Search

Objective At present, CBTC (communication based train control) precise train positioning technology is prone to high cost of engineering construction and reconstruction, positioning errors and etc. Therefore, it is necessary to upgrade the existing train positioning method. Method The current commonly used technologies for train positioning are described. Based on the feature that the train is equipped with radar protection devices under TACS (train autonomous control system), a train mileage algorithm based on radar speed measuring integral is proposed. The principle of train autonomous positioning based on mileage mark is introduced. On this basis, a train real-time positioning function based on "speed measuring radar and electronic map" under TACS is put forward, and a real-time positioning method with radar speed measuring matching the electronic map is established. The above system is verified by the simulation platform. Result & Conclusion Simulation tests verify the effectiveness of the train real-time positioning function based on "speed measuring radar and electronic map" under TACS.

This paper introduces the current situation of intelligent development of shearer at home and abroad. The shearer is currently developing towards intelligent robotics and is in the primary stage of intelligence. This paper elaborates on the development process and trends of intelligent shearer. There are six scientific research projects that have played important roles in the intelligent development of shearer, including the UK remotely operated longwall face (ROLF) program, mine operating system (MINOS), NASA long wall automation cooperation project, Australian Australian coal industry’s research program (ACARP), Australian commonwealth scientific and industrial research organization (CSIRO) project, and EU new mechanisation and automation of longwall and drivage equipment (NEMAEQ). The development trend of shearer is to use continuously developing monitoring, sensing, and remote control technologies to replace manual intervention and operation, continuously improve the production efficiency and reliability of working face equipment, and develop towards informationization, integration, unmanned, and intelligent direction. This paper introduces the key technologies of intelligent perception, intelligent control, and intelligent communication of shearer. It points out that intelligent cutting technology based on coal rock recognition, intelligent drum speed regulation technology, precise positioning technology of shearer, and planning and mining technology based on three-dimensional geological models are key technologies that urgently need to be broken through. The human-machine relationship that cannot be ignored in the intelligent development process of shearer is discussed from two aspects: dust reduction and noise reduction.

In order to solve the problem that most of the existing mine-used smart phones only have the functions of voice calls, video photos, data transmission and so on, and do not have the functions of precise positioning, position coordinate display, message linkage, an identification card based on UWB technology is designed. The identification card realizes two-way data communication with the smart phone through low-power bluetooth. The identification card completes the precise positioning with the UWB station using the TOF positioning algorithm, obtains the position coordinate information, sends it to the smart phone through the low-power bluetooth (BLE), and displays the current specific position coordinates through the mine GIS roadway map on the smart phone APP. This paper introduces the key technologies of the identification card in detail, including mine roadway position coordinate model, precise positioning algorithm, message linkage reliable transmission mechanism, low power consumption sleep technology. The test results show that the positioning accuracy of the identification card is less than ± 0.3 meters, the positioning distance can reach 400 meters, the message linkage transmission delay is less than 2 seconds, the position coordinate display is accurate, the sleep current of the positioning module is less than 25 uA, and the average current meets the low power consumption design requirements.

This article is devoted to the positioning of glued parts by robots in the process of manufacturing automotive headlights, with the possibility of generalization to the mutual positioning of any 3D object. The authors focused on the description of the mathematical method that leads to the optimization of the robot arm setting and ensures the closest contact of the glued parts. The contact surfaces of the two joined parts are, in the ideal case, identical in shape and their optimal alignment is considered to best align the position of the nominal points on the base part with the position of the control (measured) points on the part manipulated by the robot.

Despite the swift advancement of geometric calibration techniques, the geometric performance of remote sensing imagery remains heavily contingent upon the quality and distribution of ground control data. Securing precise ground control data is often laborious, and the accuracy of open-source control data is subject to variability. This paper explores the potential of the globally dispersed International GNSS Service (IGS) network to enhance the geometric performance of remote sensing images. The IGS network, with its extensive reach, offers superior positioning and navigation products that surpass the previously mentioned sources. To establish a connection between the IGS network and remote sensing images, high-resolution GEM chips (GEMs) are firstly utilized for precise positioning. Geolocation biases of these GEMs are refined based on the identified IGS information. After that, the calibrated GEM chips are applied as control information for the geometric calibration of raw satellite images. A test dataset from the Chinese Gaofen-2 (GF-2) with various forms of coverage is experimented, with LiDAR-derived Digital Surface Models (DSMs) serving as reference for the validation of the proposed method. Compared with traditional methods using the GEMs as a direct reference, the experimental results demonstrate that the introduced IGS information enhances the geometric performance of remote sensing images, exhibiting robust generalization performance across remote sensing data from various source domains.

Objective To investigate the effect of induced defecation technique with deep colonic precision localization in patients with complex constipation. Methods Fifty-three patients with complex constipation who were admitted to and consulted by the Department of Rehabilitation Medicine Center from November 2021 to May 2022 were recruited as research subjects. All patients received induced defecation with deep colonic precision positioning, and intervention effect was analyzed, Results The colonic deep-precision positioning induced defecation technique was reported to significantly relieve abdominal discomfort, bloating, constipation, diarrhea, and other intestinal disorders in 53 individuals with complex constipation. After the intervention, the patients had defecation in 49 (92. 45%)cases and no defecation in 4 (7. 55%)cases; 51 (96. 23%) cases and no defecation in 2 (3. 77%)case after the intervention; abdominal symptoms improved in a total of 53 (100. 00%)cases. The Wexner constipation score of the patients after the intervention was significantly lower than that before the intervention (P＜0. 05). Conclusion On patients with difficult constipation, the approach of induced defecation with deep colonic precision positioning provided considerable therapeutic benefits and significantly alleviated their clinical symptoms. (目的 探讨结肠精准定位的诱导排便技术在复杂性便秘患者中的应用效果。方法 对2021年11月—2022年5月江苏省人民医院康复医学中心收治及会诊的53例复杂性便秘患者进行结肠精准定位的诱导排便, 评估干预效果。结果 53例复杂性便秘患者在排除禁忌后接受结肠精准定位的诱导排便技术干预, 腹痛、腹胀、便秘、腹泻等肠道问题得到缓解。干预后患者排便49(92. 45%)例、未排便4(7. 55%)例; 干预后排气51(96. 23%)例、未排气2(3. 77%)例; 腹部症状改善共计53(100. 00%)例, 干预后患者Wexner便秘评分低于干预前, 差异有统计学意义(P＜0. 05)。结论 结肠精准定位的诱导排便技术对复杂性便秘患者有明显治疗效果, 能够有效减轻患者临床症状。)

The precise evaluation of micro-crack sizes and locations is crucial for the safe operation of structures. Traditional detection techniques, however, suffer from low spatial resolution, making it difficult to accurately locate micrometer-scale cracks. A method and experimental study were proposed in this paper for identifying and locating micro-cracks using optical fiber strain sensing based on OFDR to address this issue. The feasibility of this method for micro-crack detection was verified by the combination of a polyimide-coated sensing optical fiber (PISOF) and tight sheath sensing optical fiber (TSSOF). A calculation method for micro-crack widths based on distributed optical fiber strain curves was established, and the test results of different optical fibers were compared. Through multiple verification experiments, it was found that the strain peak curves of both fiber types could accurately locate micro-cracks with a precision of 1 mm. Additionally, the crack widths could be obtained by processing the distributed strain curves using a computational model, enabling the accurate capture of micro-crack characteristics at the 10 μm level. A strong linear relationship was observed between the optical fiber stretching length and the crack width. Notably, the relative error in calculating the crack width from the strain curve of PI fiber was very small, while a linear relationship existed between the maximum strain value of the TSSOF and the crack width, allowing for the calculation of the crack width based on the maximum strain value. This further validated the feasibility of the method designed in this paper for the analysis of micro-crack characteristic parameters.

A low-power multi-mode positioning information mining lamp is designed. By the fusion of multi-mode radio frequency technology and radio frequency scheduling method, the mine can realize the seamless transition and upgrading from regional positioning to ultra wideband accurate positioning; PA power amplifier and LNA low noise amplifier are used to optimize the transmission distance and ranging accuracy of UWB radio frequency technology, so as to solve the base station capacity and economic cost of underground location service system; at the same time, the upgradable design can realize the differentiated customized use needs, and can better provide underground location information services for coal mines.

The advantages and disadvantages of five commonly used mining monorail cranes, namely explosion-proof diesel engine monorail crane, explosion-proof battery monorail crane, pneumatic monorail crane, rope traction monorail crane, and cable dragging monorail crane, are analyzed. It is pointed out that explosion-proof diesel engine monorail crane and explosion-proof battery monorail crane have been widely used for underground equipment and material transportation in coal mines due to their strong transportation capacity. The explosion-proof battery monorail crane has green and clean features. It has gradually become a key research and development equipment for underground auxiliary transportation in coal mines. This paper analyzes the research status of the mining monorail crane system from four aspects of battery drive, positioning, measurement and control, and information transmission. It is pointed out that the current mining monorail crane system has low automation and intelligence levels. To achieve intelligent transportation of the monorail crane, it is necessary to study the key technologies such as lithium battery explosion-proof and battery management of the monorail crane, global and local fusion precise positioning, multi-sensor information fusion intelligent measurement and control, edge computing information transmission, etc. For the explosion-proof and battery management technology of lithium battery, a topology optimization design method of explosion-proof large capacity lithium battery structure based on variable density method, and a balanced management scheme based on improved sparrow search algorithm/genetic algorithm are proposed. For precise positioning technology, a global positioning method based on inertial navigation and odometer fusion, and a local positioning method based on visual+UWB combination are proposed. For intelligent measurement and control technology, an intelligent detection method based on recursive least squares algorithm/second-order approximate extended Kalman filter , the real-time construction method for follow-up electronic fences, and vector control method based on fuzzy rules are proposed. For the information transmission technology, the 'local-short range-ground' communication system architecture based on the fusion of 5G network and the distributed data calculation and transmission method based on edge computing are proposed. The proposal of key technical issues and solutions for intelligent monorail cranes in coal mines provides a new approach to accelerate the development of intelligent monorail cranes in coal mines.

With the rapid development of civil aviation industry, more and more tasks are required to fuel the aircraft. At present, the aircraft refueling task is mainly assigned to the refueling personnel by the dispatcher of the fuel supplier, one by one, according to the flight refueling information, after receiving the task, the refueling operator drives the refueling vehicle to the aircraft for refueling operation. The realization of electronic, information and big data analysis technology has gradually opened up the information channel of refueling system. Based on a large number of multi-dimensional data, according to the characteristics of aircraft refueling operation, an intelligent dispatching method for aircraft refueling vehicle is provided, which can automatically assign refueling tasks, avoid flight delays and the resulting serious waste of resources and can reduce the workload of the dispatcher. Through the intelligent dispatch, refueling resources can be reasonably allocated to ensure the timely refueling of aircraft and smooth completion of flight support tasks.

Aiming at the practical problem of the difficulty in identifying associated users when abnormal line loss occurs in the station area, a method for judging and accurately locating the line loss abnormality in the station area based on the correlation measurement algorithm is proposed. Firstly, the optimal clustering number of the data set is determined by the gap statistics-contour coefficient fusion algorithm, and on this basis, the dichotomous K-means++ is used to construct the station area line loss standard library. Secondly, the station area line loss anomaly identification is completed based on the standard library and then the abnormal time is determined. The Spearman correlation coefficient (SCC) and Euclidean-discrete Frand#233;chet distance (E-DFD) of each user's power and line loss during the abnormal time is calculated. And based on SCC and E-DFD, a comprehensive evaluation index to analyze user relevance is estabilished. Finally, the technique for order preference by similarity to an ideal solution (TOPSIS) is used to sort the comprehensive evaluation index values to achieve precise positioning of abnormally associated users. The calculation example uses real field data in a certain area to analyze, and the results show that the method proposed in this paper has better performance in clustering effectiveness, calculation time, and identification accuracy.

At present, most of the positioning methods of underground tunneling equipment in coal mines adopt single auxiliary measurement methods such as machine vision, odometer and total station to combine with inertial navigation measurement to suppress the cumulative position error caused by inertial navigation solution over time. However, the single auxiliary measurement method is easy to be affected by the underground environment, and there are certain errors in position measurement, which leads to the reduction of the precision of the combined measurement method with inertial navigation. In order to solve the above problems, taking shield roadheader robot system in coal mine as the research object, a combined positioning method of strapdown inertial navigation+digital total station+displacement sensor is proposed. Firstly, the position and attitude angle parameters of the roadheader robot are calculated by using strapdown inertial navigation. Secondly, the position information of the roadheader robot measured by the digital total station and calculated by the displacement sensor are used to feedback and correct the position information calculated by the strapdown inertial navigation, so as to reduce the cumulative position error generated by the inertial navigation over time. Finally, the position and attitude angle information calculated by the strapdown inertial navigation, the position information obtained by the total station measurement and the position information estimated by the displacement sensor are fused by the multi-information fusion algorithm based on the federated filter, so as to obtain the accurate position and attitude information of the roadheader robot. The simulation and industrial experiment results show that the combined positioning method can well suppress the accumulative position solution errors of pure inertial navigation and realize the precise positioning of the shield roadheader robot in coal mines. The position errors in the x-axis and y-axis directions are controlled at ±0.03 m and ±0.02 m respectively, which meets the requirements of the underground driving face.

High-precision positioning from Global Navigation Satellite Systems (GNSS) has garnered increased interest due to growing demand in various applications, like autonomous car navigation and precision agriculture. Precise Point Positioning (PPP) offers a distinct advantage over differential techniques by enabling precise position determination of a GNSS rover receiver through the use of external corrections sourced from either the Internet or dedicated correction satellites. However, PPP’s implementation has been challenging due to the need to mitigate numerous GNSS error sources, many of which are eliminated in differential techniques such as Real-Time Kinematics (RTK) or overlooked in Standard Point Positioning (SPP). This paper extensively reviews PPP’s error sources, such as ionospheric delays, tropospheric delays, satellite orbit and clock errors, phase and code biases, and site displacement effects. Additionally, this article examines various PPP models and correction sources that can be employed to address these errors. A detailed discussion is provided on implementing the standard dual-frequency (DF)-PPP to achieve centimeter- or millimeter-level positioning accuracy. This paper includes experimental examples of PPP implementation results using static data from the International GNSS Service (IGS) station network and a kinematic road test based on the actual trajectory to showcase DF-PPP development for practical applications. By providing a fusion of theoretical insights with practical demonstrations, this comprehensive review offers readers a pragmatic perspective on the evolving field of Precise Point Positioning.

This paper proposes an implementation scheme of wireless upgrade firmware program based on UWB and ZigBee technologies. This method adopts one-to-many networking mode and infinite loop multi-broadcast mechanism to realize the location card batch wireless upgrade, which improves the speed, concurrent capacity and efficiency of wireless upgrade. The test results show that the concurrent number of locating card in batch upgrade is not limited. Within the coverage area of 100 meters, 95% locating cards are successfully upgraded once, 5% locating cards need to wait for two cycles, and the wireless upgrade time is less than 5 minutes. Therefore, this method provides a fast, reliable and convenient wireless upgrade way for a large number of locating card upgrade firmware programs.

Underground coal mines belong to the GNSS-denied environment, and the Strapdown Inertial Navigation System (SINS) has a significant advantage in the precise positioning of equipment in this environment because of its operation without requiring interaction with external information and strong anti-interference capabilities. Nonetheless, the vibrations of the installation platform adversely affect the positioning accuracy of SINS. This article focuses on the monorail crane in coal mines as the subject of research, developing a dynamic model for the motion unit consisting of the “track + drive unit + driver’s cab”, while analyzing the relationship between track roughness conditions and the vibration excitation of this unit. Subsequently, utilizing the dynamic model, the study calculated the angular and linear vibration characteristics and formulated models to address coning error and sculling error specific to the SINS in this vibration condition. Lastly, by employing a multi-sample compensation algorithm, this article compensated for positioning errors in the SINS caused by track roughness-induced vibrations during uniform straight-line motion of the motion unit, thus achieving optimal positioning information for the monorail crane. The simulation results demonstrated that employing a four-sample compensation algorithm reduces the coning error in SINS positioning calculations by a minimum of 50% and decreases the sculling error by at least 31%, satisfying the positioning accuracy requirements for precise parking of the monorail crane during the transportation phase, while establishing the foundation for autonomous precise positioning and integrated navigation of underground track transport equipment in coal mines.

Aiming at the problem that the underground positioning of coal mine mostly depends on RFID positioning technology, and the upgrade cost of accurate positioning is high, a multi-positioning technology protocol fusion positioning system is proposed. While compatible with regional positioning, the system can realize the access of ZigBee technology and UWB technology positioning equipment, reduce the cost of precise positioning upgrade, realize the upgrading of coal mine personnel positioning technology, promote the fusion development of RFID regional positioning and ZigBee and UWB precise positioning technology, further improve the positioning accuracy of underground positioning system, and build a highly reliable and full coverage information system interactive network, this paper proposes a positioning system which can realize three positioning methods for data interaction, to meet the application requirements of different areas and different application scenarios.

The positioning accuracy of the precise personnel positioning system in underground mine is affected by the non-line-of-sight error and clock error. At present, the system mostly uses Kalman filter-based positioning method to reduce the error, but the positioning accuracy is not high when there is gross error in the measured data. In order to solve this problem, a precise personnel positioning method in underground mine based on grey prediction model is proposed. When a person carrying a marker card enters the coverage area of the positioning reader, the positioning reader calculates the measured distance between the marker card and the reader through wireless positioning technology and stores the measured distance into the data cache area. According to the measured distance in the data cache area, the GM (1, 1) model is used to calculate the predicted distance between the marker card and the reader at the next moment. When the prediction accuracy level of this predicted distance is excellent and the difference with the measured distance exceeds the error judgment threshold, the predicted distance is used to replace the measured distance to achieve the optimal compensation of the distance measurement error. The test results show that the method is not affected by the distance measurement error. When there is a gross error in the measured distance, the positioning accuracy of this method is significantly better than that of the Kalman filter-based positioning method.

Thalamic hemorrhage is one of deep-seating cerebral lesions. Conservative therapy is preferred to patients with minor thalamic hemorrhage, and external ventricular drainage is usually applied in patients with cerebral ventricular hemorrhage. However, the prognosis of some patients is poor. This study intends to explore that minimally invasive puncture to remove hematoma in patients with the thalamic hemorrhage volume less than 15 ml with disturbance of consciousness (especially the expansion of the hematoma to the hypothalamus or midbrain) is an alternative method. In clinical practice, a wedge-shaped sign of thalamic hemorrhage could be observed in CT images in coronal plane, which was featured by the compression of hematoma on the third ventricle and the aqueduct of midbrain shaped like a wedge into the mesencephalon. The obstruction of cerebrospinal fluid circulation was then evaluated. For persistent hematoma oppression, the precise positioning of stereotactic instrument could be applied to rapidly and effectively remove the oppression, thus improving life quality of affected patients.

Today’s technological developments make it possible to use machines to perform specific tasks instead of humans. However, the challenge for such autonomous devices is to precisely move and navigate in constantly changing external environments. In this paper, the influence of varying weather conditions (air temperature, humidity, wind speed, atmospheric pressure, type of satellite systems used/satellites visible, and solar activity) on the accuracy of position determination was analyzed. To reach the receiver, a satellite signal must travel a great distance and pass through all layers of the Earth’s atmosphere, the variability of which causes errors and delays. Moreover, the weather conditions for receiving data from satellites are not always favorable. In order to investigate the impact of delays and errors on position determination, the measurements of the satellite signal were conducted, the motion trajectories were determined, and the standard deviations of these trajectories were compared. The results obtained show that it is possible to achieve high precision in determining the position, but varying conditions, such as solar flares or satellites’ visibility, meant that not all measurements are able to achieve the required accuracy. The use of the absolute method of satellite signal measurements contributed to this to a large extent. To increase the accuracy of positioning by GNSS systems, it is first of all proposed to use a dual-frequency receiver that eliminates ionospheric refractions.

Aiming at characteristics of electrical explosion-proof and large wireless transmission attenuation in underground coal mine, 5G technology and its application scope were analyzed.Mine-used 5G should adopt intrinsically safe explosion-proof. Mine-used 5G for control should have strong anti-interference ability. Mine-used 5G should be used for remote control of coal mining face and tunneling face. Mine-used 5G should be used for ground remote control of unmanned vehicle in underground coal mine. Mine-used 5G that has not been developed for characteristics of mine mobile communication is less cost-effective than mine-used WiFi mobile communication system. It is strictly forbidden to replace mine-used wired dispatching communication system with mine-used 5G mobile communication system. Mine-used 5G that is not developed for coal mine safety monitoring characteristics cannot replace coal mine safety monitoring system. Positioning accuracy of mine-used 5G that has not been developed for precise positioning characteristics of mine moving target is lower than that of mine-used UWB precision positioning system. Transmission rate of mine-used 5G in frequency range of 450-6 000 MHz is lower than that of mine-used WiFi6. Reliability of mine-used 5G that is not developed for monitoring characteristics of fixed equipment in underground coal mine is lower than that of mine-used wired monitoring system. It is urgent to research and develop mine-used 5G based on characteristics of safe production in coal mine, not just for explosion-proof transformation of existing ground 5G products.

Abstract Ionospheric disturbances are the phenomena which adversely affect the performance of precise positioning. This holds true even for multi-constellation relative positioning supported with network-derived ionospheric corrections. In such scenario the unfavorable effect is caused by a poor accuracy of corrections, which, in turn, is driven by the deterioration of the spatial interpolation process. The positioning becomes even more challenging in a wide-area scenario with baselines over 100 km. In this paper, we assess the methodology which aims at reliable and accurate wide-area RTK and rapid static positioning in the presence of severe ionospheric conditions. The approach takes advantage of multi-constellation network ionospheric corrections and an algorithm which allows the elimination of the temporal variations of the ionospheric delay. The experimental evaluation was performed on the basis of multi-station RTK and static positioning using GPS, BDS and Galileo data collected at high latitudes during the ionospheric storm on August 25–26, 2018. The results confirmed the deterioration of the accuracy of the network ionospheric corrections and consequently a decline in the positioning performance with routine models such as ionosphere-float and ionosphere-weighted. On the other hand, the results obtained with the application of the developed methodology demonstrated a very distinctive improvement in the ambiguity resolution domain and thus proved the advantage over benchmark models. In this case, the developed methodology allowed up to 20% enhancement of the ambiguity success rate with respect to benchmark strategies.

Aiming at the problem that trilateration positioning algorithm based on weighted least squares (WLS) lost positioning information in linearization process, an improved trilateration positioning algorithm was proposed. In the algorithm, WLS algorithm is used to roughly estimate coordinates of unknown nodes, and lost positioning information is used to construct positioning model, so precise positioning is achieved by solving the positioning model. The simulation results show that positioning accuracy of the proposed algorithm is obviously higher than that of the trilateration positioning algorithm based on WLS, and the larger the length-width ratio of roadway is, the better the positioning performance of the proposed algorithm is.

The advances in low-latency communications networks and the ever-growing amount of devices offering localization and navigation capabilities opened a number of opportunities to develop innovative network-based collaborative solutions to satisfy the increasing demand for positioning accuracy and precision. Recent research works indeed, have fostered the concept of networked Global Navigation Satellite System (GNSS) receivers supporting the sharing of raw measurements with other receivers within the same network. Such measurements (i.e. pseudorange and Doppler) can be processed through Differential GNSS (DGNSS) techniques to retrieve inter-agent distances which can be in turn integrated to improve positioning performance. This article investigates an improved Bayesian estimation algorithm for a sensorless, tight-integration of DGNSS-based collaborative measurements through a modified Particle Filter (PF), namely Cognitive PF. Differently from Extended Kalman Filter and Uscented Kalman Filter indeed, a PF natively support the non-Gaussian noise distribution which characterizes DGNSS-based inter-agent distances. The proposed Cognitive PF is hence designed, implemented and optimized according to the architecture of a proprietary Inertial Navigation System (INS)-free Global Navigation Satellite System (GNSS) software receiver. Experimental tests performed through realistic radio-frequency GNSS signals showed a remarkable improvement in positioning accuracy w.r.t. reference PF and EKF architectures.

The anti-jamming antenna is one of the most efficient ways to resist the adversary effect of the interference signal in GNSS positioning. Most anti-jamming antennas can adaptively adjust the radiation figure of the antenna to minimize the interference impact. A side effect of changing the radiation figure is that the antenna phase center (APC) is also changed accordingly. Meanwhile, a stable phase center is a prerequisite for high precision GNSS positioning, thus the anti-jamming and high-precision becomes a dilemma for the GNSS antenna design. This study proposed an efficient antenna phase center variation (PCV) compensation algorithm for the anti-jamming antennas which enables real-time high-precision applications with the anti-jamming antennas. The performance of the algorithm is evaluated with the short baseline tests, and the results indicate that the proposed algorithm can reduce the carrier phase residuals by compensation of the anti-jamming antenna PCV and consequently, the 3D root mean squares (RMS) of real-time kinematic (RTK) positioning in two experiments is improved by 42.3% and 9.7% respectively. After PCV correction, the RTK positioning with the anti-jamming antennas achieves better than 4 cm accuracy.

GNSS positioning in urban scenarios suffers for the scarce visibility of satellites. Integration with 5G services for positioning could improve this situation. In this paper, the digital surface models (DSMs) relevant to different urban scenarios, namely residential streets and urban canyons, are simulated around one observer in northern Italy (Milano) for one day of the year chosen as an example. The time series of the number of in-view GNSS satellites, their geometry and the derived quality indexes (position dilution of precision (PDOP)) are computed and analyzed. As expected, in urban canyons, a significant number of epochs does not provide four satellites within view, and many more epochs present really mediocre PDOPs. In residential streets, the situation is always quite fair. Different geometric configurations of 5G base stations are simulated around the observer. The availability of 5G times of arrival (ToAs) and their differences (TDoAs) is hypothesized, and the integration of these observations with GNSS pseudoranges is analyzed, again in terms of the PDOPs. In residential streets, 5G availability improves the positioning. In urban canyons, the optimal configuration of 5G base stations (five base stations around the observer) completely solves the positioning problem for all the epochs of the day. Less favorable configurations (four and three base stations) improve epochs with poor PDOPs in a GNSS-only configuration. They allow the positioning of epochs with few satellites but cannot completely replace the GNSS.

Mobile laser scanning technology used for deformation detection of shield tunnel is usually two-dimensional, which is expanded into three-dimensional (3D) through mileage, resulting in low positioning accuracy. This study proposes a 3D laser point cloud positioning method that is divided into rings in the mileage direction and blocks in the ring direction to improve the positional accuracy for shield tunnels. First, the cylindrical tunnel wall is expanded into a plane and the bolt holes are extracted using the self-adaptive parameter adjustment cloth simulation filter (CSF) algorithm combined with a density-based spatial clustering of applications with noise (DBSCAN) algorithm. Second, the mean-shift algorithm is used to obtain the center point of the bolt hole, and a model is designed to recognize the center point of different splicing blocks. Finally, the center point is combined with the standard straight-line equation to fit the straight-line positioning seam, achieving an accurate ring and block segmentation of a shield tunnel as a 3D laser point cloud. The proposed method is compared with existing methods to verify its feasibility and high accuracy using the seams located by the measured tunnel point cloud data and in the measured point cloud. The average differences between the circumferential seams positioned using the proposed method and those in the point cloud at the left waist, vault, and right waist were 3, 4, and 5 mm, respectively, and the average difference between the longitudinal seams was 3.4 mm The proposed research method provides important technical and theoretical support for tunnel safety monitoring and detection.

This review paper presents research results on geodetic positioning and applications carried out in Poland, and related to the activities of the International Association of Geodesy (IAG) Commission 4 “Positioning and Applications” and its working groups. It also constitutes the chapter 4 of the national report of Poland for the International Union of Geodesy and Geodynamics (IUGG) covering the period of 2015-2018. The paper presents selected research, reviewed and summarized here, that were carried out at leading Polish research institutions, and is concerned with the precise multi-GNSS (Global Navigation Satellite Systems) satellite positioning and also GNSS-based ionosphere and troposphere modelling and studies. The research, primarily carried out within working groups of the IAG Commission 4, resulted in important advancements that were published in leading scientific journals. During the review period, Polish research groups carried out studies on multi-GNSS functional positioning models for both relative and absolute solutions, stochastic positioning models, new carrier phase integer ambiguity resolution methods, inter system bias calibration, high-rate GNSS applications, monitoring terrestrial reference frames with GNSS, assessment of the real-time precise satellite orbits and clocks, advances in troposphere and ionosphere GNSS remote sensing methods and models, and also their applications to weather, space weather and climate studies.

Benefitting from the multifunctional properties of knitted fabrics with elasticity, flexibility, and high resilience, knitted strain sensors based on structure and strain performance are widely utilized in sports health due to their adaptability to human movements. However, the fabrication process of common strain sensors mainly relies on experienced technicians to determine the best sensor size through repeated experiments, resulting in significant size errors and a long development cycle. Herein, knitted strain sensors based on plain knit were fabricated with nylon/spandex composite yarn and silver-plated nylon yarn using a flat knitting process. A size prediction model of knitted strain sensors was established by exploring the linear relationship between the conductive area size of samples and knitting parameters via SPSS regression analysis. Combined with stable structures and high performance of good sensitivity, stability, and durability, the knitted strain sensors based on size prediction models can be worn on human skin or garments to monitor different movements, such as pronunciation and joint bending. This research indicated that the reasonable size control of the knitted strain sensor could realize its precise positioning in intelligent garments, exhibiting promising potential in intelligent wearable electronics.

The Satellite Positioning and Orbit Determination System (SPODS) is a software package for GNSS positioning/orbit determination, developed by the Xi’an Research Institute of Surveying and Mapping. So far it has been able to analyse GPS data and has the capability of high precision GPS positioning and orbit determination. The underlying theory and the performance evaluation are briefly addressed in this paper. The experiments are carried out with GPS data collected from about 127 IGS stations during 4~10 January 2009. The results show that the RMS 1D difference is 1.1cm between SPODS orbits and final IGS combined orbits, and that the repeatability of daily solutions of station coordinates is 1.5mm for horizontal components, and 4.5mm for vertical component, and that the consistency of ERP solutions with IGS final products is 0.025mas, 0.093 mas and 0.013ms/d respectively for pole coordinates and LOD.

With more goods to be transported oversea, traffic and vessels’ dimensions increase while berthing areas merely remain constant and thus challenge ship masters and pilots to maneuver in small basins with dense traffic even in bad weather situations. Too fast approaches or steep angles of attack result in damages to fenders, quay walls, or even impact the hull structure. We propose a shore-based, vessel-independent berthing assistant system to support sailors by Reference Points that are aligned to a quay’s meter markings and identify the precise berthing location by measuring distance and approach speed. For this purpose, we define the concept of a Berthing Support Area (BSA), which specifies an area in which, subject to constraints, safe berthing is provided. Within this area there are Reference Points, perpendicular distance measurements at arbitrary positions, which are implemented with a set of LiDAR sensors that have been integrated into the quay wall. In a test campaign with a vessel equipped with DGPS sensors, we sailed seven different maneuvers and evaluated the precision and the accuracy of the Reference Points for speed and distance measurements.

The aim of this study was to investigate the precise clinical use of Sinitang decoction (SNT) in ulcerative colitis (UC). Network pharmacology-based analysis of the drug components–targets–diseases–pathways was used to predict the possible clinical applications of SNT. Next, 2,4,6-trinitrobenzenesulfonic acid (TNBS) was used to establish a rat model of UC, and the efficacy of SNT against UC was tested, followed by a proteomic analysis of the specific signatures regulated by SNT against UC. SNT was predicted to be effective in inflammatory bowel disease, UC, and several other diseases. In the rats with UC, SNT decreased the disease activity index and colon mucosal damage index compared to the untreated UC model rats. Additionally, SNT reversed the upregulated levels of serum tumor necrosis factor (TNF)-α, prostaglandin E2 (PGE2), interleukin (IL)-6, and nitric oxide (NO) in UC model rats. The proteomic analysis identified 78 proteins that were differentially regulated by SNT in the rats with UC, which were associated with the Gene Ontology terms sulfur compound binding, calcium ion binding, and Toll-like receptor (TLR)-4 binding. Among these differentially regulated proteins, C-reactive protein (CRP) and collagen alpha-1(XII) chain (COL12A1) were found to be signature proteins associated with the efficacy of SNT against UC. This study represents the first precise investigation of the efficacy and mechanisms of SNT against UC, and shows that SNT is a promising candidate for personalized management of UC.

Ionospheric irregularities impair Global Navigation Satellite System (GNSS) signals and, in turn, affect the performance of GNSS positioning. Such effects are especially evident at low and high latitudes, which are currently gaining the attention of research and industry sectors. This study evaluates the impact of ionospheric irregularities on GNSS positioning in Greenland. We assess the performance of positioning methods that meet the demands of a wide range of users. In particular, we address the needs of the users of mass-market single-frequency receivers and those who require a solution of high precision provided by geodetic dual-frequency receivers. We take advantage of the datasets collected during three ionospheric storms: the St. Patrick’s Day storm of March 17, 2015, the storm on June 22, 2015, and another on August 25–26, 2018. We discover a significant impact of the ionospheric disturbances on the ambiguity resolution performance and the accuracy of the float solution in Real Time Kinematics (RTK) positioning. Next, assessing the single-frequency ionosphere-free Precise Point Positioning (PPP), we demonstrate that the model is generally unaffected by ionospheric disturbances. Hence, the model is predestined for the application by the users of single-frequency receivers in the areas of frequent ionospheric disturbances. Finally, based on the observation analyses, we reveal that phase signals on the L2 frequency band are more prone to cycle slips induced by ionospheric irregularities than those transmitted on the L1. Such signal properties explain a noticeable decline in the dual-frequency RTK performance during the ionospherically disturbed period and merely no effect for the single-frequency ionosphere-free PPP model.

For the traditional autonomous navigation vehicle(AGV), the problem of high-precision path tracking and precise positioning of key points can not be satisfied. A combination method of key point precise location and path correction based on fuzzy control is proposed for the first time. Firstly, the four wheel differential kinematic model of AGV is established, position bias and angle deviation are used as inputs and the deviation rectification control is output. A two-dimensional fuzzy controller is designed to realize quick deviation correction. In addition, aiming at high-precision positioning requirements for special points, according to the size of each frame sampled image, the coordinate model is fixed. The two-dimensional code contour is obtained by three point positioning method, and then the offset is computed by the offset of the center point. Lastly, the precise positioning is got.

The use of GPS positioning and navigation capabilities in mobile phones is present in our daily lives for more than a decade, but never with the centimeter level of precision that can actually be reached with several of the most recent smartphones. The introduction of the new GNSS systems (Global Navigation Satellite Systems), the European system Galileo, is opening new horizons in a wide range of areas that rely on precise georeferencing, namely the mass market smartphones apps. The constant growth of this market has brought new devices with innovative capabilities in hardware and software. The introduction of the Android 7 by Google, allowing access to the GNSS raw code and phase measurements, and the arrival of the new chip from Broadcom BCM47755 providing dual frequency in some smartphones came to revolutionize the positioning performance of these devices as never seen before. The Xiaomi Mi8 was the first smartphone to combine those features, and it is the device used in this work. It is well known that it is possible to obtain centimeter accuracy with this kind of device in relative static positioning mode with distances to a reference station up to a few tens of kilometers, which we also confirm in this paper. However, the main purpose of this work is to show that we can also get good positioning accuracy using long baselines. We used the ability of the Xiaomi Mi8 to get dual frequency code and phase raw measurements from the Galileo and GPS systems, to do relative static positioning in post-processing mode using wide baselines, of more than 100 km, to perform precise surveys. The results obtained were quite interesting with RMSE below 30 cm, showing that this type of smartphone can be easily used as a low-cost device, for georeferencing and mapping applications. This can be quite useful in remote areas where the CORS networks are not dense or even not available.

The use of carrier phase data is the main driver for high-precision Global Navigation Satellite Systems (GNSS) positioning solutions, such as Real-Time Kinematic (RTK). However, carrier phase observations are ambiguous by an unknown number of cycles, and their use in RTK relies on the process of mapping real-valued ambiguities to integer ones, so-called Integer Ambiguity Resolution (IAR). The main goal of IAR is to enhance the position solution by virtue of its correlation with the estimated integer ambiguities. With the deployment of new GNSS constellations and frequencies, a large number of observations is available. While this is generally positive, positioning in medium and long baselines is challenging due to the atmospheric residuals. In this context, the process of solving the complete set of ambiguities, so-called Full Ambiguity Resolution (FAR), is limiting and may lead to a decreased availability of precise positioning. Alternatively, Partial Ambiguity Resolution (PAR) relaxes the condition of estimating the complete vector of ambiguities and, instead, finds a subset of them to maximize the availability. This article reviews the state-of-the-art PAR schemes, addresses the analytical performance of a PAR estimator following a generalization of the Cramér–Rao Bound (CRB) for the RTK problem, and introduces Precision-Driven PAR (PD-PAR). The latter constitutes a new PAR scheme which employs the formal precision of the (potentially fixed) positioning solution as selection criteria for the subset of ambiguities to fix. Numerical simulations are used to showcase the performance of conventional FAR and FAR approaches, and the proposed PD-PAR against the generalized CRB associated with PAR problems. Real-data experimental analysis for a medium baseline complements the synthetic scenario. The results demonstrate that (i) the generalization for the RTK CRB constitutes a valid lower bound to assess the asymptotic behavior of PAR estimators, and (ii) the proposed PD-PAR technique outperforms existing FAR and PAR solutions as a non-recursive estimator for medium and long baselines.

GNSS signals arriving at receivers at the surface of the Earth are weak and easily susceptible to interference and jamming. In this paper, the impact of jamming on the reference station in carrier phase-based relative baseline solutions is examined. Several scenarios are investigated in order to assess the robustness of carrier phase-based positioning towards jamming. Among others, these scenarios include a varying baseline length, the use of single- versus dual-frequency observations, and the inclusion of the Galileo and GLONASS constellations to a GPS only solution. The investigations are based on observations recorded at physical reference stations in the Danish TAPAS network during actual jamming incidents, in order to realistically evaluate the impact of real-world jamming on carrier phase-based positioning accuracy. The analyses performed show that, while there are benefits of using observations from several frequencies and constellations in positioning solutions, special care must be taken in solution processing. The selection of which GNSS constellations and observations to include, as well as when they are included, is essential, as blindly adding more jamming-affected observations may lead to worse positioning accuracy.

In Global Navigation Satellite Systems (GNSS) positioning, one often tries to establish a mathematic model to capture the systematic behaviors of observations as much as possible. However, the observation residuals still exhibit, to a great extent, as (somewhat systematic) signals. Nevertheless, those systematic variations are referred to as the unmodelled errors, which are difficult to be further modelled by setting up additional parameters. Different from the random errors, the unmodelled errors are colored and time correlated. In general, the larger the time correlations are, the more significant the unmodelled errors. Hence, understanding the time correlations of unmodelled errors is important to develop the theory for processing the unmodelled errors. In this study, we compare and analyze the time correlations caused by unmodelled errors of Global Positioning System (GPS) and BeiDou signals. The time correlations are estimated based on the residuals of double differenced observations on 11 baselines with different lengths. The results show that the time correlation patterns are different significantly between GPS and BeiDou observations. Besides, the code and phase data from the same satellite system are also not the same. Furthermore, the unmodelled errors are affected by not only the baseline length, but also some other factors. In addition, to make use of the time correlations with more efficiency, we propose to fit the time correlations by using exponent and quadratic models and the fitting coefficients are given. Finally, the sequential adjustment method considering the time correlations is implemented to compute the baseline solutions. The results show that the solutions considering the time correlations can objectively reflect the actual precisions of parameter estimates.

With great potential for being applied to Internet of Things (IoT) applications, the concept of cloud-based Snapshot Real Time Kinematics (SRTK) was proposed and its feasibility under zero-baseline configuration was confirmed recently by the authors. This article first introduces the general workflow of the SRTK engine, as well as a discussion on the challenges of achieving an SRTK fix using actual snapshot data. This work also describes a novel solution to ensure a nanosecond level absolute timing accuracy in order to compute highly precise satellite coordinates, which is required for SRTK. Parameters such as signal bandwidth, integration time and baseline distances have an impact on the SRTK performance. To characterize this impact, different combinations of these settings are analyzed through experimental tests. The results show that the use of higher signal bandwidths and longer integration times result in higher SRTK fix rates, while the more significant impact on the performance comes from the baseline distance. The results also show that the SRTK fix rate can reach more than 93% by using snapshots with a data size as small as 255 kB. The positioning accuracy is at centimeter level when phase ambiguities are resolved at a baseline distance less or equal to 15 km.

Global navigation satellite systems (GNSSs) play a key role in intelligent transportation systems such as autonomous driving or unmanned systems navigation. In such applications, it is fundamental to ensure a reliable precise positioning solution able to operate in harsh propagation conditions such as urban environments and under multipath and other disturbances. Exploiting carrier phase observations allows for precise positioning solutions at the complexity cost of resolving integer phase ambiguities, a procedure that is particularly affected by non-nominal conditions. This limits the applicability of conventional filtering techniques in challenging scenarios, and new robust solutions must be accounted for. This contribution deals with real-time kinematic (RTK) positioning and the design of robust filtering solutions for the associated mixed integer- and real-valued estimation problem. Families of Kalman filter (KF) approaches based on robust statistics and variational inference are explored, such as the generalized M-based KF or the variational-based KF, aiming to mitigate the impact of outliers or non-nominal measurement behaviors. The performance assessment under harsh propagation conditions is realized using a simulated scenario and real data from a measurement campaign. The proposed robust filtering solutions are shown to offer excellent resilience against outlying observations, with the variational-based KF showcasing the overall best performance in terms of Gaussian efficiency and robustness.

The paper analyzed the number of various types of accidents, deaths and their ratios in Chinese coal mines from 2004 to 2015, and analyzed existing problems of coal mine accident emergency rescue technology and equipment. Occurrence of accidents mainly relies on manual discover, and emergency response time is long. Emergency communication and precision personnel positioning systems in underground coal mine are vulnerable to disaster, where disaster location and/or personnel position cannot be determined. Remote sensing range of disaster environment is small, the reliability is poor, and it is difficult to meet needs of disaster relief. Emergency scheme has poor pertinence and applicability. Emergency decision making is mainly depended on experience. Efficiency of manual demolition and support rescue equipment is low. Wind flow after disaster cannot be controlled real-timely and effectively, etc. It put forward emergency rescue technology of coal mine accident and key scientific and technical problems of equipment: ① determination method and technology of identification and spread range of serious accidents in coal mine; ② intelligent emergency scheme and rescue assistant decision making technology based on big data; ③ anti disaster emergency communication technology for coal mine; ④ precision personnel positioning technology in disaster (difficult); ⑤ intelligent control technology of wind flow after fire, gas and coal dust explosion disasters; ⑥ evacuation guidance technology for people in distress; ⑦ flying robot technology for monitoring disaster environment; ⑧ gas remote sensing technology in disaster environment; ⑨ rapid construction technology for rescue channel, etc.

The paper presents national report of Poland for IAG on positioning and applications. The selected research presented was carried out at leading Polish research institutions and concern precise multi-GNSS satellite positioning - relative and absolute - and also GNSS-based ionosphere and troposphere modelling and studies. The research resulted in noticeable advancements in these subjects confirmed by the development of new algorithms and methods. New and improved methods of precise GNSS positioning were developed, and also GNSS metrology was studied. New advanced troposphere models were presented and tested. In particular, these models allowed testing IPW variability on regional and global scales. Also, new regional ionosphere monitoring web-based services were developed and launched.

In order to solve the problem that existing personnel locating system can not meet large data access requirement of large-scale coal mines, Hadoop was proposed to be used in personnel positioning software system, and parallel computing model MapReduce and non-relational database HBase were used to realize parallel access of personnel positioning data. The application of Hadoop can significantly improve data processing performance, real-time performance and scalability of personnel positioning software system.

Global Navigation Satellite Systems (GNSS) are the main source of position, navigation, and timing (PNT) information and will be a key player in the next-generation intelligent transportation systems and safety-critical applications, but several limitations need to be overcome to meet the stringent performance requirements. One of the open issues is how to provide precise PNT solutions in harsh propagation environments. Under nominal conditions, the former is typically achieved by exploiting carrier phase information through precise positioning techniques, but these methods are very sensitive to the quality of phase observables. Another option that is gaining interest in the scientific community is the use of large bandwidth signals, which allow obtaining a better baseband resolution, and therefore more precise code-based observables. Two options may be considered: (i) high-order binary offset carrier (HO-BOC) modulations or (ii) the concept of GNSS meta-signals. In this contribution, we assess the time-delay and phase maximum likelihood (ML) estimation performance limits of such signals, together with the performance translation into the position domain, considering single point positioning (SPP) and RTK solutions, being an important missing point in the literature. A comprehensive discussion is provided on the estimators’ behavior, the corresponding ML threshold regions, the impact of good and bad satellite constellation geometries, and final conclusions on the best candidates, which may lead to precise solutions under harsh conditions. It is found that if the receiver is constrained by the receiver bandwidth, the best choices are the L1-M or E6-Public Regulated Service (PRS) signals. If the receiver is able to operate at 60 MHz, it is recommended to exploit the full-bandwidth Galileo E5 signal. In terms of robustness and performance, if the receiver can operate at 135 MHz, the best choice is to use the GNSS meta-signals E5 + E6 or B2 + B3, which provide the best overall performances regardless of the positioning method used, the satellite constellation geometry, or the propagation conditions.

The berthing of an ultra large ship is always a difficult issue and becomes yet more complex when vessels must be handled in restricted manoeuvring areas of limited depth, exposed to a forceful crosswind, or manoeuvring in a strong current, or all three. The final approaching manoeuvre and precise positioning is particularly demanding at container terminals where many STS cranes are located along the quay, seriously limiting margin for error in the process of mooring a ship, especially when the cranes are located nearby a bridge wing or at the very edge of the pier. In order to avoid collisions, the final manoeuvre (side-push) must be fully controlled; the ship’s orientation must be parallel with the quay while maintaining the minimum lateral approaching velocity without significantly shifting the vessel longitudinally. The mooring of a Ro-Ro vessel is occasionally even more challenging: a precise docking manoeuvre is normally executed without any towing assistance. In this paper low cost laser-based berthing and docking systems developed for the ports of Koper and Swinousce are presented and several berthing manoeuvres are analysed and compared with the most commonly used GNSS-based navigational aid system portable pilot units (PPU).

This contribution analyzes the fundamental performance limits of traditional two-step Global Navigation Satellite System (GNSS) receiver architectures, which are directly linked to the achievable time-delay estimation performance. In turn, this is related to the GNSS baseband signal resolution, i.e., bandwidth, modulation, autocorrelation function, and the receiver sampling rate. To provide a comprehensive analysis of standard point positioning techniques, we consider the different GPS and Galileo signals available, as well as the signal combinations arising in the so-called GNSS meta-signal paradigm. The goal is to determine: (i) the ultimate achievable performance of GNSS code-based positioning systems; and (ii) whether we can obtain a GNSS code-only precise positioning solution and under which conditions. In this article, we provide clear answers to such fundamental questions, leveraging on the analysis of the Cramér–Rao bound (CRB) and the corresponding Maximum Likelihood Estimator (MLE). To determine such performance limits, we assume no external ionospheric, tropospheric, orbital, clock, or multipath-induced errors. The time-delay CRB and the corresponding MLE are obtained for the GPS L1 C/A, L1C, and L5 signals; the Galileo E1 OS, E6B, E5b-I, and E5 signals; and the Galileo E5b-E6 and E5a-E6 meta-signals. The results show that AltBOC-type signals (Galileo E5 and meta-signals) can be used for code-based precise positioning, being a promising real-time alternative to carrier phase-based techniques.

Wheel flats have become a major problem affecting the long-term service of railway systems. Wheels with flats create intermittent impact loads to trains and rails. This not only accelerates the deterioration of vehicle and track components but also leads to abnormal wheel-rail contact conditions. An effective method for detecting wheel conditions is urgently needed to ensure the operation of the railway and provide guidance for the repair of wheels. However, most previous researches have used qualitative detection methods, and hence have been unable to achieve accurate positioning of the wheel flats. In addition, the theoretical basis for the layout scheme for wheel flat detection sensors is lacking, making it impossible to meet the needs of field applications. In this study, we simulated the spatial distribution characteristics of rail strain, under different wheel flat conditions, and based on this, a layout scheme of multisensor arrays was proposed which more effectively captured the responses of the wheel flats. A wheel flat recognition and precise positioning method based on multisensor fusion was designed. The algorithm was validated through the combination of experimental and simulation methods. The result shows that the algorithm can ideally detect and locate the wheel flats under complex conditions.

Technical development, new applications and requests for increased accuracy in georeferencing are setting new demands for accuracy and reliability of reference frames. Due to crustal deformations and local movements of benchmarks, a static reference network deteriorates with time, thus eventually requiring update of the whole system. Technically, renewal of a reference frame is straightforward and should be done whenever enough new data or updated information exist to get an improvement in accuracy. An example is the International Terrestrial Reference Frame, ITRF, which is renewed regularly. The situation is more complicated with national reference frames which may have been given a legal status, and parameters defined by the national legislation. Even without that, renewal and implementation of such a frame is a multi-million euro project taking years to complete. Crustal deformations and movements deteriorate static reference frames (defined by fixed/static coordinates of benchmarks) with time. Eventually, distortions in a static reference frame will become bigger than the uncertainties of GNSS measurements, thus deteriorating the obtainable accuracy of the measurement technique. Instead of a static reference frame, one can use semi-kinematic or kinematic approach where either the transformation from global to the national reference frame or the coordinates of reference frame benchmarks are time-dependent. In this paper we give a short overview of the topic, and discuss on technical issues and future aspects of the reference frames in the viewpoint of National Mapping and Cadastre Authorities (NMA) with an example on the national strategy in Finland.

In view of problem that the accuracy of existing personnel positioning system is not high and ca't meet demand of precise positioning, a precise positioning method of underground moving target based on distance measurement technology was proposed. The method uses RSSI and TOF ranging technology to calculate accurate position of moving target, and can use historical data to estimate current location of the target in failure ranging caused by communication barriers. The experimental results show that the method can effectively obtain the moving target location, and has low computation complexity and good real-time performance, so it can be used for accurate personnel positioning in mine underground.

Most underground positioning systems can only provide regional positioning function and are unable to provide accurate real-time location information for personnels or equipments, a design scheme of underground precise positioning system based on CSS technology was proposed. The system uses SDS-TWR localization algorithm and positioning management protocol to get high positioning accuracy. Meanwhile, it does't need to do clock synchronization, which enhances realizability and stability of the system. The testing results show that the system realizes high-precision positioning for underground equipments and personnels, which positioning accuracy is less than 3 m and the farthest transmission distance is 350 m.

This study analyzed the application of the XBee technology for control applications embedded in big machinery. In particular, it presented the control layout, topology, design of frames, and error control mechanisms that are required for implementing wireless control networked applications. This study was devoted to presenting experimental use cases of wireless control systems that help the scientific community to design and implement new control systems. Experimental tests were carried out over a Single Input Single Output (SISO) control application to evaluate its use in close loop applications. The results of these tests have been discussed in detail. In order to clarify the use of XBee in control applications, a high precision positioning application has been presented. It involved a piezoelectric actuator that was remotely controlled by means of a Proportional Integral (PI) controller, which was implemented in LabVIEW over a NI myRIO platform. Both the sensor and the actuators were connected with the NI myRIO by means of the XBee anthenae. The results showed that even though XBee technologies present some drawbacks, such as a lower performance when compared to wired connections and the influence of interferences, they have the potential to be used in some scenarios for non-critical control applications.