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Author

Yang Gao

Bio: Yang Gao is an academic researcher from University of Calgary. The author has contributed to research in topics: Precise Point Positioning & Global Positioning System. The author has an hindex of 28, co-authored 160 publications receiving 3607 citations. Previous affiliations of Yang Gao include York University & Liaoning Technical University.


Papers
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Journal ArticleDOI
21 Jan 2008-Sensors
TL;DR: A better understanding of the strengths and weaknesses of oil spill surveillance sensors will improve the operational use of these sensors for oil spill response and contingency planning.
Abstract: Reducing the risk of oil spill disasters is essential for protecting the environmentand reducing economic losses Oil spill surveillance constitutes an important component ofoil spill disaster management Advances in remote sensing technologies can help to identifyparties potentially responsible for pollution and to identify minor spills before they causewidespread damage Due to the large number of sensors currently available for oil spillsurveillance, there is a need for a comprehensive overview and comparison of existingsensors Specifically, this paper examines the characteristics and applications of differentsensors A better understanding of the strengths and weaknesses of oil spill surveillancesensors will improve the operational use of these sensors for oil spill response andcontingency planning Laser fluorosensors were found to be the best available sensor for oilspill detection since they not only detect and classify oil on all surfaces but also operate ineither the day or night For example, the Scanning Laser Environmental AirborneFluorosensor (SLEAF) sensor was identified to be a valuable tool for oil spill surveillanceHowever, no single sensor was able to provide all information required for oil spillcontingency planning Hence, combinations of sensors are currently used for oil spillsurveillance Specifically, satellite sensors are used for preliminary oil spill assessmentwhile airborne sensors are used for detailed oil spill analysis While satellite remote sensingis not suitable for tactical oil spill planning it can provide a synoptic coverage of theaffected area

279 citations

Book ChapterDOI
Sunil Bisnath1, Yang Gao1
01 Jan 2009
TL;DR: In this article, the authors summarized the Working Group's findings concerning the state of PPP technology, and discussed the probable near-term future potential and limitations of the technique, and investigated specific aspects of the method.
Abstract: The Precise Point Positioning Working Group within the Next Generation RTK Sub-Commission of IAG Commission 4 has been involved with Precise Point Positioning (PPP) developments for the past few years. The information presented here summarizes the Working Group’s findings concerning the state of PPP technology, and discusses the probable near-term future potential and limitations of the technique. The broad question of the place of PPP within the future spectrum of space geodetic measurement techniques is addressed by investigating specific aspects of the method

238 citations

Journal ArticleDOI
TL;DR: The results indicate that the convergence time can be significantly reduced with the addition of GLonASS data, and the positioning accuracy is not significantly improved by adding GLONASS data if there is a sufficient number of GPS satellites with good geometry.
Abstract: A combination of GPS and GLONASS observations can offer improved reliability, availability and accuracy for precise point positioning (PPP). We present and analyze a combined GPS/GLONASS PPP model, including both functional and stochastic components. Numerical comparison and analysis are conducted with respect to PPP based on only GPS or GLONASS observations to demonstrate the benefits of the combined GPS/GLONASS PPP. The observation residuals are analyzed for more appropriate stochastic modeling for observations from different navigation systems. An analysis is also made using different precise orbit and clock products. The performance of the combined GPS/GLONASS PPP is assessed using both static and kinematic data. The results indicate that the convergence time can be significantly reduced with the addition of GLONASS data. The positioning accuracy, however, is not significantly improved by adding GLONASS data if there is a sufficient number of GPS satellites with good geometry.

232 citations

Journal ArticleDOI
TL;DR: Numerical results indicate that the new method is superior to the traditional PPP processing method in terms of positional accuracy, convergence speed, and filter stability.
Abstract: This paper describes a carrier-phase–based precise point positioning (PPP) method based a new observation model. Unlike the traditional PPP processing method, the new method allows for exploitation of the integer characteristics of carrier-phase ambiguities. The new method also opens the door for the development of new algorithms for ambiguity resolution to support real-time PPP applications in the future. Numerical results indicate that the new method is superior to the traditional PPP processing method in terms of positional accuracy, convergence speed, and filter stability.

182 citations

Journal ArticleDOI
TL;DR: The results indicate that the system time differences of GPS with BeiDou, GLONASS and Galileo are very stable over time with STD values of better than 1.1 ns.

155 citations


Cited by
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Journal ArticleDOI
TL;DR: The constraints and limitations of existing map matching algorithms are uncovered by an in-depth literature review and some ideas for monitoring the integrity of map-matching algorithms are presented.
Abstract: Map-matching algorithms integrate positioning data with spatial road network data (roadway centrelines) to identify the correct link on which a vehicle is travelling and to determine the location of a vehicle on a link. A map-matching algorithm could be used as a key component to improve the performance of systems that support the navigation function of intelligent transport systems (ITS). The required horizontal positioning accuracy of such ITS applications is in the range of 1 m to 40 m (95%) with relatively stringent requirements placed on integrity (quality), continuity and system availability. A number of map-matching algorithms have been developed by researchers around the world using different techniques such as topological analysis of spatial road network data, probabilistic theory, Kalman filter, fuzzy logic, and belief theory. The performances of these algorithms have improved over the years due to the application of advanced techniques in the map matching processes and improvements in the quality of both positioning and spatial road network data. However, these algorithms are not always capable of supporting ITS applications with high required navigation performance, especially in difficult and complex environments such as dense urban areas. This suggests that research should be directed at identifying any constraints and limitations of existing map matching algorithms as a prerequisite for the formulation of algorithm improvements. The objectives of this paper are thus to uncover the constraints and limitations by an in-depth literature review and to recommend ideas to address them. This paper also highlights the potential impacts of the forthcoming European Galileo system and the European Geostationary Overlay Service (EGNOS) on the performance of map matching algorithms. Although not addressed in detail, the paper also presents some ideas for monitoring the integrity of map-matching algorithms. The map-matching algorithms considered in this paper are generic and do not assume knowledge of ‘future’ information (i.e. based on either cost or time). Clearly, such data would result in relatively simple map-matching algorithms.

799 citations

Journal ArticleDOI
Maorong Ge, Gerd Gendt, Markus Rothacher, Chuang Shi1, Jingbin Liu1 
TL;DR: It is shown that UPDs are rather stable in time and space, and can be estimated with high accuracy and reliability through a statistical analysis of the ambiguities estimated from a reference network.
Abstract: Precise Point Positioning (PPP) has been demonstrated to be a powerful tool in geodetic and geodynamic applications. Although its accuracy is almost comparable with network solutions, the east component of the PPP results is still to be improved by integer ambiguity fixing, which is, up to now, prevented by the presence of the uncalibrated phase delays (UPD) originating in the receivers and satellites. In this paper, it is shown that UPDs are rather stable in time and space, and can be estimated with high accuracy and reliability through a statistical analysis of the ambiguities estimated from a reference network. An approach is implemented to estimate the fractional parts of the single-difference (SD) UPDs between satellites in wide- and narrow-lane from a global reference network. By applying the obtained SD-UPDs as corrections to the SD-ambiguities at a single station, the corrected SD-ambiguities have a naturally integer feature and can therefore be fixed to integer values as usually done for the double-difference ones in the network mode. With data collected at 450 stations of the International GNSS Service (IGS) through days 106 to 119 in 2006, the efficiency of the presented ambiguity-fixing strategy is validated using IGS Final products. On average, more than 80% of the independent ambiguities could be fixed reliably, which leads to an improvement of about 27% in the repeatability and 30% in the agreement with the IGS weekly solutions for the east component of station coordinates, compared with the real-valued solutions.

741 citations

Journal ArticleDOI
TL;DR: A survey of the information sources and information fusion technologies used in current in-car navigation systems is presented and the pros and cons of the four commonly used information sources are described.
Abstract: In-car positioning and navigation has been a killer application for Global Positioning System (GPS) receivers, and a variety of electronics for consumers and professionals have been launched on a large scale. Positioning technologies based on stand-alone GPS receivers are vulnerable and, thus, have to be supported by additional information sources to obtain the desired accuracy, integrity, availability, and continuity of service. A survey of the information sources and information fusion technologies used in current in-car navigation systems is presented. The pros and cons of the four commonly used information sources, namely, 1) receivers for radio-based positioning using satellites, 2) vehicle motion sensors, 3) vehicle models, and 4) digital map information, are described. Common filters to combine the information from the various sources are discussed. The expansion of the number of satellites and the number of satellite systems, with their usage of available radio spectrum, is an enabler for further development, in combination with the rapid development of microelectromechanical inertial sensors and refined digital maps.

524 citations

Journal ArticleDOI
TL;DR: In this paper, the authors presented a GPS+GLONASS+BeiDou+Galileo four-system model to fully exploit the observations of all these four navigation satellite systems for real-time precise orbit determination, clock estimation and positioning.
Abstract: In this contribution, we present a GPS+GLONASS+BeiDou+Galileo four-system model to fully exploit the observations of all these four navigation satellite systems for real-time precise orbit determination, clock estimation and positioning. A rigorous multi-GNSS analysis is performed to achieve the best possible consistency by processing the observations from different GNSS together in one common parameter estimation procedure. Meanwhile, an efficient multi-GNSS real-time precise positioning service system is designed and demonstrated by using the multi-GNSS Experiment, BeiDou Experimental Tracking Network, and International GNSS Service networks including stations all over the world. The statistical analysis of the 6-h predicted orbits show that the radial and cross root mean square (RMS) values are smaller than 10 cm for BeiDou and Galileo, and smaller than 5 cm for both GLONASS and GPS satellites, respectively. The RMS values of the clock differences between real-time and batch-processed solutions for GPS satellites are about 0.10 ns, while the RMS values for BeiDou, Galileo and GLONASS are 0.13, 0.13 and 0.14 ns, respectively. The addition of the BeiDou, Galileo and GLONASS systems to the standard GPS-only processing, reduces the convergence time almost by 70 %, while the positioning accuracy is improved by about 25 %. Some outliers in the GPS-only solutions vanish when multi-GNSS observations are processed simultaneous. The availability and reliability of GPS precise positioning decrease dramatically as the elevation cutoff increases. However, the accuracy of multi-GNSS precise point positioning (PPP) is hardly decreased and few centimeter are still achievable in the horizontal components even with 40 $$^{\circ }$$ elevation cutoff. At 30 $$^{\circ }$$ and 40 $$^{\circ }$$ elevation cutoffs, the availability rates of GPS-only solution drop significantly to only around 70 and 40 %, respectively. However, multi-GNSS PPP can provide precise position estimates continuously (availability rate is more than 99.5 %) even up to 40 $$^{\circ }$$ elevation cutoff (e.g., in urban canyons).

517 citations

Journal ArticleDOI
22 Dec 2015-Sensors
TL;DR: A model of real-time kinematic decimeter-level positioning with BeiDou Navigation Satellite System triple-frequency signals over medium distances with relatively high accuracy and high fixing rate is developed, displaying significant advantage comparing to traditional carrier-smoothed code differential positioning method.
Abstract: Many applications, such as marine navigation, land vehicles location, etc., require real time precise positioning under medium or long baseline conditions. In this contribution, we develop a model of real-time kinematic decimeter-level positioning with BeiDou Navigation Satellite System (BDS) triple-frequency signals over medium distances. The ambiguities of two extra-wide-lane (EWL) combinations are fixed first, and then a wide lane (WL) combination is reformed based on the two EWL combinations for positioning. Theoretical analysis and empirical analysis is given of the ambiguity fixing rate and the positioning accuracy of the presented method. The results indicate that the ambiguity fixing rate can be up to more than 98% when using BDS medium baseline observations, which is much higher than that of dual-frequency Hatch-Melbourne-Wubbena (HMW) method. As for positioning accuracy, decimeter level accuracy can be achieved with this method, which is comparable to that of carrier-smoothed code differential positioning method. Signal interruption simulation experiment indicates that the proposed method can realize fast high-precision positioning whereas the carrier-smoothed code differential positioning method needs several hundreds of seconds for obtaining high precision results. We can conclude that a relatively high accuracy and high fixing rate can be achieved for triple-frequency WL method with single-epoch observations, displaying significant advantage comparing to traditional carrier-smoothed code differential positioning method.

382 citations