Modern Global Positioning System Research Articles

Principle and performance of multi-frequency and multi-GNSS PPP-RTK

PPP-RTK which takes full advantages of both Real-Time Kinematic (RTK) and Precise Point Positioning (PPP), is able to provide centimeter-level positioning accuracy with rapid integer Ambiguity Resolution (AR). In recent years, with the development of BeiDou Navigation Satellite System (BDS) and Galileo navigation satellite system (Galileo) as well as the modernization of Global Positioning System (GPS) and GLObal NAvigation Satellite System (GLONASS), more than 140 Global Navigation Satellite System (GNSS) satellites are available. Particularly, the new-generation GNSS satellites are capable of transmitting signals on three or more frequencies. Multi-GNSS and multi-frequency observations become available and can be used to enhance the performance of PPP-RTK. In this contribution, we develop a multi-GNSS and multi-frequency PPP-RTK model, which uses all the available GNSS observations, and comprehensively evaluate its performance in urban environments from the perspectives of positioning accuracy, convergence and fixing percentage. In this method, the precise atmospheric corrections are derived from the multi-frequency and multi-GNSS observations of a regional network, and then disseminated to users to achieve PPP rapid AR. Furthermore, a cascade ambiguity fixing strategy using Extra‐Wide‐Lane (EWL), Wide-Lane (WL) and L1 ambiguities is employed to improve the performance of ambiguity fixing in the urban environments. Vehicle experiments in different scenarios such as suburbs, overpasses, and tunnels are conducted to validate the proposed method. In suburbs, an accuracy of within 2 cm in the horizontal direction and 4 cm in the vertical direction, with the fixing percentage of 93.7% can be achieved. Compared to the GPS-only solution, the positioning accuracy is improved by 87.6%. In urban environments where signals are interrupted frequently, a fast ambiguity re-fixing can be achieved within 5 s. Moreover, multi-frequency GNSS signals can further improve the positioning performance of PPP-RTK, particularly in the case of small amount of observations. These results demonstrate that the multi-frequency and multi-GNSS PPP-RTK is a promising tool for supporting precise vehicle navigation.

Cloud-Based Vehicle Tracking System

The need for vehicle tracking system in real time is growth continues due to increase the cases of theft. This type of system in real time needs to transmit large data with huge number of HTTP request to the server to keep tracking and monitoring in real time, thus causes spend extremely high cost every month for transportation the information on tracking vehicles to server therefor the needs for reducing the number of transportation and data size that transmits in each HTTP request to save expenses. This paper designed and implement an integrated vehicle tracking system in real time to track vehicle anywhere and anytime. This system is divided into two parts: vehicle tracking part and monitoring part. Tracking part is represented by installation the electronic devices in the vehicle using modern Global Positioning System (GPS), microcontroller Arduino UNO R3 and SIM800L GSM/GPRS modem. GPS is determined location of the vehicle via received coordinates from satellites such as latitude and latitude with accuracy ranging approximately 2.5 meters; the coordinates faked to add a type of protection to information on vehicles without effecting on characterizing real time tracking before sending it via a General Packet Radio service (GPRS). The monitoring part is in the cloud and will receive the coordinates and displays it on a map in a web page. The main contribution of this system is it reduced data size that sent from in-vehicle device via selected only necessary data for tracking vehicle from NEMA sentences of GPS and reduced number of HTTP request that sent to remote server via constrain the transmission of information with the movement of vehicles, since when vehicle moved the coordinates each 10s and did not send anything when the vehicle stopped thus will reduce the cost of expenses every month. This system can be utilized to track and monitoring the vehicles of large universities, companies, organization and also can be used in army vehicles and police vehicles.
 
 

Assessment of L5 frequency on real-time GPS orbit and clock estimation

Real-time precise Global Navigation Satellite System (GNSS) satellite orbit and clock products are the prerequisite of real-time GNSS-based applications. With the modernization of Global Positioning System (GPS) constellation and construction of other GNSS constellations, the number of GNSS satellites transmitting multi-frequency signals is increasing rapidly. While the benefit of multi-frequency to Precise Point Positioning (PPP) and Precise Clock Estimation (PCE) has been evaluated by many researchers, the impact of multi-frequency on orbit and clock estimation is still limited, especially in real-time mode. Different from the dual-frequency model, the Inter-Frequency Clock Bias (IFCB) must be treated carefully in the triple-frequency model. In this contribution, the triple-frequency model for real-time GPS satellite orbit and clock estimation is derived and the influence of L5 frequency observations on real-time GPS satellite orbit and clock are analyzed. With observation data from globally distributed stations spanning January 1 to 14 of 2018, real-time GPS orbit and clock are estimated with both dual-frequency and triple-frequency observations. Numerical experiments indicate that, compared to the International GNSS Service (IGS) final orbit, the L5 frequency observations improve the consistency of the normal component with about 0.2 cm, however lead to a decrease of consistency in the radial component with about 0.6 cm; the influence on the tangential direction varies with different number of stations. The potential reason for this phenomenon may partly be attributed to the absence of accurate antenna information for L5 frequency. However, due to the tight constraint of dynamic force model on orbit, the overall differences for each component is less than 1.0 cm, which means the contribution of the third frequency observation on the orbit is limited.

Functional Return to Play after Surgical Treatment of Lower-Extremity Injuries using Global Positioning System Profiles in Elite College Football Players

Category: Sports Introduction/Purpose: Return to sport criteria after surgical treatment of lower extremity injuries are highly variable and without consensus. Thigh measurements assessing atrophy, single-leg hop testing and isokinetic strength measurements are commonly used metrics when considering return to sport after surgical treatment of lower-extremity injuries. Yet, these modalities are limited in scope, as they do not fully or accurately evaluate functional movements required in elite athletics. Alternatively, using new Global Positioning System (GPS) technology, a wide breadth of functional movements can be tracked for each athlete, which can be used as a comparative self-control in the event of an injury. This data proposes a more comprehensive, dynamic and longitudinal comparison of athlete performance, which may more accurately reflect functional return to sport in elite athletes after surgery. Methods: Over a three-year period, GPS data was collected on thirteen elite American College Football players at a single FBS Subdivision University. A total of 300 data points per athlete were collected for every practice, scrimmage and game starting in spring prep and extending through regular season, and post-season play. A total of 5.7 million data points including total distance traveled, average and maximum velocity, acceleration profiles, and explosive change of direction through inertial movement analysis were prospectively collected and analyzed. Individual pre-injury GPS functional profiles for each of the thirteen athletes were used as baseline, healthy comparisons, and functional recovery was determined prospectively during return to play progression after lower extremity surgery. Return to sport was allowed when post-operative GPS profiles demonstrated equivalence or superiority of all parameters compared to pre-injury measurements. Results: All thirteen players returned to sport after all measured parameters were equal to or greater than pre-injury levels. Conclusion: Modern GPS technology employed during preseason, regular season and post-season establishes an individualized, baseline, profile of lower-extremity function which allows for postoperative comparison and prospective assessment of safe return to play in elite football players.

Modelling and Comparison of Tracking Loops for GPS Signal

Nowadays, Global Positioning System (GPS) applications are widely spread and affect all aspects of our modern lives. They can be found in many different fields, such as aviation, environment, marine, space, surveying, mapping, and military operations. In military, the GPS is employed in missile guidance, vessels and aircraft navigation, location, communication network timing, etc. The GPS receiver is required to be more and more robust to withstand harsh condition, for example losing signal or jamming. This paper demonstrates the implementation and simulation of an advanced tracking technique that is used in modern GPS receivers - a vector tracking loop. Brief related principles of a GPS receiver are introduced. The principle of traditional tracking loop is shown and compared to the vector tracking loop. An extended Kalman filter is employed as a vector tracking algorithm. The extended Kalman filter uses pseudo range rate, which is computed from both the code and the carrier to constrain the receiver velocity. The acquired results are compared and advantages of the vector tracking algorithm against the traditional tracking loop are presented in this paper, including characteristics of the vector tracking loop.

Simulation and Performance Evaluations of the New GPS L5 and L1 Signals

The Global Positioning System (GPS) signals are used for navigation and positioning purposes by a diverse set of users. As a part of GPS modernization effort L5 has been recently introduced for better accuracy and availability service. This paper intends to study and simulate the GPS L1/L5 signal in order to fulfill the following two objectives. The first aim is to point out some important features/differences between current L1 (whose characteristics have been fairly known and documented) and new L5 GPS signal for performance evaluation purpose. The second aim is to facilitate receiver development, which will be designed and assembled later for the actual acquisition of GPS data. Simulation has been carried out for evaluation of correlation properties and link budgeting for both L1 and L5 signals. The necessary programming is performed in Matlab.

Interval dogs: Results and evaluation of Global Positioning System units in measuring athletic performance in stock-herding dogs

Abstract The skilled movement of livestock by dogs is highly valued among livestock handlers in the harsh farming environment of Australia. However, their workload has not been studied empirically. This pilot study aimed to measure the distance, speed, and heart rate of a group of sheep dogs (n = 6) working during an 11-day period of peak activity (shearing). In addition, it sought to determine the technological capabilities and limits of a modern Global Positioning System (GPS) device for monitoring working dogs during peak work. Distances recorded ranged from 1.7 km up to 68.3 km in a day. The furthest cumulative distance covered by a dog during the study period was 279.2 km. The maximum speed recorded in the yard area was 37.01 km/h. Because of the limitations of the equipment and the nature of the work, we were unable to measure heart rate reliably. The GPS units used in the study were effective at measuring the considerable variation in movement and speed of the dogs while working. However, battery life limitations prevented recording of the dogs' full activity over each day. Characterizing elite and peak performance in these working dogs may assist in comparisons with other sporting and working breeds and in identifying phenotypic traits of value in herding and related working contexts.

Improvement of Klobuchar model for GNSS single-frequency ionospheric delay corrections

Broadcast ionospheric model is currently an effective approach to mitigate the ionospheric time delay for real-time Global Navigation Satellite System (GNSS) single-frequency users. Klobuchar coefficients transmitted in Global Positioning System (GPS) navigation message have been widely used in various GNSS positioning and navigation applications; however, this model can only reduce the ionospheric error by approximately 50% in mid-latitudes. With the emerging BeiDou and Galileo, as well as the modernization of GPS and GLONASS, more precise ionospheric correction models or algorithms are required by GNSS single-frequency users. Numerical analysis of the initial phase and nighttime term in Klobuchar algorithm demonstrates that more parameters should be introduced to better describe the variation of nighttime ionospheric total electron content (TEC). In view of this, several schemes are proposed for the improvement of Klobuchar algorithm. Performance of these improved Klobuchar-like models are validated over the continental and oceanic regions during high (2002) and low (2006) levels of solar activities, respectively. Over the continental region, GPS TEC generated from 35 International GNSS Service (IGS) and the Crust Movement Observation Network of China (CMONOC) stations are used as references. Over the oceanic region, TEC data from TOPEX/Poseidon and JASON-1 altimeters are used for comparison. A ten-parameter Klobuchar-like model, which describes the nighttime term as a linear function of geomagnetic latitude, is finally proposed for GNSS single-frequency ionospheric corrections. Compared to GPS TEC, while GPS broadcast model can correct for 55.0% and 49.5% of the ionospheric delay for the year 2002 and 2006, respectively, the proposed ten-parameter Klobuchar-like model can reduce the ionospheric error by 68.4% and 64.7% for the same period. Compared to TOPEX/Poseidon and JASON-1 TEC, the improved ten-parameter Klobuchar-like model can mitigate the ionospheric delay by 61.1% and 64.3% in 2002 and 2006, respectively.

Side peak cancellation method for sine-BOC(m,n)-modulated GNSS signals

Abstract In this paper, we propose an efficient scheme for side peak cancelation in binary offset carrier (m,n) (BOC(m,n)) with integer modulation order. The proposed scheme reduces significantly the width of the main peak of the auto-correlation function (ACF) and thus the range of influence of the multipath (MP) in BOC-modulated signals. It is based on the use of reference ACFs like that of ideal pseudo random noise (PRN) code generated by linear feedback shift register (LFSR) and used in global positioning system (GPS) and the Russian Globalnaya Navigatsionnaya Sputnikovaya Sistema (GLONASS). In MP environment, the proposed method is used in combination with fast iterative maximum likelihood algorithm (FIMLA) that is adapted to future modernized GPS and Galileo signals. As a result, the obtained ACF of the proposed scheme does not contain any side peaks, and thus, the discriminator function (DF) has no ambiguity in the delay-locked loop (DLL) code tracking operation. The simulation results show that the proposed technique has superior performances in MP mitigation and permits the same resistance to noise compared to the traditional techniques.

Predicting the Success Rate of Long-baseline GPS+Galileo (Partial) Ambiguity Resolution

This contribution covers precise (cm-level) relative Global Navigation Satellite System (GNSS) positioning for which the baseline length can reach up to a few hundred km. Carrier-phase ambiguity resolution is required to obtain this high positioning accuracy within manageable observation time spans. However, for such long baselines, the differential ionospheric delays hamper fast ambiguity resolution as based on current dual-frequency Global Positioning System (GPS). It is expected that the modernization of GPS towards a triple-frequency system, as well as the development of Galileo towards a full constellation will be beneficial in speeding up long-baseline ambiguity resolution. In this article we will predict ambiguity resolution success rates for GPS+Galileo for a 250 km baseline based on the ambiguity variance matrix, where the Galileo constellation is simulated by means of Yuma almanac data. From our studies it can be concluded that ambiguity resolution will likely become faster (less than ten minutes) in the case of GPS+Galileo when based on triple-frequency data of both systems, however much shorter times to fix the ambiguities (one-two minutes) can be expected when only a subset of ambiguities is fixed instead of the complete vector (partial ambiguity resolution).

Hidden in plain sight: mixed methods and the marble orchards of the Vlach Rom (Gypsies) in Toledo, Ohio

While American Romanies live a remarkably secretive cultural existence, their grave locations and memorial stones offer accessible evidence about their history and active, on-going communities. This article elaborates a less-intrusive ethnographic method that uses Romani cemetery data to explore and map the distributions and social networks of American Romani communities. This case study identifies Vlach Rom memorial sites located in Toledo, Ohio's Calvary Catholic Cemetery. Data were gathered on the memorials and spatially cataloged using a global positioning system (GPS). Additionally, genealogical data on the families were collected whenever available in order to construct and map family networks. Conjectures explaining the spatial distribution were tested by empirically investigating geographic information system (GIS) maps of different gravesite attributes. Land availability was the most likely factor determining the distribution. Evidence of Toledo Rom history and cultural practices were also gathered and reviewed from a qualitative analysis of the memorial stones. These discoveries have the potential to advance Romany studies—by applying modern analytic tools, GPS and GIS hardware and software to reveal otherwise “hidden” knowledge.

Location‐only and use‐availability data: analysis methods converge

Location‐only and use‐availability data: analysis methods converge

Performance of new BOC-AW-modulated signals for GNSS system

Abstract In this paper, we propose efficient signal waveforms (WFs) with optimized spectrum for multipath (MP) mitigation and jamming reduction in global navigation satellite system. These WFs are based on the use of sine-phased binary offset carrier (BOC) with adjustable width (BOC-AW). They are generated by adjusting the width of the three-level WF {-1, 0, 1}. By exploiting the three-level BOC-AW subcarriers in sine-phasing signal model, we developed several forms of BOC-AW by means of superposition and width adjustment. The resulting power spectral densities and autocorrelation functions of the proposed WFs were calculated and introduced. Also calculated were the spectral separation coefficients (SSCs) and the Cramér-Rao lower bounds (CRLBs). The SSCs and CRLBs prove the efficiency of the proposed WFs in terms of interference separation. In addition, the simulation results show that the proposed WFs present better performances in MP mitigation compared to the WFs adopted by the Galileo and global positioning system modernization.

Analysis of tidal signals in surface displacement measured by a dense continuous GPS array

We analyze the tidal displacement signals, for the eight major diurnal and semidiurnal tides, from Global Positioning System (GPS) measurements made at the Western United States over the past 16years with 1075 independent stations. By careful examinations among inland versus coastal GPS data we are able to demonstrate that estimated precisions down to the level of ∼0.1mm (horizontal) and ∼0.3mm (vertical) have been reached for the tidal signals, and that at such precisions coherent spatial patterns are revealed in the residual tidal amplitudes and phases after the removal of a priori modeled effects of body tides and ocean tidal loading (OTL). We demonstrate the facility of modern precise GPS data in not only constraining the ocean tide models but, more significantly, in providing source data in terms of regional, complex Love numbers for geophysical inference of the heterogeneities of elastic and inelastic structures in the solid Earth's deep interior on tidal timescales.

Cycle slip detection using multi-frequency GPS carrier phase observations: A simulation study

The detection and repair of the cycle slip or gross error is a key step for high precision global positioning system (GPS) carrier phase navigation and positioning due to interruption or unlocking of GPS signal. A number of methods have been developed to detect and repair cycle slips in the last two decades through cycle slip linear combinations of available GPS observations, but such approaches are subject to the changing GPS sampling and complex algorithms. Furthermore, the small cycle slip and gross error cannot be completely repaired or detected if the sampling is quite longer under some special observation conditions, such as Real Time Kinematic (RTK) positioning. With the development of the GPS modernization or Galileo system with three frequencies signals, it may be able to better detect and repair the cycle slip and gross error in the future. In this paper, the cycle slip and gross error of GPS carrier phase data are detected and repaired by using a new combination of the simulated multi-frequency GPS carrier phase data in different conditions. Results show that various real-time cycle slips are completely repaired with a gross error of up to 0.2 cycles.

Accuracy and modernization of the global positioning system

The development and the present concept of the Global Positioning System (GPS) are presented clearly. There is also a short description of the basic operation principle and of the main GPS characteristics given, as well as its accuracy. The present accuracy of the system is mostly appropriate for orientation, nautical navigation, land navigation and aero navigation; however, for many other activities better accuracy is required. The article analyses methods to improve the characteristics of the satellite positioning system so as to comply with more stringent safety demands. The paper gives a clear overview of the development of a GPS modernization program up to the year 2030. .

Spacecraft Navigation Using the Modernized Global Positioning System Signal

Navigation is examined using information that is presently known about the modernized GPS signal. Although the full signal has not yet been fielded, its technical description can be used to predict its performance. The ranging accuracy of the new signal is compared to the classic signal. First, the signals are described. The correlation processes and consequent tracking accuracies are then determined. Finally the effect of multipath on the M-code is examined as a method to assess the future performance of the broadcast ephemeris. In most cases the performance of the modernized GPS signal is improved over the classic GPS signal, implying that it would be advantageous for receivers to employ it.

Space Weather and the Global Positioning System

Space Weather and the Global Positioning System

Load Response on a Large Suspension Bridge during the NYC Marathon Revealed by GPS and Accelerometers

Global Positioning System (GPS) geodesy is a well-known tool to measure the long-term surface deformation of the Earth at various temporal and spatial scales, and it is widely used in studies of geodynamics. GPS dual-frequency geodetic-quality receivers are typically sampled at rates of 15 to 30 s and analyzed in a batch mode over intervals from one hour to 24 hours. Recently, 1-Hz or greater rate sampled continuous GPS has been recognized as useful in combination with seismometers to capture the long-period seismic waves from large earthquakes and to detect volcano inflation and tsunamigenic landsliding (Bock et al. 2000; Larson et al. 2003; Bock et al. 2004; Mattia et al. 2004). Modern GPS receivers are capable of sampling at rates as high as 50 Hz (Genrich and Bock 2006). The impact of heavy pedestrian movement on a highway suspension bridge has not yet been documented by precise observations, nor has it been modeled, although the impact of vehicles and wind was observed and used to constrain theoretical analysis (Nakamura 2000; Roberts et al. 2004; Guo et al. 2005). A large crowd can gather on a highway suspension bridge under extreme natural or human-generated conditions like earthquakes or power blackouts (Julavits 2003); an unpredicted response to the crowd was observed on a foot-bridge (Strogatz et al. 2005). Using GPS observations, here we evaluate the deflection of a large suspension bridge that connects Brooklyn with Staten Island at the mouth of upper New York Bay under the load of marathon runners and under the load of vehicles. Furthermore, by combining GPS and accelerometer data, we find that the runners excited the vibrations of the bridge at a modal frequency of 2.8 Hz, vastly different from the first vertical frequency of 0.13 Hz excited by vehicles. Our …

GPSによる三周波数アンビギュイテイ決定(AMBIGUITY RESOLUTION : AR)に関する研究

As part of the modernization of GPS (Global positioning system), a third civil frequency at 1176.45MHz will be added to the GPS system. The carrier-phase differential user will be a prime beneficiary. From the results of ambiguity success rate (ASR) using data from triple frequencies signal simulation, the benefits from the triple frequency in ambiguity resolution (AR) can be confirmed. It can be found that in the triple frequencies, AR will be improved under short and medium baseline (about less than 30km) by using widelane method. But the longer distance user of carrier-phase differential measurement will see limited gains from the new frequency because of ionosphere error. If the geometry-free method is used, AR will become independent on the baseline influence, and can be improved by only reducing carrier phase signal noise.