints was influenced by any displacements of restrained joints. These translations and rotations increase almost nearly proportional to the increased displacement value. In the simulation epoch of 10 years, the greatest value displacement of North is approximately 18-26 cm, East is around 6-18 cm and Up is about 15-50 cm. These values are assumed as linear function of the displacement of two month epochs. The great effect occurs on the upper deck with the value of U1 = ±6 cm (point 67), U2 = ±30 cm (point 68), U3 = ±60 cm (point 78), R1 = ±3 radian ix (point 80), R2 = ±0.5 radian (point 67) and R3 = ±1 radian (point 84). The greatest effect arises at the translation in the direction of Z. In the seabed, the achievement value of R1 = ±5 radian (point 13), R2 = ±0.3 radian (point 14), R3 = ±0.1 radian (point 14) with no translation effect of in the directions of X, Y and Z. The occurring translations and rotations in the structural joints contribute to the stability of the platform, confirming deformation monitoring to be a viable technique in structural integrity assessment. The deformation analysis indicated coordinate differences among the three epoch observations, however, a significant test did not categorise these as a significant displacement. To conclude, a precise GPS relative positioning technique was found to be a reliable approach for offshore platform monitoring deformation, enabling precise detection to a few millimeters. This level of precision could be increased with implementation of processing and observational strategies

Mass-Market Receiver for Static Positioning: Tests and Statistical Analyses

Nowadays, there are several low cost GPS receivers able to provide both pseudorange and carrier phase measurements in the L1band, that allow to have good realtime performances in outdoor condition. The present paper describes a set of dedicated tests in order to evaluate the positioning accuracy in static conditions. The quality of the pseudorange and the carrier phase measurements let hope for interesting results. The use of such kind of receiver could be extended to a large number of professional applications, like engineering fields: survey, georeferencing, monitoring, cadastral mapping and cadastral road. In this work, the receivers performance is verified considering a single frequency solution trying to fix the phase ambiguity, when possible. Different solutions are defined: code, float and fix solutions. In order to solve the phase ambiguities different methods are considered. Each test performed is statistically analyzed, highlighting the effects of different factors on precision and accurac

Achieving genuinely dynamic road user charging : issues with a GNSS-based approach

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