System error iterative identification for underwater positioning based on spectral clustering

The observation error model of the underwater acous-tic positioning system is an important factor to influence the positioning accuracy of the underwater target.For the position inconsistency error caused by considering the underwater tar-get as a mass point,as well as the observation system error,the traditional error model best estimation trajectory(EMBET)with little observed data and too many parameters can lead to the ill-condition of the parameter model.In this paper,a multi-station fusion system error model based on the optimal polynomial con-straint is constructed,and the corresponding observation sys-tem error identification based on improved spectral clustering is designed.Firstly,the reduced parameter unified modeling for the underwater target position parameters and the system error is achieved through the polynomial optimization.Then a multi-sta-tion non-oriented graph network is established,which can address the problem of the inaccurate identification for the sys-tem errors.Moreover,the similarity matrix of the spectral cluster-ing is improved,and the iterative identification for the system errors based on the improved spectral clustering is proposed.Finally,the comprehensive measured data of long baseline lake test and sea test show that the proposed method can accu-rately identify the system errors,and moreover can improve the positioning accuracy for the underwater target positioning.

Measuring the Accuracy and Precision of the Garmin GPS Positioning in Forested Areas： A Case Study in Taxiarchis-Vrastama University Forest

In this paper, it is attempted to examine and compare different orientation, one recreational and another more precise, in the performance of two （global positioning system） receivers of forested areas. In doing this, a field test on horizontal and vertical positional errors of GPS positioning at different points in the forested area of Taxiarchis-Vrastama University forest was conducted. The two GPS receivers were used to determine the positional accuracy of a selected number of points under tree canopies. Specifically, the precision and accuracy of Garmin＇s GPS positioning at different points were calculated and compared with the corresponding positioning and accuracy of another GPS system, namely the TOPCON GPS. By the calculation of various measures of accuracy and precision suitable for GPS receivers and the use of statistical methods, accuracy between the different receivers differed significantly is shown. Also, regression analysis revealed that the basal area and the number of available satellites are the most important factors for predicting position error.

How crystal configuration affects the position detection accuracy in pixelated molecular SPECT imaging systems?

It is well known that inter-crystal scattering and penetration(ICS-P) are major spatial resolution limiting parameters in dedicated SPECT scanners with pixelated crystal.In this study,the effect of ICS-P on crystal identification in different crystal configurations was evaluated using GATE Monte Carlo simulation.A ^(99m)Tc pencil-beam toward central crystal element was utilized.Beam incident angle was assumed to vary from 0° to 45° in 5° steps.The effects of various crystal configurations such as pixel-size,pixel-gap,and crystal material were studied.The influence of photon energy on the crystal identification(CI) was also investigated.Position detection accuracy(PDA) was defined as a factor indicating performance of the crystal.Furthermore,a set of ^(99m)Tc point-source simulations was performed in order to calculate peak-to-valley(PVR) ratio for each configuration.The results show that the CsI(Na)manifests higher PDA than NaI(TI) and YAP(Ce).In addition,as the incident angle increases,the crystal becomes less accurate in positioning of the events.Beyond a crystal-dependent critical angle,the PDA monotonically reduces.The PDA reaches 0.44 for the CsI(Na) at 45° beam angle.The PDAs obtained by the point-source evaluation also behave the same as for the pencil-beam irradiations.In addition,the PVRs derived from flood images linearly correlate their corresponding PDAs.In conclusion,quantitative assessment of ICS-P is mandatory for scanner design and modeling the system matrix during iterative reconstruction algorithms for the purpose of resolution modeling in ultra-high-resolution SPECT.

Error Analysis on the Positioning Accuracy of a Pneumatic Vibration Isolator

A method of error analysis on the positioning accuracy of a pneumatic vibration isolator was proposed.First,the necessity of positioning accuracy was studied,in addition to the key factors associated with positioning accuracy.These analyses indicated that the positioning accuracy of the pneumatic vibration isolator was mainly attributed to the position error of the push button and the gap between the spindle and valve stem.Second,the error model of the positioning accuracy of the pneumatic vibration isolator was established through geometric simplification and geometric calculation.There are different methods used to calculate the position error of the push button for the different valves.Finally,an example analysis evaluating the impact of a specific two-position three-way valve on the positioning accuracy was given by means of error distribution.Experimental results validated the accuracy of the error model and the example analysis.This error model can be used to guide the structural parameter optimization design according to the requirements for positioning accuracy.

A Review of Device-Free Indoor Positioning for Home-Based Care of the Aged:Techniques and Technologies

With the development of urbanization,the problem of neurological diseases brought about by population aging has gradually become a social problem of worldwide concern.Aging leads to gradual degeneration of the central nervous system,shrinkage of brain tissue,and decline in physical function in many elderlies,making them susceptible to neurological diseases such as Alzheimer’s disease(AD),stroke,Parkinson’s and major depressive disorder(MDD).Due to the influence of these neurological diseases,the elderly have troubles such as memory loss,inability to move,falling,and getting lost,which seriously affect their quality of life.Tracking and positioning of elderly with neurological diseases and keeping track of their location in real-time are necessary and crucial in order to detect and treat dangerous and unexpected situations in time.Considering that the elderly with neurological diseases forget to wear a positioning device or have mobility problems due to carrying a positioning device,device-free positioning as a passive positioning technology that detects device-free individuals is more suitable than traditional active positioning for the home-based care of the elderly with neurological diseases.This paper provides an extensive and in-depth survey of device-free indoor positioning technology for home-based care and an in-depth analysis of the main features of current positioning systems,as well as the techniques,technologies andmethods they employ,fromthe perspective of the needs of the elderly with neurological conditions.Moreover,evaluation criteria and possible solutions of positioning techniques for the home-based care of the elderly with neurological conditions are proposed.Finally,the opportunities and challenges for the development of indoor positioning technology in 6G mobile networks for home-based care of the elderly with neurological diseases are discussed.This review has provided comprehensive and effective tracking and positioning techniques,technologies and methods for the elderly,by which we can obtain the location information of the elderly in real-time and make home-based care more comfortable and safer for the elderly with neurological diseases.

Positioning accuracy of IGPS

The positioning accuracy of a short-haul target-locating system,the inverse-GPS(IGPS) ,was analyzed in detail. The relationship between IGPS and the positioning error was discussed. The multiplicative error minimal bound of the geometric dilution of precision (GDOP) about the four-base-station IGPS was also investigated. In order to clarify the practical implementation of IGPS,the multiplicative and additive error factors which affect the positioning accuracy and theoretical estimation of positioning accuracy were presented. By analyzing the experiments of locating a target's position in virtual three-dimensional areas,the positioning performance of IGPS was illustrated. The results show that the multiplicative and additive error factors should be eliminated in IGPS to improve the positioning accuracy.

Trajectory Control: Directional MWD Inversely New Wellbore Positioning Accuracy Prediction Method

The deviation control of directional drilling is essentially the controlling of two angles of the wellbore actually drilled, namely, the inclination and azimuth. In directional drilling the bit trajectory never coincides exactly with the planned path, which is usually a plane curve with straight, building, holding, and dropping sections in succession. The drilling direction is of course dependant on the direction of the resultant forces acting on the bit and it is quite a tough job to hit the optimum target at the hole bottom as required. The traditional passive methods for correcting the drilling path have not met the demand to improve the techniques of deviation control. A method for combining wellbore surveys to obtain a composite, more accurate well position relies on accepting the position of the well from the most accurate survey instrument used in a given section of the wellbore. The error in each position measurement is the sum of many independent root sources of error effects. The relationship between surveys and other influential factors is considered, along with an analysis of different points of view. The collaborative work describes, establishes a common starting point of wellbore position uncertainty model, definition of what constitutes an error model, mathematics of position uncertainty calculation and an error model for basic directional service.

Comparison of density and positioning accuracy of PS extracted from super-resolution PSI with those from traditional PSI

In the application of persistent scatterer interferometry(PSI),deformation information is extracted from persistent scatterer(PS)points.Thus,the density and position of PS points are critical for PSI.To increase the PS density,a time-series InSAR chain termed as"super-resolution persistent scatterer interferometry"(SR-PSI)is proposed.In this study,we investigate certain important properties of SR-PSI.First,we review the main workflow and dataflow of SR-PSI.It is shown that in the implementation of the Capon algorithm,the diagonal loading(DL)approach should be only used when the condition number of the covariance matrix is sufficiently high to reduce the discontinuities between the joint images.We then discuss the density and positioning accuracy of PS when compared with traditional PSI.The theory and experimental results indicate that SR-PSI can increase the PS density in urban areas.However,it is ineffective for the rural areas,which should be an important consideration for the engineering application of SR-PSI.Furthermore,we validate that the positioning accuracy of PS can be improved by SRPSI via simulations.

Accuracy Analysis of Position Estimation Based on Measurements of Received Signal Strength Difference

The performance of a cellular location system based on received signal strength difference （RSSD） is investigated. In the cellular location system, each mobile station needs to measure the signal strength transmitted by surrounding base stations, and sends its measurements to the service base station. Using the strength difference between the service base station and neighboring base stations, the position of a mobile station is estimated. The related Cramer-Rao lower bound （CRLB） on the location error of this method was derived, and numerical simulations are made to discuss the influences of the number of base stations, correlation coefficient of shadowing attenuation, and cell radius on CRLB. The results show that the CRLB is positively correlated with the standard deviation of shadowing attenuation and cell radius, but negatively correlated with the number of base stations and the correlation coefficient of shadowing attenuation. In addition, the CRLB results obtained in this paper were compared with those of the cellular location system based on received signal strength （RSS） measurements, which reveals that the former is more tight.

An Analysis on Position Estimation, Drifting and Accumulated Error Accuracy during 3D Tracking in Electronic Handheld Devices

This work focuses on a brief discussion of new concepts of using smartphone sensors for 3D painting in virtual or augmented reality. Motivation of this research comes from the idea of using different types of sensors which exist in our smartphones such as accelerometer, gyroscope, magnetometer etc. to track the position for painting in virtual reality, like Google Tilt Brush, but cost effectively. Research studies till date on estimating position and localization and tracking have been thoroughly reviewed to find the appropriate algorithm which will provide accurate result with minimum drift error. Sensor fusion, Inertial Measurement Unit (IMU), MEMS inertial sensor, Kalman filter based global translational localization systems are studied. It is observed, prevailing approaches consist issues such as stability, random bias drift, noisy acceleration output, position estimation error, robustness or accuracy, cost effectiveness etc. Moreover, issues with motions that do not follow laws of physics, bandwidth, restrictive nature of assumptions, scale optimization for large space are noticed as well. Advantages of such smartphone sensor based position estimation approaches include, less memory demand, very fast operation, making them well suited for real time problems and embedded systems. Being independent of the size of the system, they can work effectively for high dimensional systems as well. Through study of these approaches it is observed, extended Kalman filter gives the highest accuracy with reduced requirement of excess hardware during tracking. It renders better and faster result when used in accelerometer sensor. With the aid of various software, error accuracy can be increased further as well.

空间目标天基光学定位方法综述

近年来空间目标定位领域不断结合网络协同、多模融合等探测技术,发展迅速。其中,基于天基光学探测的定位方法以隐蔽性好、测量精度高的独特优势在民用和国防领域应用广泛。为了分析不同情景下适用于不同类型目标的定位方法,针对基于天基光学探测的空间小目标定位进行综述。首先介绍天基光学探测技术的发展、空间目标的分类和特点以及空间目标定位的概念。然后着重分析适用于空间“小、弱”目标的单星和多星定位方法,并对近年提出的异质传感器联合定位展开说明。最后,依据成像过程建立空间目标定位误差分析模型,分析定位精度的影响因素占比并根据现存问题做出总结和展望。

一种LOS环境下基于目标运动形式的TDOA定位方法

时差定位(Time Difference of Arrival,TDOA)是一种广泛应用的被动定位技术,具有定位精度高、组网能力强、系统鲁棒性强等特点。针对运动目标定位计算复杂、精度收敛较慢等问题,在给出视距(Line of Sight,LOS)环境下定位模型的基础上,提出了定位适用于多站时差定位系统的定位方法,该方法将组群时差定位关系方程合理地线性化为统计估计问题,利用在线迭代实时求解目标位置。给出了针对目标不同运动特性条件下的多平台协同定位算法及其仿真结果,仿真结果表明所述方法可以实现对目标的精确定位,并且分析了运动形式对于定位精度的影响,仿真结果对于系统的工程设计具有指导作用。

GNSS基准站信噪比联合卫星系统综合定权的手机RTK定位

随着智能手机芯片和天线性能的不断提升,基于手机的高精度定位逐渐引起学术界和工业界的广泛关注.相较于单点定位,实时动态(real-time kinematic,RTK)定位通常表现出更高的定位性能.然而,目前对于手机RTK定位的随机模型的研究仍相对较少.因此,文中以小米8为例,重点探讨了智能手机在多系统RTK定位情境下的随机模型.研究结果表明:不同系统的卫星伪距噪声存在显著差异,而相位噪声的差异则较小.基于此,本文提出了一种基站信噪比联合卫星系统间综合定权的随机模型.相对于传统的信噪比模型更准确地考虑了不同系统之间的权重分配.并在开阔和遮挡条件下进行了静态和动态实验.结果表明:相比于传统的信噪比模型,新模型在静态开阔、静态遮挡、动态开阔和动态遮挡下三维方向的RTK定位精度分别提升了18.7%、18.3%、3.3%和4.6%.

智能手机GNSS数据质量分析与随机模型建立

为提高移动智能终端定位精度,利用小米8和华为Mate20手机采集多个卫星系统的观测数据并进行质量分析,通过不同卫星系统的伪距残差分别对信噪比模型参数进行估计,最后进行静态伪距单点定位实验。结果表明,手机端观测的BDS和GPS伪距精度接近,且高于GLONASS;相较于高度角,伪距残差与信噪比的相关性更强;在信噪比模型参数估计中,小米8拟合效果优于华为Mate20,BDS拟合效果差于其他卫星系统;参数拟合后的信噪比模型在水平和高程方向的定位精度分别为2.37 m和8.38 m,相较于高度角模型,定位精度提升约10%。

顾及置信概率稳定的中误差归一化算法研究

随着地理信息领域软硬件快速发展,地理信息大数据成为支撑多项重大工程的主要数据源。对海量数据成果进行高效、可靠的质量评价一直是研究热点。位置精度作为地理信息数据质量的核心指标之一,表征数据坐标与真实坐标相似度量程度,中误差是目前位置精度的主要量化指标。本文对检测点样本量、中误差及置信概率间关系开展对比研究,基于t分布-卡方分布尺度转换提出面向同一置信概率的中误差归一化算法。通过试验验证,在68.3%置信概率下对不同检测点样本量的位置精度尺度进行了稳定表征,对不同尺度下地理信息数据位置精度表征稳定性进行了探索,为不同检测点样本量下位置精度的高可信比较统一了尺度,有利于增强地理信息数据位置精度比较的公平性。

永磁定位系统磁传感器的两步迭代优化标定方法

为减小磁传感器位置、方向和灵敏度系数误差对永磁定位系统定位定向精度的影响,提出了一种基于最小二乘法的两步迭代(TSI)磁传感器标定方法。首先,校准磁传感器的方向和灵敏度系数,再进行位置校准,多次迭代后可以得到稳定的标定参数。其次,使用粒子群优化(PSO)算法与序列二次规划(SQP)算法结合进行迭代求解,在算法优化过程中,增加三组未知数约束,提高求解精度。最后对比使用不同标定方法的永磁定位系统定位定向精度,测试结果表明,所提标定方法较传统基于最小二乘的标定方法的系统定位精度提高20.48%,定向精度提高35.55%。

20°上臂倾斜位摄片法在肱骨外髁骨折中的应用价值

目的浅析20°上臂倾斜位摄片法在肱骨外髁骨折中的应用价值。方法选取2022年6月至2023年5月江西省儿童医院收治的50例肱骨外髁骨折患儿作为研究对象,所有患儿均采用传统正位与20°上臂倾斜位摄片法,手术结果作为金标准。并根据Jakob分类法进行二次评估,测量不同体位X线正位平片中骨块内侧与外侧的移位距离。结果50例肱骨外髁骨折患儿中,标准位摄片法的Jakob分型为:Ⅰ度29例、Ⅱ度17例、Ⅲ度4例;20°上臂倾斜位摄片法的Jakob分型为:Ⅰ度19例、Ⅱ度27例、Ⅲ度4例。经过测量可知,20°上臂倾斜位摄片法的异位距离大于标准位摄片法,差异有统计学意义(P<0.05)。20°上臂倾斜位摄片法准确率高于标准位摄片法,差异有统计学意义(P<0.05)。50例肱骨外髁骨折患儿中,手术结果为金标准,45例结果正确,5例结果错误;20°上臂倾斜位摄片法灵敏度为97.73%、特异度为66.67%、准确度为94.00%。结论在肱骨外髁骨折中采用20°上臂倾斜位摄片法,能够快速显示患儿肱骨外髁骨折的骨块移位程度,提高诊断的准确率,为临床治疗提供有利的参考依据。

应用激光跟踪仪和单目视觉检测三维水模体定位精度方法研究

针对三维水模体检测方法较少、检测过程复杂等问题,提出基于激光跟踪仪和单目视觉的三维水模体定位精度检测方法。激光跟踪仪三维水模体定位精度检测对比实验验证三维水模体在有水和无水的情况下定位精度一致。单目视觉三维水模体定位精度检测实验结果表明:X轴、Y轴、Z轴和空间对角线的定位误差均在0.050 mm以内,重复性分别为0.030 mm,0.064 mm,0.056 mm,0.140 mm,X轴和Y轴的垂直度为0.800 mm,Y轴和Z轴的垂直度为0.761 mm,X轴和Z轴的垂直度为0.503 mm,与激光跟踪仪的测量精度在一个量级。最后,经不确定度分析得到相邻点距离测量误差的标准差为0.0187 mm,满足检测要求。两种方法都能实现非接触测量,简化冗杂的检测过程,可满足医院对医用直线加速器的日常检测需求。

单目视觉与IMU融合的室内定位方法研究

为提高室内环境下移动载体自主定位的定位精度,提出一种融合单目视觉和IMU的自主定位算法。基于视觉SLAM框架VINS-Mono,首先提取图像点特征并进行光流跟踪,在此基础上同时提取图像的线特征并计算描述子进行匹配,对场景结构提供额外的约束;然后在后端将点、线特征和IMU信息进行整合并通过滑窗模型进行优化,以提高后端位姿估计的精度;最后通过仿真和智能小车进行实验验证。结果表明上述定位算法相较于VINS-Mono的定位误差均方根平均降低了8%~13%,证明所提算法达到了提升定位精度的效果且满足定位实时性要求。

机器人几何参数标定误差模型对定位精度影响研究

机器人几何参数误差是影响机器人定位精度的主要因素,通过对几何参数标定能够有效提高机器人定位精度。为了解决机器人在标定过程中的奇异性问题,采用改进的Denavit-Hartenberg(MDH)方法建立机器人几何参数模型,根据微分误差原理分别建立了机器人几何参数标定位姿误差和位置误差及姿态误差模型,并通过对几何参数冗余性分析及采用Levenberg-Marquardt(LM)算法辨识几何参数误差,研究不同误差模型对机器人定位精度影响。实验结果表明:采用位姿误差模型对机器人几何参数标定后其末端位置和姿态精度均能提升约75%,适于在有高精度定位要求的机器人中推广应用。