scholarly journals Locata Network Design and Reliability Analysis for Harbour Positioning

2014 ◽  
Vol 68 (2) ◽  
pp. 238-252 ◽  
Author(s):  
Ling Yang ◽  
Yong Li ◽  
Wei Jiang ◽  
Chris Rizos
Keyword(s):  
Failure Modes ◽  
Satellite System ◽  
Fault Identification ◽  
Positioning System ◽  
Algorithm Performance ◽  
Protection Level ◽  
Receiver Autonomous Integrity Monitoring ◽  
Global Navigation Satellite ◽  
Port Areas

To meet the accuracy, integrity, continuity and availability required for many navigation applications the Locata technology can provide an alternative to satellite-based navigation in difficult Global Navigation Satellite System (GNSS) signal environments, especially for applications in port areas and in constricted waterways. Unlike GNSS constellations, a LocataNet – a local constellation of LocataLites – can be designed specifically for different environments to avoid signal blockages, interference or poor geometry. By using Locata technology, the optimal performance within particular areas can always be guaranteed. This paper demonstrates the influence of LocataNet configuration on the reliability and integrity of the Locata positioning system. The performance of the Locata system is investigated using the Receiver Autonomous Integrity Monitoring (RAIM) concept. Fault Detection and Exclusion (FDE) algorithm performance is validated through the computation of the Dilution of Precision (DOP), the Horizontal Protection Level (HPL) and the correlation coefficient between two failure modes that can indicate the quality of fault identification. The experimental analysis shows that a good configuration of LocataLites will enhance the accuracy and reliability of the navigation system.

scholarly journals Analyses of the sensitivity of multi-constellation advanced receiver autonomous integrity monitoring vertical protection level availability to error parameters and a failure model over China

2018 ◽  
Vol 10 (6) ◽  
pp. 168781401877619 ◽  
Author(s):  
Xueen Zheng ◽  
Ye Liu ◽  
Guochao Fan ◽  
Jing Zhao ◽  
Chengdong Xu
Keyword(s):  
Satellite System ◽  
Protection Level ◽  
Integrity Monitoring ◽  
System Service ◽  
Service Stations ◽  
Receiver Autonomous Integrity Monitoring ◽  
Global Navigation Satellite ◽  
Range Error ◽  
Monitoring Algorithm ◽  
Advanced Receiver

The availability of advanced receiver autonomous integrity monitoring for vertical guidance down to altitudes of 200 ft (LPV-200) is discussed using real satellite orbit/ephemeris data collected at eight international global navigation satellite system service stations across China. Analyses were conducted for the availability of multi-constellation advanced receiver autonomous integrity monitoring and multi-fault advanced receiver autonomous integrity monitoring, and the sensitivity of availability in response to changes in error model parameters (i.e. user range accuracy, user range error, Bias-Nom and Bias-Max) was used to compute the vertical protection level. The results demonstrated that advanced receiver autonomous integrity monitoring availability based on multiple constellations met the requirements of LPV-200 despite multiple-fault detections that reduced the availability of the advanced receiver autonomous integrity monitoring algorithm; the advanced receiver autonomous integrity monitoring availability thresholds of the user range error and Bias-Nom used for accuracy were more relevant to geographic information than the user range accuracy and Bias-Max used for integrity at the eight international global navigation satellite system service stations. Finally, the possibility of using the advanced receiver autonomous integrity monitoring algorithm for a Category III navigation standard is discussed using two sets of predicted errors, revealing that the algorithm could be used in 79% of China.

Failure Modes and Models for Integrated GPS/INS Systems

2007 ◽  
Vol 60 (2) ◽  
pp. 327-348 ◽  
Author(s):  
Umar Iqbal Bhatti ◽  
Washington Yotto Ochieng
Keyword(s):  
Failure Modes ◽  
Cost Effective ◽  
Satellite System ◽  
Integrated System ◽  
Data Consistency ◽  
Coupling Mechanism ◽  
Integrity Monitoring ◽  
Potential Failure ◽  
Receiver Autonomous Integrity Monitoring ◽  
Global Navigation Satellite

GPS is the most widely used global navigation satellite system. By design, there is no provision for real time integrity information within the Standard Positioning Service (SPS). However, in safety critical sectors like aviation, stringent integrity performance requirements must be met. This can be achieved externally or at the receiver level through receiver autonomous integrity monitoring (RAIM). The latter is a cost effective method that relies on data consistency, and therefore requires redundant measurements. An external aid to provide this redundancy can be in the form of an Inertial Navigation System (INS). This should enable continued performance even during RAIM holes (when no redundant satellite measurements are available). However, due to the inclusion of an additional system and the coupling mechanism, integrity issues become more challenging. To develop an effective integrity monitoring capability, a good understanding of the potential failure modes of the integrated system is vital. In this paper potential failure modes of integrated GPS/INS systems are identified. This is followed by the specification of corresponding models that would be required to investigate the capability of existing integrity algorithms and to develop enhancements or new algorithms.

scholarly journals Multi-Layer Defences for Robust GNSS Timing Retrieval

Sensors ◽  
2021 ◽  
Vol 21 (23) ◽  
pp. 7787
Author(s):  
Ciro Gioia ◽  
Daniele Borio
Keyword(s):  
Global Navigation Satellite System ◽  
Interference Mitigation ◽  
Satellite System ◽  
Navigation Satellite ◽  
Integrity Monitoring ◽  
Gnss Receivers ◽  
Mitigation Techniques ◽  
Receiver Autonomous Integrity Monitoring ◽  
Global Navigation Satellite

A multi-layered interference mitigation approach can significantly improve the performance of Global Navigation Satellite System (GNSS) receivers in the presence of jamming. In this work, three levels of defence are considered including: pre-correlation interference mitigation techniques, post-correlation measurement screening and FDE at the Position, Velocity, and Time (PVT) level. The performance and interaction of these receiver defences are analysed with specific focus on Robust Interference Mitigation (RIM), measurement screening through Lock Indicator (LIs) and Receiver Autonomous Integrity Monitoring (RAIM). The case of timing receivers with a known user position and using Galileo signals from different frequencies has been studied with Time-Receiver Autonomous Integrity Monitoring (T-RAIM) based on the Backward-Forward method. From the experimental analysis it emerges that RIM improves the quality of the measurements reducing the number of exclusions performed by T-RAIM. Effective measurements screening is also fundamental to obtain unbiased timing solutions: in this respect T-RAIM can provide the required level of reliability.

scholarly journals Galileo L10 Satellites: Orbit, Clock and Signal-in-Space Performance Analysis

Sensors ◽  
2021 ◽  
Vol 21 (5) ◽  
pp. 1695
Author(s):  
Constantin-Octavian Andrei ◽  
Sonja Lahtinen ◽  
Markku Poutanen ◽  
Hannu Koivula ◽  
Jan Johansson
Keyword(s):  
Performance Indicators ◽  
Satellite System ◽  
Short Term ◽  
Orbital Inclination ◽  
Navigation Data ◽  
Periodic Signals ◽  
Global Navigation Satellite ◽  
Minor Correction ◽  
Very High

The tenth launch (L10) of the European Global Navigation Satellite System Galileo filled in all orbital slots in the constellation. The launch carried four Galileo satellites and took place in July 2018. The satellites were declared operational in February 2019. In this study, we report on the performance of the Galileo L10 satellites in terms of orbital inclination and repeat period parameters, broadcast satellite clocks and signal in space (SiS) performance indicators. We used all available broadcast navigation data from the IGS consolidated navigation files. These satellites have not been reported in the previous studies. First, the orbital inclination (56.7±0.15°) and repeat period (50680.7±0.22 s) for all four satellites are within the nominal values. The data analysis reveals also 13.5-, 27-, 177- and 354-days periodic signals. Second, the broadcast satellite clocks show different correction magnitude due to different trends in the bias component. One clock switch and several other minor correction jumps have occurred since the satellites were declared operational. Short-term discontinuities are within ±1 ps/s, whereas clock accuracy values are constantly below 0.20 m (root-mean-square—rms). Finally, the SiS performance has been very high in terms of availability and accuracy. Monthly SiS availability has been constantly above the target value of 87% and much higher in 2020 as compared to 2019. Monthly SiS accuracy has been below 0.20 m (95th percentile) and below 0.40 m (99th percentile). The performance figures depend on the content and quality of the consolidated navigation files as well as the precise reference products. Nevertheless, these levels of accuracy are well below the 7 m threshold (95th percentile) specified in the Galileo service definition document.

scholarly journals Assessing the quality of ionospheric models through GNSS positioning error: methodology and results

GPS Solutions ◽  
2019 ◽  
Vol 24 (1) ◽  
Author(s):  
Adrià Rovira-Garcia ◽  
Deimos Ibáñez-Segura ◽  
Raul Orús-Perez ◽  
José Miguel Juan ◽  
Jaume Sanz ◽  
...  
Keyword(s):  
Satellite System ◽  
Ionospheric Delay ◽  
Single Frequency ◽  
Positioning Error ◽  
Dual Frequency ◽  
Error Sources ◽  
Ionospheric Models ◽  
Evaluation Metric ◽  
Global Navigation Satellite

Abstract Single-frequency users of the global navigation satellite system (GNSS) must correct for the ionospheric delay. These corrections are available from global ionospheric models (GIMs). Therefore, the accuracy of the GIM is important because the unmodeled or incorrectly part of ionospheric delay contributes to the positioning error of GNSS-based positioning. However, the positioning error of receivers located at known coordinates can be used to infer the accuracy of GIMs in a simple manner. This is why assessment of GIMs by means of the position domain is often used as an alternative to assessments in the ionospheric delay domain. The latter method requires accurate reference ionospheric values obtained from a network solution and complex geodetic modeling. However, evaluations using the positioning error method present several difficulties, as evidenced in recent works, that can lead to inconsistent results compared to the tests using the ionospheric delay domain. We analyze the reasons why such inconsistencies occur, applying both methodologies. We have computed the position of 34 permanent stations for the entire year of 2014 within the last Solar Maximum. The positioning tests have been done using code pseudoranges and carrier-phase leveled (CCL) measurements. We identify the error sources that make it difficult to distinguish the part of the positioning error that is attributable to the ionospheric correction: the measurement noise, pseudorange multipath, evaluation metric, and outliers. Once these error sources are considered, we obtain equivalent results to those found in the ionospheric delay domain assessments. Accurate GIMs can provide single-frequency navigation positioning at the decimeter level using CCL measurements and better positions than those obtained using the dual-frequency ionospheric-free combination of pseudoranges. Finally, some recommendations are provided for further studies of ionospheric models using the position domain method.

scholarly journals Deriving surface soil moisture from reflected GNSS signal observations from a grassland site in southwestern France

2017 ◽  
Author(s):  
Sibo Zhang ◽  
Jean-Christophe Calvet ◽  
José Darrozes ◽  
Nicolas Roussel ◽  
Frédéric Frappart ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Land Surface ◽  
Land Surface Model ◽  
Ground Surface ◽  
Satellite System ◽  
Surface Model ◽  
Global Navigation Satellite ◽  
Grassland Site

Abstract. This work aims to assess the estimation of surface volumetric soil moisture (VSM) using the Global Navigation Satellite System Interferometric Reflectometry (GNSS-IR) technique. Year-round observations were acquired from a grassland site in southwestern France using an antenna consecutively placed at two contrasting heights above the ground surface (3.3 or 29.4 m). The VSM retrievals are compared with two independent reference datasets: in situ observations of soil moisture, and numerical simulations of soil moisture and vegetation biomass from the ISBA (Interactions between Soil, Biosphere and Atmosphere) land surface model. Scaled VSM estimates can be retrieved throughout the year removing vegetation effects by the separation of growth and senescence periods and by the filtering of the GNSS-IR observations that are most affected by vegetation. Antenna height has no significant impact on the quality of VSM estimates. Comparisons between the VSM GNSS-IR retrievals and the in situ VSM observations at a depth of 5 cm show a good agreement (R2 = 0.86 and RMSE = 0.04 m3 m−3). It is shown that the signal is sensitive to the grass litter water content and that this effect triggers differences between VSM retrievals and in situ VSM observations at depths of 1 cm and 5 cm, especially during light rainfall events.

Urban Fleet Monitoring with GPS and GLONASS

1998 ◽  
Vol 51 (3) ◽  
pp. 382-393 ◽  
Author(s):  
M. Tsakiri ◽  
M. Stewart ◽  
T. Forward ◽  
D. Sandison ◽  
J. Walker
Keyword(s):  
Global Positioning System ◽  
Public Transport ◽  
Urban Areas ◽  
Dead Reckoning ◽  
Satellite System ◽  
Basic Function ◽  
Positioning System ◽  
Positioning Systems ◽  
Global Positioning ◽  
Global Navigation Satellite

The increasing volume of traffic in urban areas has resulted in steady growth of the mean driving time on fixed routes. Longer driving times lead to significantly higher transportation costs, particularly for vehicle fleets, where efficiency in the distribution of their transport tasks is important in staying competitive in the market. For bus fleets, the optimal control and command of the vehicles is, as well as the economic requirements, a basic function of their general mission. The Global Positioning System (GPS) allows reliable and accurate positioning of public transport vehicles except within the physical limitations imposed by built-up city ‘urban canyons’. With a view to the next generation of satellite positioning systems for public transport fleet management, this paper highlights the limitations imposed on current GPS systems operating in the urban canyon. The capabilities of a future positioning system operating in this type of environment are discussed. It is suggested that such a system could comprise receivers capable of integrating the Global Positioning System (GPS) and the Russian equivalent, the Global Navigation Satellite System (GLONASS), and relatively cheap dead-reckoning sensors.

Accounting for Inter-System Bias in DGNSS Positioning with GPS/GLONASS/BDS/Galileo

2017 ◽  
Vol 70 (4) ◽  
pp. 686-698 ◽  
Author(s):  
Hui Liu ◽  
Bao Shu ◽  
Longwei Xu ◽  
Chuang Qian ◽  
Rufei Zhang ◽  
...  
Keyword(s):  
Global Positioning System ◽  
Simple Algorithm ◽  
Satellite System ◽  
Harsh Environments ◽  
Positioning System ◽  
Gnss Positioning ◽  
Global Positioning ◽  
System Bias ◽  
Global Navigation Satellite ◽  
Reliability And Availability

Code Differential Global Positioning System (DGPS) is widely used in satellite navigation and positioning because of its simple algorithm and preferable precision. Multi-Global Navigation Satellite System (GNSS) is expected to enhance the accuracy, reliability and availability of Differential GNSS (DGNSS) positioning. Traditional DGNSS models should set separate clock parameters due to the clock differences between the different systems. Awareness of the Inter-System Bias (ISB) could help to maximise the redundancy of the positioning model, thus improving the performance of multi-GNSS positioning. This paper aims to examine the inter-system bias of GPS/GLONASS/BeiDou (BDS)/Galileo and their benefits in DGNSS positioning. Results show that Differential ISB (DISB) characteristics vary with different receiver types and systems. The size of DISB could reach metre-level and the precision of estimated DISBs can reach approximately several centimetres within tens of epochs. Therefore, a new real-time DGNSS model that accounts for ISB is proposed. After differential ISBs are initialised, positioning with four satellites from arbitrarily the same or different systems can be realised. Moreover, compared with the traditional DGNSS model, the precision of the positioning results with the new model are obviously improved, especially in harsh environments.

scholarly journals Determination of sea surface height from moving ships with dynamic corrections

2012 ◽  
Vol 2 (3) ◽  
pp. 172-187 ◽  
Author(s):  
J. Reinking ◽  
A. Härting ◽  
L. Bastos
Keyword(s):  
Satellite System ◽  
Ocean Dynamics ◽  
Sea Surface ◽  
Sea Surface Heights ◽  
Positioning Analysis ◽  
Remote Sensing Techniques ◽  
Global Navigation Satellite

AbstractWith the growing global efforts to estimate the influence of civilization on the climate change it would be desirable to survey sea surface heights (SSH) not only by remote sensing techniques like satellite altimetry or (GNSS) Global Navigation Satellite System reflectometry but also by direct and in-situ measurements in the open ocean. In recent years different groups attempted to determine SSH by ship-based GNSS observations. Due to recent advances in kinematic GNSS (PPP) Precise Point Positioning analysis it is already possible to derive GNSS antenna heights with a quality of a few centimeters. Therefore it is foreseeable that this technique will be used more intensively in the future, with obvious advantages in sea positioning. For the determination of actual SSH from GNSS-derived antenna heights aboard seagoing vessels some essential hydrostatic and hydrodynamic corrections must be considered in addition to ocean dynamics and related corrections. Systematic influences of ship dynamics were intensively analyzed and sophisticated techniques were developed at the Jade University during the last decades to precisely estimate mandatory corrections. In this paper we will describe the required analyses and demonstrate their application by presenting a case study from an experiment on a cruise vessel carried out in March 2011 in the Atlantic Ocean.

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