Search

Location verification is a promising approach among various ADS-B security mechanisms, which can monitor announced positions in ADS-B messages with estimated positions. Based on common assumption that the attacker is equipped with only a single device, this mechanism can estimate the position state through analysis of time measurements of messages using multilateration algorithm. In this paper, we propose the formal model of multidevice false data injection attacks in the ATC system against the location verification. Assuming that attackers equipped with multiple devices can manipulate the ADS-B messages in distributed receivers without any mutual interference, such attacker can efficiently construct attack vectors to change the results of multilateration. The feasibility of a multidevice false data injection attack is demonstrated experimentally. Compared with previous multidevice attacks, the multidevice false data injection attacks can offer lower cost and more covert attacks. The simulation results show that the proposed attack can reduce the attackers' cost by half and achieve better time synchronization to bypass the existing anomaly detection. Finally, we discuss the real-world constraints that limit their effectiveness and the countermeasures of these attacks. [ABSTRACT FROM AUTHOR]

Radiolocation systems for aviation based on Multi-Lateration (MLAT) typically use a set of synchronised ground sensors to receive radio signals broadcast by onboard transmitters. In most cases, the sensor synchronisation in Wide Area Multi-Lateration Systems (WAM) is provided by Global Navigation Satellite System (GNSS) receivers. However, in the case of synchronisation failure, there is still a possibility to estimate the coordinates of the tracked aircraft by using the measurements of the time of arrival taken by non-synchronised sensors. The article presents the principle of operation and equations for calculating the coordinates of an aircraft in an asynchronous multi-lateration system, together with the results of a computer simulation allowing comparison of the accuracy of position estimation between the asynchronous and the typical, synchronous MLAT. This paper contains also some comments on the required stability of the clock source for the sensors working in an asynchronous MLAT system. [ABSTRACT FROM AUTHOR]

Multilateration (MLAT) system estimates the position of an aircraft using Time Difference of Arrival (TDOA) measurements estimated at spatially located Ground Receiving Station (GRS) pairs with a lateration algorithm. The Position Estimation (PE) accuracy of an MLAT system depends on several factors, one of which is the choice of reference station used to generate the TDOA estimations for use with the lateration algorithm. Furthermore, the closed-form lateration algorithm is known to introduce bias in the PE process. Thus, a bias analysis and improvement in the PE accuracy of an MLAT system with a reference selection technique is presented in the paper. The analysis is carried out for a square GRS configuration with each GRS equipped with a receiver whose Time of Reception (TOR) error Standard Deviation (SD) is assumed 1 nsec. Monte Carlo simulation result of lateration algorithm with reference selection technique shows a reduction of at least 75 % in both the overall PE Mean Square Error (MSE) and bias. Furthermore, the PE Root Mean Square Error (RMSE) obtained by the lateration algorithm is reduced by at least 50 % out of which 36 % of the reduced PE RMSE is contributed only by the TOR estimation error. [ABSTRACT FROM AUTHOR]

This paper examines the potential in extracting the instantaneous location of maritime moving targets using a passive multistatic radar with Global Navigation Satellite Systems (GNSS) as illuminators of opportunity and a single receiver. This paper presents a theoretical framework for the localization of a moving target from a set of bistatic range measurements. The algorithm and its predicted accuracy are presented. The localization is achieved by what is essentially a multilateration technique, which can be applied while the transmitting platform is also in motion. The algorithms and the accuracy predictions, as a function of the number of transmitters, have been experimentally confirmed via a dedicated experimental campaign, where two different maritime targets were detected by up to 12 GNSS satellites belonging to different satellite constellations (GPS, GLONASS, and Galileo) simultaneously. To the best of the author’s knowledge, these are the first results of their kind and on this scale not only for GNSS-based passive radar but also for multistatic radar in general. [ABSTRACT FROM AUTHOR]

The positioning of ocean bottom seismometers (OBS) is a key step in the processing flow of OBS data, especially in the case of self popup types of OBS instruments. The use of first arrivals from airgun shots, rather than relying on the acoustic transponders mounted in the OBS, is becoming a trend and generally leads to more accurate positioning due to the statistics from a large number of shots. In this paper, a linearization of the OBS positioning problem via the multilateration technique is discussed. The discussed linear solution solves jointly for the average water layer velocity and the OBS position using only shot locations and first arrival times as input data. [ABSTRACT FROM AUTHOR]

A multilateration system estimates the position of emitter using time difference of arrival (TDOA) measurements with a lateration algorithm. It involves solving a set of hyperbolic plane equations to determine the position of the emitter given the TDOA measurements that corresponds to the path difference (PD) measurement in distance. A performance model is developed using the relative maximum error bound (RMEB) which relates the plane equation condition number, the relative ground receiving station (GRS) geometry and the PD measurement error to estimate the position estimation (PE) error. By using air traffic monitoring for civil aviation as an application, Monte Carlo simulation verifies the PE error of the performance model for a square GRS configuration. The coverage assumed a 360° bearing, a range of up to 200 km and a maximum altitude of 15 km. Simulation results also show that the performance model estimates the horizontal position error with a maximum absolute error of 0.1 km up to a range of 200 km at an altitude of 15 km and a minimum absolute error of 0.2 km at an altitude of 15 km. [ABSTRACT FROM AUTHOR]

This paper investigates the effectiveness and applicability of fusing three wireless positioning algorithms to determine the positions and track nomadic sensor nodes in real environment conditions. We fuse finger printing and atomic multilateration processes to give the system the best feasible region and to ensure that the later does not sway much due to accumulative errors. The extended Kalman filter is then used for refining the estimated position in near real time. The paper further assesses the response speed and the accuracy of estimating the position of the nomadic nodes with a prudent distribution of the processing load. [ABSTRACT FROM AUTHOR]

Multilateration based approaches are widely accepted as the most adequate solution for geometric characterisation of medium and large machine tools. However, its application, either in a sequential mode or in a simultaneous approach, leads to industrial limitations such as total time consumption or thermal drift that prevent an automatic calibration. This work presents an integrated multilateration verification procedure where a tracking interferometer is directly attached to the manufacturing system spindle as a tool, which tackles several of the mentioned limitations. Results of both simulations and experimental tests show that levels of uncertainty in the range of micrometres can be guaranteed. [ABSTRACT FROM AUTHOR]

The localization of emitters using an array of sensors or antennas is a prevalent issue approached in several applications. There exist different techniques for source localization, which can be classified into multilateration, received signal strength (RSS) and proximity methods. The performance of multilateration techniques relies on measured time variables: the time of flight (ToF) of the emission from the emitter to the sensor, the time differences of arrival (TDoA) of the emission between sensors and the pseudo-time of flight (pToF) of the emission to the sensors. The multilateration algorithms presented and compared in this paper can be classified as iterative and non-iterative methods. Both standard least squares (SLS) and hyperbolic least squares (HLS) are iterative and based on the Newton-Raphson technique to solve the non-linear equation system. The metaheuristic technique particle swarm optimization (PSO) used for source localisation is also studied. This optimization technique estimates the source position as the optimum of an objective function based on HLS and is also iterative in nature. Three non-iterative algorithms, namely the hyperbolic positioning algorithms (HPA), the maximum likelihood estimator (MLE) and Bancroft algorithm, are also presented. A non-iterative combined algorithm, MLE-HLS, based on MLE and HLS, is further proposed in this paper. The performance of all algorithms is analysed and compared in terms of accuracy in the localization of the position of the emitter and in terms of computational time. The analysis is also undertaken with three different sensor layouts since the positions of the sensors affect the localization; several source positions are also evaluated to make the comparison more robust. The analysis is carried out using theoretical time differences, as well as including errors due to the effect of digital sampling of the time variables. It is shown that the most balanced algorithm, yielding better results than the other algorithms in terms of accuracy and short computational time, is the combined MLE-HLS algorithm. [ABSTRACT FROM AUTHOR]

Localization accuracy and low operating costs are substantial and key issues in operating and managing wireless sensor networks. The literature has many algorithms which used optimization techniques to promote the localization accuracy. This paper proposes a novel and an efficient algorithm based on state of art of black box optimization techniques, in order to promote the localization accuracy. This optimization technique is called hierarchical structure poly-particle swarm optimization. The proposed algorithm considers that the ranging technique is based on the cheapest distance estimation method which is receive signal strength indicator (RSSI). The proposed algorithm is more charming to promote the localization accuracy, where it has special characteristics such as the easy implementation of HSPPSO. In addition, RSSI is the cost efficiency measurement method. Simulation results demonstrate the effectiveness of the proposed algorithm comparing to other algorithms which based on optimization, e.g., ant colony, genetic algorithm, and basic PSO. This is clearly evident in some of the evaluation metrics such as localization accuracy, localization rate, and complexity. [ABSTRACT FROM AUTHOR]

In the Federal Aviation Administration's (FAA) performance based navigation strategy announced in 2016, the FAA stated that it would retain and expand the Distance Measuring Equipment (DME) infrastructure to ensure resilient aircraft navigation capability during the event of a Global Navigation Satellite System (GNSS) outage. However, the main drawback of the DME as a GNSS back up system is that it requires a significant expansion of the current DME ground infrastructure due to its poor distance measuring accuracy over 100 m. The paper introduces a method to improve DME distance measuring accuracy by using a new DME pulse shape. The proposed pulse shape was developed by using Genetic Algorithms and is less susceptible to multipath effects so that the ranging error reduces by 36.0-77.3% when compared to the Gaussian and Smoothed Concave Polygon DME pulses, depending on noise environment. [ABSTRACT FROM AUTHOR]

In this paper, a complete and rigorous mathematical model for secondary surveillance radar systematic errors (biases) is developed. The model takes into account the physical effects systematically affecting the measurement processes. The azimuth biases are calculated from the physical error of the antenna calibration and the errors of the angle determination dispositive. Distance bias is calculated from the delay of the signal produced by the refractivity index of the atmosphere, and from clock errors, while the altitude bias is calculated taking into account the atmosphere conditions (pressure and temperature). It will be shown, using simulated and real data, that adapting a classical bias estimation process to use the complete parametrized model results in improved accuracy in the bias estimation. [ABSTRACT FROM AUTHOR]

This paper presents an improved indoor localization system based on radio frequency (RF) and ultrasonic signals, which we named the SNSH system. This system is composed of a transmitter mounted in a mobile target and a series of receiver nodes that are managed by a coordinator. By measuring the Time Delay of Arrival (TDoA) of RF and ultrasonic signals from the transmitter, the distance from the target to each receiver node is calculated and sent to the coordinator through the CAN network, then all the information is gathered in a PC to estimate the 3D position of the target. A sine wave detector and dynamic threshold filter are applied to provide excellent accuracy in measuring the range from the TDoA results before multilateration algorithms are realized to optimize the accuracy of coordinate determination. Specifically, Linear Least Square (LLS) and Nonlinear Least Square (NLS) techniques are implemented to contrast their performances in target coordinate estimation. RF signal encoding/decoding time, time delay in CAN network and math calculation time are carefully considered to ensure optimal system performance and prepare for field application. Experiments show that the sine wave detector algorithm has greatly improved the accuracy of range measurement, with a mean error of 2.2 mm and maximum error of 6.7 mm for distances below 5 m. In addition, 3D position accuracy is greatly enhanced by multilateration methods, with the mean error in position remaining under 15 mm. Furthermore, there are 90% confidence error values of 23 mm for LLS and 20 mm for NLS. The update in the overall system has been verified in real system operations, with a maximum rate of 25 ms, which is a better result than many other existing studies. [ABSTRACT FROM AUTHOR]

Multilateration estimates aircraft position using the Time Difference Of Arrival (TDOA) with a lateration algorithm. The Position Estimation (PE) accuracy of the lateration algorithm depends on several factors which are the TDOA estimation error, the lateration algorithm approach, the number of deployed GRSs and the selection of the GRS reference used for the PE process. Using the minimum number of GRSs for 3D emitter PE, a technique based on the condition number calculation is proposed to select the suitable GRS reference pair for improving the accuracy of the PE using the lateration algorithm. Validation of the proposed technique was performed with the GRSs in the square and triangular GRS configuration. For the selected emitter positions, the result shows that the proposed technique can be used to select the suitable GRS reference pair for the PE process. A unity condition number is achieved for GRS pair most suitable for the PE process. Monte Carlo simulation result, in comparison with the fixed GRS reference pair lateration algorithm, shows a reduction in PE error of at least 70 % for both GRS in the square and triangular configuration. [ABSTRACT FROM AUTHOR]

The location determination technique using time difference of arrival (TDOA) measurements has been widely used in the military and observation industry. The accuracy of geolocation estimation is a very significant problem because measurement data are affected by environmental noise. Environmental noise occurs due to measurement error and the non-line of sight (NLOS) problem. This paper presents a Kalman filter-based NLOS section identification method and an iterative estimation of emitter location using the recursive weighted least square (RWLS) algorithm. Using fixed receivers with known locations, we obtain TDOA data that contain environmental noise. We identify the NLOS section of each receiver using a Kalman filter. Using the identified line of sight (LOS) TDOA measurements, we accurately derive the estimated location of an emitter with a fast calculation speed using the proposed RWLS algorithm when we receive additional TDOA data. In order to confirm the performance of the RWLS algorithm, the presented simulation results show that the proposed technique achieves improved accuracy and speed for estimating the emitter location. [ABSTRACT FROM AUTHOR]

The use of stochastic filtering techniques for aircraft tracking based on the data of multilateration surveillance system is considered. The recurrent algorithm of aircraft tracking is synthesized, computer simulation and result analysis are performed. [ABSTRACT FROM AUTHOR]

Navigation and guidance systems are a critical part of any autonomous vehicle. In this paper, a novel sensor grid using 40 KHz ultrasonic transmitters is presented for adoption in indoor 3D positioning applications. In the proposed technique, a vehicle measures the arrival time of incoming ultrasonic signals and calculates the position without broadcasting to the grid. This system allows for conducting silent or covert operations and can also be used for the simultaneous navigation of a large number of vehicles. The transmitters and receivers employed are first described. Transmission lobe patterns and receiver directionality determine the geometry of transmitter clusters. Range and accuracy of measurements dictate the number of sensors required to navigate in a given volume. Laboratory experiments were performed in which a small array of transmitters was set up and the sensor system was tested for position accuracy. The prototype system is shown to have a 1-sigma position error of about 16 cm, with errors between 7 and 11 cm in the local horizontal coordinates. This research work provides foundations for the future development of ultrasonic navigation sensors for a variety of autonomous vehicle applications. [ABSTRACT FROM AUTHOR]

Wireless sensor networks enable a wealth of new applications in areas such as military, medical, environmental, transportation, smart city, and so on. In many of these scenarios, we need to measure in a secure way the positions of the sensors. Existing range-based techniques for secure positioning require a burdensome infrastructure, with many fixed anchors. Reducing the infrastructure would reduce deployment cost and foster the adoption of secure positioning solutions in wireless sensor networks. In this article, we propose SPEM, a secure positioning system based on multilateration and ultra-wideband (UWB) distance bounding protocols. The key idea behind SPEM is to leverage the low probability that an adversary has of controlling enlargement attacks against UWB. We estimate such a probability by a thorough study and signal-level simulations of the UWB physical layer. We test SPEM both in a simulated environment and in a real indoor environment using real UWB transceivers. We show that SPEM needs far less infrastructure than state-ofthe- art solutions (-22% to -93%, depending on the anchor deployment method), while achieving high levels of security against smart and determined adversaries. [ABSTRACT FROM AUTHOR]

Multilateration measurement using laser trackers suffers from a cumbersome solution method for high-precision measurements. Errors are induced by the self-calibration routines of the laser tracker software. This paper describes an optimization solution model for laser tracker multilateration measurement, which effectively inhibits the negative effect of this self-calibration, and further, analyzes the accuracy of the singular value decomposition for the described solution model. Experimental verification for the solution model based on laser tracker and coordinate measuring machine (CMM) was performed. The experiment results show that the described optimization model for laser tracker multilateration measurement has good accuracy control, and has potentially broad application in the field of laser tracker spatial localization. [ABSTRACT FROM AUTHOR]

The demand for indoor navigation is increasingly urgent in many applications such as safe management of underground spaces or location services in complex indoor environment, e.g. shopping centres, airports, museums, underground parking lot and hospitals. Indoor navigation is still a challenging research field, as currently applied indoor navigation algorithms commonly ignore important environmental and human factors and therefore do not provide precise navigation. Flexible and detailed networks representing the connectivity of spaces and considering indoor objects such as furniture are very important to a precise navigation. In this paper we concentrate on indoor navigation considering obstacles represented as polygons. We introduce a specific space subdivision based on a simplified floor plan to build the indoor navigation network. The experiments demonstrate that we are able to navigate around the obstacles using the proposed network. Considering to well-known path-finding approaches based on Medial Axis Transform (MAT) or Visibility Graph (VG), the approach in this paper provides a quick subdivision of space and routes, which are compatible with the results of VG. [ABSTRACT FROM AUTHOR]

This paper explores the value of Conceptual Metaphor Theory (CMT) in the interdisciplinary study of emotion. The insights provided by a quantitative, corpus-based analysis of anger metaphors in three languages (English, Spanish, Russian) are compared to those obtained from two other methodologies of a more psycholinguistic kind: a feature-rating and a labelling task. The three methodologies are used to test in language several hypotheses on cross-cultural differences in anger experiences derived from earlier findings in emotion psychology. The three methods are found to be complementary and provide convergent evidence that support the hypotheses, with each method contributing additional pertinent data on some of the issues addressed. We discuss the contribution of CMT, its relative importance and specificity, and highlight several methodological and analytical adaptations that CMT studies should undergo for its results to become more informative to other disciplines in the study of emotion. [ABSTRACT FROM AUTHOR]

An efficient path planning approach in mobile beacon localization for the randomly deployed wireless sensor nodes is proposed in this paper. Firstly, in order to improve localization accuracy, the weighting function based on the distance between nodes is constructed. Moreover, an iterative multilateration algorithm is also presented to avoid decreasing the localization accuracy. Furthermore, a path planning algorithm based on grid scan which can traverse entirely in sensor field is described. At the same time, the start conditions of localization algorithm are also proposed to improve localization accuracy. To evaluate the proposed path planning algorithm, the localization results of beacon nodes randomly deployed in sensor field are also provided. The proposed approach can provide the deployment uniformly of virtual beacon nodes among the sensor fields and the lower computational complexity of path planning compared with method which utilizes only mobile beacons on the basis of a random movement. The performance evaluation shows that the proposed approach can reduce the beacon movement distance and the number of virtual mobile beacon nodes by comparison with other methods. [ABSTRACT FROM AUTHOR]

This paper deals with a calibration procedure of a 3D working space based on multilateration using a unique tracking interferometer. The key point of the procedure, detailed for a Cartesian CMM, is the definition of a reference measuring system built from the successive locations of a single tracer independently of the machine kinematics. Procedure limits are thus highlighted and can be classified into three types: limits of the devices (interferometer and measuring rule performances), limits linked to the use of a single tracer (reflector reorientation for visibility purposes), and limits linked to the algorithm. To evaluate associated uncertainties, a virtual measurement module has been developed which simulates a realistic 3D calibration and allows the study of the influence of each uncertainty component on the calibration procedure. The approach applied to the calibration of a virtual CMM proves that the simulation module is an efficient tool to investigate uncertainties associated with calibration procedures based on multilateration using a single tracer. [ABSTRACT FROM AUTHOR]

For real-time and precise measurement of molten steel level in tundish during continuous casting, slag level and slag thickness are needed. Among which, the problem of slag thickness measurement has been solved in our previous work. In this paper, a systematic solution for slag level measurement based on laser triangulation is proposed. Being different from traditional laser triangulation, several aspects for measuring precision and robustness have been done. First, laser line is adopted for multi-position measurement to overcome the deficiency of single point laser range finder caused by the uneven surface of the slag. Second, the key parameters, such as installing angle and minimum requirement of the laser power, are analyzed and determined based on the gray-body radiation theory to fulfill the rigorous requirement of measurement accuracy. Third, two kinds of severe noises in the acquired images, which are, respectively, caused by heat radiation and Electro-Magnetic Interference (EMI), are cleaned via morphological characteristic of the liquid slag and color difference between EMI and the laser signals, respectively. Fourth, as false target created by stationary slag usually disorders the measurement, valid signals of the slag are distinguished from the false ones to calculate the slag level. Then, molten steel level is obtained by the slag level minus the slag thickness. The measuring error of this solution is verified by the applications in steel plants, which is ±2.5 mm during steady casting and ±3.2 mm at the end of casting. [ABSTRACT FROM AUTHOR]

A new methodology to measure thermal distortion in large machine tools is proposed in this paper. The advantage of this method is that a single tracking interferometer can be used to measure thermal distortion of machines with large work volumes while maintaining low enough measurement cadence and uncertainty. A multilateration scheme is conducted using a single laser tracking device positioned on top of the machine table which is automated, and for each target point, all laser stations are reached prior to moving to the next target point; then, the whole measurement cycle is repeated during the test. For measuring angular thermal distortion, precision electronic levels are located in machine ram and column top; also, temperatures are registered in key points of the machine. Experimental measurements on a large column-type milling machine are done, and the effectiveness of the proposed methodology is verified. [ABSTRACT FROM AUTHOR]

Low-cost Radio Frequency Identification (RFID) location sensing algorithm is practical and crucial for urban infrastructure location. Current RFID location algorithms are based on fixed multiple RFID reader or reference points (reader or tag) with known position, which is cost and difficult to deployment in urban environment. The objective of this study is to develop a low-cost location sensing algorithm using RFID technique to locate urban infrastructure. This paper presents an algorithm based on multilateration with the integration of mobile RFID and Global Position System (GPS). The mobility of RFID reader can measure many distances between different RFID reader positions and target tag which represent multilateration. The GPS provides coordination of RFID reader. The location of tag is calculated based on triangle geometric property. The redundant observation is adopted to get the optimum location. In practice, the only one RFID reader is necessary, thus the cost is reduced hardly. The performance and accuracy assessment are conducted in field experiment. The experiment proves that the proposed low-cost location sensing algorithm is able to location the urban infrastructure with smaller position error. The lower cost makes it even more economically feasible than other algorithm. [ABSTRACT FROM AUTHOR]

Node flip ambiguity is a key problem that needs to be addressed for range-based node localization in wireless sensor networks. In this paper we have implemented robustness analysis for node multilateration localization in wireless sensor networks. A robustness criterion, called orthogonal projection algorithm (OPA), to detect flip ambiguity for range-based nodes multilateration localization method is proposed. The basic idea of OPA comes from the orthogonal projection principle, and it has the low computational complexity. On the basis of OPA, we further derive an expression to quantify the probability of flip ambiguity occurrences. Theoretical analysis and numerical simulation results demonstrate that OPA has good detection results and the low computational complexity, the expression for calculating probability of flip ambiguity occurrences is feasible. [ABSTRACT FROM AUTHOR]

Precision positioning of an object relative to a reference point is a common task in many activities of production engineering. Sensor technologies for single axis measurement, either linear or rotary, which form the fundamentals of measurement technologies for precision positioning, are reviewed. Multi-axis coordinate measurement methods such as triangulation and multilateration, as well as Cartesian and polar systems for specifying the position in a plane or three-dimensional (3D) space are then presented, followed by a discussion on traceability and standards. Some advanced applications of measurement technologies for precision positioning in manufacturing industries are also demonstrated. [ABSTRACT FROM AUTHOR]

In this paper, we will present a method for through-the-wall localisation of targets in 3D space by ultra-wideband (UWB) radar. The targets are moving or static uncooperative human beings and the localisation is based on the time-of-arrival (TOA) measurement. The presented method is based on the use of a specific antenna array layout, which simplifies the problem of the 3D multilateration method to the solution of two 2D localisation problems. Through-the-wall as well as the line-of-sight measurements were done for both static and moving person scenarios and the results of the selected scenarios are described in this paper. [ABSTRACT FROM AUTHOR]

Highlights: [•] An ‘open-loop’ tracking interferometer is proposed for multilateration measurement. [•] The laser beam is regulated toward the command target position. [•] It may significantly reduce the manufacturing cost of conventional tracking interferometers. [•] Its measurement uncertainty is studied both experimentally and analytically. [•] This paper focuses on the measurement of the target's two-dimensional position. [Copyright &y& Elsevier]

Highlights: [•] This paper proposes an intercomparion on multilateration technic between 5 teams. [•] Work underlines effect of strategy in the multilateration. [•] Multilateration robustness for CNC machine compensation was tested. [Copyright &y& Elsevier]

Abstract: A new method for a location service in the wide area multilateration (WAM) system is outlined. This method, which is called asynchronous WAM (AWAM), enables calculation of the geographical position of an aircraft without knowledge of relative time differences (RTDs) between measuring ground stations (sensors). The AWAM method is based on the measurement of round trip times (RTTs) between the aircraft and the serving ground station, and the solution of a nonlinear system of equations with ten variables. The elimination of the RTD parameters significantly simplifies the localization process in real-life WAM system. The proposed asynchronous method could be an alternative solution for the synchronous one as a backup method during the system's failure or as an independent method. The paper concentrates on the description of the method, solving the nonlinear system of equations with ten variables and simulation results. [Copyright &y& Elsevier]

SUMMARY Multilateration is an aircraft surveillance system for airport surface movement utilizing hyperbolic positioning. The system performance is sometimes degraded by multipath signals in airport apron areas. ENRI has proposed an enhanced multilateration system named OCTPASS (Optically Connected Passive Surveillance System), which has interference immunity in a multipath environment. This paper describes evaluation results for OCTPASS prototype equipment. [ABSTRACT FROM AUTHOR]

Most applications of wireless sensor networks (WSNs) rely on data about the positions of sensor nodes, which are not necessarily known beforehand. Several localization approaches have been proposed but most of them omit to consider that WSNs could be deployed in adversarial settings, where hostile nodes under the control of an attacker coexist with faithful ones. Verifiable multilateration (VM) was proposed to cope with this problem by leveraging on a set of trusted landmark nodes that act as verifiers. Although VM is able to recognize reliable localization measures, it allows for regions of undecided positions that can amount to the 40 percent of the monitored area. We studied the properties of VM as a noncooperative two-player game where the first player employs a number of verifiers to do VM computations and the second player controls a malicious node. The verifiers aim at securely localizing malicious nodes, while malicious nodes strive to masquerade as unknown and to pretend false positions. Thanks to game theory, the potentialities of VM are analyzed with the aim of improving the defender's strategy. We found that the best placement for verifiers is an equilateral triangle with edge equal to the power range $(R)$, and maximum deception in the undecided region is approximately $(0.27R)$. Moreover, we characterizedâin terms of the probability of choosing an unknown node to examine furtherâthe strategies of the players. [ABSTRACT FROM PUBLISHER]

A connectivity-based and anchor-free three-dimensional localization (CATL) scheme is presented for largescale sensor networks with concave regions. It distinguishes itself from previous work with a combination of three features: (1) it works for networks in both 2D and 3D spaces, possibly containing holes or concave regions; (2) it is anchor-free and uses only connectivity information to faithfully recover the original network topology, up to scaling and rotation; (3) it does not depend on the knowledge of network boundaries, which suits it well to situations where boundaries are difficult to identify. The key idea of CATL is to discover the notch nodes, where shortest paths bend and hop-count-based distance starts to significantly deviate from the true Euclidean distance. An iterative protocol is developed that uses a notch-avoiding multilateration mechanism to localize the network. Simulations show that CATL achieves accurate localization results with a moderate per-node message cost. [ABSTRACT FROM AUTHOR]

Highlights: [•] Influence of commercial laser tracker in volumetric verification. [•] Self calibration techniques of laser trackers. [•] Different ways of applying multialterarion with laser tracker. [•] Influences of measurement noise in volumetric verification. [•] The influence of laser tracker positioning. [ABSTRACT FROM AUTHOR]

The linear and rotary axes are fundamental parts of multi-axis machine tools. The geometric error components of the axes must be measured for motion error compensation to improve the accuracy of the machine tools. In this paper, a simple method named the three-point method is proposed to measure the geometric error of the linear and rotary axes of the machine tools using a laser tracker. A sequential multilateration method, where uncertainty is verified through simulation, is applied to measure the 3D coordinates. Three non-collinear points fixed on the stage of each axis are selected. The coordinates of these points are simultaneously measured using a laser tracker to obtain their volumetric errors by comparing these coordinates with ideal values. Numerous equations can be established using the geometric error models of each axis. The geometric error components can be obtained by solving these equations. The validity of the proposed method is verified through a series of experiments. The results indicate that the proposed method can measure the geometric error of the axes to compensate for the errors in multi-axis machine tools. [ABSTRACT FROM AUTHOR]

Several rain drop size distribution (DSD) point measurement technologies exist, but all are unable to sample either short timescales or the large drop tail of the DSD due to inherent instrumental limitations. The development of an acoustic water tank disdrometer (AWTD) is described, which improves the sampling statistics by increasing the catchment area. This is achieved by distinguishing individual drops, locating them on the surface of the tank then converting the impact pressure into a drop size. Wavelet decomposition is used to distinguish the broadband, short duration impact events and a fast multilateration method is used to position the drop. Issues relating to the different types of noise are also investigated and mitigated. Also, further work on inverting the measured acoustic intensity into a DSD, by fitting sampling distributions, is presented. Six months of data were collected in the Eastern UK. The AWTD then converted the data into DSDs and the results were compared to a commercially available co-located laser precipitation monitor. The sampling errors are far lower due to the increased catchment size, and hence the large drop sized tail of the DSD is greatly improved. DSD results compare favourably to other disdrometers for drop diameters greater than 1.8 mm. Below this size individual drops become increasingly difficult to detect and are underestimated. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a general framework for tracking the time differences of arrivals of multiple acoustic sources recorded by distributed microphone pairs. Tracking is based on a three-stage analysis. Complex-valued propagation models are extracted at different time instants and frequencies using either the independent component analysis or the phase of the cross-power spectrum evaluated at each microphone pair. In both cases, approximated densities of the propagation time delays are derived through the generalized state coherence transform. A sequential Bayesian tracking scheme with an integrated activity detection is finally implemented through disjoint particle filters based on a track-before-detect strategy. Experiments on both synthetic and real data recorded by two distributed microphone pairs show that the proposed framework can detect and track up to five sources simultaneously active in a reverberant environment. [Copyright &y& Elsevier]

A conventional multilateration is a two-step process where, in the first step the time difference of arrivals (TDOA) of a signal at multiple sensors are estimated, and in the second step, these TDOAs are used in some position fixing technique to estimate the location of an emitter. Several estimators have been proposed over the years for the estimation of the TDOAs. Many techniques have been proposed for position fixing as well. Much of the research on position fixing has been focused on obtaining a simplified closed form solution. For the unknown deterministic signal model, Stein had derived the maximum-likelihood estimator (MLE) for the TDOA between two sensors, which is the peak location of the cross-correlation function. Since the asymptotic variance of an MLE approaches the Cramer-Rao lower bound (CRLB), which is the inverse of the negative of the expected value of the curvature of the log-likelihood function, using this as a motivation, we propose a weighted least squares type position fixing technique where the weights are computed from the curvature of the log-likelihood function. [ABSTRACT FROM PUBLISHER]

The International Civil Aviation Organization (ICAO) has decided to adopt Communications, Navigation, and Surveillance/Air Traffic Management (CNS/ATM) as the 21st century standard for navigation. Accordingly, ICAO members have provided an impetus to develop related technology and build sufficient infrastructure. For aviation surveillance with CNS/ATM, Ground-Based Augmentation System (GBAS), Automatic Dependent Surveillance-Broadcast (ADS-B), multilateration (MLAT) and wide-area multilateration (WAM) systems are being established. These sensors can track aircraft positions more accurately than existing radar and can compensate for the blind spots in aircraft surveillance. In this paper, we applied a novel sensor fusion method with Interacting Multiple Model (IMM) filter to GBAS, ADS-B, MLAT, and WAM data in order to improve the reliability of the aircraft position. Results of performance analysis show that the position accuracy is improved by the proposed sensor fusion method with the IMM filter. [ABSTRACT FROM AUTHOR]

User localization is one of the key service-enablers in broadband mobile communications. Moreover, from a different point of view, next steps towards automatic network optimization also depend upon the capability of the system to perform real-time user localization, in order to obtain the traffic distribution. The aim of this paper is to get deeper into the feasibility and accuracy of different localization mechanisms ranging from triangulation to database correlation. Call tracing data extracted from a real operating mobile network have been used to assess these algorithms after the execution of an extensive measurements campaign. Results show that enhanced triangulation offers the best performance even outperforming other more sophisticated mechanisms like fingerprinting, without introducing any change in the network and without requiring any special characteristic of the user equipment. Indeed, the lack of precision of channel estimates, which for the same position could differ up to 10 dB, introduces a large uncertainty that harms localization mechanisms based on database correlation. Finally, this paper identifies the areas for improvement in triangulation to reach its maximum potential, provides details for its implementation and analyzes the performance of the different proposed enhancements. [ABSTRACT FROM AUTHOR]

In this study, a constrained total least-squares (CTLS) algorithm for estimating the position and velocity of a moving source with sensor location uncertainties that uses the time difference of arrival and frequency difference of arrival measurements of a signal received at a number of sensors is proposed. The CTLS method, as a natural extension of LS when noise occurs in all the data and the noise components of the coefficients are linearly dependent, is more appropriate than the LS method for the above problem. By utilising the Lagrange multipliers technique, the known relation between the intermediate variables and the source localisation coordinates has been exploited to constrain the solution. In addition, the Lagrange multipliers can be obtained efficiently and robustly, which can allow real-time implementation as well as ensure global convergence. After a perturbation analysis, the bias and covariance of the proposed CTLS algorithm are also derived, indicating that the proposed CTLS algorithm is an unbiased estimator, and it could achieve the Crame'r-Rao lower bound (CRLB) when the measurement noise and the sensor location errors are sufficiently small. The simulation results show that the proposed estimator achieves remarkably better performance than the TLS and two-step weighted least squares approach, which makes it possible that the CRLB is attained at a sufficiently high noise level before the threshold effect occurs. [ABSTRACT FROM AUTHOR]

In distance vector (DV)-hop localisation, the estimated distances between unknown nodes and anchors are usually determined through multiplying the hop-count and the average per-hop distance, so the per-hop distance represents a physical distance. Unfortunately, in practice, wireless communication networks may be affected by the environment, which makes the per-hop distance deviating from the physical distance. A number of improved DV-hop localisation algorithms have been proposed previously, which give the weight to the per-hop distance. When applied as it is, sub-optimal results were achieved as the differences between per-hop distances and physical distances could not be determined. In this Letter, the authors analyse the error during the process of converting hop distances to physical distances and take advantage of the optimal weighted function, which achieves a more accurate distance conversion model. Then, they correct the estimated position of unknown nodes according to the relationship between the estimated distances calculated by hop-distance conversion and the distances from the estimated positions of unknown nodes to anchor nodes. The simulation results show that the localisation performance of the proposed algorithm is better than the existing weighted methods in irregular areas. [ABSTRACT FROM AUTHOR]

Localization error is the main criteria to decide the efficiency on any localization approach. In case of range‐free hop‐based localization approaches, position coordinates estimation is done through the common steps like the calculation of the minimum hop count, hop size, and then later on applying the multilateration or least square approach. There are many improvements that have been made in the form of various algorithms through some changes in the common steps for the reduction of localization error. It has been observed that the existing algorithms are still having the highest value of localization error. To overcome the deficiencies in the existing algorithms, a novel distance error correction metric–based approach has been introduced. This paper presents a distance error correction–based algorithm (DEC‐hop) for the hop‐based localization approach for a wireless sensor network. Distance‐based error correction factor that is introduced in this paper further reduces the localization error value to some extent. For measuring the effectiveness and the preciseness of the given approach, it is inspected with other improved algorithms based on DV‐hop. Simulation results have confirmed that the proposed error correction–based algorithm outperforms the other variety of improved hop‐based algorithms. Results are analyzed in terms of various factors like the localization error, accuracy, and error variance against the parameters of interest taken as node amount, anchor ratio, and communication range of the node. This work presents a distance error correction–based algorithm (DEC‐hop) for the hop‐based localization approach for a wireless sensor network. It is inspected with other improved algorithms based on the DV‐hop. Results are analyzed in terms of various factors like the localization error, accuracy, and error variance against the parameters of interest taken as node amount, anchor ratio, and communication range of the node. Also, the statistical analysis is being done for each one of the comparison. [ABSTRACT FROM AUTHOR]

Most of the range-free localisation techniques compute the position of a node through multilateration based on distances between nodes. The least squares estimation (LSE) based multilateration is used to determine the position of a node – which is optimal estimation method if all the variances of distance errors are equal. In range-free localisation, the distances to the anchors are usually estimated by multiplying the hop count and the hop length. Since the estimated hop length is error prone, the distance estimation error and the error variance usually increase as the hop count increases. If the conventional multilateration algorithm, which gives the same weights to the estimated distances, is applied as it is, suboptimal result will be achieved because the variances of the distance estimation errors cannot be equal. In this Letter, we analyse the reliability of estimated distance and propose a novel LSE based multilateration which considers the reliability of estimated distance. Simulation results show that the proposed method improves performance compared with the existing methods. [ABSTRACT FROM AUTHOR]

The original version of this article unfortunately contained a mistake. [ABSTRACT FROM AUTHOR]

The development and validation of a portable coordinate measurement solution for fiducialization of compact linear collider (CLIC) components is presented. This new solution addresses two limitations of high-accuracy state-of-the-art coordinate measuring machines, i.e. lack of portability and limited measurement volume. The solution is based on frequency scanning interferometry (FSI) distances and the multilateration coordinate measurement technique. The developments include a reference sphere for localizing the FSI optical fiber tip and a kinematic mount for repositioning the reference sphere with sub-micrometric repeatability. This design enables absolute distance measurements in different directions from the same point, which is essential for multilateration. A multilateration test bench built using these prototypes has been used to fiducialize a CLIC cavity beam position monitor and 420 mm-long main beam quadrupole magnet. The combined fiducialization uncertainty achieved is 3.5 μm (k  =  1), which is better than the CLIC 5 μm (k  =  1) uncertainty specification. [ABSTRACT FROM AUTHOR]