Showing papers in "Annual of Navigation in 2017"
TL;DR: In this article, the authors explore civil maritime transportation's vulnerability to deceptive GPS signals and develop a detection technique that is compatible with sensors commonly available on modern ships and demonstrate the capability of an attacker to control a maritime surface vessel by broadcasting counterfeit civil GPS signals.
Abstract: An attacker's ability to control a maritime surface vessel by broadcasting counterfeit civil Global Positioning System (GPS) signals is analyzed and demonstrated. The aim of this work is to explore civil maritime transportation's vulnerability to deceptive GPS signals and to develop a detection technique that is compatible with sensors commonly available on modern ships. It is shown that despite access to a variety of high-quality navigation and surveillance sensors, modern maritime navigation depends crucially on satellite navigation and that a deception attack can be disguised as the effects of slowly-changing ocean currents. An innovations-based detection framework that optimally chooses the measurement sampling interval to minimize the probability of a ship exceeding its alert limits without detection is developed and analyzed. A field experiment confirms the vulnerability analysis by demonstrating hostile control of a 65-m yacht in the Mediterranean Sea. Copyright © 2017 Institute of Navigation
176 citations
TL;DR: Past and ongoing high-altitude GPS research efforts at NASA GSFC and elsewhere are described, details on the design of the MMS GPS navigation system are provided, and on-orbit performance data from the first phase are extrapolated to predict performance in the second phase.
Abstract: NASA's Magnetospheric Multiscale (MMS) mission, launched in March of 2015, consists of a controlled formation of four spin-stabilized spacecraft in similar highly elliptic orbits reaching apogee at radial distances of 12 and 25 Earth radii (RE) in the first and second phases of the mission. Navigation for MMSis achieved independently on-board each spacecraft by processing Global Positioning System (GPS) observables using NASA Goddard Space Flight Center (GSFC)'s Navigator GPS receiver and the Goddard Enhanced Onboard Navigation System (GEONS) extended Kalman filter software. To our knowledge, MMS constitutes, by far, the highest-altitude operational use of GPS to date and represents a high point of over a decade of high-altitude GPS navigation research and development at GSFC. In this paper we will briefly describe past and ongoing high-altitude GPS research efforts at NASA GSFC and elsewhere, provide details on the design of the MMS GPS navigation system, and present on-orbit performance data from the first phase. We extrapolate these results to predict performance in the second phase orbit, and conclude with a discussion of the implications of the MMS results for future high-altitude GPS navigation, which we believe to be broad and far-reaching.
45 citations
TL;DR: 3D mapping is used to aid conventional ranging-based GNSS positioning in urban areas and predicts Non-Line-Of-Sight (NLOS) reception over a large search area to improve horizontal and vertical accuracy.
Abstract: GNSS positioning performance in dense urban areas is severely degraded due to the obstruction and reflection of the signals by the surrounding buildings. A basic GNSS position solution can exhibit errors of tens of meters, sometimes more. Here, 3D mapping is used to aid conventional ranging-based GNSS positioning. Terrain height-aiding contributes an additional virtual ranging measurement to the position solution. In addition, 3D city models predict Non-Line-Of-Sight (NLOS) reception over a large search area. The resulting NLOS probabilities aid a consistency checking algorithm that selects and weights the signal used for the final position solution. Iteration then refines the position solution. Practical test results demonstrate improvement in the horizontal and vertical accuracy of conventional ranging-based GNSS positioning in urban areas by a factor of 2.5 and 5, respectively. Using the new technique, the Root Mean Square (RMS) position error in dense urban areas was found to be 20.8 m horizontally and 12.2 m vertically. Copyright © 2017 Institute of Navigation
42 citations
TL;DR: The experimental results show that CSITAN + WRIT can achieve better accuracy and higher success rate of matching and can improve the possibilities of the occurrence of large matching errors than traditional SITAN methods in areas with smooth gravity.
Abstract: The robustness of the Sandia Inertial Terrain-Aided Navigation (SITAN) algorithm has a pivotal influence on underwater vehicles' Gravity-Aided Inertial Navigation Systems (GAINS). An abrupt glitch of the accuracy of the GAINS will evolve into a disaster when vehicles pass through areas of smooth gravity. In order to resolve vulnerability issues of initial error and linearization error, we propose the Correlation SITAN algorithm with Weight-Reducing Iteration Technique (CSITAN + WRIT), in which the correlation process equals Terrain Contour Matching (TERCOM). The CSITAN algorithm is a Multipoint-based Extended Kalman Filtering (MEKF) method, which can work in real time. First, we need to derive the state equation and observation equation of the Multipoint-based SITAN algorithm based on the principle of the traditional SITAN algorithm. Then the accuracy of the state prediction can be improved, and the linearization error can be reduced by the correlation method based on TERCOM. Finally, the WRIT is utilized to reduce the possible influence of gross errors existing in the results of the MEKF and to extract a value with higher precision. The experimental results show that CSITAN + WRIT can achieve better accuracy and higher success rate of matching and can improve the possibilities of the occurrence of large matching errors than traditional SITAN methods in areas with smooth gravity. Copyright © 2017 Institute of Navigation
35 citations
TL;DR: In this article, the performance analysis of signals from the Galileo satellites in the E1 and E5a frequency bands and GPS L5 signals as measured by DLR's experimental ground-based augmentation system is presented.
Abstract: This paper presents the performance analysis of signals from the Galileo satellites in the E1 and E5a frequency bands and GPS L5 signals as measured by DLR’s experimental ground-based augmentation system. The results show that the raw noise and multipath level of Galileo signals and of the GPS L5 signals are smaller than that of GPS L1. The new signals are also less sensitive to the choice of carrier-smoothing time constant. Furthermore, the inter-frequency biases that affect dual-frequency processing are investigated. These biases differ between satellites and depend on satellite and receiver hardware, but they can be determined a priori. With known receiver and antenna configurations, it is possible to correct for these biases. A residual uncertainty associated with the bias correction has to be taken into account. This can be modeled as part of the ground and airborne bounding standard deviations (spr_gnd and spr_air) used in GBAS processing.
32 citations
TL;DR: Results reveal that orbit and clock error distributions are non-zero mean on a monthly basis, although biases tend to reduce as sample set size increases.
Abstract: This paper presents a User Range Accuracy (URA)/Signal-in-Space Accuracy (SISA) analysis to support ARAIM based on a time-dependent statistical characterization of orbit and clock error observations. By comparing precise orbits to broadcast ephemeris for each individual GPS and Galileo satellite, this work computes the Signal-in-Space Range Error (SISRE) that needs to be overbounded by the URA/SISA value included in the Integrity Support Message (ISM). Service data from January 2008 to February 2015 for GPS and from March to June 2015 for Galileo are processed, showing that range error is mainly driven by satellite's clock performance. In order for the ISM generation to account for the variation in error biases and standard deviation, GPS service history is broken down into monthly, quarterly, and yearly datasets. Results reveal that orbit and clock error distributions are non-zero mean on a monthly basis, although biases tend to reduce as sample set size increases.
30 citations
TL;DR: In this paper, a machine learning algorithm was proposed to detect phase scintillation based on frequency domain features, which achieved a detection accuracy of 92 percent using data from Poker Flat, Jicamarca, Singapore, and Hong Kong.
Abstract: Ionospheric phase scintillation can cause errors or outage in GNSS navigation solutions. Timely detection of phase scintillation will enable adaptive processing to mitigate its effects on navigation solutions. This paper presents a machine-learning algorithm to autonomously detect phase scintillation based on frequency domain features. Validation using data from Gakona shows phase scintillation detection accuracy around 92 percent. Test results using data from Poker Flat, Jicamarca, Singapore, and Hong Kong demonstrate the capability of the trained detector to be applied more generally. Performance evaluation reveals that the values of phase scintillation index s? may be poor indications of scintillation activities. Concurrent phase and amplitude scintillation detection using similar machine-learning algorithms is further investigated with low-latitude data. Results suggest that at low latitudes an amplitude detector alone is sufficient to capture scintillation in general, while at high latitudes, a phase scintillation detector is necessary to capture the dominating phase scintillation events.
29 citations
TL;DR: In this paper, a characterization of L-band ionospheric scintillation observed at a single site in the Arctic auroral zone, and an analysis of GPS-based point positioning error caused by carrier phase data degradation during scintillations is presented.
Abstract: This paper presents a characterization of L-band ionospheric scintillation observed at a single site in the Arctic auroral zone, and an analysis of GPS-based point positioning error caused by carrier phase data degradation during scintillation. Observed amplitude and phase scintillations of L1CA, L2C, and L5 signals during auroral electrojet activities driven by space weather disturbances show the following three types: continuous, intermittent, and spike (sudden intensity drop). The relations of scintillation strength between different signals are derived for carrier phase, signal intensity, and code-carrier divergence fluctuations, showing precise linear relation, de-correlation, and different linear fitting slope, respectively. These relations can help predict phase scintillation behavior of one signal from measurements of another, except for amplitude scintillation. Experiments of precise point positioning show that phase data degradation due to scintillation can cause significant positioning error increase if the scintillation effects are not considered carefully in GNSS data processing and design of positioning approaches. Copyright © 2017 Institute of Navigation
29 citations
22 citations
TL;DR: In this article, a strategy to mitigate the ionospheric impact on RTK positioning with an experimental result is presented, which explores two approaches that can be applied simultaneously: a) to mitigate scintillation effect on the GNSS signals by refining the stochastic model of the corresponding observations and b) to precisely estimate the residual double difference ionosphere delay by exploiting an accurate TEC map.
Abstract: Ionospheric conditions at low latitudes are extremely harsh due to the frequent occurrence of scintillation and the presence of strong TEC gradients. For this study, the Sao Paulo state region in Brazil is chosen as a test area. This study presents a strategy to mitigate the ionospheric impact on RTK positioning with an experimental result. The proposed strategy explores two approaches that can be applied simultaneously: a) to mitigate the scintillation effect on the GNSS signals by refining the stochastic model of the corresponding observations and b) to precisely estimate the residual double difference ionospheric delay by exploiting an accurate TEC map.
The strategy was tested on a long baseline kinematic processing under strong scintillation conditions (DOY21 in 2014). Significant improvements were observed when the combined use of the two mitigation approaches described above was compared with the use of conventional state-of-the-art approaches.
20 citations
TL;DR: In this article, a real-time three-dimensional ionospheric tomography technique using GNSS measurements was proposed. But the results were not in good agreement with both the electron density profiles obtained by radio occultation measurements by the COSMIC satellite and the ionosphere peak densities obtained by vertical radio sounding measurements (ionosondes).
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.
TL;DR: In this article, experimental results obtained during live GNSS jamming tests performed in a road environment are presented, where different jamming detection strategies are considered with specific focus on signal agnostic approaches where no stringent model assumptions are made for the detector design.
Abstract: This paper presents experimental results obtained during live GNSS jamming tests performed in a road environment. Different jamming detection strategies are considered with specific focus on signal agnostic approaches where no stringent model assumptions are made for the detector design. A measurement station made of a commercial GPS high-sensitivity receiver and an SDR front-end was deployed and used to collect measurements in the presence of jamming. The tests were performed using three different jammers and considering the effects introduced by a vehicle moving at different speeds. The advantages and shortcomings of the different detection approaches are analyzed, and the most effective detection strategies are selected. Copyright © 2017 Institute of Navigation
TL;DR: The use of an adaptive orbital filter to aid the GNSS acquisition and tracking modules and to strongly increase the achievable navigation accuracy is proposed.
Abstract: Recent studies have shown that weak Global Navigation Satellite System (GNSS) signals could potentially be used to navigate from the Earth to the Moon. This would increase autonomy, robustness and flexibility of the navigation architectures for future lunar missions. However, the utilization of GNSS signals at very high altitudes close to the Moon can be significantly limited by the very low power levels seen at the receiver’s antenna. This can result in a strongly reduced visibility of the GNSS satellites, which can worsen the already poor relative geometry of the GNSS receiver to the GNSS satellites. Furthermore, during most of a Moon Transfer Orbit (MTO), the very weak GNSS signals are also affected by Doppler shifts and Doppler rates larger than the ones generally experienced on the Earth, due to the much higher relative dynamics between the receiver and the transmitters. As a consequence, commercial GNSS receivers for terrestrial use cannot successfully acquire and track such signals. More advanced architectures and specific implementations are thus required to use GNSS for lunar missions. In this paper we propose the use of an adaptive orbital filter to aid the GNSS acquisition and tracking modules and to strongly increase the achievable navigation accuracy. The paper describes the orbital filter architecture and tests results carried out by processing realistic radio frequency (RF) signals generated by our Spirent GSS 8000 full constellation simulator for a highly elliptical MTO.
TL;DR: eLoran is a high power, Low Frequency, ground wave radio broadcast system, capable of providing 10-meter positioning accuracy, Stratum-1 frequency distribution, and Universal Time Coordinated (UTC) timing well within one microsecond across very large areas (1,000 miles).
Abstract: More and more systems are becoming solely dependent on GPS or other Global Navigation Satellite
Systems (GNSS) for their precise position, timing, and frequency information. Along with this explosive growth comes an increasing awareness of GNSS vulnerabilities such as interference, jamming, and spoofing. eLoran is a high-power, low-frequency, ground-wave radio broadcast system, capable of providing 10-meter positioning accuracy, Stratum-1 frequency distribution, and UTC timing well within 1 µs across very large areas (1,000 mi). Application of differential corrections for timing further improves the accuracy to better than 100 ns. eLoran is a proven technology, well established for providing services very similar to those delivered by GNSS, with characteristics and failure modes that are complementary to GNSS.
This paper discusses the general concept of eLoran timing and UTC distribution, and the current prototype service. It highlights plans for an initial four-station CONUS-wide timing service, which can be expanded to provide increased coverage and redundancy and deeper penetration into buildings. Additional stations enable positioning and navigation services.
TL;DR: The main focus of the proposed solution is concentrated on the procedure defining the best possible manoeuvre for each vessel when avoiding a collision is no longer possible.
Abstract: Abstract The paper presents a concept of the new algorithm solving Last Moment Manoeuvre problem. Last Moment Manoeuvre means that action taken only by one vessel is not enough to avoid collision. This is why both vessels have to synchronize their manoeuvres to pass each other. The main focus of the proposed solution is concentrated on the procedure defining the best possible manoeuvre for each vessel when avoiding a collision is no longer possible. For simplification, the assumption that the parameters of the vessels involved in the Last Moment Manoeuvre meet Standards for Ships Manoeuvrability set out in the IMO resolution, will be adopted. The algorithm presented in the paper will be implemented and tested in the commercial system.
TL;DR: In this paper, a fault exclusion algorithm and a formula for the position error bounds after an exclusion event for Advanced Receiver Autonomous Integrity Monitoring (ARIMA) is presented, which exploits the ambiguity as to which measurement must be excluded and a pre allocation of the integrity budget to the exclusion outcomes.
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.
TL;DR: This paper shows that the solution separation statistic is closely linked to the optimal detection statistics, and that in the case of many one-dimensional threats, the optimal statistics can be expressed as a function of the solution separations corresponding to each threat.
Abstract: One of the most commonly used detection statistics in autonomous integrity monitoring is the solution separation statistic. In this paper, we show that the solution separation statistic is closely linked to the optimal detection statistics. More precisely, we show that in the case of one threat, even multi-dimensional, the optimal detection statistic is the solution separation, and that in the case of many one-dimensional threats, the optimal statistics can be expressed as a function of the solution separations corresponding to each threat. This is achieved by casting the search of the optimal detection region as a mini-max problem and by using the Neyman–Pearson lemma to limit the search of the detection regions to a class of regions parameterized by a bias. These results allow us to establish a lower bound on the minimum achievable integrity risk. Copyright © 2017 Institute of Navigation
TL;DR: The preliminary results presented in this paper demonstrate some of the performance capabilities and robustness characteristics of the ETF.
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.
TL;DR: Current state of bathymetric survey concerning deep ocean rather than shallow areas, which are better surveyed due to safety of navigation concerns, is presented.
Abstract: Abstract The paper presents current state of bathymetric survey concerning deep ocean rather than shallow areas, which are better surveyed due to safety of navigation concerns. Rules and requirements of the new challenge, called the Shell Ocean Discovery XPRIZE, became a starting point for a discussion about the possibilities of mapping large areas of the ocean using up-to-date and new technology. The amount of bathymetric data available nowadays and the current state of ocean map compilations are also discussed in the paper as a motivation to inspire the new initiatives in the deep ocean.
TL;DR: In this paper, the aspect ratio (ratio of maximum to minimum eigenvalue) for the covariance matrix of the imperfectly decorrelated signal is used to identify a bound for the worst-case (largest) missed-detection and false-alarm probabilities for a chisquare monitor in which the input signal vector cannot be perfectly decorrelated.
Abstract: This paper identifies a bound for the worst-case (largest) missed-detection and false-alarm probabilities for a chisquare monitor in which the input signal vector cannot be perfectly decorrelated. A new method for bounding monitor missed-detection performance is introduced that leverages the aspect ratio (ratio of maximum to minimum eigenvalue) for the covariance matrix of the imperfectly decorrelated signal. An application to signal deformation monitoring (SDM) for the global positioning system (GPS) indicates that the new bound is both tight and relatively inexpensive to compute.
TL;DR: A new methodology to enhance the GNSS parameter estimation accuracy in multipath fading environments using the frequency diversity reception is proposed herein and results show that frequency diversity based combined tracking results in improved performance compared to that of single frequency tracking.
Abstract: A new methodology to enhance the GNSS parameter estimation accuracy in multipath fading environments using the frequency diversity reception is proposed herein. In such environments, fading occurrences observed in different frequency bands are independent of each other. Characteristics of frequency diversity reception using GPS L1 and L2C signals in dense fading conditions are first discussed and compared with those of spatial diversity reception. Comparative analyses of characterization metrics between frequency diversity and spatial diversity signals support the argument that the former is as effective as the latter. A frequency diversity based combined tracking approach is then proposed, and the performance is evaluated using the data collected in dense foliage and residential environments. Results show that frequency diversity based combined tracking results in improved performance compared to that of single frequency tracking. 3D position error reduction achieved by the proposed method is 52% in foliage conditions and 50% in residential environments. Copyright © 2017 Institute of Navigation
TL;DR: The method for determining the suboptimal route of sailing vessels operating in a restricted area of the sea using an heuristic algorithm, and the appropriate application routing for fixed starting points and targets is designed in the method.
Abstract: Abstract The method for determining the suboptimal route of sailing vessels operating in a restricted area of the sea are proposed in the paper. The dynamics of the environment including weather conditions and speed characteristics of ships sailing are considered. As optimization criterion, measure sailing time T, and the number of maneuvers performed ω, are taken into account. An heuristic algorithm, and the appropriate application routing for fixed starting points and targets is designed in the method. In addition author analyzed the behavior of the algorithm, depending on the number of direction changes of the course, and granularity of the description of the surface of area.
TL;DR: In this paper, the authors present the achievements in satellite altimetry in all the above disciplines obtained in the last years and present the results of the investigations and possible products of satellite-altimetry will provide a good material for the GGOS (Global Geodetic Observing System) and institutions of IAS (International Altimetry Service).
Abstract: Abstract One of the fundamental problems of modern geodesy is precise definition of the gravitational field and its changes in time. This is essential in positioning and navigation, geo-physics, geodynamics, oceanography and other sciences related to the climate and Earth’s environment. One of the major sources of gravity data is satellite altimetry that provides gravity data with almost 75% surface of the Earth. Satellite altimetry also provides data to study local, regional and global geophysical processes, the geoid model in the areas of oceans and seas. This technique can be successfully used to study the ocean mean dynamic topography. The results of the investigations and possible products of altimetry will provide a good material for the GGOS (Global Geodetic Observing System) and institutions of IAS (International Altimetry Service). This paper presents the achievements in satellite altimetry in all the above disciplines obtained in the last years.
TL;DR: In this paper, the authors present an implementation of variable IF correlation in acquisition and its multipath performance with a theoretical background analysis, and the preliminary test results demonstrate increased code tracking accuracy as well as increased positioning performance.
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.
TL;DR: Results from the data sets for 5 baselines demonstrate that the wide-lane (WL) integer-fixing success rates of 95% to 99% can be achieved within 50 independent epochs and show the potential for achieving reliable and high-precision positioning with sparsely distributed ground stations regionally or globally.
Abstract: Article free to read on jounal website. A key challenge of wide-area kinematic positioning using the BeiDou system is to reduce the effects of the elevation-dependent hardware biases in code signals. Based on three geometry-free/ionosphere-free combinations, the elevation-dependent code biases are modeled for all BeiDou satellites. Results from the data sets for 5 baselines of 533 to 2545 km demonstrate that the wide-lane (WL) integer-fixing success rates of 95% to 99% can be achieved within 50 independent epochs. Under the condition of HDOP less than 2, the overall RMS statistics of ionospheric-free WL single-epoch solutions achieve 24 to 50 cm in the horizontal direction. Smoothing processing over the moving window of 40 epochs reduces the RMS values by a factor of about 2. Considering the distance-independent nature, the above results show the potential for achieving reliable and high-precision positioning with sparsely distributed ground stations regionally or globally.
TL;DR: In this article, a methodology to reassess the tropospheric threat within two main steps: an analysis of European meteorological data and a new bounding methodology for dealing with the troposphere threat and its impact on vertical protection levels.
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.
TL;DR: validation of previously created stochastic ships traffic stream model by the real data of ships delays on Świnoujście — Szczecin waterway and total waiting time of ships have been applied.
Abstract: Abstract Paper presents validation of previously created stochastic ships traffic stream model by the real data of ships delays on Świnoujście — Szczecin waterway. The model is mostly based on Monte Carlo methodology. The model is microscopic which means that each ship’s model is treated as separate object possessing given attributes. As the main parameter of presented validation total waiting (delay) time of ships have been applied. The time of ships delays was possessed from Szczecin VTS centre and compared with the model output.
TL;DR: The proposed improved compressed GNSS acquisition method using adjacent part differential coherence reduces the impact of bit sign and frequency error on the integration amplitude and has better detection probability and lower MAT than DCGAM under the same false alarm probability.
Abstract: Due to the influence of bit sign and frequency error on integration peak, the Deterministic Compressed GNSS Acquisition Method (DCGAM) has poor detection performance in high dynamic environments. For fast acquisition in high dynamic environments, this paper has proposed an improved compressed GNSS acquisition method using adjacent part differential coherence. First, the adjacent part differential coherence process between the two neighbor milliseconds is used. This reduces the impact of bit sign and frequency error on the integration amplitude. Then, the decision variable is built when the differential signal goes through the compressed process. The detection probability, false alarm probability, and miss probability are derived to calculate the Mean Acquisition Time (MAT). Finally, the simulation results show that the proposed method has better detection probability and lower MAT than DCGAM under the same false alarm probability. Moreover, the experimental results yield these same results. Copyright © 2017 Institute of Navigation