Impact of one satellite outage on ARAIM depleted constellation configurations

Advanced Receiver Autonomous Integrity Monitoring(ARAIM) is a new technology that will provide worldwide coverage of vertical guidance in aviation navigation. The ARAIM performance and improvement under depleted constellations is a practical problem that needs to be faced and researched further. It is a shortcut that improves the availability in position domain whose key idea is to replace the conventional least squares process with a non-least-squares estimator to lower the integrity risk in exchange for a slight increase in nominal position error. The contributions given in this paper include two parts: First, the impacts of one satellite outage on different constellations are analyzed and compared. The conclusion is that GPS is more sensitive and vulnerable to one satellite outage. Second, a constellation weighted ARAIM(CW-ARAIM)position estimator is proposed. The position solution is replaced by a constellation weighted average solution to eliminate the constellation difference. The new solution will move close to the constellation solutions with respect to the accuracy requirement. The simulation results under baseline GPS and Galileo dual-constellation show that the one GPS satellite outage will knock the availability from 91% to only 50%. The performance remains stable with one Galileo satellite outage. With the assistance of the CW-ARAIM method, the availability can increase from 50% to more than80% under depleted GPS configurations. Even without any satellite outage, the proposed method can effectively improve the availability from 91.29% to 98.75%. The test results under optimistic constellations further verify that a balanced constellation is more important than more satellites on orbit and the superiority of CW-ARAIM method is still effective.

Integrity monitoring of fixed ambiguity Precise Point Positioning(PPP)solutions

Traditional positioning methods,such as conventional Real Time Kinematic(cRTK)rely upon local reference networks to enable users to achieve high-accuracy positioning.The need for such relatively dense networks has significant cost implications.Precise Point Positioning(PPP)on the other hand is a positioning method capable of centimeter-level positioning without the need for such local networks,hence providing significant cost benefits especially in remote areas.This paper presents the state-of-the-art PPP method using both GPS and GLONASS measurements to estimate the float position solution before attempting to resolve GPS integer ambiguities.Integrity monitoring is carried out using the Imperial College Carrier-phase Receiver Autonomous Integrity Monitoring method.A new method to detect and exclude GPS base-satellite failures is developed.A base-satellite is a satellite whose measurements are differenced from other satellite’s measurements when using between-satellite-differenced measurements to estimate position.The failure detection and exclusion methods are tested using static GNSS data recorded by International GNSS Service stations both in static and dynamic processing modes.The results show that failure detection can be achieved in all cases tested and failure exclusion can be achieved for static cases.In the kinematic processing cases,failure exclusion is more difficult because the higher noise in the measurement residuals increases the difficulty to distinguish between failures associated with the base-satellite and other satellites.

New methods for dual constellation single receiver positioning and integrity monitoring

Navigation system integrity monitoring is crucial for mission(e.g.safety)critical applications.Receiver autonomous integrity monitoring(RAIM)based on consistency checking of redundant measurements is widely used for many applications.However,there are many challenges to the use of RAIM associated with multiple constellations and applications with very stringent requirements.This paper discusses two positioning techniques and corresponding integrity monitoring methods.The first is the use of single frequency pseudorange-based dual constellations.It employs a new cross constellation single difference scheme to benefit from the similarities while addressing the differences between the constellations.The second technique uses dual frequency carrier phase measurements from GLONASS and the global positioning system for precise point positioning.The results show significant improvements both in positioning accuracy and integrity monitoring as a result of the use of two constellations.The dual constellation positioning and integrity monitoring algorithms have the potential to be extended to multiple constellations.

Advances in BeiDou Navigation Satellite System(BDS)and satellite navigation augmentation technologies

Several noteworthy breakthroughs have been made with the BeiDou Navigation Satellite System(BDS)and other global navigation satellite systems as well as the associated augmentation systems,such as the commissioning of the BDS-3 preliminary system and the successful launch of the first BDS-3 GEO satellite which carries the satellite-based augmentation payload.Presently,BDS can provide basic services globally,and its augmentation system is also being tested.This paper gives an overview of BDS and satellite navigation augmentation technologies.This overview is divided into four parts,which include the system segment technologies,satellite segment technologies,propagation segment technologies,and user segment technologies.In each part,these technologies are described from the perspectives of preliminary information,research progress,and summary.Moreover,the significance and progress of the BeiDou Satellite-based Augmentation System(BDSBAS),low earth orbit augmentation,and the national BeiDou ground-based augmentation system are presented,along with the airborne-based augmentation system.Furthermore,the conclusions and discussions covering popular topics for research,frontiers in research and development,achievements,and suggestions are listed for future research.

Correction to: Advances in BeiDou Navigation Satellite System (BDS) and satellite navigation augmentation technologies

Correction to:Satell Navig(2020)1:12 https://doi.org/10.1186/s43020-020-00010-2 In the original publication of this article(Li et al.2020),there are several corrections as below:1.In the first paragraph of this article,the sentence“In recent years,China has been actively promoting the con-struction and development of the BeiDou Navigation Sat-ellite System(BDS),and by the end of the year 2000 the construction of BDS-1 was complete and BDS-1 began to provide GPS services for China.”should be changed into“In recent years,China has been actively promoting the construction and development of the BeiDou Navigation Satellite System(BDS),and by the end of the year 2000 the construction of BDS-1 was completed and BDS-1 began to provide services for China.”The word“GPS”should be removed.

Integration of GPS with a WiFi high accuracy ranging functionality

High accuracy seamless positioning is required to support a vast number of applications in varying operational environments.Over the last few years,the global positioning system(GPS)has become the de facto technology for positioning applications.However,its performance is limited in indoor and dense urban environments due to multipath as well as signal attenuation and blockage.A number of techniques integrating GPS with other positioning technologies have been developed to address the limitations of standalone GPS in these difficult environments.While most of the developed techniques cover the outages of GPS in such environments,they do not provide acceptable performance,in terms of positioning accuracy,especially for some mission-critical(e.g.safety)applications.This paper proposes a tightly coupled(i.e.in the measurement domain)GPS/WiFi integration method which,in addition to addressing GPS outages,improves the overall positioning accuracy to the meter-level,thus satisfying the requirements of a number of location based services and intelligent transport systems applications.The performance of the proposed GPS/WiFi integration method is assessed for a number of scenarios in a simulation environment for an identified dense urban area in London,UK.