Distance Measurement Error Research Articles

Toward Accurate Human Tracking: Modeling Time-of-Arrival for Wireless Wearable Sensors in Multipath Environment

For time-of-arrival-(TOA)-based indoor human tracking system, the wireless channel between human body surface and external reference node can be regarded as the source of inaccuracy. Since only the arrival time of direct path provides accurate range estimate, the nonline of sight caused by human body leads to undetectable direct path condition and thus results in a significant distance measurement error. In this paper, we measured TOA ranging error for indoor human tracking applications inside a typical office environment. A large number of TOA ranging samples was obtained and statistically analyzed. The TOA ranging error was modeled as a Gaussian random variable with the parameters, including position of target sensor, angle between human facing direction, and direction of transmitter–receiver, signal-to-noise ratio, and bandwidth of the system. As a validation of proposed model, excellent agreement has been found between empirical measurement and model-based software simulation.

CC-KF: Enhanced TOA Performance in Multipath and NLOS Indoor Extreme Environment

Time-of-arrival (TOA)-based indoor geolocation suffer from huge distance measurement error caused by multipath and nonline-of-sight (NLOS) conditions. In this paper, we presented a new distance mitigation algorithm based on channel classification and Kalman filter to enhanced TOA performance in multipath and NLOS indoor extreme environment. This algorithm could significantly reduce the ranging error caused by the extreme channel condition in indoor area. We compared the performance of our algorithm with the traditional TOA distance mitigation algorithms, such as Kalman filter, biased Kalman filter, binary hypothesis testing, and ANN, using a commercially available TOA-based geolocation system in typical indoor and underground environments. Results show the performance of our algorithm is much superior to the others.

The Research on the Error Correcting Method for Acoustic Measurement the Missing Distance of Moving Areal Target

In this paper, the effects on measurement missing distance due to the movement of target are analyzed, and the new method for missing distance measurement error correcting based on space coordinates correction is studied. With the optimal one-dimensional search algorithm in the miss distance calculation obviously increase the processing speed. The simulation results show that this kind of error correction method can effectively reduce the miss distance measurement error.

The local standard of rest from data on young objects with account for the Galactic spiral density wave

To estimate the peculiar velocity of the Sun with respect to the Local Standard of Rest (LSR), we used young objects in the Solar neighborhood with distance measurement errors within 10%-15%. These objects were the nearest Hipparcos stars of spectral classes O-B2.5, masers with trigonometric parallaxes measured by means of VLBI, and two samples of the youngest and middle-aged Cepheids. The most significant component of motion of all these stars is induced by the spiral density wave. As a result of using all these samples and taking into account the differential Galactic rotation, as well as the influence of the spiral density wave, we obtained the following components of the vector of the peculiar velocity of the Sun with respect to the LSR: (Uo,Vo,Wo)_{LSR}=(6.0,10.6,6.5)+\-(0.5,0.8,0.3) km/s. We have found that components of the Solar velocity are quite insensitive to errors of the distance Ro in a broad range of its values, from Ro=7.5 kpc to Ro=8.5 kpc, that affect the Galactic rotation curve parameters. In the same time, the Solar velocity components(Uo)_{LSR} and (Vo)_{LSR}$ are very sensitive to the Solar radial phase in the spiral density wave.

Impact of thermal diffusion and other abundance anomalies on cosmological uses of galaxy clusters

Depending on the topology of the magnetic field and characteristics of turbulent motions, diffusion can significantly affect the distribution of elements, in particular helium, in the intracluster medium (ICM). As has been noted previously, an incorrect assumption about the helium abundance will lead to an error in the iron abundance determined from X-ray spectroscopy. The corresponding effect on the temperature measurement is negligibly small. An incorrectly assumed helium abundance will also lead to a systematic error in angular distance measurements based on X-ray and Sunyaev-Zeldovich (SZ) observations of clusters of galaxies. Its magnitude is further amplified by the associated error in the metal abundance determination, the impact being larger at lower ICM temperatures. Overall, a factor of 2-5 error in the helium abundance will lead to an ~ 10-25 % error in the angular distance. We solve the full set of Burgers equations for a multi-component intracluster plasma to determine the maximal effect of diffusion on the interpretation of X-ray and microwave observations of clusters of galaxies. For an isothermal cluster, gravitational sedimentation can lead to up to a factor of ~ 5-10 enhancements of helium and metal abundances in the cluster center on a ~ 3-7 Gyr timescale. In cool-core clusters on the contrary, thermal diffusion can counteract gravitational sedimentation and effectively remove helium and metals from the cluster inner core. In either case, a significant, up to ~ 40 %, error in the metal abundances determined by means of X-ray spectroscopy is possible. The angular distance determined from X-ray and SZ data can be underestimated by up to ~ 10-25 %.

Distributed location model and algorithm with position uncertainty

The localization of multiple mobile terminals (MTs) is an encouraging paradigm of applications in wireless networks. Peer-to-peer communication between MTs facilitates the cooperative localization of multiple MTs. For sake of low complexity and high robustness, investigations often focus on the distributed algorithm in cooperative localization. However, the impact from position uncertainty of cooperative MT lacks of analysis in related works. A new distributed location model, as well as corresponding algorithm, is devised when considering both the distance measurement error and the position uncertainty of MTs, which is more judicious than the traditional model for distributed cooperative localization scenario. In addition, the performance of proposed algorithm is analyzed through Cramér-Rao lower bound (CRLB). Simulations indicate that the algorithm outperforms traditional methods in terms of accuracy and robustness.

Design and Implement of the Car Reversing Automatic Anti-Collision Control System

There are considerable difference between the actual distance and that measured by infrared or ultrasonic ranging. The car reversing isnt intelligent enough. In order to solve the issues, this paper design an automatic car reversing auxiliary systems based on monocular sight. The system hardware mainly consists of image collection module, embedded micro-controller, and electronic braking module. On the basis of the distance measurement algorithm based on monocular sight, the real-time distance to the front vehicle can be measured and can be auxiliary controlled via the data exchange among vehicle electrical control units. The vehicle dynamic driving experiment verifies the high reliability of the vehicle automatic reversing auxiliary system based on monocular sight. The distance measurement errors are less than 2% when the distance to the front barriers is in the range of 20m~70m. The system can satisfy the real-time requirements for the vehicle intelligent auxiliary braking.

Identifying and filtering noise caused by sensor set switching in UWB indoor position tracking

Trilateration calculations are affected by errors in distance measurements from the set of fixed points to the object of interest. When these errors are systemic, each distinct set of fixed points can be said to exhibit a unique set noise. For ultra-wideband (UWB) indoor position tracking, the set of fixed points is a set of sensors measuring the distance to a tracked tag. In this paper we develop a noise model for this sensor set noise, along with a particle filter that uses our set noise model. We test our methods on a real UWB system. Our methods showed an approximately 15% improvement in accuracy over the raw measurements.

Optimal Trajectory Planning and Coordinated Tracking Control Method of Tethered Space Robot Based on Velocity Impulse

The tethered space robot (TSR) is a new concept of space robot which consists of a robot platform, space tether and operation robot. This paper presents a multi-objective optimal trajectory planning and a coordinated tracking control scheme for TSR based on velocity impulse in the approaching phase. Both total velocity impulse and flight time are included in this optimization. The non-dominated sorting genetic algorithm is employed to obtain the optimal trajectory Pareto solution using the TSR dynamic model and optimal trajectory planning model. The coordinated tracking control scheme utilizes optimal velocity impulse. Furthermore, the PID controller is designed in order to compensate for the distance measurement errors. The PID control force is optimized and distributed to thrusters and the space tether using a simulated annealing algorithm. The attitude interferential torque of the space tether is compensated a using time-delay algorithm through reaction wheels. The simulation results show that the multi-objective optimal trajectory planning method can reveal the relationships among flight time, fuel consumption, planar view angle and velocity impulse number. This method can provide a series of optimal trajectory according to a number of special tasks. The coordinated control scheme can significantly save thruster fuel for tracking the optimal trajectory, restrain the attitude interferential torque produced by space tether and maintain the relative attitude stability of the operation robot.

A Millimeter-Wave Low-Power Active Backscatter Tag for FMCW Radar Systems

In this paper, a fully integrated active backscatter transponder based on the switched injection-locked oscillator (SILO) principle for frequency-modulated continuous-wave radar applications is presented. Furthermore, a method to characterize a SILO amplifier is extended and utilized to measure the system parameters of the presented backscatter tag that operates at 34.45 GHz. It is digitally tunable from 32.7 to 35.4 GHz and reaches an unpulsed output power of 5 dBm. Above injection power levels of $-\hbox{53 dBm}$ , the SILO tag responds phase coherent at its maximum output power. In system measurements, the SILO backscatter transponder was used to perform distance measurements at ranges from 0.7 to 11.5 m. A remarkably good mean distance measurement error of 7 cm with a standard deviation of 10 cm was achieved in a strong multipath environment. The single measurement precision is below 3 mm.

Performance Evaluation of a Decentralized Multitarget-Tracking Algorithm Using a LIDAR Sensor Network With Stationary Beams

A LIght Detection And Ranging (LIDAR) sensor network to track walking persons inside a surveillance area is investigated. A small number of sensor nodes with spatially stationary and partially overlapping narrow LIDAR beams are chosen in order to keep the costs to a minimum. As a consequence of this network topology, the area of surveillance is not fully covered with LIDAR beams, and thus, accurate tracking of persons walking inside the area of surveillance is challenging, particularly in a multitarget situation. To tackle this problem, multitarget tracking based on a sophisticated decentralized track-to-track fusion architecture is developed and evaluated in this paper: Dynamic multihypothesis tracking (MHT) by independent local trackers is carried out in all sensor nodes; then, local track favorites are sent to a fusion center, where global track candidates are derived and fed back to the local trackers in order to improve local tracking. With this architecture, a track association success rate of (98.8 ± 0.3)% and a mean square position error of Δp = 6.7 cm were derived from 1000 random pairs of intersecting trajectories of two persons walking (mean velocity 1.5 m/s) across a rectangular surveillance area of size 20 m × 10 m. The tracking performances as functions of target velocity <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">v</i> and target radius <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</i> were quantified. Furthermore, the tracking performances as functions of the distance measurement error Δ <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</i> and beamwidth 2β as the most important parameters were obtained. The performance of the proposed algorithm was also experimentally evaluated.

Reconstructing cosmological initial conditions from galaxy peculiar velocities – II. The effect of observational errors

The Reverse Zeldovich Approximation (RZA) is a reconstruction method which allows to estimate the cosmic displacement field from galaxy peculiar velocity data and to constrain initial conditions for cosmological simulations of the Local Universe. In this paper, we investigate the effect of different observational errors on the reconstruction quality of this method. For this, we build a set of mock catalogues from a cosmological simulation, varying different error sources like the galaxy distance measurement error (0 - 20%), the sparseness of the data points, and the maximum catalogue radius (3000 - 6000 km/s). We perform the RZA reconstruction of the initial conditions on these mock catalogues and compare with the actual initial conditions of the simulation. We also investigate the impact of the fact that only the radial part of the peculiar velocity is observationally accessible. We find that the sparseness of a dataset has the highest detrimental effect on RZA reconstruction quality. Observational distance errors also have a significant influence, but it is possible to compensate this relatively well with Wiener Filter reconstruction. We also investigate the effect of different object selection criteria and find that distance catalogues distributed randomly and homogeneously across the sky (such as spiral galaxies selected for the Tully-Fisher method) allow for a higher reconstruction quality than if when data is preferentially drawn from massive objects or dense environments (such as elliptical galaxies). We find that the error of estimating the initial conditions with RZA is always dominated by the inherent non-linearity of data observed at z=0 rather than by the combined effect of the observational errors. Even an extremely sparse dataset with high observational errors still leads to a good reconstruction of the initial conditions on a scale of about 5 Mpc/h.

Localization algorithm based on minimum condition number for wireless sensor networks

During range-based self-localization of Wireless Sensor Network (WSN) nodes, the number and placement methods of beacon nodes have a great influence on the accuracy of localization. This paper proves a theorem which describes the relationship between the placement of beacon nodes and whether the node can be located in 3D indoor environment. In fact, as the highest locating accuracy can be acquired when the beacon nodes form one or more equilateral triangles in 2D plane, we generalizes this conclusion to 3D space, and proposes a beacon nodes selection algorithm based on the minimum condition number to get the higher locating accuracy, which can minimize the influence of distance measurement error. Simulation results show that the algorithm is effective and feasible.

Ring retroreflector system consisting of cube-corner reflectors with special coating

The ring retroreflector system (RS) consisting of cube-corner reflectors (CCRs) with a special coating of reflecting surfaces, intended for uniaxially Earth-oriented navigation satellites, is considered. The error of distance measurement caused by both the laser pulse delay in the CCR and its spatial position (CCR configuration) is studied. It is shown that the ring RS, formed by the CCR with a double-spot radiation pattern, allows the distance measurement error to be essentially reduced.

3D Localization Algorithms for Wireless Sensor Networks

Wireless sensor networks have a great impact on long time monitoring applications (environment monitoring, security surveillance, habitat monitoring etc.) but its potential is yet to be discovered, where it can be deployed in time critical situations when disaster happens. There is a significant gap between existing applications of sensor networks and the requirement of applications supporting rescue operations that involves the catastrophe of human lives. As we are dealing with the human lives here, we can't just rely on the localization schemes that depend upon the connectivity information (range-free) algorithms only. Further, rescue operations are carried out in highly noisy environments, so distance based (range-based) localization algorithms generate high error in distance measurements. An efficient algorithm is needed that can measure the location of the sensor nodes near to the living being or being attached to them in 3-D space with a high accuracy. To achieve such kind of accuracy a combination of both the strategies is required. Further, the algorithms should be efficient and less resource consuming for getting executed on sensor nodes with low processing power. This research proposes an algorithm which incorporates both the range-based and range- free strategies. Keywords - Wireless sensor network (WSN), Localization.

RSS Assisted TOA-Based Indoor Geolocation

The huge distance measurement error in indoor areas and the difficulty of error estimation have posed great challenges to the design of practical TOA-based indoor geolocation systems. In this paper, we presented an RSS assisted TOA-based indoor localization algorithm, which uses RSS to estimate the range of DME for reference node selection and position estimation. This algorithm effectively improves the accuracy of distance measurement and position estimation, and thus improve the localization accuracy of the system. The algorithm is applied into a practical TOA-based indoor geolocation system, developed based on a commercially available device. The results of performance evaluation in a typical office environment show that the localization accuracy of our proposed algorithm is better than the conventional algorithms.

Range imaging: a new method for high-resolution topographic measurements in small- and medium-scale field sites

Topographic measurements are essential for the study of earth surface processes. Three-dimensional data have been conventionally obtained through terrestrial laser scanning or photogrammetric methods. However, particularly in steep and rough terrain, high-resolution field measurements remain challenging and often require new creative approaches. In this paper, range imaging is evaluated as an alternative method for obtaining surface data in such complex environments. Range imaging is an emerging time-of-flight technology, using phase shift measurements on a multi-pixel sensor to generate a distance image of a surface. Its suitability for field measurements has yet not been tested. We found ambient light and surface reflectivity to be the main factors affecting error in distance measurements. Low-reflectivity surfaces and strong illumination contrasts under direct exposure to sunlight lead to noisy distance measurements. However, regardless of lighting conditions, the accuracy of range imaging was markedly improved by averaging multiple images of the same scene. For medium ambient lighting (shade) and a light-coloured surface the measurement uncertainty was approximately 9 mm. To further test the suitability of range imaging for field applications we measured a reach of a steep mountain stream with a horizontal resolution of approximately 1 cm (in the focal plane of the camera), allowing for the interpolation of a digital elevation model on a 2 cm grid. Comparison with an elevation model obtained from terrestrial laser scanning for the same site revealed that both models show similar degrees of topographic detail. Despite limitations in measurement range and accuracy, particularly at bright ambient lighting, range imaging offers three-dimensional data in real time and video mode without the need of post-processing. Therefore, range imaging is a useful complement or alternative to existing methods for high-resolution measurements in small- to medium-scale field sites. Copyright © 2012 John Wiley & Sons, Ltd.

The Design of Millimeter-Level Ultrasonic Distance Measurement Circuit

By analyzing the causes of ultrasonic distance measurement error, through the use of temperature compensation, and increasing the measured time interval to the microsecond level, ultrasonic ranging circuit can achieve the millimeter level. After the circuit design and construction, the ultrasonic range finder was calibrated from 1cm to 21cm. The measurement results show that in the scope of work, the linearity reached 0.999623; the measurement of the ultrasonic range finder achieved the millimeter level.

Cosmology with the lights off: Standard sirens in the Einstein Telescope era

We explore the prospects for constraining cosmology using gravitational-wave (GW) observations of neutron-star binaries by the proposed Einstein Telescope (ET), exploiting the narrowness of the neutron-star mass function. This builds on our previous work in the context of advanced-era GW detectors. Double neutron-star (DNS) binaries are expected to be one of the first sources detected after ``first-light'' of Advanced LIGO. DNS systems are expected to be detected at a rate of a few tens per year in the advanced era, but the proposed ET could catalog tens, if not hundreds, of thousands per year. Combining the measured source redshift distributions with GW-network distance determinations will permit not only the precision measurement of background cosmological parameters, but will provide an insight into the astrophysical properties of these DNS systems. Of particular interest will be to probe the distribution of delay times between DNS-binary creation and subsequent merger, as well as the evolution of the star-formation rate density within ET's detection horizon. Keeping ${H}_{0}$, ${\ensuremath{\Omega}}_{m,0}$ and ${\ensuremath{\Omega}}_{\ensuremath{\Lambda},0}$ fixed and investigating the precision with which the dark-energy equation-of-state parameters could be recovered, we found that with ${10}^{5}$ detected DNS binaries, we could constrain these parameters to an accuracy similar to forecasted constraints from future $\mathrm{CMB}+\mathrm{BAO}+\mathrm{SNIa}$ measurements. Furthermore, modeling the merger delay-time distribution as a power-law ($\ensuremath{\propto}{t}^{\ensuremath{\alpha}}$) and the star-formation rate density as a parametrized version of the Porciani and Madau SF2 model, we find that the associated astrophysical parameters are constrained to within $\ensuremath{\sim}10%$. All parameter precisions scaled as $1/\sqrt{N}$, where $N$ is the number of cataloged detections. We also investigated how parameter precisions varied with the intrinsic underlying properties of the Universe and with the distance reach of the network (which is affected, for instance, by the low-frequency cutoff of the detector). We also consider various sources of distance-measurement errors in the third-generation era and how these can be folded into the analysis.

A Novel Secure Localization Scheme for Wireless Sensor Networks

Localization has great significance for theoretical study and practical applications in wireless sensor networks. Meanwhile, security has been a serious issue and great challenge for the development of localization technologies since attackers can alter localization information to affect the accuracy of localization results. In this paper, we propose a novel secure localization scheme based on signcryption (SLBS) that will allow sensors to assure the confidentiality and integrity of their location information. We perform analysis to explain why SLBS can enhance the security and accuracy of localization through the signcryption mechanism and simulation to verify the performance of SLBS. The analysis and simulation serve to demonstrate that SLBS can effectively reduce localization errors in hostile environments and keep the distance measurement errors within a small range.