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Journal ArticleDOI

Height Aiding, C/N 0 Weighting and Consistency Checking for GNSS NLOS and Multipath Mitigation in Urban Areas

02 Jul 2013-Journal of Navigation (Cambridge University Press)-Vol. 66, Iss: 05, pp 653-669
TL;DR: Three different techniques for mitigating the impact of non-line-of-sight (NLOS) reception and multipath interference on position accuracy without using additional hardware are investigated, testing them using data collected at multiple sites in central London.
Abstract: Multiple global navigation satellite system (GNSS) constellations can dramatically improve the signal availability in dense urban environments. However, accuracy remains a challenge because buildings block, reflect and diffract the signals. This paper investigates three different techniques for mitigating the impact of non-line-of-sight (NLOS) reception and multipath interference on position accuracy without using additional hardware, testing them using data collected at multiple sites in central London. Aiding the position solution using a terrain height database was found to have the biggest impact, improving the horizontal accuracy by 35% and the vertical accuracy by a factor of 4. An 8% improvement in horizontal accuracy was also obtained from weighting the GNSS measurements in the position solution according to the carrier-power-to-noise-density ratio (C/N0). Consistency checking using a conventional sequential elimination technique was found to degrade horizontal positioning performance by 60% because it often eliminated the wrong measurements in cases when multiple signals were affected by NLOS reception or strong multipath interference. A new consistency checking method that compares subsets of measurements performed better, but was still equally likely to improve or degrade the accuracy. This was partly because removing a poor measurement can result in adverse signal geometry, degrading the position accuracy. Based on this, several ways of improving the reliability of consistency checking are proposed.

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Citations
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Journal ArticleDOI
TL;DR: This study demonstrates that 3D city models are employed in at least 29 use cases that are a part of more than 100 applications that could be useful for scientists as well as stakeholders in the geospatial industry.
Abstract: In the last decades, 3D city models appear to have been predominantly used for visualisation; however, today they are being increasingly employed in a number of domains and for a large range of tasks beyond visualisation. In this paper, we seek to understand and document the state of the art regarding the utilisation of 3D city models across multiple domains based on a comprehensive literature study including hundreds of research papers, technical reports and online resources. A challenge in a study such as ours is that the ways in which 3D city models are used cannot be readily listed due to fuzziness, terminological ambiguity, unclear added-value of 3D geoinformation in some instances, and absence of technical information. To address this challenge, we delineate a hierarchical terminology (spatial operations, use cases, applications), and develop a theoretical reasoning to segment and categorise the diverse uses of 3D city models. Following this framework, we provide a list of identified use cases of 3D city models (with a description of each), and their applications. Our study demonstrates that 3D city models are employed in at least 29 use cases that are a part of more than 100 applications. The classified inventory could be useful for scientists as well as stakeholders in the geospatial industry, such as companies and national mapping agencies, as it may serve as a reference document to better position their operations, design product portfolios, and to better understand the market.

547 citations

Journal ArticleDOI
TL;DR: An overview of the past and current literature discussing the GNSS integrity for urban transport applications is provided so as to point out possible challenges faced by GNSS receivers in such scenario.
Abstract: Integrity is one criteria to evaluate GNSS performance, which was first introduced in the aviation field. It is a measure of trust which can be placed in the correctness of the information supplied by the total system. In recent years, many GNSS-based applications emerge in the urban environment including liability critical ones, so the concept of integrity attracts more and more attention from urban GNSS users. However, the algorithms developed for the aerospace domain cannot be introduced directly to the GNSS land applications. This is because a high data redundancy exists in the aviation domain and the hypothesis that only one failure occurs at a time is made, which is not the case for the urban users. The main objective of this paper is to provide an overview of the past and current literature discussing the GNSS integrity for urban transport applications so as to point out possible challenges faced by GNSS receivers in such scenario. Key differences between integrity monitoring scheme in aviation domain and urban transport field are addressed. And this paper also points out several open research issues in this field.

265 citations


Cites methods from "Height Aiding, C/N 0 Weighting and ..."

  • ...at different levels, for example, the antenna design techniques [13], [14], the receiver-based techniques [15], as well as the post-receiver techniques [16], which help to improve accuracy and reliability of the GNSS positioning in urban environment....

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Journal ArticleDOI
TL;DR: A rectified positioning method using a basic three-dimensional city building model and ray-tracing simulation to mitigate the signal reflection effects is developed and successfully defines a positioning accuracy based on the distribution of the candidates and their pseudorange similarity.
Abstract: The current low-cost global navigation satellite systems (GNSS) receiver cannot calculate satisfactory positioning results for pedestrian applications in urban areas with dense buildings due to multipath and non-line-of-sight effects. We develop a rectified positioning method using a basic three-dimensional city building model and ray-tracing simulation to mitigate the signal reflection effects. This proposed method is achieved by implementing a particle filter to distribute possible position candidates. The likelihood of each candidate is evaluated based on the similarity between the pseudorange measurement and simulated pseudorange of the candidate. Finally, the expectation of all the candidates is the rectified positioning of the proposed map method. The proposed method will serve as one sensor of an integrated system in the future. For this purpose, we successfully define a positioning accuracy based on the distribution of the candidates and their pseudorange similarity. The real data are recorded at an urban canyon environment in the Chiyoda district of Tokyo using a commercial grade u-blox GNSS receiver. Both static and dynamic tests were performed. With the aid of GLONASS and QZSS, it is shown that the proposed method can achieve a 4.4-m 1ź positioning error in the tested urban canyon area.

151 citations


Cites background from "Height Aiding, C/N 0 Weighting and ..."

  • ...Consistency checking can also be used to identify both NLOS and multipath-contaminated signals (Groves and Jiang 2013)....

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Journal ArticleDOI
TL;DR: In this article, shadow matching has been adapted to work on an Android smartphone and presented the first comprehensive performance assessment of smartphone GNSS shadow matching, which significantly improves cross-street positioning accuracy in dense urban environments.
Abstract: Global Navigation Satellite System (GNSS) shadow matching is a new positioning technique that determines position by comparing the measured signal availability and strength with predictions made using a three-dimensional (3D) city model. It complements conventional GNSS positioning and can significantly improve cross-street positioning accuracy in dense urban environments. This paper describes how shadow matching has been adapted to work on an Android smartphone and presents the first comprehensive performance assessment of smartphone GNSS shadow matching. Using GPS and GLONASS data recorded at 20 locations within central London, it is shown that shadow matching significantly outperforms conventional GNSS positioning in the cross-street direction. The success rate for obtaining a cross-street position accuracy within 5 m, enabling the correct side of a street to be determined, was 54·50% using shadow matching, compared to 24·77% for the conventional GNSS position. The likely performance of four-constellation shadow matching is predicted, the feasibility of a large-scale implementation of shadow matching is assessed, and some methods for improving performance are proposed. A further contribution is a signal-to-noise ratio analysis of the direct line-of-sight and non-line-of-sight signals received on a smartphone in a dense urban environment.

116 citations


Cites background from "Height Aiding, C/N 0 Weighting and ..."

  • ...IP address: 54.190.19.90, on 25 Mar 2022 at 00:15:45, subject to the Cambridge Core terms of use, available at and multipath interference (Groves and Jiang, 2013)....

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20 Sep 2013
TL;DR: In this paper, the authors present a new multipath detection technique based on comparing the measured C/N0 on multiple frequencies and also new dual-polarization results, which is shown to improve the performance of a number of multipath and/or NLOS mitigation techniques in dense urban areas.
Abstract: Non-line-of-sight (NLOS) reception and multipath interference are major causes of poor GNSS positioning accuracy in dense urban environments. They are commonly grouped together. However, both the mechanisms by which they cause position errors and many of the techniques for mitigating those errors are quite different [1]. For example, correlation-based multipath mitigation has no effect on the errors caused by NLOS reception. University College London (UCL) has investigated the performance of a number of multipath and/or NLOS mitigation techniques in dense urban areas, including C/N0-based solution weighting [2], advanced consistency checking [3], dual-polarization NLOS detection [4] and vector tracking [5]. In this paper, we present a new multipath detection technique based on comparing the measured C/N0 on multiple frequencies and also new dual-polarization results. Meanwhile, other researchers have demonstrated NLOS detection using a panoramic camera [6, 7] or 3D city model [8, 9] and detection of NLOS and multipath using an antenna array [10]. All of these techniques bring some improvement in positioning performance in urban environments, but none of them eliminate the effects of both NLOS reception and multipath interference completely. As the different techniques are largely complementary, best performance is obtained by using several of them in combination, a portfolio approach. This paper comprises three parts. The first presents a feasibility study on a new multipath detection technique using multi-frequency C/N0 measurements. Constructive multipath interference results in an increase in the measured C/N0, whereas destructive multipath interference results in a decrease. As the phase of a reflected signal with respect to its directly received counterpart depends on the wavelength, the multipath interference may be constructive on one frequency and destructive on another. Thus, by comparing the difference in measured C/N0 between two frequencies with what would normally be expected for that signal at that elevation angle, strong multipath interference may be detected. However, the converse is not true because, depending on the path delay, the phase of the multipath interference may also be consistent across the two frequencies. Consistency across three frequencies in the presence of multipath interference is much less likely than consistency across two. Therefore, by comparing C/N0 measured across three (or more) frequencies, the chance of detection is improved substantially, noting that reliability is less critical as part of a portfolio approach to multipath detection than for a stand-alone technique. Experimental results are presented demonstrating the potential of this approach using GPS and GLONASS data collected in Central London. The second part of the paper presents the results of the first multi-constellation test of the dual-polarization NLOS detection technique pioneered at UCL [4]. This separately correlates the right hand circularly polarized (RHCP) and left hand circularly polarized (LHCP) outputs of a dual-polarization antenna and differences the resulting C/N0 measurements, producing a result that is positive for directly received signals and negative for most NLOS signals. Data was collected at six different sites in Central London and NLOS reception of both GPS and GLONASS signals was detected. Position solutions with the NLOS signals removed are compared with the corresponding all-satellite solutions. The final part of the paper addresses the portfolio approach to NLOS and multipath mitigation. Each technique is assessed qualitatively for its ease of implementation and its efficiency at detecting or directly mitigating both NLOS reception and multipath mitigation. A compatibility matrix is then presented showing which techniques may be combined without conflict. Suitable portfolios are then proposed both for professional-grade and for consumer-grade user equipment. References [1] Groves, P. D., Principles of GNSS, inertial, and multi-sensor integrated navigation systems, Second Edition, Artech House, 2013. [2] Jiang, Z., P. Groves, W. Y. Ochieng, S. Feng, C. D. Milner, and P. G. Mattos, “Multi-Constellation GNSS Multipath Mitigation Using Consistency Checking,” Proc. ION GNSS 2011. [3] Jiang, Z., and P. Groves, “GNSS NLOS and Multipath Error Mitigation using Advanced Multi-Constellation Consistency Checking with Height Aiding,” Proc. ION GNSS 2012. [4] Jiang, Z., and P. D. Groves, “NLOS GPS Signal Detection Using A Dual-Polarisation Antenna,” GPS Solutions, 2012, DOI: 10.1007/s10291-012-0305-5. [5] Hsu, L.-T., P. D. Groves, and S.-S. Jan, “Assessment of the Multipath Mitigation Effect of Vector Tracking in an Urban Environment,” Proc ION Pacific PNT, 2013. [6] Marais, J., M. Berbineau, and M. Heddebaut, “Land Mobile GNSS Availability and Multipath Evaluation Tool,” IEEE Transactions on Vehicular Technology, Vol. 54, No. 5, 2005, pp. 1697-1704. [7] Meguro, J., et al., “GPS Multipath Mitigation for Urban Area Using Omnidirectional Infrared Camera,” IEEE Transactions on Intelligent Transportation Systems, Vol. 10, No. 1, 2009, pp. 22-30. [8] Obst, M., S. Bauer, and G. Wanielik, “Urban Multipath Detection and mitigation with Dynamic 3D Maps for Reliable Land Vehicle Localization,” Proc. IEEE/ION PLANS 2012. [9] Peyraud, S., et al., “About Non-Line-Of-Sight Satellite Detection and Exclusion in a 3D Map-Aided Localization Algorithm,” Sensors, Vol. 13, 2013, pp. 829-847. [10] Keshvadi, M. H., A. Broumandan, and G. Lachapelle, “Analysis of GNSS Beamforming and Angle of Arrival Estimation in Multipath Environments," Proc ION ITM, San Diego, CA, January 2011, pp. 427-435.

106 citations


Cites background or methods or result from "Height Aiding, C/N 0 Weighting and ..."

  • ...Map-indicated height can also be used as an additional measurement or constraint to improve the robustness of consistency checking [3][30]....

    [...]

  • ...Thus consistency checking using sequential testing actually degrades the average positioning accuracy in dense urban environments [3][10]....

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  • ...This effect can be seen both in some of the results presented in Section 3 and in in the results presented in [3]....

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  • ...Thus, this method can only ever be partially effective and tests in a dense urban environment suggest that elevation-based weighting has little impact on positioning performance [3]....

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  • ...In each case, measurements were weighted according to the satellite elevation angle as described in [3]....

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References
More filters
Journal Article
TL;DR: Differential GPS and Integrity Monitoring differential GPS Pseudolites Wide Area Differential GPS Wide Area Augmentation System Receiver Autonomous Integrity Monitoring Integrated Navigation Systems Integration of GPS and Loran-C GPS and Inertial Integration Receiver Aut autonomous Integrity Monitoring Availability for GPS Augmented with Barometric Altimeter Aiding and Clock Coasting
Abstract: Differential GPS and Integrity Monitoring Differential GPS Pseudolites Wide Area Differential GPS Wide Area Augmentation System Receiver Autonomous Integrity Monitoring Integrated Navigation Systems Integration of GPS and Loran-C GPS and Inertial Integration Receiver Autonomous Integrity Monitoring Availability for GPS Augmented with Barometric Altimeter Aiding and Clock Coasting GPS and Global Navigation Satellite System (GLONASS) GPS Navigation Applications Land Vehicle Navigation and Tracking Marine Applications Applications of the GPS to Air Traffic Control GPS Applications in General Aviation Aircraft Automatic Approach and Landing Using GPS Precision Landing of Aircraft Using Integrity Beacons Spacecraft Attitude Control Using GPS Carrier Phase Special Applications GPS for Precise Time and Time Interval Measurement Surveying with the Global Position System Attitude Determination Geodesy Orbit Determination Test Range Instrumentation.

2,409 citations

Book
01 Jan 1996
TL;DR: Differential GPS and Integrity Monitoring Differential GPS Pseudolites Wide Area differential GPS Wide Area Augmentation System Receiver Autonomous Integrity Monitoring Integrated Navigation Systems Integration of GPS and Loran-C GPS and Inertial Integration Receiver Autonomic Integrity Monitoring Availability for GPS Augmented with Barometric Altimeter Aiding and Clock Coasting GPS and Global Navigation Satellite System (GLONASS) GPS Navigation Applications Land Vehicle Navigation and Tracking Marine Applications Applications of the GPS to Air Traffic Control GPS Applications in General Aviation Aircraft Automatic Approach and Landing of Aircraft Using Integrity Beacons Spacecraft Attitude
Abstract: Differential GPS and Integrity Monitoring Differential GPS Pseudolites Wide Area Differential GPS Wide Area Augmentation System Receiver Autonomous Integrity Monitoring Integrated Navigation Systems Integration of GPS and Loran-C GPS and Inertial Integration Receiver Autonomous Integrity Monitoring Availability for GPS Augmented with Barometric Altimeter Aiding and Clock Coasting GPS and Global Navigation Satellite System (GLONASS) GPS Navigation Applications Land Vehicle Navigation and Tracking Marine Applications Applications of the GPS to Air Traffic Control GPS Applications in General Aviation Aircraft Automatic Approach and Landing Using GPS Precision Landing of Aircraft Using Integrity Beacons Spacecraft Attitude Control Using GPS Carrier Phase Special Applications GPS for Precise Time and Time Interval Measurement Surveying with the Global Position System Attitude Determination Geodesy Orbit Determination Test Range Instrumentation.

2,275 citations

Journal ArticleDOI
TL;DR: A new robust estimator MLESAC is presented which is a generalization of the RANSAC estimator which adopts the same sampling strategy as RANSac to generate putative solutions, but chooses the solution that maximizes the likelihood rather than just the number of inliers.

2,267 citations


"Height Aiding, C/N 0 Weighting and ..." refers background or methods in this paper

  • ...A common RANSAC cost function, based purely on the size of individual “residual” and assuming a Gaussian distribution, is defined by (Torr and Zisserman, 2000) as Ci(ei) = ∑m j=1 k(eij, δ), (12) where k(eij, δ) = eij/σρj e i j 4 δ δ/σρj eij . δ { , (13) where σρj is given by (7) or (8)....

    [...]

  • ...A common RANSAC cost function, based purely on the size of individual “residual” and assuming a Gaussian distribution, is defined by (Torr and Zisserman, 2000) as...

    [...]

  • ...The RANSAC technique was previously proposed for computer image processing to deal with data sets with high proportions of outliers (Torr and Zisserman, 2000)....

    [...]

  • ...This is because the least-squares estimation method performs poorly on data sets containing a high proportion of outliers (Torr and Zisserman, 2000)....

    [...]

  • ...Assuming that each set of measurements has the same probability of being selected, q is estimated to be (Torr and Zisserman, 2000)...

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Book
31 Dec 2007
TL;DR: In this paper, the authors present a single-source reference for navigation systems engineering, providing both an introduction to overall systems operation and an in-depth treatment of architecture, design, and component integration.
Abstract: Navigation systems engineering is a red-hot area. More and more technical professionals are entering the field and looking for practical, up-to-date engineering know-how. This single-source reference answers the call, providing both an introduction to overall systems operation and an in-depth treatment of architecture, design, and component integration. This book explains how satellite, on-board, and other navigation technologies operate, and it gives practitioners insight into performance issues such as processing chains and error sources. Providing solutions to systems designers and engineers, the book describes and compares different integration architectures, and explains how to diagnose errors. Moreover, this hands-on book includes appendices filled with terminology and equations for quick referencing.

1,351 citations


"Height Aiding, C/N 0 Weighting and ..." refers background or methods in this paper

  • ...5 A set of “residuals” for this MSS, ei, is then calculated using ei = z̃− ẑ+i, (11) where ẑ+i is the set of measurements predicted from the ith MSS position and time solution, x̂+i (Groves, 2013)....

    [...]

  • ...The line-of-sight vectors 656 PAUL D GROVES AND ZIYI JIANG VOL. 66 and predicted pseudo-ranges, ρ̂ j−a,C , are given by ueaj ≈ r̂eej − r̂e−ea r̂eej − r̂e−ea ∣∣∣ ∣∣∣ , (4) ρ̂j−a,C = r̂eej − r̂e−ea [ ]T r̂eej − r̂e−ea [ ]√ + δρ̂a−c + δj[GLδρ̂GL−c + δρ̂j−ie,a, (5) where r̂eej is the position of satellite j, r̂ e− ea is the predicted user position, δρ̂ a− c is the predicted receiver clock offset, δρ̂GL−c is the predicted GLONASS-GPS timing offset, δρ̂ j−ie,a is the satellite j Sagnac correction and δj[GL is 1 for GLONASS satellites and 0 otherwise (Groves, 2013)....

    [...]

  • ...…r̂eej is the position of satellite j, r̂ e− ea is the predicted user position, δρ̂ a− c is the predicted receiver clock offset, δρ̂GL−c is the predicted GLONASS-GPS timing offset, δρ̂ j−ie,a is the satellite j Sagnac correction and δj[GL is 1 for GLONASS satellites and 0 otherwise (Groves, 2013)....

    [...]

  • ...Once the MSS has been generated, an exact position and time solution, x̂+i, may be obtained using leastsquares estimation (Groves, 2013) x̂+i = x̂− +He,iG −1(z̃i − ẑi−), (10) where HG e,i comprises the rows of the measurement matrix, HG e , given by (3), which correspond to the ith MSS, ẑi−…...

    [...]

  • ...The resulting code tracking error depends on the receiver design as well as the direct and reflected signal strengths, path delay and phase difference, and can be up to half a code chip (Van Nee, 1992; Braasch, 1996; Groves, 2013)....

    [...]

Book
01 Apr 2013
TL;DR: The second edition of the Artech House book Principles of GNSS, Inertial, and Multisensor Integrated Navigation Systems as discussed by the authors offers a current and comprehensive understanding of satellite navigation, inertial navigation, terrestrial radio navigation, dead reckoning, and environmental feature matching.
Abstract: This newly revised and greatly expanded edition of the popular Artech House book Principles of GNSS, Inertial, and Multisensor Integrated Navigation Systems offers you a current and comprehensive understanding of satellite navigation, inertial navigation, terrestrial radio navigation, dead reckoning, and environmental feature matching . It provides both an introduction to navigation systems and an in-depth treatment of INS/GNSS and multisensor integration. The second edition offers a wealth of added and updated material, including a brand new chapter on the principles of radio positioning and a chapter devoted to important applications in the field. Other updates include expanded treatments of map matching, image-based navigation, attitude determination, acoustic positioning, pedestrian navigation, advanced GNSS techniques, and several terrestrial and short-range radio positioning technologies. The book shows you how satellite, inertial, and other navigation technologies work, and focuses on processing chains and error sources. In addition, you get a clear introduction to coordinate frames, multi-frame kinematics, Earth models, gravity, Kalman filtering, and nonlinear filtering. Providing solutions to common integration problems, the book describes and compares different integration architectures, and explains how to model different error sources. You get a broad and penetrating overview of current technology and are brought up to speed with the latest developments in the field, including context-dependent and cooperative positioning. DVD Included: Features eleven appendices, interactive worked examples, basic GNSS and INS MATLAB simulation software, and problems and exercises to help you master the material.

483 citations


"Height Aiding, C/N 0 Weighting and ..." refers background or methods in this paper

  • ...5 A set of “residuals” for this MSS, ei, is then calculated using ei = z̃− ẑ+i, (11) where ẑ+i is the set of measurements predicted from the ith MSS position and time solution, x̂+i (Groves, 2013)....

    [...]

  • ...The line-of-sight vectors 656 PAUL D GROVES AND ZIYI JIANG VOL. 66 and predicted pseudo-ranges, ρ̂ j−a,C , are given by ueaj ≈ r̂eej − r̂e−ea r̂eej − r̂e−ea ∣∣∣ ∣∣∣ , (4) ρ̂j−a,C = r̂eej − r̂e−ea [ ]T r̂eej − r̂e−ea [ ]√ + δρ̂a−c + δj[GLδρ̂GL−c + δρ̂j−ie,a, (5) where r̂eej is the position of satellite j, r̂ e− ea is the predicted user position, δρ̂ a− c is the predicted receiver clock offset, δρ̂GL−c is the predicted GLONASS-GPS timing offset, δρ̂ j−ie,a is the satellite j Sagnac correction and δj[GL is 1 for GLONASS satellites and 0 otherwise (Groves, 2013)....

    [...]

  • ...…r̂eej is the position of satellite j, r̂ e− ea is the predicted user position, δρ̂ a− c is the predicted receiver clock offset, δρ̂GL−c is the predicted GLONASS-GPS timing offset, δρ̂ j−ie,a is the satellite j Sagnac correction and δj[GL is 1 for GLONASS satellites and 0 otherwise (Groves, 2013)....

    [...]

  • ...Once the MSS has been generated, an exact position and time solution, x̂+i, may be obtained using leastsquares estimation (Groves, 2013) x̂+i = x̂− +He,iG −1(z̃i − ẑi−), (10) where HG e,i comprises the rows of the measurement matrix, HG e , given by (3), which correspond to the ith MSS, ẑi−…...

    [...]

  • ...where ẑ+i is the set of measurements predicted from the i MSS position and time solution, x̂+i (Groves, 2013)....

    [...]