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   ISSN (Online) 2161-4296
   Published by John Wiley and Sons Homepage  [1597 journals]
  • An Implementation of Variable IF Tracking Loop (VITAL) and Initial Test
    • Authors: Chun Yang; Thomas Pany, Andrey Soloviev
      Abstract: Correlation at an intermediate frequency (IF) produces a composite correlation function of an envelope being that of the underlying code and an internal structure being that of the IF carrier. By varying the IF, one can introduce zero-crossings to the envelope so as to shape and sharpen the main peak. Such a variable peak is desired for accurate timing of the direct signal while isolating close-in multipath and spoofing signals. The functionality of variable IF correlation in acquisition and its multipath performance are analyzed in a recent paper published in this journal. In this paper, the details of an implementation of variable IF tracking loop are presented with a theoretical background analysis. A publically available open-source software GPS receiver (SoftGNSS V3.0) is modified into variable IF tracking loop and tested on real-world GPS C/A-code signals. The preliminary test results demonstrate increased code tracking accuracy as well as increased positioning performance. Copyright © 2017 Institute of Navigation
      PubDate: 2017-12-03T20:25:48.430951-05:
      DOI: 10.1002/navi.212
  • Performance Analysis of Optimal Combinations for Triple-Frequency BDS
    • Authors: Leizheng Shu; Wenbin Wang, Ran Ding, Huabo Wei
      Abstract: A theoretical and experimental investigation on the BeiDou Navigation Satellite System triple-frequency combination theory is presented. The optimal combination strategies under different application circumstances are given in consideration of the combination wavelength, noise, and ionosphere amplification factor as the main criteria. On this basis, the performance of BeiDou Navigation Satellite System triple-frequency optimal combinations, in regard to ambiguity resolution and relative positioning accuracy, is verified by four static tests with baseline lengths of 4.8, 12.4, 20, and 36.8 km, respectively. Finally, a few suggestions about the optimal phase combinations used in relative navigation applications are given. Copyright © 2017 Institute of Navigation
      PubDate: 2017-11-16T19:40:47.819324-05:
      DOI: 10.1002/navi.211
  • Improving DCB Estimation Using Uncombined PPP
    • Authors: Yan Xiang; Yang Gao
      Abstract: Differential Code Biases (DCBs) are much more relevant when GNSS data processing with code measurements is involved, such as in ionospheric sensing, positioning, and timing. The current approach to estimate DCBs is based on carrier-phase smoothed code observations together with ionospheric modeling. A limiting factor of the method is the effect of the leveling errors from the smoothing process on the DCB estimate. To reduce the leveling errors, a new DCB estimation method based on an Uncombined Precise Point Positioning (UPPP) model is proposed. A month's data from a global network in a high solar activity year from May 1 to 31, 2014 are processed to validate the method. The results show that most satellite DCB estimates are found to be more stable than when using the smoothed code method. The improvement can be up to about 0.22 ns. The stability and accuracy of the receiver DCB estimates is also enhanced. Copyright © 2017 Institute of Navigation
      PubDate: 2017-10-26T18:10:40.176741-05:
      DOI: 10.1002/navi.207
  • Observability Analysis and Concept of Usage of Air Data Attitude and
           Heading Reference Systems (AD-AHRS)
    • Authors: Fedor Baklanov; Johann Dambeck
      Abstract: This paper addresses the problem of proper integration of an inertial navigation system with an air data system. First, we present a mathematical formalism of the system's mechanization, i.e., navigation equations for spheroidal Earth, air data observation equations, and error propagation equations for optimal Kalman filtering. Next, an analytical observability analysis is conducted and demonstrated by means of a simulation. Finally, we draw conclusions about expected benefits and the most suitable applications. Copyright © 2017 Institute of Navigation
      PubDate: 2017-10-23T21:12:28.909066-05:
      DOI: 10.1002/navi.206
  • The Next Generation GPS Time
    • Authors: Ken L. Senior; Michael J. Coleman
      Abstract: The next generation Global Positioning System (GPS) ground control segment will entail a number of GPS ground system upgrades from the existing ground control segment. One of these upgrades is the inclusion of a new modernized timescale algorithm used to generate GPS Time. The timescale is currently being designed as a separate modular unit (given the acronym ETF, or Ensemble Timescale Filter) within the ground system navigation package and is based upon a U-D Kalman Filter implementation that utilizes measurements of all clocks in the ground network and satellite constellation.The new ETF module will include a number of features that improve the stability of the GPS Time timescale and provide more user/operator autonomy to include: multi-weight clock weighting for better handling of mixed clock types in the same filter; automated clock break detection and handling; robust outlier and anomalous clock behavior mitigation; admission of multiple external timescale solutions, including alternate ETF realizations; and adaptive clock parameter estimation. The preliminary results presented in this paper demonstrate some of the performance capabilities and robustness characteristics of the ETF. Published 2017. This article is a U.S. Government work and is in the public domain in the USA.
      PubDate: 2017-10-09T01:06:05.351705-05:
      DOI: 10.1002/navi.208
  • Characterization of Tropospheric Gradients for the Ground-Based
           Augmentation System Through the Use of Numerical Weather Models
    • Authors: Alizé Guilbert; Carl Milner, Christophe Macabiau
      Abstract: In the scope of the Single European Sky Air Traffic Management Research (SESAR) Work Package 15.3.7, a number of research threads are being undertaken to improve the performance of multi-constellation multi-frequency ground-based augmentation system to support CAT II/III precision approaches. Several challenges and key issues must be solved including those related to atmospheric modeling.However, there are a number of arguments for revisiting this topic and specifically addressing the tropospheric threat. First, recent observations, reported at the last International Civil Aviation Organization Navigation System Panel meeting, showed unexpected atmospheric behavior. The source could be related to a non-modeled behavior of the troposphere. Second, in the advent of dual-frequency ground-based augmentation system, the main contributor to the atmospheric error will come from the tropospheric delay.That is why this paper explains a methodology to reassess the tropospheric threat within two main steps: an analysis of European meteorological data and an analysis of a new bounding methodology for dealing with the troposphere threat and its impact on vertical protection levels. Copyright © 2017 Institute of Navigation
      PubDate: 2017-10-03T01:56:30.891463-05:
      DOI: 10.1002/navi.205
  • Issue Information
    • Pages: 409 - 409
      Abstract: No abstract is available for this article.
      PubDate: 2017-12-25T17:58:56.260692-05:
      DOI: 10.1002/navi.155
  • Real-Time Ionosphere Monitoring by Three-Dimensional Tomography over Japan
    • Authors: Susumu Saito; Shota Suzuki, Mamoru Yamamoto, Akinori Saito, Chia-Hun Chen
      Pages: 495 - 504
      Abstract: This paper reports on the development of a real-time three-dimensional ionospheric tomography technique using GNSS measurements. GPS measurement data from 200 GPS receivers distributed throughout Japan are analyzed in real time to calculate ionospheric Total Electron Contents (TECs). The three-dimensional ionospheric electron density distribution was reconstructed using the tomography technique from the slant TEC data. The tomography results were found to be in good agreement with both the electron density profiles obtained by radio occultation measurements by the COSMIC satellite and the ionospheric peak densities obtained by vertical radio sounding measurements (ionosondes). The real-time ionospheric tomography system commenced operation in March 2016 and it continuously produces three-dimensional electron density distributions over Japan every 15 min with latency of about 6 min. This system is a very powerful tool for monitoring the ionosphere in real time, which could both improve the performance of GNSS-based systems and further the understanding of ionospheric variations. Copyright © 2017 The
      Authors . Journal of the Institute of Navigation published by Wiley Periodicals, Inc. on behalf of Institute of Navigation
      PubDate: 2017-12-14T20:04:54.235912-05:
      DOI: 10.1002/navi.213
  • Protection Levels after Fault Exclusion for Advanced RAIM
    • Authors: Juan Blanch; Todd Walter, Per Enge
      Pages: 505 - 513
      Abstract: We present a fault exclusion algorithm and a formula for the position error bounds after an exclusion event for Advanced Receiver Autonomous Integrity Monitoring. This algorithm has both a low computational load and an analytical proof of integrity. To mitigate the loss of performance associated with false exclusion, the method both exploits the ambiguity as to which measurement must be excluded and a pre-allocation of the integrity budget to the exclusion outcomes. The algorithm is evaluated for a GPS-Galileo Advanced RAIM scenario. We show that with this algorithm, the addition of the exclusion option does not impact the protection levels compared to detection only and that when the faults are large enough, the effect on the user is equivalent to the effect of an outage. Copyright © 2017 Institute of Navigation
      PubDate: 2017-12-06T19:05:38.819787-05:
      DOI: 10.1002/navi.210
  • Corrigendum
    • Pages: 535 - 535
      PubDate: 2017-12-25T17:58:54.653698-05:
      DOI: 10.1002/navi.209
  • Issue Information
    • Pages: 537 - 541
      Abstract: No abstract is available for this article.
      PubDate: 2017-12-25T17:58:54.538224-05:
      DOI: 10.1002/navi.156
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