Real-time Global Positioning System Research Articles

A Performance Evaluation of Location Prediction Position-Based Routing Using Real GPS Traces for VANET

Vehicular ad-hoc network (VANET) is an emerging paradigm for road transportation which minimizes traffic, accidents and improves fuel efficiency. VANET uses the position of the vehicle obtained from satellite system such as global positioning system (GPS), global navigation satellite system, Compass and Galileo as a location id in position-based routing protocol. The position obtained from the satellite system is likely to have an error due to environmental and technical issues which effect the routing performance. Thus, this paper proposes a position-based routing protocol which uses Kalman filter based location prediction technique to improve routing performance by minimizing location error. The routing protocol performance is evaluated on NS-3.23 simulator with real time GPS traces and simulator generated mobility on Two-ray ground and Winner-II propagation model for 500 m transmission range. Further, performance is compared with other prediction-based routing protocol on the metrics of packet delivery ratio, average delay and throughput.

Real-time estimation of BDS/GPS high-rate satellite clock offsets using sequential least squares

The real-time precise satellite clock product is one of key prerequisites for real-time Precise Point Positioning (PPP). The accuracy of the 24-hour predicted satellite clock product with 15 min sampling interval and an update of 6 h provided by the International GNSS Service (IGS) is only 3 ns, which could not meet the needs of all real-time PPP applications. The real-time estimation of high-rate satellite clock offsets is an efficient method for improving the accuracy. In this paper, the sequential least squares method to estimate real-time satellite clock offsets with high sample rate is proposed to improve the computational speed by applying an optimized sparse matrix operation to compute the normal equation and using special measures to take full advantage of modern computer power. The method is first applied to BeiDou Navigation Satellite System (BDS) and provides real-time estimation with a 1 s sample rate. The results show that the amount of time taken to process a single epoch is about 0.12 s using 28 stations. The Standard Deviation (STD) and Root Mean Square (RMS) of the real-time estimated BDS satellite clock offsets are 0.17 ns and 0.44 ns respectively when compared to German Research Center for Geosciences (GFZ) final clock products. The positioning performance of the real-time estimated satellite clock offsets is evaluated. The RMSs of the real-time BDS kinematic PPP in east, north, and vertical components are 7.6 cm, 6.4 cm and 19.6 cm respectively. The method is also applied to Global Positioning System (GPS) with a 10 s sample rate and the computational time of most epochs is less than 1.5 s with 75 stations. The STD and RMS of the real-time estimated GPS satellite clocks are 0.11 ns and 0.27 ns, respectively. The accuracies of 5.6 cm, 2.6 cm and 7.9 cm in east, north, and vertical components are achieved for the real-time GPS kinematic PPP.

An Outdoor Navigation System for Blind Pedestrians Using GPS and Tactile-Foot Feedback

This paper presents a novel, wearable navigation system for visually impaired and blind pedestrians that combines a global positioning system (GPS) for user outdoor localization and tactile-foot stimulation for information presentation. Real-time GPS data provided by a smartphone are processed by dedicated navigation software to determine the directions to a destination. Navigational directions are then encoded as vibrations and conveyed to the user via a tactile display that inserts into the shoe. The experimental results showed that users were capable of recognizing with high accuracy the tactile feedback provided to their feet. The preliminary tests conducted in outdoor locations involved two blind users who were guided along 380–420 m predetermined pathways, while sharing the space with other pedestrians and facing typical urban obstacles. The subjects successfully reached the target destinations. The results suggest that the proposed system enhances independent, safe navigation of blind pedestrians and show the potential of tactile-foot stimulation in assistive devices.

Real-time predication and navigation on traffic congestion model with equilibrium Markov chain

With the explosive growth of vehicles on the road, traffic congestion has become an inevitable problem when applying guidance algorithms to transportation networks in a busy and crowded city. In our study, the authors proposed an advanced prediction and navigation models on a dynamic traffic network. In contrast to the traditional shortest path algorithms, focused on the static network, the first part of our guiding method considered the potential traffic jams and was developed to provide the optimal driving advice for the distinct periods of a day. Accordingly, by dividing the real-time Global Positioning System data of taxis in Shenzhen city into 50 regions, the equilibrium Markov chain model was designed for dispatching vehicles and applied to ease the city congestion. With the reveals of our field experiments, the traffic congestion of city traffic networks can be alleviated effectively and efficiently, the system performance also can be retained.

A grid-based tropospheric product for China using a GNSS network

Tropospheric delay accounts for one source of error in global navigation satellite systems (GNSS). To better characterize the tropospheric delays in the temporal and spatial domain and facilitate the safety-critical use of GNSS across China, a method is proposed to generate a grid-based tropospheric product (GTP) using the GNSS network with an empirical tropospheric model, known as IGGtrop. The prototype system generates the GTPs in post-processing and real-time modes and is based on the undifferenced and uncombined precise point positioning (UU-PPP) technique. GTPs are constructed for a grid form ( $$2.0{^{\circ }}\times 2.5{^{\circ }}$$ latitude–longitude) over China with a time resolution of 5 min. The real-time GTP messages are encoded in a self-defined RTCM3 format and broadcast to users using NTRIP (networked transport of RTCM via internet protocol), which enables efficient and safe transmission to real-time users. Our approach for GTP generation consists of three sequential steps. In the first step, GNSS-derived zenith tropospheric delays (ZTDs) for a network of GNSS stations are estimated using UU-PPP. In the second step, vertical adjustments for the GNSS-derived ZTDs are applied to address the height differences between the GNSS stations and grid points. The ZTD height corrections are provided by the IGGtrop model. Finally, an inverse distance weighting method is used to interpolate the GNSS-derived ZTDs from the surrounding GNSS stations to the location of the grid point. A total of 210 global positioning system (GPS) stations from the crustal movement observation network of China are used to generate the GTPs in both post-processing and real-time modes. The accuracies of the GTPs are assessed against with ERA-Interim-derived ZTDs and the GPS-derived ZTDs at 12 test GPS stations, respectively. The results show that the post-processing and real-time GTPs can provide the ZTDs with accuracies of 1.4 and 1.8 cm, respectively. We also apply the GTPs in real-time kinematic GPS PPP, and the results show that the convergence time of the PPP solutions is shortened. These results confirm that the GTPs can act as an efficient information source to augment GNSS positioning over China.

Study on Tracked Combine Harvester Dynamic Model for Automated Navigation Purposes

This research describes the tracked combine harvester dynamic model developed based on the sensors measurements for the controlling of tracked combine harvester and the application of automated navigation. Real time global positioning system and inertial measurement unit were equipped on the tracked combine harvester for obtaining the position, direction of travel, angular rate etc. Circular and sinusoidal trajectories were performed by the tracked combine harvester over the concrete and soil ground from a set of steering commands to evaluate the tracked combine harvester dynamic model. The results indicate that the computed harvester state, angular yaw rate, soil parameter, track coefficients, turning radius and sideslip angle from the tracked combine harvester dynamic model and sensors measurements can be used to control an autonomous tracked combine harvester during nonlinear maneuverability.

Towards adaptable and tunable cloud-based map-matching strategy for GPS trajectories

Smart cities have given a significant impetus to manage traffic and use transport networks in an intelligent way. For the above reason, intelligent transportation systems (ITSs) and location-based services (LBSs) have become an interesting research area over the last years. Due to the rapid increase of data volume within the transportation domain, cloud environment is of paramount importance for storing, accessing, handling, and processing such huge amounts of data. A large part of data within the transportation domain is produced in the form of Global Positioning System (GPS) data. Such a kind of data is usually infrequent and noisy and achieving the quality of real-time transport applications based on GPS is a difficult task. The map-matching process, which is responsible for the accurate alignment of observed GPS positions onto a road network, plays a pivotal role in many ITS applications. Regarding accuracy, the performance of a map-matching strategy is based on the shortest path between two consecutive observed GPS positions. On the other extreme, processing shortest path queries (SPQs) incurs high computational cost. Current map-matching techniques are approached with a fixed number of parameters, i.e., the number of candidate points (NCP) and error circle radius (ECR), which may lead to uncertainty when identifying road segments and either low-accurate results or a large number of SPQs. Moreover, due to the sampling error, GPS data with a high-sampling period (i.e., less than 10 s) typically contains extraneous datum, which also incurs an extra number of SPQs. Due to the high computation cost incurred by SPQs, current map-matching strategies are not suitable for real-time processing. In this paper, we propose real-time map-matching (called RT-MM), which is a fully adaptive map-matching strategy based on cloud to address the key challenge of SPQs in a map-matching process for real-time GPS trajectories. The evaluation of our approach against state-of-the-art approaches is performed through simulations based on both synthetic and real-world datasets.

Taxi Dispatch With Real-Time Sensing Data in Metropolitan Areas: A Receding Horizon Control Approach

Traditional taxi systems in metropolitan areas often suffer from inefficiencies due to uncoordinated actions as system capacity and customer demand change. With the pervasive deployment of networked sensors in modern vehicles, large amounts of information regarding customer demand and system status can be collected in real time. This information provides opportunities to perform various types of control and coordination for large-scale intelligent transportation systems. In this paper, we present a receding horizon control (RHC) framework to dispatch taxis, which incorporates highly spatiotemporally correlated demand/supply models and real-time Global Positioning System (GPS) location and occupancy information. The objectives include matching spatiotemporal ratio between demand and supply for service quality with minimum current and anticipated future taxi idle driving distance. Extensive trace-driven analysis with a data set containing taxi operational records in San Francisco, CA, USA, shows that our solution reduces the average total idle distance by 52%, and reduces the supply demand ratio error across the city during one experimental time slot by 45%. Moreover, our RHC framework is compatible with a wide variety of predictive models and optimization problem formulations. This compatibility property allows us to solve robust optimization problems with corresponding demand uncertainty models that provide disruptive event information.

Cell-based construction site simulation model for earthmoving operations using real-time equipment location data

AbstractBackgroundSimulation is a proven technique for effective construction site layout planning and heavy equipment resource optimization. Traditional simulation uses historical data as input for task durations. Data is fed into activity cycle diagrams which many times do not consider any of the rapidly changing spatial constraints that are present on a construction site. Very little research has been conducted towards more realistic, real-time simulation involving data gathering from live actors and documenting the effect of potential changes to such a spatial-temporal work environment.MethodsCell-based simulation, incorporating continuous spatial changes to the site layout during project operations and real-time Global Positioning System (GPS) location tracking data from equipment resources, is introduced for more realistic and rapid modeling. The potential of analyzing and visualizing the effects of spatial consideration of varying resource combinations in earthmoving cycles on productivity and site congestion are explored. It provides insight and awareness in decision making for resource management, site layout and internal traffic control planning.ResultsThe proposed cell-based simulation system handles complex and more realistic scenarios. Various cell parameters were tested in a case study of common earthmoving operations. The advantages of the cell-based over a traditional simulation model include ease of visualization and simplicity in modeling spatial constraints (e.g., ramp restricting traffic to one-way flow). The system provides full control over the flow of resources by using predefined rules or algorithms. It simplifies the design process since, except for some certain key cells, other ordinary cells followed the same rules without being programmed individually. Future research may involve multiple, non-interacting crews competing for resources and study of time-space conflicts in more detail.ConclusionsThe presented cell-based simulation system is able to model and visualize the cyclic activities of earthmoving equipment that occur on a construction site in greater detail than previous simulation methods have done. Using near real-time location data from equipment as input value in the simulation helps construction site project engineers, planners, and managers to improve coordination and monitoring of such construction resources.

Retrieving real-time precise co-seismic displacements with a standalone single-frequency GPS receiver

Nowadays, Global Positioning System (GPS) plays an increasingly important role in retrieving real-time precise co-seismic displacements for geo-hazard monitoring and early warning. Several real-time positioning approaches have been demonstrated for such purpose, such as real-time kinematic relative positioning, precise point positioning, etc., where dual-frequency geodetic receivers are applied for the removal of ionosphere delays by inter-frequency combination. At the same time, it would be also useful to develop efficient algorithms for estimating precise displacements with low-cost GPS receivers since they can make a denser network or multi-sensors combination without putting too much financial burden. In this contribution, we present a new method to retrieve precise co-seismic displacements in real-time using a standalone single-frequency receiver. In the new method, observations prior to an earthquake are utilized to establish a precise ionospheric delay prediction model, so that precise co-seismic displacements can be obtained without any convergence process. Our method was validated with an outdoor experiment as well as by re-processing of 1-Hz GPS data collected by the GEONET network during the 2011 Tohoku Mw 9.0 earthquake. For the latter, RMS against dual-frequency receivers constituted 2cm for horizontal components and 3cm for the vertical component.We specially address the observation biases and their impact on the accuracy of single frequency positioning. Our approach makes real-time GPS displacement monitoring with dense network much more affordable in terms of financial costs.

Impacts of real-time satellite clock errors on GPS precise point positioning-based troposphere zenith delay estimation

Global Positioning System (GPS) has become a cost-effective tool to determine troposphere zenith total delay (ZTD) with accuracy comparable to other atmospheric sensors such as the radiosonde, the water vapor radiometer, the radio occultation and so on. However, the high accuracy of GPS troposphere ZTD estimates relies on the precise satellite orbit and clock products available with various latencies. Although the International GNSS Service (IGS) can provide predicted orbit and clock products for real-time applications, the predicted clock accuracy of 3 ns cannot always guarantee the high accuracy of troposphere ZTD estimates. Such limitations could be overcome by the use of the newly launched IGS real-time service which provides $$\sim $$ 5 cm orbit and 0.2–1.0 ns (an equivalent range error of 6–30 cm) clock products in real time. Considering the relatively larger magnitude of the clock error than that of the orbit error, this paper investigates the effect of real-time satellite clock errors on the GPS precise point positioning (PPP)-based troposphere ZTD estimation. Meanwhile, how the real-time satellite clock errors impact the GPS PPP-based troposphere ZTD estimation has also been studied to obtain the most precise ZTD solutions. First, two types of real-time satellite clock products are assessed with respect to the IGS final clock product in terms of accuracy and precision. Second, the real-time GPS PPP-based troposphere ZTD estimation is conducted using data from 34 selected IGS stations over three independent weeks in April, July and October, 2013. Numerical results demonstrate that the precision, rather than the accuracy, of the real-time satellite clock products impacts the real-time PPP-based ZTD solutions more significantly. In other words, the real-time satellite clock product with better precision leads to more precise real-time PPP-based troposphere ZTD solutions. Therefore, it is suggested that users should select and apply real-time satellite products with better clock precision to obtain more consistent real-time PPP-based ZTD solutions.

Formation, Growth and Variability of Sand Spit at Rushikulya River Mouth, South Odisha Coast, India

Sand spits are depositional landform and most active features near the coastal bays and inlets. The combine interactions between the wind, wave transformation, tidal variation, availability of sediment and river discharge decide the spit morphology, growth and orientation. The beaches around Rushikula river inlet is known as one of the largest rookeries of the olive ridley turtle. The spatial and temporal evolution of the sand spit, geomorphology changes and sediment distribution based on the data collected during 2005-2011 at different time intervals on the both sides of the inlet are assessed. Shoreline oscillation and geomorphology are monitored using real time global positioning system (RTK-GPS). The shoreline undergoes natural phases of erosion and deposition process, however, the entrapment of huge longshore sediment during southwest monsoon months near the river inlet triggers northerly progression of the sand spit and small temporary islands that are highly conducive for formation of nesting habitat. Sediment samples (n=210) collected at different transects representing fore, mid and backshore are analyzed to understand the role of grain size in erosion/ accretion process.

Research on Indoor 3D Location Technology Based on RSSI

With the rapid development of mobile communication, the GPS (Global Positioning System) which provides real-time global positioning system has not been able to meet the needs of the indoor accurate positioning. Through simulation, this paper implements the method of indoor three-dimensional positioning based on RSSI compared the positioning accuracy under several kinds of noise. We achieve the good indoor three-dimensional positioning method with the combination of cost, positioning accuracy and positioning precision through the filter and secondary positioning which establishes special propagation model for various different environments.

Using a least squares support vector machine to estimate a local geometric geoid model

In this study, test-region global positioning system (GPS) control points exhibiting known first-order orthometric heights were employed to obtain the points of plane coordinates and ellipsoidal heights by using the real-time GPS kinematic measurement method. Plane-fitting, second-order curve-surface fitting, back-propagation (BP) neural networks, and least-squares support vector machine (LS-SVM) calculation methods were employed. The study includes a discussion on data integrity and localization, changing reference-point quantities and distributions to obtain an optimal solution. Furthermore, the LS-SVM was combined with local geoidal-undulation models that were established by researching and analyzing3 kernel functions. The results indicated that the overall precision of the local geometric geoidal-undulation values calculated using the radial basis function (RBF) and third-order polynomial kernel function was optimal and the root mean square error (RMSE) was approximately ± 1.5 cm. These findings demonstrated that the LS-SVM provides a rapid and practical method for determining orthometric heights and should serve as a valuable academic reference regarding local geoid models.

2010 Chile and 2011 Tohoku Tsunami Profiles Measured by GPS Buoys and Coastal Wave and Tide Gauges in a Nationwide Ocean Wave Information Network for Ports and Harbors

AbstractThis paper introduces the tide data acquisition and processing procedures in the Nationwide Ocean Wave Information Network for Ports and Harbors (NOWPHAS), especially those for global positioning system (GPS) buoys that measure water surface elevations using real-time kinematic GPS technology at water depths of 100–400 m and 10–20 km from the coastline. It then describes specific features of the 2010 Chile tsunami and the 2011 Tohoku tsunami, including foreshock and main shock profiles, which were measured along the Japanese coast by the NOWPHAS equipment. In the main shock of the 2011 Tohoku tsunami, the GPS buoy at a water depth of 204 m off Kamaishi Bay showed that the first wave crest consisted of primary slow and subsequent quick rises, and exceeded 6 m approximately 30 min after the earthquake occurrence. Some geometrically adjacent sets of GPS buoys, coastal wave gauges, and coastal tide gauges revealed the tsunami propagation and amplification near the coast.

Preliminary Design for near Real-Time GPS Meteorology over Peninsular Malaysia (G-MeM)

This paper presents a conceptual approach for near real time Global Positioning System (GPS) meteorology in Malaysia using combined space- and ground-based GPS observations. Data from a single GPS station is utilised to derive wet refractivities for comparison with radio occultation (RO). This study shows that the wet refractivities from the ground-based GPS present similar patterns and better correlation with the radiosonde data than that from the space-based GPS RO data at altitudes between 0 - 5 km. Similarly, the wet refractivities derived from RO are more highly correlated with the radiosonde data than the ground-based GPS at altitudes above 5 km. The residual Nwvary from -9.25 - 21.136 N-unit at 00 h UTC for the ground-based GPS while for the GPS RO, it is -19 - 9.259 N-unit at 00 h UTC.

Forest Offence Types, Trends and Lapses: Case Study of the Nkawie Forest District of Ghana from 2005-2010

The documented analysis of the forest offences revealed eight forest offence types with prevalent cases being chainsaw milling, illegal logging and illegal farming. Between 2005 and 2010, the district recorded 121 offences with more offences occurring in the on-reserve areas than in the off-reserve areas. The timber species, which was most exploited illegally is Triplochiton scleroxylon (wawa), a scarlet star-rated species, which is under imminent economic threat. Analyses of the official records revealed lapses in record keeping since there are no references to the outcomes of most offences, especially those relating to cases under investigation by the Police and Regional Forest Services Division. A call for capacity development of the frontline staff of the Forest Services Division at the District levels is paramount especially in detecting, collecting, entering and analyzing forest offences cases and outcomes as well as training in forest investigation and incident management. Furthermore, equipping the district offices with the requisite technological equipment like computers and accessories, software and real-time Global Positioning System (GPS) trackers will enhance effective monitoring and data management of forest resources especially when Ghana is committed in ensuring timber legality under the Voluntary Partnership Agreement.

Testing of GPS Accuracy for Precision Forestry Applications

The use of existing geospatial technologies such as GIS and global positioning systems (GPS) to precision forestry is booming. The objective of this study was to examine the applicability of GPS and radio beacon differential global positioning system (RBN DGPS) for forestry machinery positioning. This would be an important step toward the realization of site-specific chemical application in China. A Trimble AG132 GPS receiver was mounted on a moveable platform and real-time differential GPS signals were obtained from the Yangtze River Beacon Station. The experiments were conducted on campus of Nanjing Forestry University, China. GPS data were collected and downloaded into a laptop computer via a RS-232 serial port and customer-developed data-acquisition software. Two tests were conducted: (1) a stationary test (where the mobile platform was maintained at a fixed location) in an open sky and forest condition to examine the precision (repeatability) of GPS signals, and (2) a mobile test (where the platform was moving) to examine the dynamic conformity degree. Analysis of variance was used to clarify the effects of positioning mode and stand area on the precision of GPS. In the stationary test, the variability of X and Y coordinates is smaller in RBN DGPS mode than that in the non-differential mode; and the performance of GPS in terms of position dilution of precision, horizontal dilution of precision, vertical dilution of precision, time dilution of precision values, effective positioning rate and the number of visible satellites was superior when used in RBN DGPS mode. In the mobile test, the desired traces of the moveable platform (circles) were much better followed by the GPS locations recorded in the RBN DGPS mode. Compared with non-differential mode, RBN DGPS is more suitable for precision forestry positioning requirements. RBN DGPS improves accuracy both in open sky and forest condition, and the service is available to end users in China with no additional costs.

Ailanthus altissima (tree of heaven): Spread and harmfulness in a case-study urban area

Among the woody and shrubby weeds colonising non-crop areas in the Apulia Region (South Italy), Ailanthus altissima (tree of heaven), an exotic invasive species, is one of the worst, because of its fast growth and root-sucker production. It reaches the heart of protected areas and spreads everywhere in urban and peri-urban areas creating dense stands. As there are no official monitoring protocols for weed mapping, a method based on real-time global positioning system (GPS) on satellite maps was set up. Due to this method, the distribution, spread, size, density and harmfulness of A. altissima were assessed across the wide urban area of Bari (South Italy) by mapping all the individual plants and areas/stands of plants. In Bari, along a total of 76 km of roads mapped, 170 very large (diameter >18 cm), 231 large (diameter 8–18 cm), 130 medium (diameter 3–8 cm), 53 small (diameter < 3 cm) single plants, and 70 high, 63 medium and 13 low density areas were detected. This indicated that A. altissima (tree of heaven) was very widespread in the study area. Moreover, 35 types of damage or potential risks were recorded covering functional, environmental, health and safety and aesthetic aspects and then classified according to frequency and location. The real-time GPS method proved to be very useful for providing a speedy and accurate record of the data.

A Latent Source Model to Detect Multiple Spatial Clusters With Application in a Mobile Sensor Network for Surveillance of Nuclear Materials

Potential nuclear attacks are among the most devastating terrorist attacks, with severe loss of human lives as well as damage to infrastructure. To deter such threats, it becomes increasingly vital to have sophisticated nuclear surveillance and detection systems deployed in major cities in the United States, such as New York City. In this article, we design a mobile sensor network and develop statistical algorithms and models to provide consistent and pervasive surveillance of nuclear materials in major cities. The network consists of a large number of vehicles on which nuclear sensors and Global Position System (GPS) tracking devices are installed. Real time sensor readings and GPS information are transmitted to and processed at a central surveillance center. Mathematical and statistical analyses are performed, in which we mimic a signal-generating process and develop a latent source modeling framework to detect multiple spatial clusters. A Monte Carlo expectation-maximization algorithm is developed to estimate model parameters, detect significant clusters, and identify their locations and sizes. We also determine the number of clusters using a modified Akaike Information Criterion/Bayesian Information Criterion. Simulation studies to evaluate the effectiveness and detection power of such a network are described.