Position Of Reference Point Research Articles

A Map-Aided Fast Initialization Method for the Magnetic Positioning of Vehicles

Magnetic positioning is a promising technique for vehicles in global navigation satellite system (GNSS)-denied scenarios. In general, a fixed-length magnetic sequence is required to provide an initial positioning result, which means that users need to wait a relatively long distance. To minimize this initialization distance, a map-aided fast initialization method, including magnetic database construction and magnetic positioning, is proposed in this paper. For magnetic database construction, a multisource fused database is established using a precise and effective strategy in which the positions of reference points (RPs) and the diverse information of paths are obtained from the map and the magnetic field is calculated using data collected during driving. For magnetic positioning, we innovatively propose a coarse–fine combination method that improves the positioning accuracy within a short distance. In the coarse map matching stage, by detecting the vehicle’s motion and utilizing the topological relationships between paths, the search range is precisely narrowed. In the fine magnetic localization stage, an improved mean absolute difference (MAD) metric and a derivative metric are combined to form a joint matching criterion to determine the positioning result. The experimental results illustrate the importance of each module in the proposed method, which improves the precision of the database up to 80% and significantly shortens the initialization distance up to 50%.

Indoor positioning fingerprint database construction based on CSA-DBSCAN and RCVAE-GAN

With the increasing size of buildings, in order to achieve high-precision indoor positioning services, it is a challenging task to build an offline fingerprint database with high quality, high density and less manpower and material consumption. Aiming to solve the problem of low-quality WiFi indoor positioning fingerprint inventory constructed by traditional methods, which affects positioning accuracy and incurs high costs, this paper proposes a method for indoor positioning fingerprint database construction based on Crow Search Algorithm Optimizes Density Clustering (CSA-DBSCAN) and Regressor Conditional VAE Generative Adversarial Network (RCVAE-GAN). Collecting only a tiny amount of sparse reference point position coordinates and RSS data makes it possible to construct a high-quality WiFi indoor positioning fingerprint database. Firstly, the method utilizes the density clustering method based on Crow Search Algorithm Optimization (CSA-DBSCAN) to process RSS data collected from the reference point. This helps minimize the impact of abnormal RSS data on creating the fingerprint database. Secondly, the RCVAE-GAN depth generation model was developed. The model consists of an encoder E, a generator G, a discriminator D, and a regressor R. After constructing the model, the data with abnormal RSS will be removed and input into the model for pre-training and joint training, resulting in a high-quality deep-generation model. Finally, a high-quality and high-density fingerprint database is constructed by combining the collected reference points with fingerprint data generated by the depth generation model. Experimental results show that the proposed method reduces the root mean square error (RMSE) deviation of the generated fingerprint data by 38% and 12% respectively, compared to the RBF interpolation method and the CVAE-GAN method in the same experimental scenario. The constructed fingerprint database is used for positioning, improving positioning accuracy by 70% and 65% respectively. The method described in this paper can construct a high-quality fingerprint database, effectively improving the efficiency of fingerprint database construction and reducing the costs associated with labor and time.

Prototype System for Unmanned Reference Point Determination at the Sub‐Millimeter Level

AbstractThe determination of reference points for telescopes is crucial for obtaining the local‐tie vector for a multi‐technology co‐located station. Traditional methods suffer from labor‐intensive fieldwork, long execution cycles, and systematic errors due to the incident angle of the total station's laser beam on the prism. In this paper, we propose an algorithm aligning the prism pointing vector with the prism‐to‐total station vector and introduce a pan‐tilt platform and the Tianma VGOS telescope for sub‐millimeter unmanned reference point monitoring. Our results show that the prototype system based on the pan‐tilt achieves a formal error of ±100 μm (1σ) in reference point positions with just 2.5 hr of automated monitoring. The consistency of reference point positions is comparable to the local control network accuracy. Single‐direction observations may introduce a deviation of ±1 mm in the reference point compared to multiple direction observations. Preliminary experiments on the Tianma VGOS telescope have also shown that this system can efficiently automate the monitoring of prism scatter points (one measurement every minute) and achieve sub‐millimeter horizontal precision in reference point positions within a single day.

Multi-scale peridynamic investigation of chloride penetration in concrete under drying-wetting cycles

A multi-scale peridynamic (PD) model was developed to simulate chloride penetrating process in concrete under drying-wetting cycles. The meso‑structure characteristics of concrete and advection-diffusion were considered simultaneously. The governing equations of chloride penetrating during drying-wetting cycles was originally established under the framework of PD theory. Subsequently, the corresponding boundary conditions for wetting and drying process were constructed. The accumulative effect of chloride under drying-wetting cycles was taken into account with the superposition method. Numerical examples demonstrate that the multi-scale PD model is robust and efficient in capturing the variation of chloride concentration and relative humidity. The results show that with the approach to the exposed surface, the differentials of relative humidity rise significantly. The chloride concentration is affected by positions of reference points and relative humidity. Namely, it increases first and then decrease or remain constant during every drying-wetting cycle. Notably, the maximum chloride concentration occurs in a region adjacent to exposed surface rather than on the exposed surface, which coincides well with the experimental phenomenon reported in the literature.

Quantum-inspired optimization algorithm with adaptive correction of energy position: Methodology and a case study

Efficient and stable global optimizers constitute a noteworthy arena of academic study and real-world applications. Since Multi-scale Quantum Harmonic Oscillator Algorithm inspired by the quantum motion for solving optimization problems was proposed, considerable contributions regarding this algorithm have been achieved in recent years. Nevertheless, issues such as the aggregation effect during sampling as well as recurrence and blindness in random searches hinder the performance of the algorithm. Motivated by this situation, a variant of Multi-scale Quantum Harmonic Oscillator Algorithm is put forward to improve the efficiency of the system convergence while maintaining the solution diversity. The measurement of the solution position through the collapse of the quantum state to the classical state is realized by means of quantum Monte Carlo simulations, and the energy position is established as a metric for energy observation. Then, the adaptive correction of the energy position is explored to improve algorithm performance. The core idea of our mechanism is to adaptively guide the candidate solutions toward convergence to the ground state by means of attractive factors based on the relationship among the energy positions of several reference points. Experimental results obtained on the CEC2013 benchmark functions and a real-world application indicate that the performance of our scheme is competitive and that it achieves prominence among the compared algorithms as the dimensionality increases.

GEODETIC WORKS TO DETERMINE VERTICAL MOVEMENTS AT THE ZHAMBYL GEODYNAMIC POLYGON

This article discusses the issues of determining the current movements of the Earth's surface by geodetic methods at the Zhambyl predictive geodynamic polygon. The article discusses the characteristics of predictive polygons in the Republic of Kazakhstan. The data of vertical movements of the Earth's surface on the territory of the Zhambyl geodynamic polygon are presented. The results of high-precision leveling for 2020 and 2022 are presented, which made it possible to plot vertical displacement graphs and analyze changes in the position of geodetic reference points. The analysis showed that in the study area there are slight vertical displacements from -0.01 to -0.06 mm/year, which do not exceed the allowable possible accumulation of measurement errors.

Coherence and coherence vortex embedded in partially coherent Gaussian beam background during propagation

This work presents theoretical analysis on coherence vortex of partially coherent vortex beam (PCVB) during propagation. Complex degree of coherence is analyzed to explore the coherence singularity embedded in PCVB in detail. It is shown that observation of coherence singularity is related to position of reference point, and coherence singularities appear in pairs while the reference point is located far from the center. Detailed investigation reveals that it is easy to distinguish coherence singularity for the case of near field and for the case of original PCVB with high coherence.

An Image Planar Positioning Method Base on Fusion of Dual-View Airborne SAR Data

Effective utilization of airborne synthetic-aperture (Airborne SAR) imagery often requires precise location of each image pixel. Historically, the positioning of airborne SAR imagery either relies on the use of reliable reference points to determine the relative position of the image, or requires the precise motion information of the aircraft and the characteristics of the SAR data collection system as input to determine the absolute position of the image. However, for many applications, the accuracy of traditional positioning methods is not high due to the challenge in obtaining the accurate geographic positions of reliable reference points and the inaccuracy of the recorded aircraft motion information. This study introduces an airborne SAR image planar positioning approach based on the premise that the systematic positioning error of the dual-view airborne SAR images are relatively consistent. The suggested planar positioning method applies the positioning auxiliary parameters of the initial ground-range airborne SAR image to ascertain the transformation relationship between the target’s initial geographic position and pixel position, and it then uses the equivalent equation for the position of the homologue point to assess the systematic positioning error of the SAR image and determine the geographic position of a pixel in a digital SAR image. This approach has advantages over previous techniques in that it requires no precise geographic position information of the ground reference points, and on the basis of using the RD model to accomplish coarse positioning of four corners of SAR image, it no longer needs aircraft trajectory data. Tests were conducted using two airborne SAR images actually captured, and the experimental results indicate that the proposed method can achieve high precision planar positioning of dual-view airborne SAR images. Error sources are analyzed and recommendations are given to improve image positioning accuracy in future airborne SARs.

Schemes for locating and fixing the object in self-centering mechanisms with a set of hidden bases

The updated provisions of the basing theory and the updated composition of the bases are given: installation, guide, support, double guide, double support, and triple support. Base combinations form five sets, each of which can be implemented using explicit or hidden bases or their combinations. It is shown that basing an object with sets of hidden bases causes the greatest difficulties, and a feature of basing an object with hidden bases is determining the position of reference points using the contact points of the object, implemented by the installation elements. When basing an object with a hidden base, the position of the reference point is determined by a self-centering mechanism using the points of contact with the basing object. Various schemes of constructive solutions for basing and fixing objects in sets of hidden bases in self-centering mechanisms are considered.

FEATURES OF CREATION AND RESTORATION OF SUPPORTING GEODESIC NETWORK IN ROAD CONSTRUCTION MEASUREMENTS

The success of the implementation of projects of capital repairs, reconstruction or new construction of roads and man-made structures depends on the quality of geodetic support. Geodetic marking works must accompany the process of construction or repair work. Particular attention should be paid to the peculiarities of the creation and restoration of the geodetic support network in road construction, as these issues have a primary impact on the success of development and implementation of repair and construction projects and therefore affect the entire life cycle of the highway. The laying of points of the geodetic reference network is performed in order to ensure topographic survey at the stage of surveys and to ensure further marking works at the stage of overhaul, reconstruction or new construction of the highway. The project of creating a geodetic reference network must be included in the main work program or compiled separately and agreed with the customer. The project of creating a geodetic reference network must display information on the type of network points, density and location of points, methods of geodetic measurements, coordinate systems and heights, basic requirements for the accuracy of the position of geodetic reference points and requirements for reporting materials in the technical report. The location, type of fastening, construction and external design of the points of the basic geodetic network must ensure the preservation of the spatial position, protection from damage and loss of points. Metal structures of geodetic signs and design elements must be protected from corrosion by a special anti-corrosion coating. The location of the points is determined after the reconnaissance work, study of the initial data and the needs of design, construction and operation. The proposed features of creation and restoration of the basic geodetic network in road construction are reflected in DSTU 9154:2021 «Guidance on performance of geodesic works in road building».

A novel method for generation of particle packing model used in numerical simulation for the mechanical behavior of multi-component material

This study presents a novel algorithm to establish a numerical model for the study of mechanical behavior of multi-component material such as particle reinforced metal matrix composites, concrete, particle filled polymers, etc. The algorithm consists of two steps, one is to divide the given region into sub-regions of a specified size distribution, and the other is to fill each sub-region with particles of specified shapes. During the filling process, the contact states between particles can be controlled by the number and positions of reference points. Taking the quasi-static uniaxial tensile simulation of concrete as a verification example, two concrete models with the same particle size distribution but different shapes have been established. Through the comparison of elastoplastic responses of different aggregate shape models in different tensile directions, it is concluded that the models meet the requirements of macroscopic uniformity, meso-scale randomness and statistical rationality. This verifies the feasibility of modeling method and its advantages in precise control of particle shape, distribution and other parameters.

Late Quaternary evolution of the Metaponto coastal plain, southern Italy, inferred from geomorphological and borehole data

A multidisciplinary study of a sector of the Ionian coastal belt, southern Italy, mainly based on two new boreholes approximately 25 m (MSA) and 20 m (MSB) deep, was carried out in the frame of a wider geoarchaeological project. Stratigraphic and Paleoecological data, together with geomorphological observations, have been used in order to define the Late Quaternary morpho-sedimentary evolution and its relationships with tectonic and climate forcing. The analyses of core sediments and geomorphic interpretations allowed us to reconstruct the changes in depositional setting and physical landscape starting from the MIS 5.5. To this scope, new data about sedimentary facies, benthic foraminifera and ostracod assemblages, and a set of 14C ages spanning from about 33 to 15 kyr BP are here presented. All these data revealed a strong modification of the depositional setting within the coastal plain, as inferred by the presence of marine, transitional, and continental deposits, and suggest an anomalous position of sea-level reference points. Such anomalies are clustered in two homogenous arrays that can be explained only admitting a significant tectonic uplift in recent times (i.e. about 4 mm/yr over the last 15,000 years).

Referencing for intraoperative navigation: Evaluation of human bias

Navigation-assisted surgery is the gold standard for complex reconstructive procedures of the midface and facial skeleton, and artificial and anatomical landmarks are often used for reference. The correct identification of these landmarks before surgery is crucial for the accuracy of the navigation system. This study aimed to investigate the human errors in reference point placement. This retrospective study investigated 228 reference-point positions in 51 cases where navigation was utilized. The discrepancies between the actual reference point-position and manually planned preoperative reference points were quantified using Brainlab iPlanCMF 3.0.6. The referencing methods used in these cases included dental registration splints, osteosynthesis materials, anatomical landmarks, and combinations of these methods. The average discrepancy in the actual and manually planned reference points was 0.29 ± 0.41 mm. The use of anatomical landmarks demonstrated a significantly lower deviation (p < 0.05), although the differences between the errors in reference-point placement using dental registration splints, osteosynthesis materials, or combinations of these methods were not statistically significant. The frequency of misplacement of reference points was significantly higher than expected. These errors might have been caused by human bias during manual placement of the points or intraoperative difficulties caused by extensive metal artifacts. Thus, we postulate that the surgical personnel involved in planning navigation-assisted surgery should undergo intensive training. The development of new referencing methods that are less susceptible to these causes of error might help overcome human bias.

On measuring the 3D dose distribution for notched and circular Ru-106 plaque shapes through Gafchromic film dosimetry approach

Ruthenium-106 (106Ru) plaques are specific applicators dedicated for intraocular brachytherapy. Small tumor volume and presence of vital organs in its close vicinity as well as appearance of very high dose gradient regions around the employed plaques cause unique challenges in plaque-based brachytherapy. Therefore, access to 3D dose distribution for each brachytherapy plaque is quite helpful to decide about tumor volume coverage and overexposure of surrounding sensitive organs. Current study aims to measure the 3D dose distribution for two commercially available 106Ru plaques using film dosimetry.COB (a notched-shape plaque) and CGD (a fully circular plaque) 106Ru plaques were used and dose distributions in different planes were measured by simultaneously employing a 3D printed eyeball phantom and Gafchromic EBT3 films. Finally, 3D dose distributions were acquired by interpolating the measured 2D dose data at different planes.The results showed that employing the COB plaque tilts the isodose curves toward the non-notched edge of the plaque, while no isodose tilting was observed for CGD plaque. The obtained 3D dose distributions were different for studied plaques. Non-uniform 3D dose distributions were found for both plaques which can be attributed to the plaque design and reference point position on plaque central axis.Finally, it can be concluded that the obtained 3D dose distributions can specify the optimal tumor shape which can be adequately covered by brachytherapy plaque with minimizing the dose non-uniformity and hot point formation inside the treated volume. Obtained 3D dose distribution for each plaque can be employed for patient treatment planning.

Evaluation of static belt fit and belt torso contact for children on belt-positioning booster seats

Objective: Previous studies have indicated that gap between the seatbelt and torso (reduced belt torso contact) for children on belt-positioning booster seats (BPBs) may lead to less torso engagement and increased likelihood of shoulder belt slip-off during evasive vehicle maneuvers, potentially increasing injury risk during crashes. However, current BPB belt fit measures do not quantify belt gap and may not be able to fully discriminate between designs which provide good vs. poor dynamic outcomes. The goal of this study was to evaluate both novel (belt gap characteristics) and conventional measures of seatbelt fit for BPB-seated children. Methods: Ten BPBs and three seatbelt anchor locations were investigated. Fifty volunteers (4-14 years) were recruited and each evaluated on six unique combinations of BPB and seatbelt anchor location on a vehicle rear seat in a laboratory setting. A 3 D coordinate measurement system quantified positions of anatomic, seatbelt, BPB, and vehicle reference points. Novel belt gap (gap size, length, location, and percent torso contact) and conventional belt fit (position of belt on shoulder and pelvis) metrics were calculated using anatomic and seatbelt landmarks. Variation in belt fit and belt gap outcomes due to BPB, seatbelt anchor location, and anthropometry were investigated. Results: BPBs produced significantly different outcomes, while seatbelt anchor location did not. BPBs with features that directly routed the lower portion of the shoulder belt more forward on the buckle side produced the largest (29.3 ± 12.6 mm) and longest (106.9 ± 68.2 mm) belt gap on average, while BPBs that pulled the belt less forward or did not directly route the belt produced the smallest (13.9 ± 6.7 mm) and shortest (16.9 ± 33.9 mm) gap on average. Belt gap outcomes were not strongly correlated with conventional belt fit metrics, indicating that evaluation of belt gap may provide additional insight when attempting to discriminate between BPBs which provide good vs. poor seatbelt engagement during vehicle maneuvers and crashes. Conclusions: This is the first study to evaluate belt gap characteristics for BPB-seated children. Results suggest that belt fit and belt gap are influenced by BPB design, particularly lower shoulder belt routings, and may have implications for belt engagement during dynamic events.

Development and validation of a new set-up simulator dedicated to ocular proton therapy at CNAO.

An Eye Tracking System (ETS) is used at CNAO for providing a stable and reproducible ocular proton therapy (OPT) set-up, featuring a fixation light (FL) and monitoring stereo-cameras embedded in a rigid case. The aim of this work is to propose an ETS set-up simulation algorithm, that automatically provides the FL positioning in space, according to patient-specific gaze direction and avoiding interferences with patient, beam and collimator. Two configurations are provided: one in the CT room for acquiring images required for treatment planning with the patient lying on a couch, and one related to the treatment room with the patient sitting in front of the beam. Algorithm validation was performed reproducing ETS simulation (CT) and treatment (room) set-up for 30 patients previously treated at CNAO. The positioning accuracy of the device was quantified through a set of 14 control points applied to the ETS case and localizable both in the CT volume and in room X-ray images. Differences between the position of ETS reference points estimated by the algorithm and those measured by imaging systems are reported. The corresponding gaze direction deviation is on average 0.2° polar and 0.3° azimuth for positioning in CT room and 0.1° polar and 0.4° azimuth in the treatment room. The simulation algorithm was embedded in a clinically usable software application, which we assessed as capable of ensuring ETS positioning with an average accuracy of 2mm in CT room and 1.5mm in treatment room, corresponding to gaze direction deviations consistently lower than 1°.

Dynamic Deformation Monitoring of Lotsane Bridge Using Global Positioning Systems (GPS) and Linear Variable Differential Transducers (LVDT)

The measurements and analysis of deformation of engineering structures such as dams, bridges and high-rise buildings are important tasks for civil engineers. It is evident that, all civil engineering structures are susceptible for deterioration over a period of time. Bridges in particular, deteriorate due to loading conditions, environmental changes, earth movement, material used during construction, age and corrosion of steel. Continuous monitoring of such structure is the most important aspect as it provides quantitative information, assesses the state of the structure, detects unsafe positions and proposes early safety measures to be taken before it can threaten the safety of vehicles, goods and human life. Despite government’s efforts to construct roads and highways, bridge deformation monitoring has not been given priority in most of African countries and ultimately causes some bridges to collapse unexpectedly. The purpose of this research is to integrate Global Positioning System (GPS) and Linear Variable Differential Transducers (LVDT) to monitor deformation of a bridge. The horizontal positions of reference and monitoring points were determined using Global Positioning System (GPS) while the vertical deflections, accelerations and strain were determined using Linear Variable Differential Transducers (LVDT). The maximum displacements obtained between zero and first epochs in x, y and z components were 0.798 m, at point LT08, 0.865 m at point BR13, and 0.56 m at point LT02 respectively. The maximum deflections for LVDT 1, 2 and 3 are 28.563 mm, 31.883 mm and 40.926 mm respectively. Finally, the correlation coefficient for the observations was 0.679 with standard deviations of 0.0168 and 0.0254 in x and y respectively. Our results identified some slight displacements in horizontal components at the bridge.

Smoothing method of generating flank milling tool paths for five-axis flat-end machining considering constraints

Gouging and collision avoidances, tool path smoothness, and geometric deviation should be considered concurrently when generating a five-axis flank milling tool path. The tool orientations of the generated tool path, which can achieve smooth rotary axis motions of the machine tool, can improve the machining quality. Tool orientation planning for five-axis ball-end machining does not affect the position of the ball center point. However, different from ball-end cutters, tool orientation adjustments for flat-end machining will affect the cutter reference point position, which may cause local gouging between the bottom circular edge of the flat-end cutter and the constraint surfaces of the workpiece or excess uncut material left. Hence, generating a smooth flank milling tool path for five-axis flat-end machining which meets all the requirements is a challenge. To deal with this problem, a method of smoothness flank milling tool path generation for flat-end cutters considering constraints is developed in this research, which can minimize the angular accelerations of the rotary axes. B-spline curves are used to represent the displacements of the rotary axes so that the rotary axes’ motions along the tool path can be directly smoothed. The sum of the squares of the first, second, and third derivatives of the cutter reference point trajectory and the two rotary axes’ displacement curves are then utilized as the smoothness indicators for the five-axis tool paths. The method of tool orientation and positioning adjustments for flat-end cutters based on the differential rigid body motion is also presented, ensuring the bottom circular edge of a flat-end cutter is tangent to the constraint surfaces of the workpiece along the tool path. Besides, the discrete vector model is utilized to represent the workpiece geometry, and intersection points between the discrete vectors and the tool swept envelope are calculated to determine the geometric deviation for a flank milling tool path. Finally, a multi-objective optimization problem with constraints is established to generate flank milling paths with flat-end cutters. Numerical examples and machining tests are carried out to confirm the validity and effectiveness of the proposed approach.

Assessment of Static Positioning Accuracy Using Low-Cost Smartphone GPS Devices for Geodetic Survey Points’ Determination and Monitoring

Recent developments enable to access raw Global Navigation Satellite System (GNSS) measurements of mobile phones. Initially, researchers using signals gathered by mobile phones for high accuracy surveying were not successful in ambiguity fixing. Nowadays, GNSS chips, which are built in the latest smartphones, deliver code and primarily carrier phase observations available for detailed analysis in post-processing applications. Therefore, we decided to check the performance of carrier phase ambiguity fixing and positioning accuracy results of the latest Huawei P30 pro smartphone equipped with a dual-frequency GNSS receiver. We collected 3 h of raw static data in separate sessions at a known point location. For two sessions, the mobile phone was mounted vertically and for the third one—horizontally. At the same time, a high-class geodetic receiver was used for L1 and L5 signal comparison purposes. The carrier phase measurements were processed using commercial post-processing software with reference to the closest base station observations located 4 km away. Additionally, 1 h sessions were divided into 10, 15, 20 and 30 min separate sub-sessions to check the accuracy of the surveying results in fast static mode. According to the post-processing results, we were able to fix all L1 ambiguities based on Global Positioning System (GPS)-only satellite constellation. In comparison to the fixed reference point position, all three 1 h static session results were at centimeters level of accuracy (1–4 cm). For fast static surveying mode, the best results were obtained for 20 and 30 min sessions, where average accuracy was also at centimeters level.

Slope Monitoring System

PROBLEM TO BE SOLVED: To make graspable precisely the state of a slope by reducing dispersion in slope displacement data and reducing missing data. SOLUTION: A GPS transmitter which is a reference point is arranged on a position outside the slope, and one or more GPS transmitters are arranged on positions in the slope. A monitoring center acquires reference point position information for showing the position of the reference point GPS transmitter and position information for showing the positions of the GPS transmitters arranged on the slope, and acquires slope displacement data by determining the slope displacement based on the reference point position information and the position information. The monitoring center evaluates the slope displacement data corresponding to an evaluation index specified beforehand, and displays the slope displacement data, classified by color, corresponding to the evaluation result. In the monitoring center, preference of the slope displacement data is evaluated based on the evaluation index, and the slope displacement data determined not to be preferential are taken as missing slope displacement data, and the missing slope displacement data are interpolated based on the preferential slope displacement data determined to be preferential. COPYRIGHT: (C)2004,JPO&NCIPI