1,720,967 research outputs found
Feasibility of fault exclusion related to advanced RAIM for GNSS spoofing detection
No full textThis paper will present an exercise to verify the usefulness of statistical testing of measurement residuals of an overdetermined position solution followed by measurement subset selection for spoofing detection and mitigation for certain spoofing events, to be especially beneficial when multi-GNSS is considered. Tests include utilizing dynamic GPS spoofing data from the TEXBAT testing battery. We will present that Advanced RAIM (Receiver Autonomous Integrity Monitoring) has benefits for spoof detection. RAIM is designed to catch inconsistencies in range measurements and is thus useful in defeating a surreptitious lift off spoofing attack. Inconsistencies in a lift off attack exist when the spoof signal mixes with the genuine signal of similar power levels (within a few dB). The mixing creates some measurements from genuine signals and some from the spoofed signals. ARAIM cannot however mitigate across all categories of spoofers and hence should not represent a standalone spoofing solution. Although pre-and post-correlation signal processing is definitely the most efficient way to detect and mitigate spoofing effects, checking the measurements in the navigation domain is not a lost cause, as presented herein
Development of a new ship adaptive weather routing model based on seakeeping analysis and optimization
No full textThis paper provides a new adaptive weather routing model, based on the Dijkstra shortest path algorithm, aiming to select the optimal route that maximizes the ship performances in a seaway. The model is based on a set of ship motion-limiting criteria and on the weather forecast maps, providing the sea state conditions the ship is expected to encounter along the scheduled route. The new adaptive weather routing model is applied to optimize the scheduled route in the Northern Atlantic Ocean of the S175 containership, assumed as a reference vessel, based on the weather forecast data provided by the Global WAve Model (GWAM). In the analysis, both wave and combined wind/swell wave conditions are embodied to investigate the incidence on the optimum route assessment. Furthermore, the effect of the vessel speed on the optimum route detection is also investigated. Current results clearly show that it is possible to achieve appreciable improvements, up to 50% of the ship seakeeping performances, without excessively increasing the route length and the voyage duration
A Fuzzy Logic-Based Weighting Model for GNSS Measurements from a Smartphone
No full textGNSS navigation is critical in unfavourable scenarios, where the solution can be degraded by errors such as multipath reflections and weak geometries caused by obstacles surrounding the receiver. Nonetheless, the influence of the errors can be reduced defining an adequate quality measure for each signal and, consequently, using weights inversely related to the quality of the received signals. In this paper, a quality index, obtained from the fuzzy integration of various features of the received signals and leveraged to weight each measure in a Weighted Least Square (WLS) estimation process, is validated on measurements coming from a High Sensitivity receiver embedded in a smartphone. The main objective is to validate a fuzzy control designer provided by the authors in a previous work using raw data from a smartphone to compute the navigation solution and to extend its application to the multi-GNSS constellation case. The performance of the tested weighting strategy is evaluated in the position domain and in comparison with another weighting method. GNSS real data have been collected through a smartphone located in typical urban canyon environment, and processed in Single Point Positioning. Results show an evident enhancement obtained from the application of the fuzzy logic to obtain a proper weight to be assigned to GNSS observables reproducing a stochastic model similar to the reality
NeQuick Galileo version model: Assessment of a proposed version in operational scenario
No full textThe ionosphere is one of the main error sources for single-frequency Global Navigation Satellite System (GNSS) measurements in open-sky scenario. Most widespread GNSS devices are single frequency stand-alone receivers and they can use different Ionospheric Correction Algorithms (ICA) in order to reduce the ionospheric error. In this work two ICA models are considered, specifically Klobuchar and NeQuick-G models. These algorithms are driven by parameters broadcast within GPS and Galileo navigation messages respectively. Hence no additional infrastructure is needed to reduce the ionospheric effects. The main goal of the paper is to analyze the performance of a modified approach for NeQuick-G (defined NeQuick VP) by comparing its performance, in position domain, with respect to the standard NeQuick-G algorithm and to Klobuchar one. NeQuick VP is a methodology proposed to reduce the complexity characterizing NeQuick-G model. The performance is evaluated using real data collected by an open-sky station; the results obtained are analyzed using Root Mean Square (RMS), mean and maximum errors as Key Performance Indicators (KPIs) for both horizontal and vertical components
Multi-GNSS Single Frequency Precise Point Positioning
No full textSingle Frequency-Precise Point Positioning (SF-PPP) processing strategy is a hot topic in GNSS context, owing to the advantages of a stand-alone, accurate and cost efficiency positioning. However, the existing SF-PPP methods can be hardly implemented for high-precision applications due to the large error sources that affect accuracy and converge time of PPP solution. For this aim, the paper proposes a SF-PPP approach based on the processing of code and carrier phase measurements from multi-GNSS constellation. The algorithm is tested using a static data collection carried out in an open-sky scenario. Results show a decimeter level accuracy on horizontal and vertical components of the position
GPS precise positioning techniques for remote marine applications
No full textMarine geodesy, offshore surveys and physical oceanography are usually related to the highly precise kinematic positioning of surveying platforms such as vessels, buoys and aircrafts. Currently, the Global Navigation Satellite Systems (GNSS) can provide a kinematic positioning accuracy of decimeter to centimeter level in relative mode, being potentially an appropriate choice for determining marine platform positions. However, these positioning techniques are related to the presence of reference stations and are not applicable in remote areas. In this work, two approaches are considered to determine the altitude variations of GPS antenna, which is an important parameter for the analysis of a ship motion. In detail, time-differencing of carrier phase measurements and precise point positioning approaches are applied on static data, collected by a single-frequency receiver, in order to assess the vertical variations performance
Performance Assessment of PPP Surveys with Open Source Software Using the GNSS GPS–GLONASS–Galileo Constellations
Full text linkIn this work, the performance of the multi-GNSS (Global Navigation Satellite System)
Precise Point Positioning (PPP) technique, in static mode, is analyzed. Specifically, GPS (Global
Positioning System), GLONASS, and Galileo systems are considered, and quantifying the Galileo
contribution is one of the main objectives. The open source software RTKLib is adopted to process the
data, with precise satellite orbits and clocks from CNES (Centre National d’Etudes Spatiales) and CLS
(Collecte Localisation Satellites) analysis centers for International GNSS Service (IGS). The Iono-free
model is used to correct ionospheric errors, the GOT-4.7 model is used to correct tidal effects, and
Differential Code Biases (DCB) are taken from the Deutsche Forschungsanstalt für Luftund Raumfahrt
(DLR) center. Two different tropospheric models are tested: Saastamoinen and Estimate ZTD (Zenith
Troposhperic Delay). For the proposed study, a dataset of 31 days from a permanent GNSS station,
placed in Palermo (Italy), and a dataset of 10 days from a static geodetic receiver, placed nearby the
station, have been collected and processed by the most used open source software in the geomatic
community. The considered GNSS configurations are seven: GPS only, GLONASS only, Galileo only,
GPS+GLONASS, GPS+Galileo, GLONASS+Galileo, and GPS+GLONASS+Galileo. The results show
significant performance improvement of the GNSS combinations with respect to single GNSS cases
The EGNOS Augmentation in Maritime Navigation
No full textThe objective of this work is the evaluation of the performances of EGNOS (European Geostationary Navigation Overlay System) augmentation system in maritime navigation by comparing them with those obtained by other positioning methods as Single Point Positioning (SPP) and Differential Global Positioning System (DGPS). Preliminarily, EGNOS performances in an open-sky context were evaluated through static data downloaded by EGNOS RIMS (Ranging and Integrity Monitoring Stations) located in Rome. Then, for the maritime test carried out onboard a boat in the Gulf of Naples, two dual-frequency receivers were used: Xiaomi Mi 8 smartphone and u-blox ZED-F9P multi-band GNSS (Global Navigation Satellite System) receiver, both in kinematic mode. At last, IMO (International Maritime Organization) requirements, established in IMO Resolution A.1046 (27), that a SBAS (Satellite Based Augmentation System) system in particular scenarios (coastal, inland-water, harbor navigation and ocean waters) must respect, were verified
Sea state monitoring based on ship motion measurements onboard an icebreaker in the Antarctic waters
No full textA new wave spectrum resembling procedure is applied to detect the sea state parameters, namely the wave peak period and the significant wave height based on the analysis of heave and pitch motion time series, obtained by on board measurements. The outlined procedure is applied to Laura Bassi oceanographic ship, assumed as reference vessel. Heave and pitch motion time histories are evaluated from the survey of the amplitudes of the vessel motions, starting from different sensors measures collected by a smartphone located on board the vessel. The obtained results were compared with the weather forecast data provided by the global-WAM (GWAM) model
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