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Effect of different construction materials on propagation of GPS monitoring signals
Abstract
The GPS carrier phase observations are widely used for the high precision static and kinematic positioning applications. However, GPS signals are seriously distorted when passing through walls and other obstructions. This paper focuses on this issue and outlines the research carried out to investigate the effects of some commonly used construction materials on the GPS signals. For the purpose of generating the multipath in a controlled manner, an experimental set-up is designed to test the effect of typical building surface materials (toughened glass, wood board, PVC board and ceramic tile) on positioning accuracy. The effects of signal attenuation on the accuracy of the positioning solution are explored by an improved particle filtering algorithm and some statistical methods, and reasons for these effects are further analyzed. The findings of the experimental results may be used to enhance the performance of GPS technology.
... Attention should be given to the multipath issue for effective deployments in urban environments [7]. [15] Studied the influence of five widely used materials on multipath GPS signal propagation (aluminium, glass, wood, polyvinyl chloride (PVC), and ceramic). Field assessments involving current GPS signals were used to perform the research. ...
... 3.1-In the first study, the data collection involved the comparison of the observation results from five tests that varied the material type of vertical reflective surface (aluminium panel, glass panel, ceramic panel, and wood board) at a distance of 1.50m from the receiver at an antenna Height of 1.10 m in four tests (15,16,17, and 18 February) respectively, and one test was without reflective vertical surface (No Multipath) on 19 February. The survey station is located on the roof of the Civil Engineering Department building, Al-Azhar University, Cairo, Egypt (N30°03'22" and E31°18'54"), as shown in Fig. 1 The observations were done at the same time to have the same satellite geometry. ...
... (a) (b) The higher mean error observed for the data sampled at geodetic mark 1, Figure 3a, may be explained by the interference of a steel hangar near the geodetic mark. Since the multipath is an error source in GPS signals and it refers to the signal reflected from objects in vicinity of a receiver antenna and metal materials around the GPS antenna causes the total reflection to the GPS signal [24], the steel hangar increases the multipath affecting the data. In other experiments, Figure 3b, far from this kind of interference, the mean error did not reach this value. ...
... Mark Latitude Longitude The higher mean error observed for the data sampled at geodetic mark 1, Figure 3a, may be explained by the interference of a steel hangar near the geodetic mark. Since the multipath is an error source in GPS signals and it refers to the signal reflected from objects in vicinity of a receiver antenna and metal materials around the GPS antenna causes the total reflection to the GPS signal [24], the steel Sensors 2020, 20, 1947 7 of 21 hangar increases the multipath affecting the data. In other experiments, Figure 3b, far from this kind of interference, the mean error did not reach this value. ...
This article analyzes the use of Remotely Piloted Aircrafts (RPA) in VOR (Very High Frequency Omnidirectional Range) flight inspection. Initially, tests were performed to check whether the Autopilot Positioning System (APS) met the regulatory requirements. The results of these tests indicated that the APS provided information within the standard regulations. A Hardware in the Loop (HIL) platform was implemented to perform flight tests following the waypoints generated by a mission automation routine. One test was performed without introducing disturbance into the proposed test platform. The other four tests were performed introducing errors in latitude and longitude in the APS into the platform. The errors introduced had the same characteristics as those measured in the initial tests, in order for the simulation tests to be as similar as possible to the real situation. The tests performed with positioning errors only did not lead to false misalignment detection. However, introducing positioning errors and a 4° VOR misalignment error, a misalignment of 3.99° was observed during the flight test. This is a value greater than the maximum one allowed by the regulations, and the system indicates the VOR misalignment. Five flight inspection tests were performed. In addition to the APS errors, tests with a modulation error were also conducted. Introducing a 4° VOR misalignment in conjunction with modulation error, a misalignment of 4.02° was observed, resulting in successful misalignment detection.
... Yi et al. [8] studied the effect of five commonly used materials (aluminium, glass, wood, polyvinyl chloride (PVC) and ceramic) on multipath propagation of GPS signals. The study was conducted via field evaluations using live GPS signals. ...
... This is followed by glass, ceramic, PVC and wood. These results are consistent with the findings obtained in Yi et al. [8]. Metal materials, such as, in the case of this study, aluminium, cause total reflection of GPS signals and hence, higher multipath. ...
In this study, Global Positioning System (GPS) simulation is employed to study the effect of five commonly used materials (aluminium, glass, wood, polyvinyl chloride (PVC) and ceramic) on multipath propagation of GPS signals. Based on the results of this study, it is found that multipath signals from panels made of the materials cause increase in probable error values due to errors in the GPS receiver's pseudorange measurements. The probable errors decrease with increasing distances of the panels from the GPS receiver due to decrease of strength of multipath signals. It is observed that aluminium causes the highest amount of the multipath, resulting in the highest probable errors. This is followed by glass, ceramic, PVC and wood.
... Lau et al. [175] established a Ray-Tracking model of the station environment on the basis of the study of the geometric relationship between the satellite-reflector-antenna and the characteristics of the reflective material and the antenna, which is used to reduce the multipath effect. Yi et al. [176] studied the multipath effect of the GNSS signals in the background of different building materials, and applied this pattern to improve the accuracy of measurement and positioning. Groves et al. [177] used urban 3D maps and Non-Line-Of-Sight (NLOS) signal propagation models to weaken the impact of multipath effects. ...
Deformation monitoring and dynamic characteristic analysis of bridge structures are the vital and basic requirements for the safe operation of bridges. In recent years, Global Navigation Satellite System (GNSS) has become increasingly widely used in bridge structural health monitoring with the development of the GNSS technology, especially the continuous improvement and development of China’s Beidou navigation satellite system (BDS). This article summarises the application process of GNSS dynamic deformation monitoring and the development of GNSS deformation measurement technology of bridge structural health monitoring, the dynamic characteristic identification method and its application in bridge GNSS monitoring. The positioning solution methods for GNSS monitoring, the high sampling rate GNSS receiver for monitoring, multi-frequency and multi-system GNSS monitoring and the weakening of multipath effect of GNSS monitoring are summarised in detail. Then, the conclusions and prospects are posed for future research and related application.
... Finite element method is being widely used in civil engineering issues, such as structural performance evaluation, health monitoring, reliability, resilience, optimization, damage detection, etc. [1][2][3][4][5][6][7]. For the latter four kinds of analyzes, the final results are usually obtained through a large amount of iteration steps with finite element model (FEM). ...
Mathematical modelling method (MMM) is widely applied in engineering issues. But the performance of MMMs is rarely compared, especially with high dimensional variables. This research focused on the comparison among three mostly used MMMs, i.e.,quadratic polynomial (QPMM), kriging (KMM) and neural network (NNMM), based on model updating of a bridge with 13 variables and in-situ data. Firstly, 200 indetermined samples by Latin Hypercube sampling were generated and the relevant responses were computed by finite element model (FEM). Secondly, explicit expressions of responses by MMMs were established. Finally, with the optimization program and explicit expressions, updated variable groups were optimized. From the process and results of FEM updating, it shows that all the MMMs lead to an acceptable result as the discrepancies were reduced sharply. In terms of accuracy, KMM and NNMM are better than QPMM, but in terms of efficiency, KMM is time-consuming.
... This group of techniques is called infrastructure-free techniques and includes GNSS, inertial sensors, and image-based positioning. However, receiving a GNSS signal is very problematic in building interiors because direct visibility of the GNSS signal between satellites and receivers is not allowed, which goes to a multipath effect [11]. Therefore, there have been many efforts to refine the acquired position by using high-sensitivity receivers [12] or pseudo-satellites [13] or combining GNSS with inertial sensors [14]. ...
As people grow accustomed to effortless outdoor navigation, there is a rising demand for similar possibilities indoors as well. Unfortunately, indoor localization, being one of the requirements for navigation, continues to be a problem without a clear solution. In this article, we are proposing a method for an indoor positioning system using a single image. This is made possible using a small preprocessed database of images with known control points as the only preprocessing needed. Using feature detection with the SIFT (Scale Invariant Feature Transform) algorithm, we can look through the database and find an image that is the most similar to the image taken by a user. Such a pair of images is then used to find coordinates of a database of images using the PnP problem. Furthermore, projection and essential matrices are determined to calculate the user image localization—determining the position of the user in the indoor environment. The benefits of this approach lie in the single image being the only input from a user and the lack of requirements for new onsite infrastructure. Thus, our approach enables a more straightforward realization for building management.
... However, GPS is unreliable in built-up areas or indoors as no line of sight (LOS) connection is available. In addition, GPS suffers from signal attenuation on through material propagation [4]. The limited positioning accuracy of several meters [5] is not sufficient for many indoor localization use cases. ...
This paper experimentally investigates passive human visible light sensing (VLS). A passive VLS system is tested consisting of one light emitting diode (LED) and one photodiode-based receiver, both ceiling-mounted. There is no line of sight between the LED and the receiver, so only reflected light can be considered. The influence of a human is investigated based on the received signal strength (RSS) values of the reflections of ambient light at the photodiode. Depending on the situation, this influence can reach up to ± 50 % . The experimental results show the influence of three various clothing colors, four different walking directions and four different layouts. Based on the obtained results, a human pass-by detection system is proposed and tested. The system achieves a detection rate of 100% in a controlled environment for 21 experiments. For a realistic corridor experiment, the system keeps its detection rate of 100% for 19 experiments.
... iv) GPS wave distance signals. Yi et al, (2012), mentioned that The multipath signals are always delayed compared to the line of sight LOS signals because of the longer travel paths caused by reflections. From the geometrical relations shown in figure 1, the wave path difference ∆ between indirect and direct signal lengths from the satellite antenna to the receiving antenna can be calculated as follows: ∆ = AB + BC = BC · cos (180° − 2β) + S sin β = 2S·sinβ-S sin β+S sin β = 2S ·sin β ...
Global Positioning System (GPS) results are suffering from one of the major errors in high precision GPS positioning, the ones caused by reflections, known as Multipath error. Here, we study some of the multipath factors affecting on the accuracy observables obtained from GPS measurements. This will be achieved through monitoring and record the multipath effect according to different types of surface which reflected the signals specific set of generating and monitoring systems for multipath signal is established and a series of controlled experiments are carried out. Experimental results show that Aluminium caused the highest amount of multipath. This is followed by Glass and Wood.
... This could be due to inherent differences in the GPS antenna used by each device or to the collar and housing for each unit. The metal hose clamps of the COTS collars may have impeded GPS signals (see Yi et al., 2012), and the weight of the housing caused it to typically hang below the cow's neck. Conversely, the iGotU devices were housed in a nylon pouch stitched to the collar (after Knight et al., 2018) that would not impede GPS signal. ...
Global Positioning System (GPS) tracking devices are a fundamental technology for quantifying the distribution and movement of livestock across landscapes. Although costs of GPS devices have decreased, it is still cost prohibitive to implement a large number of collars per study. Our objective was to develop and test a low-cost GPS collar using commercial off-the-shelf (COTS) electronic components to study livestock distribution and movement. Our COTS GPS tracker was built using the popular Arduino open-source microcontroller and a low-power timer board to cycle a GPS at defined intervals. Location data were saved to a data card in an open format for easy analysis. Total cost per COTS GPS device (including housing and collar) was $54.78. Average displacement from a known location and 95% circular error probability was 4.58 m, commensurate with other GPS collars. We tested durability and field performance of 25 COTS GPS collars against 24 existing GPS collars recording data at 5-min intervals in a southwest Idaho, United States study area. Our COTS GPS design and test showed that it is possible to manufacture low-cost location tracking devices, but the limitations of such devices must be considered relative to study objectives and duration. Low-cost location trackers will encourage collection of a higher density of location information to better understand patterns of livestock use in rangeland landscapes.
... Leptich et al. [10] further found that GPS accuracy of hand-held devices was impacted by obstruction of the antenna by aircraft surfaces. GNSS signals are also strongly influenced by materials frequently found in aircraft construction, including aluminum and plastic, due to multipath errors [11]. ...
Global Navigation Satellite System (GNSS) receivers make use of the United States' Global Positioning System (GPS), Russia's Global Navigation Satellite System (GLONASS), Europe's Galileo, China's Beidou, and Japan's Quasi-Zenith Satellite System constellations to determine the geolocation of the receiver based on the location of satellites and measurements of the distance and travel time of the GNSS signals. GNSS signals are dependent on line of sight to satellites with reflections or obstructions resulting in errors in the estimated position [1]. GNSS systems, while having their origin in military applications [2], have been adopted for many civilian uses from recreational navigation [3] to automated vehicle location systems [4]. While the GPS Standard Positioning Service without any correction sources establishes a 30 m range error limit for civilian use, GPS receivers typically perform better than this standard with errors primarily from atmospheric interference [5]. This is further improved in mobile devices by assisted GPS, WiFi, and cellular positioning when available [6].
... The average values have been computed and tabulated in Table 1. However the uncertainty analysis of the experimental results have to be done to ensure the accuracy of the results further [17,18]. The lower value of standard deviation and error indicates the closeness of experimental results to the mean value. ...
In electrical discharge machining, the performance measures are mainly influenced by the discharge energy developed during the machining process. Owing to its higher strength, stainless steel can be easily machined by electrical discharge machining under the presence of dielectric medium. Since the surface quality of high strength workpiece is influenced by white layer formation, it is very essential to analyze the effects of discharge energy distribution and process parameters on white layer formation in machining process. In the present study, an endeavor has been attempted to analyze the influence of a modified pulse energy generator system on performance measures. From the experimental results, it has been observed iso energy pulse generator has created thinner and more symmetrical white layer thickness on the machined workpiece owing to its ability to produce lower discharge energy pulses with nearly uniform energy distribution. Peak current has been observed as significant factor on determining white layer formation in the EDM process.
... Yoshimoto et al. (2014) noticed significant particle breakage after cyclic shear increased with higher confining pressures and explained that breakage was caused more by the shear stress rather than the normal stress. The sand crushing is expected to occur under cyclic loading such as earthquake or structure vibration (Yi et al. 2001(Yi et al. , 2012a(Yi et al. , 2012b. Fig. 11 illustrates the influence of the confining pressure σ c ' on the liquefaction resistance strength and relative breakage B r of Aio sand. ...
This paper presents an investigation of the liquefaction characteristics and particle crushing of isotropically consolidated silica sand specimens at a wide range of confining pressures varying from 0.1 MPa to 5 MPa during undrained cyclic shearing. Different failure patterns of silica sand specimens subjected to undrained cyclic loading were seen at low and high pressures. The sudden change points with regard to the increasing double amplitude of axial strain with cycle number were identified, regardless of confining pressure. A higher cyclic stress ratio caused the specimen to liquefy at a relatively smaller cycle number, conversely producing a larger relative breakage Br. The rise in confining pressure also resulted in the increasing relative breakage. At a specific cyclic stress ratio, the relative breakage and plastic work increased with the rise in the cyclic loading. Less particle crushing and plastic work consumption was observed for tests terminated after one cyclic loading. Majority of the particle crushing was produced and majority of the plastic work was consumed after the specimen passed through the phase transformation point and until reaching the failure state. The large amount of particle crushing resulted from the high-level strain induced by particle transformation and rotation.
... gov/orms/goa) and Coulomb US Geological Survey. For this study, we used GIPSY OASIS II developed by the Jet Propulsion Laboratory (JPL) as single-receiver ambiguity resolution in kinematic positioning (function of time) or PPP (Webb and Zumberge 1996;Yi et al. 2011Yi et al. , 2012Yi et al. , 2013cCheng et al. 2017), RINEX 2.11 input file format, measurement types: dual frequency P code and phase; JPL's precise orbit and clock products in the ITRF08 reference system, cutoff 5 , average PDOP less than 2, IGS standards satellite antenna phase centre offset, antenna type in RINEX input file, tropospheric gradients (Bar-Sever et al. 1998), second-order ionospheric delay (Kedar et al. 2003). ...
GPS measurements recorded at active sites in central Italy during the seismic events of greatest magnitude (24 August, 26 and 30 October 2016) were processed in kinematic mode according to the Precise Point Positioning (PPP) technique. The resulting data were the displacements and, by derivation with respect to time, the velocities and instantaneous horizontal accelerations. Elastic response spectra along the orthogonal walls of the site (if the GPS antenna was fixed to a building) or along the geographical directions (if the antenna was fixed to the ground) were obtained from the derived accelerations. The maximum amplitudes, i.e. “peak vibrations”, were then extracted from the response spectra. These peaks, unlike the co-seismic movements, represent the maximum instantaneous vibrations recorded following the “shock” produced by the seismic waves and thus are representative of both the discomfort perceived by the populations and the structural damage. This study shows that GPS is becoming an increasingly important tool to measure and monitor the dynamic responses of a structure. The results also provide a complete picture of the displacements induced by the seismic sequences in the earthquake-affected areas, leaving unresolved some questions concerning the localization of the phenomena and the causes of the structural deformations.
... First, multipath effect is highly correlated with the environment nearby, depending on the structure material, satellite angle elevation, distance from reflector object (structure) to the receiver antenna, as aforementioned, among others. Yi et al. (2012) compared multipath errors from different materials and the largest errors in the estimated coordinates were caused by an aluminum plate, followed by toughened glass, ceramic tile, polyvinyl chloride (PVC) and wood boards. ...
Continuous monitoring of large structures is essential to ensure their integrity. Many instruments and methods have been developed to support structure monitoring. Global Positioning System (GPS) plays an important role in such task thanks to the precision and millimeter level accuracy of the provided position information in near real-time. However, installing a GPS receiver can be a really difficult task depending on the structure, mainly when it is under collapse danger. To address this issue, this paper presents a new methodology for structure monitoring, without installing a receiver directly on the structure. Instead, a time-frequency analysis of the multipath effect, caused by GPS signal reflections, is performed. As this effect repeats in consecutive days, a change on its pattern indicates structure movement. This work investigates the feasibility of using wavelet spectra analysis of the multipath signal to monitor structure movement. An experiment simulating a structure movement was carried out and real GPS data were collected. Pseudorange and carrier phase data were evaluated using different wavelet bases. The experimental results have shown that the proposed methodology has great potential for detection of structure movements, especially using the pseudorange signals combined to Symmlets wavelet basis with 10 vanishing moments. From Receiver Operating Characteristic (ROC) analysis, accuracy measure, Spearman and Matthews correlation coefficients, the simulated movement was correctly detected for all signals at a 5% significance level.
... As we know, every kind of waves contains the information about the physical properties of the propagation medium. Therefore, the analysis of wave propagation is not only of great significance in theoretical study but also of distinctive practical value in many engineering fields such as geotechnical engineering, oil exploration, earthquake engineering, and vibration test [1][2] . To achieve that, it is essential to study the relation between the parameters about the physical properties of the medium and the waves propagating in it. ...
The frequency effects on the velocities and attenuations of the bulk waves in a saturated porous medium are numerically studied in the cases of considering and neglecting the compressibility of solid grain, respectively. The results show that the whole frequency can be divided into three parts, i.e., low frequency band, medium frequency band, and high frequency band, according to the variation curves and the characteristic frequency. The compressibility of the solid grain affects the P 1 wave distinctively, the S wave tiny, and the P 2 wave little. The effects of the porosity and Poisson’s ratio on the bulk waves are numerically analyzed. It is found that both the porosity and Poisson’s ratio have obvious effects on the bulk waves. Compared with the results in the case of neglecting the porosity-moduli relation, the results in the case of considering the porosity-moduli relation are more reasonable. The results in the case of considering the porosity-moduli relation can be degenerated into the results of elastic solid and pure fluid, while the results in the case of neglecting the porosity-moduli relation cannot be degenerated into the results of elastic solid and pure fluid. Therefore, the porosity-moduli relation must be considered in the parametric study for a certain porous medium.
... Most of these factors are closely related to the reflecting environment. In order to systematically conclude the effects of different construction materials on the GPS signals, Yi et al. (2012b) devised a novel experimental set-up to test the effect of typical building surface materials on positioning accuracy (Fig. 25). They found that the wood board caused the smallest error to the positioning solutions, followed by the PVC board, ceramic tile, toughened glass, and aluminum plate. ...
... This permitted to study the effect of a passing train on the GPS recordings in systematic experiments under controlled conditions (only noise in measurements). The output of this study, summarized below, is that the train passage produces a dynamic multipath (Moschas and Stiros, in press a) with spectral characteristics very different from the common "static" multipath (Han and Rizos 1997, Ge et al. 2000, Kaplan and Hegarty 2006, Yi et al. 2012b) and which is reflected in noise of the rover coordinates; an effect broadly analogous to the effect of rotors and of the changing position of flying helicopters (Matayoshi and Okuno 2007). This noise correlates with specific features (reflective surfaces) of the train passing in front of the receiver, and its amplitude does not present a systematic value as it depends on the constellation of tracked satellites at the time of measurements. ...
Measurement of deflections of certain bridges is usually hampered by corruption of the GPS signal by multipath associated with passing vehicles, resulting to unrealistically large apparent displacements. Field data from the Gorgopotamos train bridge in Greece and systematic experiments revealed that such bias is due to superimposition of two major effects, (i) changes in the geometry of satellites because of partial masking of certain satellites by the passing vehicles (this effect can be faced with solutions excluding satellites that get temporarily blocked by passing vehicles) and (ii) dynamic multipath caused from reflection of satellite signals on the passing trains, a high frequency multipath effect, different from the static multipath. Dynamic multipath seems to have rather irregular amplitude, depending on the geometry of measured satellites, but a typical pattern, mainly consisting of a baseline offset, wide base peaks correlating with the sequence of main reflective surfaces of the vehicles passing next to the antenna. In cases of limited corruption of GPS signal by dynamic multipath, corresponding to scale distortion of the short-period component of the GPS waveforms, we propose an algorithm which permits to reconstruct the waveform of bridge deflections using a weak fusion of GPS and RTS data, based on the complementary characteristics of the two instruments. By application of the proposed algorithm we managed to extract semi-static and dynamic displacements and oscillation frequencies of a historical railway bridge under train loading by using noisy GPS and RTS recordings. The combination of GPS and RTS is possible because these two sensors can be fully collocated and have complementary characteristics, with RTS and GPS focusing on the long- and short-period characteristics of the displacement, respectively.
... Some researchers studied the optimal sensor installation method, in order to make the sensor networks work more efficiently. Li et al. and Yi et al. have systematically studied this issue proposed some meaningful optimal sensor installation methods and algorithms [1][2][3][4]. Brillouin optical time-domain analysis technology (BOTDA) is a distributed optical fiber strain sensing technology based on stimulated Brillouin backscatter principle, which breaks through the traditional concept of point sensing and realizes the continuous distributed monitoring in its true sense. The sensing gauge and the spatial resolution in the temperature and strain measurement can reach a higher level than other sensing technologies. ...
The paper reports the application of the distributed optical fiber sensing technology and the FBG sensing technology in bridge strain monitoring; the overall changeable characteristics of the whole structure can be obtained through the distributed optical fiber sensing technology (BOTDA), meanwhile the accurate information of local important parts of the structure can be obtained through the optical fiber Bragg grating sensor (FBG), which can improve the accuracy of the monitoring. FBG sensor has a high sensitivity, but it can only realize the measurement of local discrete points for the quasidistributed sensing. BOTDA can realize the long distance and distributed measurement, but its spatial resolution is not high. FBG and BOTDA were applied together in bridge monitoring in this test, taking full advantage of the distributed BOTDA on the overall strain measurements of the structure, as well as monitoring the key parts by the arrangement of FBG. The combined application of BOTDA and FBG can achieve the overall monitoring from point to line and then to the surface and, therefore, obtain more comprehensive information on the strain of the test structure.
Antarctica is a continent that crucial for studying climate change and its progression across time, as well as analyzing and forecasting local and global change. In this environment, due to the challenges caused by sea-level rise, storm surges, and tsunamis, sustainability is a critical concern, particularly for coastal regions. As a result, the long-term observations that will be conducted in Antarctica are critical for monitoring the adverse impacts of climate change. In recent years, many monitoring approaches, both space, and ground-based are performed to monitor sea/ice level trends in space-based scientific investigations conducted in and around the region. In the study, based on one year of observations from the Palmer GNSS Station, used the GNSS Reflectometry technique to measure the sea level on the Antarctic Peninsula (PALM). GNSS Station observations were analyzed with a Lomb-Scargle periodogram to monitor daily sea-level changes, and results were validated with data from a co-located tide gauge (TG). The results show that the correlation between GNSS-R sea-level changes and tidal sea-level changes is found as 0.91.
Purpose
The existing literature has been mainly focused on local problems but without an overall framework for studying the top-level planning of intelligent construction from a systematic perspective. The purpose of this paper is to fill this gap.
Design/methodology/approach
This research adopts a deductive research approach.
Findings
This research proposes a reference architecture and related business scenario framework for intelligent construction based on the existing theory and industrial practice.
Originality/value
The main contribution of this research is to provide a useful reference to the Chinese government and industry for formulating digital transformation strategies, as well as suggests meaningful future research directions in the construction industry.
Recently, the topic of indoor outdoor detection (IOD) has seen its popularity increase, as IOD models can be leveraged to augment the performance of numerous Internet of Things and other applications. IOD aims at distinguishing in an efficient manner whether a user resides in an indoor or an outdoor environment, by inspecting the cellular phone sensor recordings. Legacy IOD models attempt to determine a user’s environment by comparing the sensor measurements to some threshold values. However, as we also observe in our experiments, such models exhibit limited scalability, and their accuracy can be poor. Machine learning (ML)-based IOD models aim at removing this limitation, by utilizing a large volume of measurements to train ML algorithms to classify a user’s environment. Yet, in most of the existing research, the temporal dimension of the problem is disregarded. In this paper, we propose treating IOD as a multivariate time series classification (TSC) problem, and we explore the performance of various deep learning (DL) models. We demonstrate that a multivariate TSC approach can be used to monitor a user’s environment, and predict changes in its state, with greater accuracy compared to conventional approaches that ignore the feature variation over time. Additionally, we introduce a new DL model for multivariate TSC, exploiting the concept of self-attention and atrous spatial pyramid pooling. The proposed DL multivariate TSC framework exploits only low power consumption sensors to infer a user’s environment, and it outperforms state-of-the-art models, yielding a higher accuracy combined with a smaller computational cost.
Global Navigation Satellite System Reflectometry (GNSS-R) technique is an approach that has been used in the last few years and produces effective results to estimate important climate change parameters such as snow thickness, sea level, forest biomass, growth of vegetation. In this study, the GNSS-R technique height determination accuracy was evaluated by using a vertical displacement tool that allows shifting the receiver height and measure within 1 mm accuracy. The main purpose is to investigate the accuracy of the GNSS-R technique to monitor vertical displacements of buildings which surfaces is smooth and the signal strength is high. For this purpose, height of the GNSS antenna was set to 3 heights with a 5 cm interval on the displacement tool. The signals was analyzed based on dominant signal reflection effect frequency of Signal to Noise Ratio (SNR) signals and heights were determined by Lomb-Scargle Periodogram (LSP) method. According to the results, GNSS-R technique provide sufficient accuracy with a 0.51 cm RMSE for smooth surfaces.
Indoor location remains challenging. GPS and cellular signals do not alwayspenetrate buildings well, and legacy techniques that relied in Wi-Fi broadcasts have lost their luster with the explosion of personaldevices focused on privacy and battery efficiency. In this context, Fine Timing Measurement (FTM), defined in IEEE 802.11-2016, appeared as viable solution to provide a blue dot inside. However, the Standard merely focuseson the frame exchanges, without consideringthe environment or the conditions where theywould occur. This thesis aims at analysingFTM in depth, to understand how it fits intothe mold of a modern location protocol, solving indoor navigation while ensuring end device privacy, but also allowing the infrastructure to track assets or collect analytic aboutfoot traffic.This thesis surfaces the strengths andweaknesses of FTM, and proposes implementation techniques and Standard enhance-ments to overcome the critical shortcomings.Among them, a method is proposed to facilitate the automation of Access point (re-sponding anchors) deployment, allowing themto automatically learn their geo-position. Another method is proposed to counteract the efficiency of a learning machine capable of fingerprinting client stations solely based on theirFTM exchanges. An augmentation of 802.11is suggested to limit the possibility of ranging and location attacks on FTM, and another augmentation to the Standard is designed toallow the infrastructure to also benefit from theranging exchange.
A positioning system for complex construction scenarios is necessary to apply due to the limitations of the traditional positioning system in a non-line-of-sight (NLOS) environment, in order to study the impact of obstacles on construction sites. A quantitative measurement experiment of positioning precision in an NLOS environment was conducted in a petrochemical construction site, and a large number of engineering data were obtained, which showed the feasibility of a Passive Phased Array Radar - Bluetooth Hybrid Positioning System (PPAR-B HPS). The novelty of this paper is to propose a simplified signal coverage model for rapid measurement via the analysis of on-site data of the petrochemical industry and analyze the factors affecting the positioning precision in NLOS environment via a positioning precision heatmap analysis method to promoting the development and application of positioning technology in construction sites. The effectiveness of these methods are proved by empirical and comparative research.
Model updating for bridge engineering structures to obtain precise finite element model is an efficient tool at present. But with the dimension of the potential parameters during optimization increasing, it brings a challenge to present optimization methods. To improve the performance of convergence process and the probability of detecting global extremum, a combination model updating method of modified particle swarm optimization (MPSO) and response surface method was proposed herein. MPSO has less modification to PSO as only modifying the particle position with Gaussian white noise at a probability and the performance was significantly superior than PSO illustrated by testing functions. A beam model updating example based on the proposed method was tested, the convergence ability and accuracy were compared with genetic algorithm which is widely applied in bridge model updating. Finally, the proposed method was successfully applied to model updating of an existing bridge engineering structures with thirteen variables.
During the earthquake in Emilia (Italy) of 2012, ca. 30 permanent GPS stations were in operation within a radius of about 100 km from the epicenter, each equipped with an antenna rigidly fixed to the host building and sampling the GPS signal at a high rate (> 1 Hz). From the recording of the GPS measurements, the instantaneous displacements s(t) in the North- South and East-West directions of the phase centers of the single GPS antennas at each permanent station during the most important seismic sequences were calculated in kinematic mode. Subsequently, for each of the two displacements considered as two distinct external forces, the elastic response spectra of the building were determined and from them the two periods of vibration T along two orthogonal directions coinciding with the walls of the building were extracted. The experimentally obtained periods of vibration were compared with those inferable from the technical literature. In this way, a sufficiently large sample was obtained per building type, geometry (square, rectangular, regular or irregular planimetry), height (from a minimum of 4 to a maximum of 20 m) and materials (masonry, reinforced concrete, etc.). From the computational point of view, the study confirmed that GPS is an emerging tool for monitoring dynamic displacements and the experimentally estimated value of T is always lower than the one estimated with the formulae reported in the literature. The limitations of the study lie in the impossibility to choose a priori the geometry and/or structural type of the building hosting the GPS station. © 2018, Institute of Engineering Mechanics, China Earthquake Administration and Springer-Verlag GmbH Germany, part of Springer Nature.
In the last few years, many structural monitoring studies have been performed using different techniques to measure structures of different scales such as buildings, dams or bridges. One of the mostly used tools are GPS instruments, which have been utilized in various combinations with accelerometers and some other conventional sensors. In the current study, observation series were recorded for 8 hours with GPS receivers (NovAtel) and Inclination Measurement Sensors mounted on a television tower in Istanbul, Turkey. Each series of observations collected from two different sensors were transformed into a single coordinate system (Local Topocentric Coordinates System). The positional changes of the tower were calculated from the GPS and the inclination data. These changes were plotted in two dimensions (2D) on the same graphic. Thus, the possibility of comparison and analysis were found using the data from both the GPS and the Inclinometer complement each other, in the real test area. The positional changes of the tower were modeled for further examination. As a result, the movement of the tower within an area of 1×1 cm2 was observed. Based on the results, it can be concluded that inclinometers can be used for monitoring the structural behavior of the tower.
In this study, Global Positioning Satellie (GPS) simulation is employed to study the effect of multipath on two handheld GPS receivers; Garmin GPSmap 60CSx (evaluated GPS receiver) and Garmin GPSmap 60CS (reference GPS receiver). Both GPS receivers employ the GPS L1 coarse acquisition (C/A) signal. Based on the results of this study, it is found that the decrease in number of visibles satellites due to physical obsructions and increase in number of multipath signals cause increase in probable error values, due to decreasing carrier-to-noise density (C/N0) levels for GPS satellites tracked by the receiver. In addition, the differences between horizontal positioning error (HPE) and vertical positioning error (VPE) values increase due to the removal of satellites above the horizon, while overhead satellites are maintained. Varying probable error patterns are observed for readings taken at different times. This is due to the GPS satellite constellation being dynamic, causing varying GPS satellite geometry over time, resulting in GPS accuracy being time dependent. The repeatability of multipath at stationary sites when GPS satellites are in the same positions during each orbital pass (approximately 11 min, 58 s) allows for corrections to be generated based on history of multipath occurances over time.
Previous tests conducted by the Instrumentation & Electronics Technology Division (BTIE), Science & Technology Research Institute for Defence (STRIDE), were aimed at evaluating the minimum interference signal power level required to jam the Global Positioning System (GPS) L1 coarse acquisition (C/A) signal. However, the tests were only performed using low interference power levels, for a distance of 3 m. In order to evaluate the power levels of interference signals required to jam a Garmin GPSmap 60CSx handheld receiver over various distances, a test was conducted on 21st January 2010 at the STRIDE Kajang Block B car park. It was observed that the power levels required to affect the location fixes are significantly high compared to the received GPS signal power received. This is because the noise-like C/A code structure, which spreads the L1 signal over a 2 MHz bandwidth, allows for the signal to be received at low levels of interferences. The minimum power level required to conduct GPS jamming is dependent on various error parameters, including ionospheric and tropospheric delays, satellite clock, ephemeris and multipath errors, and unintentional signal interferences and obstructions. On the whole, this test demonstrates the ease to conduct GNSS jamming. Relatively low power level interference signals, from intentional or unintentional sources, can disrupt GNSS signals over long range of distances. Given the dependence on GNSS for positioning, navigation and timing (PNT) applications, GNSS disruption could prove to be problematic, if not disastrous. Hence, GNSS vulnerability mitigations steps should be given emphasis, including PNT backups, making full use of ongoing GNSS modernisation programs, increased ability to identify and locate GNSS jammers, integrity monitoring and augmentation, and anti-jamming technologies.
The Halley VI Antarctic Research station was designed as a series of linked, ski-mounted modules. This makes it possible to relocate the station in the event that changing Antarctic conditions require it. These modules are gradually moving relative to each other, distorting the station configuration and potentially threatening the inter-module connections. In this paper we describe a scalable network of GPS receivers used to monitor this distortion. This network has been installed and operational for two months, and is measuring the relative motion of the modules to an accuracy of 1. mm, despite the station and its underlying ice shelf moving metres each day under the influence of ocean tides and glacial flow.
In order to effectively identify the abnormal monitoring data of GPS, the relational model of GPS monitoring time series is established. Then, the multi-step identification algorithm of abnormal GPS monitoring data based on the relational negative selection is proposed to overcome the drawback that the relational analysis cannot accurately determine the extent of the abnormal data. For the fixed-number and constant-sized detectors, an appropriate number of variable-sized detectors can be automatically generated by setting the space coverage rate, and the problem of space overlap is solved by Monte Carlo method. In addition, the self-representing method with self-adaptive size is proposed to solve the dynamic change of self space in negative selection algorithm, allowing the self radius adaptively adjust with the clustering features of self data, which satisfies the requirement of GPS based dynamic monitoring. Finally, the simulation data are used to verify the feasibility and efficiency of the method respectively. The analysis results show that the negative selection algorithm with self-adaptive radius can cover larger non-self space by fewer detectors, which improves the abnormal detection rate of GPS data. Moreover, the proposed algorithm can accurately determine the extent of abnormal data, which has high practical values in civil engineering. ©, 2015, Nanjing University of Aeronautics an Astronautics. All right reserved.
Since GPS has been made available for civil usage, satellite-based localization in open space has become a more and more common option for vehicular tracking and for a number of commercial applications. The accuracy of the localization results and the availability of the localization system are influenced by several factors, such as the characteristics of the devices used, the surrounding environment, and the distance from reference stations. The possibility of exploiting off-the-shelf GPS devices, in the contest of a composite multi-sensor localization, is currently being investigated within the framework of the ALARP project [9], where it is required to accurately localize workers in railway worksites. This paper presents the results of an experimental campaign aimed at determining if, and under which conditions, low-cost GPS devices can be used in such a scenario. The evaluation is performed comparing data from low-cost GPS devices to data collected using a highly accurate reference system. The analysis permits to assess the feasibility of two different, very popular, commercial GPS devices for the ALARP requirements on localization.
The bridge engineer has long needed methods of accurate global displacement measurement for use in construction and more recently in the areas of bridge health monitoring. In this paper, the reliability and practicability of using high-rate carrier phase global positioning system (GPS) receivers are investigated to characterize dynamic oscillations of bridges. Initially, the short baseline trial is conducted to study the precision and characteristics of such kind of receivers as well as the potential applications of such a high-frequency data rate. After that, the performance of high-rate GPS receivers for dynamic response tracking is validated against accelerometers through controlled experimental tests and a novel kind of wavelet packet-based filtering method is also proposed. Finally, on-site dynamic experiments are carried out to measure the bridge deck oscillation induced by different external loads. Observed data are compared with predicted values derived from modeling undertaken with the finite element (FE) analysis software. The results of all the experiments proved to be very encouraging, and showed that high-rate GPS receiver is successful in quantifying both environmental induced bridge vibrations and high-frequency transient motion caused by vehicle loading, providing the ability for verification and/or improvement of structural design and modeling.
ABSTRACT Multipath,affects ,the ,Global ,Positioning System measurements in different ways. For example, in the receiver, multipath distorts the correla tion function
This paper presents a method that is based on Electromagnetic Modeling (EM) technique for modelling GPS carrier phase multipath signals. A commercial software plus modules developed in-house are used for modeling and processing carrier phase multipath error parameters. Static multipath modeling experiments show that up to about 35% carrier phase errors and about 25% 3D positioning errors can be reduced.
It is well known that multipath disturbance is one of the major error sources impacting on high precision GPS positioning. The multipath disturbance is largely dependent on the receiver's environment since satellite signals can arrive at the receiver via multiple paths, due to reflections from nearby objects such as trees, buildings, vehicles, etc. Although the multipath effect can be reduced by choosing sites without multipath reflectors or by using choke-ring antennas to mitigate the reflected signal, it is difficult to eliminate all multipath effects from GPS observations. Since the geometry between the GPS satellites and a specific receiver-reflector location repeats every sidereal day, multipath tends to exhibit the same pattern between consecutive days. This repetition can then be useful for verifying the presence of multipath through the analysis of observations made at a static receiver on different days. In this study, the authors apply a wavelet decomposition technique to extract multipath from GPS observations. The extracted multipath signature is then applied directly to the GPS observations to correct for the multipath effects. The results show that the proposed method can be used to significantly mitigate the multipath effects at a permanent GPS station.
This paper describes GPS multi-antenna device (one GPS receiver links multiple antennas) developed by authors, and the experimental results are presented. GPS has already proven to be an efficient tool for monitoring dam deformations and stability of high-risk slopes. It offers greater accuracy than other surveying techniques. However, GPS has its disadvantages when employing for slope and dam monitoring. The major drawback has been high cost due to large-scale GPS deployments are required in monitoring sites. The conventional GPS monitoring methods, where a permanent GPS receiver must be located at each point, have significant limitations of the cost. A new approach that a single GPS receiver links multiple antennas mounted at the monitoring points, has been employed to solve these problems in this paper. A dedicated switching device has been developed by authors for this approach. Field testing results show that the dedicated switching device for GPS multi-antenna system has excellent performances. Post-processing positioning accuracy is around 1-2 mm for the deformation monitoring of the Xiaolangdi dam on the Yellow River.
We have proposed a technique based on an adaptive filter using the least-mean-square algorithm for detection of multipath change in permanent, continuously operating GPS (CGPS) stations. We have tested the technique on some experimental data, indicating that the multipath change smaller than the receiver noise level will go undetected. We have also conducted further tests with some CGPS data from the Japanese GEONET when there was a snowfall. The results show that when there is a change in the antenna environment it will indeed be detected in both the pseudo-range and carrier phase data. This technique provides an easy-to-implement, quality assurance tool for CGPS antenna environmental sensing after events such as typhoons, cyclones, snowfalls, volcano eruptions, earthquakes, etc. Other possible applications include the monitoring of slope stability and ground subsidence.
Introduction Volcanoes are an awesome display of Nature's power. In addition, volcanic explosions are often very destructive events, having a massive impact on the natural and human environment. It is therefore necessary to closely monitor volcanoes in order to mitigate the hazards arising from an eruption. Ground surface deformation can give clues to magmatic processes at depth, and is a reliable indicator of an impending eruption. The GPS technology is well suited for volcano deformation monitoring because GPS measurements can provide threedimensional positions, potentially at centimetre-level accuracy, independent of weather conditions, 24 hours per day. In addition, there is no requirement for intervisibility between stations within a GPS network, and measurements can be made over relatively long distances. Once a GPS network is installed, no human presence is needed at a potentially dangerous volcanic locale. By repeatedly measuring the same baseline vector to an accuracy commens
Multipath is one of the most important error sources in Global Navigation Satellite System (GNSS) carrier-phase-based precise
relative positioning. Its theoretical maximum is a quarter of the carrier wavelength (about 4.8cm for the Global Positioning
System (GPS) L1 carrier) and, although it rarely reaches this size, it must clearly be mitigated if millimetre-accuracy positioning
is to be achieved. In most static applications, this may be accomplished by averaging over a sufficiently long period of observation,
but in kinematic applications, a modelling approach must be used. This paper is concerned with one such approach: the use
of ray-tracing to reconstruct the error and therefore remove it. In order to apply such an approach, it is necessary to have
a detailed understanding of the signal transmitted from the satellite, the reflection process, the antenna characteristics
and the way that the reflected and direct signal are processed within the receiver. This paper reviews all of these and introduces
a formal ray-tracing method for multipath estimation based on precise knowledge of the satellite–reflector–antenna geometry
and of the reflector material and antenna characteristics. It is validated experimentally using GPS signals reflected from
metal, water and a brick building, and is shown to be able to model most of the main multipath characteristics. The method
will have important practical applications for correcting for multipath in well-constrained environments (such as at base
stations for local area GPS networks, at International GNSS Service (IGS) reference stations, and on spacecraft), and it can
be used to simulate realistic multipath errors for various performance analyses in high-precision positioning.
Multipath is one of the main causes of degraded position accuracy in the Global Navigation Satellite System (GNSS) because portions of the signals can be reflected by high buildings in dense urban areas. Multipath mitigation techniques based on hardware enhancement or signal processing help to improve GNSS accuracy for high-precision surveying. A Geographic Information System (GIS) is also used in the signal propagation model to predict multipath effects. In addition to these existing approaches, we found that spatial statistical methods are useful in multipath mitigation because the multipath produces a unique spatial distribution of user positions. In this paper, we present a spatial statistics-based simulation system for mitigating multipath and improving the accuracy in GNSS positioning. Multipath tends to be associated with spatial outliers in simulated user positions (SUPs) and contributes little to the spatial clustering of SUPs. Using these spatial characteristics, we developed a method called the “satellite participation ratio in outliers versus cluster” (SPROC) to identify multipath satellites. Once the identified multipath satellites are excluded, a user position is determined using a mean spatial center of the SUPs from the remaining satellites. The effects of such multipath mitigation were validated by examining whether the SPROC method correctly identified multipath satellites and by comparing the position errors with and without SPROC. We demonstrated the applicability of our system with a simulation experiment using a precise ephemeris for the Global Positioning System (GPS) and the orbital parameters for the proposed constellations of the GALILEO and the Quasi-Zenith Satellite System (QZSS). In our simulation of Shinjuku ward in Tokyo, the user-equivalent range error (UERE) other than multipath was virtually generated and added to the multipath delay. The pattern of position errors with and without SPROC showed that the improvements in accuracy were considerable at locations close to buildings.
In order to effectively improve the precision of GPS positioning results, the theoretical and experimental studies on multipath effect were carried on. A set of simulating and monitoring system for GPS multipath signals was established, and the continuously two-day-long GPS monitoring data were obtained by means of placing reflecting objects at different heights and distances from the receiver antenna. The improved particle filtering algorithm is the first time being used in the GPS data post-processing. The results indicates that the improved particle filtering algorithm can effectively eliminate the GPS signal receiver's system noise, and the relevance of continuously two-day-long multipath signals after denoising has the large scale enhancement compared with before denoising. It is found that the multipath errors caused by reflecting objects at different distances have certain regularity; the multipath errors reduce with the distances increase, and the reduction gets smaller when the same distance is increased.
The Global Positioning System (GPS) has been used in the health monitoring of large structures in recent years since it is weather independent, capable of autonomous operation, and does not require a line-of-sight, between target points. In this paper, a structural health, monitoring system based on the GPS is devised for a highrise building. The field data, such as wind speed, wind direction and displacement responses were simultaneously and continuously measured under strong wind conditions. The relation between velocity components of the atmospheric wind and pressure fluctuations on the roof of the building are analyzed using the wavelet scalogram and. wavelet coherence method, and a statistical significance level estimation method based on Monte Carlo simulation is presented to isolate the meaningful coherence from the spurious noise map. Finally, the responses of the high-rise building are investigated using the Periodogram method to conclude that the identified results agree well with the results computed by the Finite Element Method (FEM).
Nowadays, there are many larger and taller engineering structures than in the past. These structures are commonly designed
to be more flexible. Thus, they are sensitive to severe wind gust and earthquake tremor. For the dynamic response prediction,
finite element (FE) modal updating and structural health monitoring, the dynamic characteristics of a structure are becoming
increasingly important. The aim of this paper is to show an emerging tool-the real time kinematic (RTK) global positioning
system (GPS), which is used to measure and monitor the low-frequency vibration of Dalian BeiDa Bridge, a medium span suspension
bridge. The modal analysis is firstly performed on the developed three-dimensional FE model according to the original blue
prints of the bridge to provide the analytical frequencies and mode shapes. The field ambient vibration tests using the accelerometers
on the bridge deck are conducted just prior to the use of the GPS system in order to validate the FE model. And then, the
calibration test is done to assess the dynamic displacement measurement accuracy of the GPS in three orthogonal directions.
The GPS signal properties, such as the amplitude, standard deviations (STD), power spectral density (PSD), and probability
density functions (PDF), are studied in details. After that, a structural health monitoring system based on the GPS is devised
and installed on the bridge to provide real-time measurement of deck movement. The output-only modal parameter identification
is carried out by using the Periodogram method to investigate the responses of the bridge. The result shows that the spectral
densities of the displacements measured by the GPS correspond well with the results by the FEM analysis and the accelerometer
vibration test. It is concluded that the GPS method is reliable and useful to clarify the ambient vibration response behaviors
of the flexible structures. The integration of the GPS and accelerometer methods results in a hybrid arrangement that can
help to eliminate some disadvantages of the two devices used separately.
Keywordshealth monitoring-global positioning system-real-time kinematic-suspension bridge-modal analysis
The in-situ verification of structural performance under the action of wind requires monitoring technologies capable of capturing not only the resonant response features, but also the background and mean response components. This study explores the use of high-precision global positioning systems (GPS) toward that end. In this study, the performance of GPS for resonant response tracking is first validated in full scale against accelerometers, and then its ability to track both background and resonant response data is verified through controlled field tests. As the valuable low-frequency regime of this sensing technology is often compromised by long-period distortions known as multipath effects; this study then presents a means to characterize this phenomenon using Fourier and wavelet spectra and the GPS Distortion Signature. The latter diagnostic is shown to isolate multipath effects in controlled field testing. However, even when a GPS Distortion Signature is not available on-site, it is shown that multipath effects can still be removed by filtering to permit a rare comparison of the relative contributions of background and resonant responses in full scale to wind tunnel predictions.
Global Positioning System (GPS) has been successfully used to measure displacements of oscillating flexible civil engineering structures such as long suspension bridges and high-rise buildings, and to derive their modal frequencies, usually up to 1 Hz, but there is evidence that these limits can be exceeded using high frequency GPS receivers. Based on systematic experiments in computer controlled oscillations with one- and three-degrees of freedom we investigated the potential of GPS, first to record higher oscillation frequencies, at least up to 4 Hz at the minimum resolution level of this instrument for kinematic applications (⩾5 mm), and second, to identify more than one dominant frequency. Data were processed using least squares-based spectral analysis and wavelet techniques which permit to analyze entire time series, even those of too short duration or those characterized by gaps, in both the frequency and the time domain.The ability of GPS to accurately measure frequencies of oscillations of relatively rigid (modal frequencies 1–4 Hz) civil engineering structures is demonstrated in the cases of two bridges.The outcome of this study is that GPS is suitable for the identification of dynamic characteristics of even relatively rigid (modal frequencies up to 4 Hz) civil engineering structures excited by various loads (wind, traffic, earthquakes, etc.) if displacements are above the uncertainty level of the method (⩾5 mm). Structural health monitoring of a wide range of structures appears therefore a promising field of application of GPS.
This paper aims to investigate how 1m LiDAR data and 2D building footprints can be used to predict GPS multipath effects in
urban areas. A ray tracing model is implemented in order to model reflected and diffracted GPS signals. Some preliminary results
are presented and explained in detail.
This paper describes an automated method for predicting the number of satellites visible to a GPS receiver, at any point on the Earth's surface at any time. Intervisibility analysis between a GPS receiver and each potentially visible GPS satellite is performed using a number of different surface models and satellite orbit calculations. The developed software can work with various ephemeris data, and will compute satellite visibility in real time. Real‐time satellite availability prediction is very useful for mobile applications such as in‐car navigation systems, personal navigations systems and LBS. The implementation of the method is described and the results are reported.
We developed a comprehensive simulation system for evaluating satellite-based navigation services in highly built-up areas; the system can accommodate Global Positioning System (GPS) multipath effects, as well as line-of-sight (LOS) and dilution of position (DOP) issues. For a more realistic simulation covering multipath and diffracted signal propagations, a 3D-ray tracing method was combined with a satellite orbit model and three-dimensional (3D) geographic information system (GIS) model. An accuracy estimation model based on a 3D position determination algorithm with a theoretical delay-locked loop (DLL) correlation computation could measure the extent to which multipath mitigation improved positioning accuracy in highly built-up areas. This system could even capture the multipath effect from an invisible satellite, one of the greatest factors in accuracy deterioration in highly built-up areas. Further, the simulation results of satellite visibility, DOP, and multipath occurrence were mapped to show the spatial distribution of GPS availability. By using object-oriented programming, our simulation system can be extended to other global navigation satellite systems (GNSSs) simply by adding the orbital information of the corresponding GNSS satellites. We demonstrated the applicability of our simulation system in an experimental simulation for Shinjuku, an area of Tokyo filled with skyscrapers.
A kind of all-round GPS multipath signal testing device, Utility model patent certificate
- T H Yi
- H N Li
T.H. Yi, H.N. Li, A kind of all-round GPS multipath signal testing device, Utility model patent certificate, PR China, Patent No. ZL200920013309.9, 2010.