Unknown Coordinates Research Articles

A Hybrid Approach for Localisation of Sensor Nodes in Remote Locations

A Wireless Sensor Network (WSN) is a network of sensor nodes using low-power wireless technology to collect data in a region of interest (ROI). Due to their low energy, locating sensor nodes in large outdoor areas is challenging, which precludes GPS integration. WSNs typically comprise a small number of beacon nodes (BN) whose locations are known in advance, with most nodes deployed at unknown coordinates within the ROI. Endeavours to determine the locations of such unknown WSN nodes are largely based on the impractical assumption that every unknown node (UN) is within the communication range of BNs. Subsequently, these approaches utilise at least two BNs to determine the position of one UN. The Received Signal Strength Indicator (RSSI) or Angle of Arrival (AoA) values of the signals from the BNs form the basis for such localisation. This paper suggests an iterative hybrid approach incorporating AoA and RSSI techniques, achieving accurate localisation with just one BN. The iterative method gradually covers the region, avoiding the unrealistic assumption of having all UNs within range. It also presents an innovative use of a unipolar stepper motor for AoA measurements. Experiments in a simulated environment and a real-world prototype validate the approach’s effectiveness.

Subspace‐based distributed target detection method with small training data samples

AbstractDetecting distributed targets precisely in homogeneous environments has been a hot topic in radar signal processing. Generally, distributed targets are often modelled with subspace models of unknown coordinates, and clutter is modelled as the complex Gaussian distribution with zero mean and unknown covariance matrix, while covariance matrix is estimated with a set of training data without the target signal. However, in practice, the complexity of the external environment makes the training data that satisfy the condition of independent homogeneous distribution less available. Therefore, it is assumed that the covariance matrix of the clutter is persymmetric structure and the approach of dimensionality reduction using subspace transformations is introduced, two detectors based upon generalised likelihood ratio test criterion and Wald test criterion in homogeneous environments are proposed. Theoretical analyses indicate the constant false alarm rate characteristics of the two proposed detectors for unknown clutter covariance matrices. Simulation analyses indicate that the proposed detector works well even with fewer training data samples, and its detection performance outperforms that of existing contrast detectors.

MODERN METHODS OF GEODESIC MAPPING OF TERRITORIES: USE OF GPS AND GNSS TECHNOLOGIES

The necessity and expediency of introducing into geodetic production modern satellite technologies based on the use of global navigation satellite systems (GNSS) became obvious in the early 90s of the XX century. New technical means and technologies based on DPS revolutionized the geodetic methods of coordinate determination for both industrial and scientific purposes. The main tasks of GNSS-meters are the calculation with varying accuracy of the current unknown coordinates of points and the rendering in nature of points with known coordinates, as well as a number of additional applications (calculation of distances, calculation of areas, coordinate geometry, breakdown, etc.). In addition to the need to coordinate objects, measurements for GIS also contain a number of additional tasks, among which, first of all, the need to record various attribute data tied to GIS objects. Active development of earth remote sensing technologies using GPS signals began in the late 1980s. and is conducted in several directions: development of technology for building global TEM geodetic maps (GIM); development of GPS cartography methods; development of assimilation models for operational forecasting of territory parameters. The study of remote monitoring technologies using GPS/GNSS signals and the study of the dynamics of cartographic changes of various origins with their help are the subject of this article. An evaluation of the characteristics (sensitivity, spatial and temporal resolution, volume of information received, measurement range) of ground networks of GPS/GNSS receivers designed for registration and monitoring of geodetic benchmarks that mark the territory and allow for the efficient construction of a cartographic module, which is very relevant under during hostilities on the territory of Ukraine.

Calculation algorithm for electromagnetic wave processes in multi-wire intersystem ETL

The nature of the transient process and the magnitude of the overvoltages are determined by a large number of factors in the HV/EHV AC transmission networks. The paper presents the study of mathematical modelling of electromagnetic wave processes in long-distance electric transmission line (ETL). The mathematical model is based on electromagnetic processes occurring on distributed parameter lines that are characterized by specific derivatives of the system of differential equations. The application of a spline-interpolation technique enables the calculation of currents and voltages at the nodes of the scheme, which obtains the unknown coordinates of the overhead line mode at the beginning of the ETL to solve the transmission line equation. The following results are derived from computer simulations of transients during switching on. With a simulation model, the importance of intelligent control of shunt reactor (SR) and ungrounded reactor (UR) was demonstrated and considered for a 500 kV power networks.

Adaptive target detection for an FDA-MIMO radar in a mainlobe deceptive jamming and a partially homogeneous noise

In this paper, we investigate the adaptive target detection problem for a collocated frequency diverse array multiple-input multiple-output (FDA-MIMO) radar in the presence of mainlobe deceptive jamming and partially homogeneous noise with an unknown covariance matrix and scaling factor. Precisely, we establish a received signal model that includes the true target and false counterparts echoes in the presence of Gaussian noise (it includes thermal noise, interference suppression, and clutter after range compensation.). Furthermore, we consider that the range information of the true target and mainlobe deceptive targets is not identical. Therefore, we project the corresponding transmit steering vectors onto different subspaces with known subspace matrices but unknown coordinates. On the other hand, the true and false targets' receive steering vectors are considered to be from the same subspace. Finally, following the generalized likelihood ratio test (GLRT), the Rao and the Wald criteria, we design three adaptive detectors with two-step criteria, i.e., TGLRT, TRao, and TWald. We note that the proposed detectors maintain a constant false alarm rate (CFAR) against the scaling factor and the noise covariance matrix. The extensive numerical simulation results have validated the effectiveness of the proposed detectors.

A Method of Three-Dimensional Videography using Omnidirectional Cameras with Control Points of Unknown Coordinates

A Method of Three-Dimensional Videography using Omnidirectional Cameras with Control Points of Unknown Coordinates

Adaptive double subspace target detection based on gradient test: Designs and comparisons

The issue of adaptive detection for double subspace (DOS) signals under the Gaussian noise background is investigated in this paper. The DOS signal has the special structure where the rows and columns of the matrix-valued signal lie in known subspaces with unknown coordinates. To deal with the DOS signal detection problem, two kinds of Gradient tests are proposed in homogeneous environments and partially homogeneous environments. Remarkably, the Durbin test, as well as its two-step version, is also used for the detector design, which is consistent with the existing methods. To evaluate the performance of the proposed methods, both simulated data and real data collected by IPIX radar are used. The results indicate that the Gradient tests ensure the constant false alarm rate property. Furthermore, the proposed detectors obtain relatively robust characteristics and achieve superior performance to existing competitors in some scenarios.

A two-stage Bayesian model updating framework based on an iterative model reduction technique using modal responses

A two-stage Bayesian model updating framework based on an affine-invariance sampling in Transitional Markov Chain Monte Carlo (TMCMC) algorithm is proposed. In the first stage, unknown modal coordinates are identified with an improved iterative model reduction technique. Subsequently, a modified TMCMC algorithm is proposed where obtaining the statistical estimators in the usual TMCMC algorithm is not necessary. In detail, an affine-invariance sampling approach is proposed to estimate a multi-dimensional scaling (MDS) factor in the affine-transformed space that accounts for the frequencies and mode shapes which are of different natures and dimensions at the levels of likelihood, prior and posterior distributions. The TMCMC sampling adaptively utilizes the plausibility value from the proposed MDS-based tuning algorithm to improve its transition levels. The proposed algorithm in the affine-invariance sampling space accounting for the observables of different dimensions is expected to facilitate the estimation of the posterior distribution of model parameters. The effectiveness of the proposed algorithm is demonstrated by considering a simply-supported steel beam, a ten-storied reinforced concrete building model and an eight-degree-of-freedom spring–mass model for which experimental data is available. The second example demonstrates the applicability of the approach for updating large finite element models involving substructuring.

Persymmetric subspace Gradient-based detectors for distributed targets in homogeneous and partially homogeneous environments

In this paper, we consider the problem of adaptive detection for distributed targets in zero-mean Gaussian clutter with unknown persymmetric covariance matrix. The target signal is assumed to locate in a known subspace with unknown coordinates. Two persymmetric subspace detectors are designed by utilizing the Gradient criterion in homogeneous and partially homogeneous environments, respectively. Additionally, the proposed detectors are theoretically confirmed to be constant false alarm rate to the clutter covariance matrix and the power level. Moreover, numerical results show that the proposed detectors perform better than the existing competitors, especially in training-limited scenarios.

A Three-Dimensional Calibration and Reconstruction Method Using Omnidirectional Cameras with Control Points of Unknown Coordinates

A Three-Dimensional Calibration and Reconstruction Method Using Omnidirectional Cameras with Control Points of Unknown Coordinates

SEARCH FOR SMALL-SIZED OBJECTS ON THE UNDERLYING SURFACE IN FRONT OF THE AIRCRAFT

The method of searching of small-sized ground or surface objects with unknown coordinates is proposed. The search is carried out using the thermal imaging or other IR remote sensing system (RS) of underlying surface (US) in front of the aircraft. The small size of objects requires the use of narrow fields of view for detection and recognition at ranges that allow to carry out operational actions, which are provided for by the flight mission for rescue operations on land and at sea or for aircraft emergency landing on an unprepared site. Two tasks are solved: 1) the maximization of the guaranteed bandwidth of objects searching on US with given characteristics of RS and aircraft speed; 2) the determination of the optimal characteristics of remote sensing systems and aircraft speed for a given search bandwidth of the US.A periodic change in the azimuthal orientation of the narrow field of view (automatic scanning of the US by the field of view of the IR system) is used for solving given tasks. For a given operating range of the IR system the proposed algorithm ensures that the pilot or operator can view the runway on US without “dead” zones (unseen areas). The optimal value of the search effort corresponding to the detection and recognition of objects is determined. The proposed algorithm implements symmetrical scanning (scanned areas of the same shape are formed to the left and right of the flight path on US). The symmetric scanning equation is derived for prediction search efficiency. The solution of given equation makes it possible to find the dependence of the guaranteed search bandwidth on the operating range of ranges in which detection and recognition are possible for given weather conditions. The examples of using the derived equation when searching for objects in simple and difficult weather conditions are given.

The method of adaptive signal reception with adaptive antenna arrays from moving sources

Spatial signal processing in adaptive antenna arrays should provide optimal signal reception from some desired source, this requires maximizing the signal-to-noise ratio at the output of adaptive antenna arrays. This task is well studied for the case when the signal source is fixed and point, and for mobile objects often have to use complex algorithms for controlling adaptive antenna arrays. The relevance of this study is that one of the most promising approaches to solving the problem is to increase the efficiency of signal reception is the use of adaptive antenna arrays and appropriate methods of spatial signal processing.The angular dispersion of the signal is assumed to be due to its multipath propagation in the communication channel. The configuration of adaptive antenna arrays is assumed to be arbitrary. This method allows to reduce the amount of calculations compared to the method when the weight vector with adaptive antenna arrays is optimal and is selected as the eigenvector of the signal correlation matrix and it is possible to maintain the efficiency of the signal is quite high, which determines its novelty.The article analyzes the method of adaptive reception of signals from moving sources using adaptive antenna arrays which is also called the method of quasi-optimal signal processing received by adaptive antenna arrays from a moving source with unknown angular coordinates, the possibility of its reception by mobile subscribers in angular variance. quasi-optimal signal processing with other known methods of signal processing.

Persymmetric subspace GLRT-based detector for range-spread targets

In this paper, adaptive signal detection is addressed for range-spread targets in unknown zero-mean Gaussian clutter with persymmetric covariance matrix. The range-spread target can be expressed as the product of a known subspace and its unknown arbitrary coordinates. Under the above assumptions, a persymmetric subspace detector is devised by utilizing the generalized likelihood ratio test (GLRT). Moreover, the proposed persymmetric subspace GLRT-based detector is theoretically proved to be constant false alarm rate to the unknown clutter covariance matrix. Finally, the numerical results demonstrate the effectiveness of the proposed detector, compared with the existing unstructured competitors and persymmetric ones, especially in the limited training data scenarios.

Persymmetric subspace detector for distributed target in partially homogeneous environment

This paper deals with the problem of distributed target detection in partially homogeneous Gaussian clutter whose covariance matrix is unknown but persymmetric. It is assumed that primary data and training data share the same clutter covariance matrix structure but different power levels. The target signal is supposed to lie in a multi-rank subspace with unknown coordinates. A persymmetric subspace detector is designed based on the generalised likelihood ratio test criteria. It is theoretically demonstrated that the proposed detector possesses constant false alarm rate property with respect to the unknown clutter covariance matrix as well as the power level. Experimental results illustrate the performance advantage of the proposed detector over the existing competitors, especially in training-limited scenarios.

An Enhanced DV-Hop Positioning Scheme Based on Spring Model and Reliable Beacon Node Set

How to get the node position, as a hotter topic in the field of wireless communication, is the primary problem to be solved in wireless sensor networks (WSNs). The DV-Hop positioning scheme is a kind of range-free positioning scheme, which has been favored by researchers in recent years. However, the original DV-Hop scheme faces the shortcoming of low positioning precision and stability. To ameliorate the positioning capability of the DV-Hop, an enhanced DV-Hop scheme based on the spring model and reliable beacon node set has been presented in this paper. Firstly, the relationship between nodes in the network is abstracted as a spring model, and the distance between unknown nodes and beacon nodes is corrected by comprehensively considering the influence of each beacon node from the physical phenomenon of force vector decomposition. After that, based on the random sample consensus (RANSAC) algorithm, the reliable beacon nodes with smaller distance deviation to the unknown node are picked out to compute the unknown node coordinates, rather than all beacon nodes participating in the calculation. Finally, extensive experiments have been conducted on distance accuracy and positioning performance. Simulation results demonstrate that our proposed positioning scheme outperforms better than original DV-Hop and other existing improved schemes under different scenarios.

Improvement of triangle centroid localization algorithm based on PIT criterion (ITCL-PIT) for WSNs

One of the most significant study directions is node positioning in wireless sensor networks (WSNs). Because the existing RSSI-based triangle centroid localization technique is susceptible to the surrounding environment, this paper proposes an improved triangle centroid localization algorithm based on point-in-triangulation (PIT) criterion (ITCL-PIT) in terms of positioning accuracy and response speed. When combined with the actual placement situation in conventional triangle centroid localization, the suggested algorithm considers the estimated coordinates of the junction points as extra beacon nodes. As a result of the new beacon nodes, the size of the triangle in the junction region is decreased. Then, using the PIT criteria, keep calculating until the predicted position of the node is outside the triangle. Finally, the unknown node's coordinates are determined using the centroid approach. Based on the guaranteed response time, when the communication distance is 15–30 m, the ITCL-PIT method may enhance localization accuracy by up to five times when compared to the standard triangle centroid localization approach. Furthermore, the proposed technique has higher localization accuracy and faster response speed than the centroid iterative estimation approach, and the response time of the ITCL-PIT algorithm is reduced by around 17%. In addition, the experimental platform is built to ensure that the proposed strategy effectively lowers positioning error.

Development of a calibration method for a pan-tilt camera using a fixpoint and corresponding points with unknown 3D coordinates

Development of a calibration method for a pan-tilt camera using a fixpoint and corresponding points with unknown 3D coordinates

Nonlinear method for determining external orientation elements of digital images obtained from drone

We have suggested the method of application of a direct solving of the systems of nonlinear equations for finding the elements of external orientation (EEO) to perform aerial photography by unmanned aerial vehicles (UAVs). The elements of external orientation functions search for the minimum of the function F , which is the sum of squares of coordinate differences on the image and is calculated by the measured coordinates on the ground, or the minimum of the function G, which is constructed using co-linearity and is the sum of squares of differences of the given coordinates Xi, Yi, Zi (i=1,2,…,n) on the ground and those which were calculated by the values xi, yi (i=1,2,…,n) measured on the image. In contrast to the classical approach, the choice of such a type of function is due to the possibility of implementing the algorithm using mathematical packages. Since some of the unknown coordinates Xi, Yi, Zi (the origin of the coordinate system is the center of projection) are included in the function G as arguments linearly, fulfillment of the conditions of the minimum of this function (equality of partial zero derivatives) in this case is simpler. This allows us to determine them through the angular elements of the EEO, which reduces the system of six equations to the system of three equations, being dependent on the angular elements. The function G is differentiated with respect to the variables dependent on the angular elements to obtain the three other equations. The obtained in this way system of equations is solved by the parameter variation method and gives us the solution of the required EEOs with a given accuracy. The proposed algorithm gives us a real opportunity to clarify the values of EEO, moreover, the linear EEOs are determined with maximum accuracy, that makes it possible to increase the accuracy of the spatial coordinates of the points of the terrain. The application of digital image processing from UAVs will significantly extend the range of implementation of aerial photography from UAVs to solve a variety of topographic, cadastral and engineering problems. The proposed technique was tested on the relevant materials of aerial photography from UAVs at control points, which made it possible to confirm the optimality of the technique.

Inverse problem for cracked inhomogeneous Kirchhoff\u2013Love plate with two hinged rigid inclusions

We consider a family of variational problems on the equilibrium of a composite Kirchhoff–Love plate containing two flat rectilinear rigid inclusions, which are connected in a hinged manner. It is assumed that both inclusions are delaminated from an elastic matrix, thus forming an interfacial crack between the inclusions and the surrounding elastic media. Displacement boundary conditions of an inequality type are set on the crack faces that ensure a mutual nonpenetration of opposite crack faces. The problems of the family depend on a parameter specifying the coordinate of a connection point of the inclusions. For the considered family of problems, we formulate a new inverse problem of finding unknown coordinates of a hinge joint point. The continuity of solutions of the problems on this parameter is proved. The solvability of this inverse problem has been established. Using a passage to the limit, a qualitative connection between the problems for plates with flat and bulk hinged inclusions is shown.

Estimation of the synchronization error for spaced-apart ground points of satellite communication

A significant number of patents and publications in the open press show the intensity of the ongoing research to create new methods of synchronization and specialized ground-based equipment for frequency-time synchronization. The article considers the implementation of an autonomous synchronization system between ground-based satellite communication points, which is used in conditions of unfavorable reception or absence of signals from global navigation satellite systems. The paper presents studies on the assessment of the error of time synchronization of geographically separated ground points of satellite communications. The basics of constructing the receiving equipment of a radio engineering system are considered and the mutual correlation of the reference signal of the receiving equipment and the received input synchronization signal is calculated. The results of field tests of mutual synchronization equipment are presented, where the potential synchronization accuracy of equipment at ground objects with previously unknown coordinates was determined, while the synchronization equipment provided measurement of the signal propagation time from one ground object to another with the formation of universal time scales on points. The method of mutual synchronization of linked points is carried out by the duplex method at a frequency of 1065 MHz (request) and 625 MHz (response) by phase-code-manipulated signals with a base equal to 1023 and a duration of 0,1 ms.