Terms Of Positioning Accuracy Research Articles

Adaptive multisensor data fusion technique for train localisation and detection of accidental train parting

This study proposes a bilinear recursive least square based adaptive multisensor data fusion technique for the precise localisation of railway vehicles and detection of an accidental train parting to be used with the train collision avoidance system (TCAS) in Indian railways. The accurate localisation of railway vehicles during the absence of global positioning system (GPS) is a challenging task for the TCAS. One of the reliable solutions for this task may be the augmentation of GPS with the onboard multisensor system. A bilinear recursive least square adaptive filter is used here to estimate and compensate the position error of the onboard multisensor system. The impact of slack in coupling is considered for the analysis of parting detection. The performance of the proposed technique is compared with the observation error based approach, bounded offset based approach and pseudo-measurement state constraining technique. The simulation results indicate that the proposed technique is superior in terms of positional accuracy and for the detection of an accidental train parting with a minimum parting distance.

Seasonal variations of the Vertical Total Electron Content (VTEC) of the ionosphere at the GNSS cor station (SEERL) UNIBEN and three other cors stations in Nigeria

The complex environment of the Sun-Earth, which resulted in the spatial and temporal variations of the ionosphere leads to different kinds of effects on human technologies. Man’s continuous increasing utilization of space technologies in addressing it’s immediate and future needs demand quality research of the space environments, to understand the physics of the interaction of the environment with systems (both space and earth bound), and to develop methods of mitigating the environmental effects. This is one of the reasons Center of Atmospheric Research (CAR) set-up a GNSS monitoring station in Benin. The Vertical Total Electron Content (VTEC) time series of some selected days from the newly established Benin station together with three Cors stations (ABU, BKFP and CLBR) of OSGoF were subjected to the Lloyd seasonal classification in order to see their diurnal variation on season by season bases. The results show that there exist an interconnection(in term of their magnetic longitudes) between the ABU, CLBR and the BENIN stations even though BENIN station had the least Total Electron Content ( TEC) values at all the seasons. The results also clearly showed that the BENIN station offers better advantage in terms of positional accuracy. http://dx.doi.org/10.4314/njt.v37i2.1

Enrichment of OpenStreetMap Data Completeness with Sidewalk Geometries Using Data Mining Techniques.

Tailored routing and navigation services utilized by wheelchair users require certain information about sidewalk geometries and their attributes to execute efficiently. Except some minor regions/cities, such detailed information is not present in current versions of crowdsourced mapping databases including OpenStreetMap. CAP4Access European project aimed to use (and enrich) OpenStreetMap for making it fit to the purpose of wheelchair routing. In this respect, this study presents a modified methodology based on data mining techniques for constructing sidewalk geometries using multiple GPS traces collected by wheelchair users during an urban travel experiment. The derived sidewalk geometries can be used to enrich OpenStreetMap to support wheelchair routing. The proposed method was applied to a case study in Heidelberg, Germany. The constructed sidewalk geometries were compared to an official reference dataset (“ground truth dataset”). The case study shows that the constructed sidewalk network overlays with 96% of the official reference dataset. Furthermore, in terms of positional accuracy, a low Root Mean Square Error (RMSE) value (0.93 m) is achieved. The article presents our discussion on the results as well as the conclusion and future research directions.

Distributed TOA-Based Positioning in Wireless Sensor Networks: A Potential Game Approach

In this letter, we solve the problem of positioning based on the time-of-arrival technique in wireless sensor networks. Different from the traditional estimation methods, the position of a target node is considered as a strategy of anchor nodes, and the cognition information is introduced to enrich positional information. After proposing the concept of consensus of cognition and consensus of measurements, we re-investigate the positioning problem from a game-theoretic perspective. It is proved that the proposed game is an exact potential game, which exhibits attractive properties about the Nash equilibrium (NE). Then, the best response algorithm is used to achieve the NE point. The simulation results indicate that the performance of positioning with a suitable tradeoff parameter is better than the performance of recursive least-squares algorithm in terms of positional accuracy and convergence rate.

The impact of geocoding method on the positional accuracy of residential burglaries reported to police

PurposeThe purpose of this paper is to better understand the variability in burglary geocoding positional accuracy between United States Census Topologically Integrated Geographic Encoding and Referencing (TIGER)-based street geocoding and results produced using reference data made publicly available by Google.Design/methodology/approachThis research compares the Euclidian distance between ground-truthed burglaries and results produced using two different geocoding reference data sets: TIGER-based street geocoding and publicly available data within Google Earth. T-tests and z-tests are used to discern whether positional errors are statistically significant.FindingsBoth within suburban and urban jurisdictions, Google outperformed street geocoding in terms of positional accuracy. Positional errors on average were 1/4th as large for Google in a suburban setting and 1/5th as large in an urban setting compared to street geocoding.Practical implicationsPolice departments that are relying on street geocoding techniques may achieve improved spatial precision by using Google’s reference data if they contain parcel-level information. Moreover, relying on less precise spatial referencing methods may place burglaries in locations where the events do not actually occur or cluster.Originality/valueThis is the first analysis of law enforcement data to examine the positional accuracy of geocoded offense data using Google Earth compared to the commonly used street geocoding method of interpolation.

Localization of WSN using Distributed Particle Swarm Optimization algorithm with precise references

Localization is the key research area in wireless sensor networks. Finding the exact position of the node is known as localization. Different algorithms have been proposed. Here we consider a cooperative localization algorithm with censoring schemes using Crammer Rao bound (CRB). This censoring scheme can improve the positioning accuracy and reduces computation complexity, traffic and latency. Particle swarm optimization (PSO) is a population based search algorithm based on the swarm intelligence like social behavior of birds, bees or a school of fishes. To improve the algorithm efficiency and localization precision, this paper presents an objective function based on the normal distribution of ranging error and a method of obtaining the search space of particles. In this paper Distributed localization of wireless sensor networksis proposed using PSO with best censoring technique using CRB. Proposed method shows better results in terms of position accuracy, latency and complexity.

Peer‐to‐peer cooperation for GPS positioning

SummaryThis paper presents a peer‐to‐peer cooperative positioning technique together with its performance assessment. The cooperation between the two GPS receivers is realized by means of a wireless LAN connection and is significantly influenced by the accurateness of the synchronization between the two terminals. Both the outdoor‐to‐indoor and outdoor‐to‐outdoor scenarios are considered. For each scenario, we assess the satellite signal acquisition and its computational load and the performance in terms of position accuracy and time‐to‐first‐fix of the positioning procedure. Copyright © 2016 John Wiley & Sons, Ltd.

Indoor Localization of Cooperative WSN Using PSO Assisted AKF with Optimum References

Finding exact node position with adjacent nodes is known as localization. Localization of Wireless Sensor Networks (WSN) is critical for many applications in indoor environment. In cooperative WSN all nodes assist in localization process in which some nodes give inaccurate estimates. Hence selection and rejection of information from nodes is a big challenge. Crammer Rao Bound (CRB) is used to select accurate nodes as the reference nodes. Kalman filter is a repetitive filter, widely used for estimation of location in linear environment. Extended Kalman Filter (EKF) is modification to the linear Kalman Filter used in nonlinear environment. In indoor environment due to noise, multipath effects EKF do not guarantee a best solution. Particle Swarm Optimization (PSO) is a population based search algorithm, which is formulated on the swarm intelligence like social behavior of birds, bees or a school of fishes. In this paper PSO Assisted Extended Kalman Filter (PSO-AKF) with optimum references is proposed. Localization of cooperative WSN with optimum selection of reference nodes using PSO-AKF shows better results in terms of position accuracy, latency and complexity.

Poster — Thur Eve — 19: Performance assessment of a 160‐leaf beam collimation system

In this study, the performance of the new beam collimation system with 160 leaves, each with a 5 mm leaf width projected at isocenter, is evaluated in terms of positional accuracy and plan/delivery quality. Positional accuracy was evaluated using a set of static and dynamic MLC/jaw delivery patterns at different gantry angles, dose rates, and MLC/jaw speeds. The impact on IMRT plan quality was assessed by comparing against a previous generation collimation system using the same optimization parameters, while delivery quality was quantified using a combination of patient‐specific QA measurements with ion chambers, film, and a bi‐planar diode array. Positional accuracy for four separate units was comparable. The field size accuracy, junction width, and total displacement over 16 cm leaf travel are 0.3 ± 0.2 mm, 0.4 ± 0.3 mm, and 0.5 ± 0.2 mm, respectively. The typical leaf minor offset is 0.05 ± 0.04 mm, and MLC hysteresis effects are 0.2 ± 0.1 mm over 16 cm travel. The dynamic output is linear with MU and MLC/jaw speed, and is within 0.7 ± 0.3 % of the planning system value. Plan quality is significantly improved both in terms of target coverage and OAR sparing due, in part, to the larger allowable MLC and jaw speeds. γ‐index pass rates for the patient‐specific QA measurements exceeded 97% using criteria of 2%/2 mm. In conclusion, the performance of the Agility system is consistent among four separate installations, and is superior to its previous generations of collimation systems.

Reducing the Positional Error of Connectivity-Based Positioning Algorithms Through Cooperation Between Neighbors

The information available to connectivity-based positioning algorithms is the radio range of sensor devices and the position estimates of neighbors and neighbors of neighbors. This information creates special graph theoretic structures which impose new constraints on the positions of sensor devices. The new constraints sometimes lead to a feasible set of positions with disconnected regions. These properties can be used to reduce the set of feasible positions for a node. In this paper, a new fully distributed positioning algorithm, called Orbit, which exploits these properties is presented for mobile sensor networks. The algorithm uses additional constraints and trims disconnected regions. These new constraints are generated through cooperation between neighbors. The performance of Orbit is examined for many communication and mobility models, including a probabilistic communication model generated from radio experiments. Computer simulation experiments demonstrate that Orbit outperforms a recently proposed positioning algorithm in terms of positional accuracy under different models with a wide range of parameter values. Orbit is implemented on resource limited sensor devices. This implementation demonstrates the feasibility of the algorithm for sensor devices. The algorithm is tested on deployments of the sensor devices in a field and the results are comparable to those from the simulation experiments.

Spatial Scheme for Groundwater Flow and Physical Properties Distribution in Ilaro, Southwestern Nigeria

Spatial flow patterns and quality trends for groundwater in Southwestern Nigeria have been undertaken with inadequate depth of interpretation. In this study, the geographical locations of wells and respective elevation were recorded using a Global Positioning System (GPS). Well depth and water level measurements were also obtained using measuring tape. Electronic meters were employed to determine temperature, salinity, hydrogen ion concentration (pH), Total Dissolved Solids (TDS) and electrical conductivity of 109 raw water samples. Geographical Information System (GIS) softwares (Arc View 3.3 and Surfer 8) were employed in the spatial data analyses. Results show that the groundwater flows towards the Southwest and Lower Mission in the Northwest, Orita in the East and Orita-TREM in the West. The pH ranges from 6.5 to 9.5 while TDS varies between 4.81 and 483.55 mg/l. The use GIS has proved to more precise in terms of positional accuracy, than the conventional map analysis

Quality assessment for building footprints data on OpenStreetMap

In the past two years, several applications of generating three-dimensional (3D) buildings from OpenStreetMap (OSM) have been made available, for instance, OSM-3D, OSM2World, OSM Building, etc. In these projects, 3D buildings are reconstructed using the buildings’ footprints and information about their attributes, which are documented as tags in OSM. Therefore, the quality of 3D buildings relies strongly on the quality of the building footprints data in OSM. This article is dedicated to a quality assessment of building footprints data in OSM for the German city of Munich, which is one of the most developed cities in OSM. The data are evaluated in terms of completeness, semantic accuracy, position accuracy, and shape accuracy by using building footprints in ATKIS (German Authority Topographic–Cartographic Information System) as reference data. The process contains three steps: finding correspondence between OSM and ATKIS data, calculating parameters of the four quality criteria, and statistical analysis. The results show that OSM footprint data in Munich have a high completeness and semantic accuracy. There is an offset of about four meters on average in terms of position accuracy. With respect to shape, OSM building footprints have a high similarity to those in ATKIS data. However, some architectural details are missing; hence, the OSM footprints can be regarded as a simplified version of those in ATKIS data.

Minimization of Parallax Error in Dedicated Breast PET

The increase of the detector thickness and the incidence angle of impinging photons permits an enhancement of sensitivity in positron emission tomography (PET) scanners. But also increases the parallax error and leads to a worsening of spatial resolution. Instead of introducing hardware modifications in the readout electronics or in the detector, we propose in this work to model the photon penetration depth in the detector material and to account for this effect during the image reconstruction. The validation of the model was based on experimental measurements with the MAMMI breast dedicated PET. It consists of twelve detector modules of monolithic LYSO scintillators. A point-like source was acquired at several radial positions across the field of view. The performance of the model was analyzed in terms of position accuracy and spatial resolution. Full width at half maximum (FWHM) average improvement values of 1.0 mm (radial), 0.4 mm (tangential), and 0.3 mm (axial) have been measured when the photon penetration depth was taken into account. The use of the model proposed in this work allows us to design PET detectors with improved sensitivity while maintaining the spatial resolution of the scanner.

Localization Algorithm with On-line Path Loss Estimation and Node Selection

RSS-based localization is considered a low-complexity algorithm with respect to other range techniques such as TOA or AOA. The accuracy of RSS methods depends on the suitability of the propagation models used for the actual propagation conditions. In indoor environments, in particular, it is very difficult to obtain a good propagation model. For that reason, we present a cooperative localization algorithm that dynamically estimates the path loss exponent by using RSS measurements. Since the energy consumption is a key point in sensor networks, we propose a node selection mechanism to limit the number of neighbours of a given node that are used for positioning purposes. Moreover, the selection mechanism is also useful to discard bad links that could negatively affect the performance accuracy. As a result, we derive a practical solution tailored to the strict requirements of sensor networks in terms of complexity, size and cost. We present results based on both computer simulations and real experiments with the Crossbow MICA2 motes showing that the proposed scheme offers a good trade-off in terms of position accuracy and energy efficiency.

Real-time single-frequency precise point positioning: accuracy assessment

The performance of real-time single-frequency precise point positioning is demonstrated in terms of position accuracy. This precise point positioning technique relies on predicted satellite orbits, predicted global ionospheric maps, and in particular on real-time satellite clock estimates. Results are presented using solely measurements from a user receiver on the L1-frequency (C1 and L1), for almost 3 months of data. The empirical standard deviations of the position errors in North and East directions are about 0.15 m, and in Up direction about 0.30 m. The 95% errors are about 0.30 m in the horizontal directions, and 0.65 m in the vertical. In addition, single-frequency results of six receivers located around the world are presented. This research reveals the current ultimate real-time single-frequency positioning performance. To put these results into perspective, a case study is performed, using a moderately priced receiver with a simple patch antenna.

AN ELECTRO-RHEOLOGICAL (ER) ROBOTIC SYSTEM: CONTROLLER VALIDATION, TREND STUDY, COMPARISON WITH DC SERVOMOTORS, POSITION REPEATABILITY

Industrial robot arms experience position inaccuracies due to the output cogging torques of the DC servomotors. Therefore, in an attempt to resolve these position problems, an electro-rheological (ER) robotic system is considered as an actuator to drive the robot arm rapidly in both directions. This ER robotic system consists of two ER clutches, an ER brake, a gear train, an encoder and a robot arm. The ER clutches produce clockwise and anti-clockwise rotations. The ER brake decelerates and halts the robot arm. The main aim of this paper is to validate a controller model of the ER robotic arm. Next, a trend study is used to determine the optimum working conditions of the ER actuated-robotic arm. The robotic displacements of both the ER rotary devices and the commercial DC servomotors are compared in terms of position accuracy and speed of response. Finally, the repeatability of the robotic end positions is examined in order to determine the importance of the ER brake.

Geocoding Accuracy Considerations in Determining Residency Restrictions for Sex Offenders

Geocoding is commonly employed to determine the location of addresses for use in spatial analysis, including the establishment of residency restriction zones for sex offenders. Street geocoding has known limitations in terms of positional accuracy, which may adversely affect spatial analytic methods. A case study on sex offenders in Orange County, Florida, is used to characterize the positional accuracy of street geocoding and its impact on spatial analysis. Positional accuracy of street geocoded locations of sex offenders' residences, schools, and day care facilities was determined using Geographic Information Systems (GIS) by measuring the distance to the correct property boundaries. Results show that positional errors in street geocoding are substantial and may bias conclusions drawn from proximity analysis. Findings strongly suggest that street geocoding is not appropriate for assessing residency restriction violations for sex offenders. These findings have important implications for criminal justice policies related to residency restrictions for sex offenders.

Resolution of direct space charge distribution measurement methods

Spatial resolution is a key parameter for the measurement of any distribution. In the case of space charge distribution measurements, it is difficult to compare technique performances since each technique has its own resolution definition most of the time. In this paper the resolution, in terms of position accuracy and charge discernment, is determined on the basis of a unique definition for the thermal, the pressure-wave- propagation and the electro-acoustic methods and their derived techniques. It is shown that spatial resolution is similar throughout the sample in the case of the pressure- wave-propagation or the electro-acoustic methods, except if attenuation and dispersion of elastic waves are important, but decreases as the charge position inside the sample in the case of thermal method. Elastic wave methods are therefore preferable for a given signal to noise ratio as soon as the sample thickness is larger than twice the sound velocity times the excitation rise time.

Performance Evaluation of Line Simplification Algorithms for Vector Generalization

Many studies of line simplification methods have been developed; however, an evaluation of these methods is still an open issue. This paper aims to evaluate a diversity of automatic line simplification algorithms in terms of positional accuracy and processing time. Past research studies for the performance evaluation were centred on measuring the location difference between a line to be simplified and its simplified version. However, the original line contains positional uncertainty. This paper evaluates performance of the line simplification algorithms using two comprehensive measures of positional accuracy of the simplified line. These two measures include one displacement measure and one shape distortion measure, both of which are able to consider (a) the displacement between the original line and its simplified version, and (b) positional uncertainty of the original line.

High Precision Hydrostatic Actuation Systems for Micro- and Nanomanipulation of Heavy Loads

In this paper reports on an important finding, that is, hydrostatic actuation systems are able to manipulate heavy loads with submicron precision and a large stroke. In this relation, the design of a high-precision hydrostatic actuation system referred to as the ElectroHydraulic Actuator (EHA) is presented. A laboratory prototype of this system has achieved an unprecedented level of performance by being able to move a large load of 20Kg with a precision of 100nm and a stroke of 12cm. This level of performance places the hydrostatic actuation concept in competition with piezoelectric platforms in terms of positional accuracy. Experimental results from this prototype are reported and analyzed.