integrity risk
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2021 ◽  
Vol 14 (1) ◽  
pp. 128
Author(s):  
Bing Xue ◽  
Yunbin Yuan ◽  
Han Wang ◽  
Haitao Wang

Global Navigation Satellite System (GNSS) Precise Point Positioning (PPP) is an attractive positioning technology due to its high precision and flexibility. However, the vulnerability of PPP brings a safety risk to its application in the field of life safety, which must be evaluated quantitatively to provide integrity for PPP users. Generally, PPP solutions are processed recursively based on the extended Kalman filter (EKF) estimator, utilizing both the previous and current measurements. Therefore, the integrity risk should be qualified considering the effects of all the potential observation faults in history. However, this will cause the calculation load to explode over time, which is impractical for long-time missions. This study used the innovations in a time window to detect the faults in the measurements, quantifying the integrity risk by traversing the fault modes in the window to maintain a stable computation cost. A non-zero bias was conservatively introduced to encapsulate the effect of the faults before the window. Coping with the multiple simultaneous faults, the worst-case integrity risk was calculated to overbound the real risk in the multiple fault modes. In order to verify the proposed method, simulation and experimental tests were carried out in this study. The results showed that the fixed and hold mode adopted for ambiguity resolution is critical to an integrity risk evaluation, which can improve the observation redundancy and remove the influence of the biased predicted ambiguities on the integrity risk. Increasing the length of the window can weaken the impact of the conservative assumption on the integrity risk due to the smoothing effect of the EKF estimator. In addition, improving the accuracy of observations can also reduce the integrity risk, which indicates that establishing a refined PPP random model can improve the integrity performance.


Navigation ◽  
2021 ◽  
Vol 68 (4) ◽  
pp. 709-726
Author(s):  
Adyasha Mohanty ◽  
Shubh Gupta ◽  
Grace Xingxin Gao

2021 ◽  
Vol 13 (23) ◽  
pp. 4815
Author(s):  
Yuchen Liu ◽  
Yueling Cao ◽  
Chengpan Tang ◽  
Jinping Chen ◽  
Liqian Zhao ◽  
...  

To satisfy the demands of civil aviation organizations and other users of satellite navigation systems for high-precision and high-integrity service performance, many countries and regions have established satellite-based augmentation systems (SBAS) referring to the Radio Technical Commission for Aeronautics (RTCA) service standards and agreements. The BeiDou SBAS (BDSBAS) provides both single-frequency service, which augments Global Positioning System (GPS) L1 C/A signal, and dual-frequency multi-constellation (DFMC) service, which augments BeiDou Navigation Satellite System (BDS) B1C and B2a dual frequency signals presently, meeting the requirements of the RTCA DO-229D protocol and the SBAS L5 DFMC protocol requirements, respectively. As one of the main error sources, the pseudorange bias errors of BDSBAS monitoring receivers were estimated and their effect on the performance of the BDSBAS service was analyzed. Based on the user algorithms of SBAS differential corrections and integrity information, the service accuracy, integrity, and availability of the BDSBAS were evaluated using real observation data. The results show that the maximum of monitoring receiver pseudorange bias errors between L1P and L1P/L2P can reach 1.57 m, which become the most important errors affecting the performance of the BDSBAS service. In addition, the results show that the pseudorange bias of GPS BlockIII is the smallest, while that of GPS BlockIIR is the largest. Compared with the positioning accuracy of the open service of the core constellation, the positioning accuracy of the BDSBAS service can be improved by approximately 47% and 36% for the RTCA service and DFMC service, respectively. For RTCA services, the protection limit (PL) calculated with the integrity information can 100% envelop the positioning error (PE) and no integrity risk event is detected. The service availability of BDSBAS for APV-I approach is approximately 98.8%, which is mainly affected by the availability of ionospheric grid corrections in the service marginal area. For DFMC service, the integrity risk is not detected either. The service availability for CAT-I approach is 100%. Improving the availability of ionospheric grid corrections is one of the important factors to improve service performance of BDSBAS RTCA service.


2021 ◽  
Author(s):  
Zhen Gao ◽  
Kun Fang ◽  
Xiao Li ◽  
Jichao Dong ◽  
Yanbo Zhu ◽  
...  

Author(s):  
Nik Hairi Omar ◽  
Mohd Nasir Selamat ◽  
Siti Fardaniah Abdul Aziz ◽  
Rusyda Helma Mohd ◽  
Rasyidah Ismail

2021 ◽  
Vol 13 (15) ◽  
pp. 2860
Author(s):  
Cheng Liu ◽  
Yueling Cao ◽  
Gong Zhang ◽  
Weiguang Gao ◽  
Ying Chen ◽  
...  

Compared to the BeiDou regional navigation satellite system (BDS-2), the BeiDou global navigation satellite system (BDS-3) carried out a brand new integrity concept design and construction work, which defines and achieves the integrity functions for major civil open services (OS) signals such as B1C, B2a, and B1I. The integrity definition and calculation method of BDS-3 are introduced. The fault tree model for satellite signal-in-space (SIS) is used, to decompose and obtain the integrity risk bottom events. In response to the weakness in the space and ground segments of the system, a variety of integrity monitoring measures have been taken. On this basis, the design values for the new B1C/B2a signal and the original B1I signal are proposed, which are 0.9 × 10−5 and 0.8 × 10−5, respectively. The hybrid alarming mechanism of BDS-3, which has both the ground alarming approach and the satellite alarming approach, is explained. At last, an integrity risk analysis and verification work were carried out using the operating data of the system in 2019. The results show that the actual operation of the system is consistent with the conceptual design, which satisfies the integrity performance promised by BDS-3 in the ICAO SAPRs.


2021 ◽  
Author(s):  

This Annual Report reflects the work of the Office of Institutional Integrity (OII), the Sanctions Officer (SO) and the Sanctions Committee (SNC), which together are responsible for overseeing the management of integrity risk at the Inter-American Development Bank (IDB) Group.


2021 ◽  
Author(s):  
Parimal A. Patil ◽  
Prasanna Chidambaram ◽  
M Syafeeq Bin Ebining Amir ◽  
Pankaj K. Tiwari ◽  
Debasis P. Das ◽  
...  

Abstract Underground storage of CO2 in depleted gas reservoirs is a greenhouse gas reduction technique that significantly reduces CO2 released into the atmosphere. Three major depleted gas reservoirs in Central Luconia gas field, located offshore Sarawak, possess good geological characteristics needed to ensure long-term security for CO2 stored deep underground. Long-term integrity of all the wells drilled in these gas fields must be ensured in order to successfully keep the CO2 stored for decades/centuries into the future. Well integrity is often defined as the ability to contain fluids without significant leakage through the project lifecycle. In order to analyze the risk associated with all 38 drilled wells, that includes 11 plugged and abandoned (P&A) wells and 27 active wells, probabilistic risk assessment approach has been developed. This approach uses various leakage scenarios, that includes features, events, and processes (FEP). A P&A well in a depleted reservoir is a very complex system in order to assess the loss of containment as several scenarios and parameters associated to those scenarios are difficult to estimate. Based on the available data of P&A wells, a well has been selected for this study. All the barriers in the example well have been identified and properties associated with those barriers are defined in order to estimate the possible leakage pathways through the identified barriers within that well. Detailed mathematical models are provided for estimating CO2 leakage from reservoir to the surface through all possible leakage pathways. Sensitivity analysis has been carried out for critical parameters such as cement permeability, and length of cement plug, in order to assess the containment ability of that well and understand its impact on overall well integrity. Sensitivity analysis shows that permeability of the cement in the annulus, and length of cement plug in the wellbore along with pressure differential can be used as critical set of parameters to assess the risk associated with all wells in these three fields. Well integrity is defined as the ability of the composite system (cemented casings string) in the well to contain fluids without significant leakage from underground reservoir up to surface. It has been recognized as a key performance factor determining the viability of any CCS project. This is the first attempt in assessing Well Integrity risk related to CO2 storage in Central Luconia Gas Fields in Sarawak. The wells have been looked individually in order to make sure that integrity is maintained, and CO2 is contained underground for years to come.


2021 ◽  
Author(s):  
Ryujiro Ishihara ◽  
Naohide Higuchi ◽  
Yohei Mikami

Abstract This is a case study to establish the positive result of an artificial lift application of the jet pump (JP) system using the coiled tubing (CT) and the macaroni tubing (MT). It is applied to the monobore completions for the slim-hole production wells on BURAPA-A oil field, onshore Thailand, implemented by Siam Moeco Ltd. (SML, Affliated Company of Mitsui Oil Exploration Co., Ltd.). As a result of the JP introduction, the resulting production decline rate was lower and the recovery factor more than doubled, which extended field life longer than expected. SML succeeded in discovering the method to minimize the capital cost while maximizing the oil recovery with the JP system. This method has given us the chance to conduct a smaller-scale well intervention operation with only minor modification of the wellhead. We believe that it is an adequate artificial lift application for the small-size oil field. Some important lessons for the small pipe size operations were learned in this process. A pin-hole leak was detected in the CT for the main production well due to erosion and corrosion by continuous high-pressure pumping for around two years after the installation of the JP completion. After reviewing the new completion design, the type of deployment pipe was converted to the MT, which is thicker and has higher integrity than the CT. Consequently, there have been no integrity issues for the deployment pipes since the production was resumed with the new completion. In addition, using the multi finger caliper tool, it was detected that the thickness of the production tubing at the jetting area was significantly eroded, showing that the JP system has the possibility to risk the integrity for the outer string. The JP completion is a validated technology to apply for the slim-hole monobore completions to increase the recovery factor and minimize the implementation cost. In addition, the well integrity risk by the JP application to the slim-hole monobore completions was revealed, and new insights were gained, resulting in some pros and cons comparing the two types of the deployment pipes (CT & MT).


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