With the increasing number of available satellites from multi‐global navigation satellite systems (GNSS) and their applications in complicated environments, an increased number of faults in ...measurements are inevitable. Fault detection and exclusion (FDE) is an effective way to reject observation faults in order to guarantee the integrity of a GNSS positioning and navigation system. We propose a modified between‐receiver single‐differencing (SD)‐based FDE algorithm for real‐time kinematic (RTK) positioning. First, a modified between‐receiver SD model‐based FDE is proposed for testing the estimated float ambiguities. This is helpful in rejecting observations with unreliable float ambiguities and obtaining reliable double‐differencing (DD) integer ambiguities, denoted as the SD float model in the sequel. Second, DD ambiguities are resolved by the DD model and used to update the previous SD float ambiguity. After that, a modified SD fix model, taking the DD ambiguities as the known parameters, is further developed to detect any unreliable or fault‐resolved ambiguities. To verify the modified SD model‐based FDE algorithm, a kinematic vehicle test is conducted. The fault detection test statistics of the SD float model and the SD fix model, time‐to‐first‐fix, ambiguity‐fix rate, SD residuals, and positioning performances are examined. The results show that the modified FDE method can detect and exclude fault satellites accurately and effectively, which is verified by the SD residuals of fault satellites. The ambiguity‐fix rate of the proposed modified FDE algorithm is improved by approximately 3% with 70 more epochs of fixes. Regarding the 3D positioning performance, the modified proposed SD‐based FDE algorithm can achieve 54.11%, 57.78%, and 73.11% improvements for standard deviation, root mean square, and mean bias, respectively, when compared with the processing strategy without the use of the proposed FDE.
As a relative positioning technique, LiDAR-Inertial Odometry (LIO) is known to suffer from drifting and can only provide local coordinates. To compensate for these shortages of LIO, an effective way ...is to integrate global navigation satellite system (GNSS) with LIO. In this contribution, we proposed a tightly coupled GNSS RTK/INS/LiDAR system under the factor graph optimization framework, termed as FGO-GIL, to achieve high-precision and continuous navigation in urban environments. This integration system fuses raw GNSS measurements (i.e., pseudorange and carrier phase measurements) with IMU and LiDAR information at the observation level atop a factor graph. Moreover, a keyframe-based nonlinear optimization scheme is designed to efficiently utilize measurements from the mixed heterogeneous sensors. Specifically, non-keyframes are united with IMU pre-integration for inter-frame optimization, which can provide accurate and high-frequency state predictions for the scan-matching of keyframes. Sparse keyframes are used to construct LiDAR factors through matching with the submap for sliding window optimization. To evaluate the effectiveness of our approach, real-world experiments are conducted in both campus and urban environments. The results demonstrate that our system can achieve continuous decimeter-level positioning accuracy in these complex environments, outperforming other state-of-the-art frameworks.
본 논문에서는 MATLAB GUI 기반으로 개발된 다중 위성군 network RTK MAC 보정정보 생성 소프트웨어에 대해서 소개한다. 해당 소프트웨어는 GPS와 GLONASS, Galileo를 포함한 다중 위성군의 보정정보를 생성하는 알고리즘의 유효성을 평가하기 위해 시뮬레이션 데이터 기반 후처리 소프트웨어로 개발되었다. 소프트웨어 구동 결과 다중 ...위성군의 시스템별 network RTK 보정정보가 MATLAB 파일 형식으로 출력된다. 본 논문에서는 개발된 소프트웨어의 성능을 평가하기 위해 소프트웨어를 통해 생성된 보정정보를 사용자에게 적용한 후 잔여 오차를 분석하였다. 분석 결과 사용자 잔여 오차의 크기가 10 cm 이하를 유지하는 것을 확인함으로써, 유효한 network RTK 보정정보 생성이 가능함을 확인하였다.
In this paper, multi-GNSS network RTK MAC correction generation software developed based on MATLAB GUI is introduced. The software was developed as a post-processing software based on simulation data to evaluate the feasibility of an algorithm for generating correction for multi-GNSS including GPS, GLONASS, and Galileo. As a result of software operation, network RTK correction for each system of multi-GNSS is output in MATLAB file format. In this paper, to evaluate the performance of the developed software, the residual error was analyzed after applying the correction generated through the software to the user. As a result of the analysis, it was confirmed that effective network RTK correction could be generated by confirming that the residual errors of users were maintained at 10 cm or less.
PPP-RTK, known as integer ambiguity resolution-enabled precise point positioning, requires precise satellite-related products and atmospheric corrections estimated in a global navigation satellite ...system (GNSS) network. In generating these products, one commonly sends all network data to a computation center and conducts a centralized processing scheme. However, this centralized PPP-RTK faces considerable challenges in computational efficiency and model formulation with the increasing number of receivers. This work proposes a decentralized PPP-RTK processing strategy that generates products in three steps: subnetwork processing, satellite-related product integration, and atmospheric correction update. The first step divides the whole network into several subnetworks where we can impose ionosphere-weighted constraints to improve the precision of estimates. The second step integrates subnetwork-dependent satellite clocks and biases and aligns the underlying datum. The final step updates the atmospheric delays by considering the covariances between satellite-related products and atmospheric estimates. This three-step decentralized PPP-RTK processing strategy can improve computational efficiency and ensure the high precision of all products. For numerical evaluation, we collected one-week dual-frequency global positioning system (GPS) data from 82 stations, in which 44 stations were divided into four groups for product generation and 38 stations were considered users for positioning experiments. The results show, on the network side, that the decentralized PPP-RTK generates products with the same precision as that of centralized PPP-RTK and reduces the computation time by about 50%. On the user side, the decentralized PPP-RTK products perform as well as their centralized counterparts, and the time-to-first-fix (TTFF) and three-dimensional root-mean-square (RMS) are less than 3 epochs and 1.59 cm on average, respectively. Moreover, the results verify that the decentralized PPP-RTK ensures continuous positioning when users move across subnetworks.
Thyroid eye disease (TED) is a complex autoimmune disease process. Orbital fibroblasts represent the central orbital immune target. Involvement of TSH receptor (TSHR) in TED is not fully understood. ...Insulin-like growth factor-I (IGF-IR) is overexpressed in several cell types in TED, including fibrocytes and orbital fibroblasts. IGF-IR may form a physical and functional complex with TSHR.
Review literature relevant to autoantibody generation in TED and whether these induce orbital fibroblast responses directly through TSHR, IGF-IR or both.
IGF-IR has traditionally been considered a typical tyrosine kinase receptor where tyrosine residues become phosphorylated following IGF-I binding. Evidence has emerged that IGF-IR possesses kinase-independent activities and can be considered a functional RTK/GPCR hybrid, utilizing the GRK/β-arrestin system. Teprotumumab, a monoclonal IGF-IR antibody, effectively reduces TED disease activity, proptosis and diplopia In addition, the drug attenuates in vitro actions of both IGF-I and TSH in fibrocytes and orbital fibroblasts, including induction of proinflammatory cytokines by TSH and TED IgGs.
While teprotumumab has been proven effective and relatively safe in the treatment of TED, many questions remain pertaining to IGF-IR, its relationship with TSHR, and how the drug might be disrupting these receptor protein/protein interactions. Here, we propose four possible IGF-IR activation models that could underlie clinical responses to teprotumumab observed in patients with TED. Teprotumumab is associated with several adverse events, including hyperglycemia and hearing abnormalities. Underpinning mechanisms of these are being investigated. Patients undergoing treatment with drug must be monitored for these and managed with best medical practices.
The release of raw Android Global Navigation Satellite System (GNSS) measurements makes high-precision positioning achievable with low-cost smart devices. Affected by low-cost GNSS chips, linearly ...polarized antennas, and complex observation environments, Android GNSS observations usually contain a large number of outliers, which significantly degrade their positioning precision and reliability. To address this issue, a robust real-time kinematic (RTK) scheme with sliding window-based Factor Graph Optimization (FGO) was developed. The scheme adopts the GNSS carrier-phase sliding window marginalization, models the carrier-phase ambiguity as a random constant, and incorporates multiple robust estimation strategies. Vehicle kinematic positioning validations were carried out in both open-sky and complex urban environments using representative Xiaomi Mi8 and Huawei P40 smartphones. Using the proposed scheme, the RMS of the positioning errors in the east, north, and up components in the open-sky environments are 0.18 m, 0.13 m, and 0.38 m, respectively. In complex urban environments, the RMS of the positioning precisions in the east, north, and up components were as decent as 1.42 m, 1.97 m, and 2.63 m, respectively.
The validity of the results obtained within different permanent GNSS reference station networks (GNSS Network) must be periodically controlled using criteria that are generally known from statistical ...analyzes or prescribed by International Standards. Procedures for evaluating the uncertainty of measurements are defined in accordance with the purpose of the GNSS Network. The authors of this paper want to point out the need to establish requirements for periodical and systematical control of GNSS coordinates within the same permanent GNSS Network and control of GNSS coordinates between different permanent GNSS Networks measured on the same/unique point on the ground. This paper presents control procedures for three permanent GNSS reference station Networks established and operating in the Republic of Serbia. Special attention is on the analysis of data consistency within one permanent GNSS Network and the mutual consistency of GNSS data between different networks. The paper aims to promote reliance on the different GNSS Networks and contains suggestions on how GNSS Networks may prove that they are performing competently and that they can provide valid results for field measurements. Particularly highlighted is the need to plan and implement measures related to increasing the effectiveness of the GNSS system, achieving improved results, and preventing negative effects while performing field measurements. The paper presents the results for comparison, selected according to the rules for creating a Digital Cadastral Map features, i.e., points, lines, and polygon. The results for comparing point features are the GNSS coordinates. The results for comparing line features are the lengths of the line, i.e., distances, and the results for comparing polygon features are the areas of the polygons.
High-precision positioning is essential for emerging mass-market applications such as autonomous driving, unmanned aerial vehicles and intelligent transportation in complex urban canyons. Without ...global navigation satellite system (GNSS) reference stations, the real-time kinematic precise point positioning (PPP-RTK) technique is widely used in these fields because of its fast and accurate absolute positioning capability. However, in complex urban canyons, the performance of PPP-RTK deteriorates dramatically due to the satellite signal obstruction and interference. In contrast, inertial navigation system (INS) and visual navigation can provide precise relative pose estimation, but they suffer from serious error accumulation. Therefore, there is a strong complementary advantage between GNSS and INS/Vision navigation and positioning. In this study, a tightly coupled PPP-RTK/INS/Vision integration model is developed, aiming at improving the performance of PPP-RTK in terms of precision and availability to achieve robust positioning in complex urban canyons. Vehicle-borne experiments with different typical urban scenarios were carried out. We found that the positioning precision, availability and the ambiguity fixing rate of PPP-RTK can be significantly improved by tightly coupling with INS and Vision. The positioning precision of tightly coupled micro-electro-mechanical system (MEMS)-based PPP-RTK/INS/Vision is 6 cm, 5 cm and 10 cm in the east, north and up components, respectively, with an ambiguity fixing rate of 83.6% in typical urban environments, which are comparable to the statistics of a tactical-based PPP-RTK/INS tight integration. Even in complex urban canyons, the positioning precision of tightly coupled MEMS-based PPP-RTK/INS/Vision solution can still reach 11 cm, 7 cm and 13 cm in the east, north and up components, respectively, exhibiting improvements of over 90% compared to GNSS-only PPP-RTK. These results indicate that PPP-RTK tightly coupled with low-cost MEMS-IMU and monocular vision can provide high-precision and high-reliability navigation and positioning solutions even in complex urban environments.
O posicionamento em tempo real por meio do emprego dos sinais de satélites foi um avanço nas navegações aérea, marítima e terrestre com o surgimento do GPS (Global Positioning System). Contudo as ...precisões horizontais e verticais de 100 m e 150 m (nível de probabilidade de 95%) alcançadas, estando a SA (Selective Availability) ativada, passaram a não ser satisfatórias para muitas aplicações e os usuários buscaram galgar outros níveis de precisões. Esforços foram investidos no chamado posicionamento diferencial DGPS (Differential GPS), o qual possibilitou obter precisões em torno de dez vezes melhores do que as do posicionamento absoluto. Posteriormente, usando-se a fase da onda portadora, conseguiu-se realizar posicionamento com maior acurácia por meio do método RTK (Real Time Kinematic), atingindo qualidade centimétrica. Na sequência, houve uma evolução para posicionamentos em rede, empregando, por exemplo, o algoritmo de VRS (Virtual Reference Station). Vários erros nas observáveis dos satélites passaram a ser modelados com uma solução de multiestações em tempo real. A partir de 2012, surgiram serviços e produtos que favoreceram o desenvolvimento do RT-PPP (Real-Time Precise Point Positioning) baseado no conceito SSR (State Space Representation). A busca da solução das ambiguidades no RT-PPP deu origem ao PPP-RTK com menor tempo de fixação das ambiguidades e convergência para a solução acurada do posicionamento. Neste artigo apresenta-se como foi a evolução do posicionamento em tempo real, algumas das aplicações no âmbito nacional e as perspectivas desta modalidade de posicionamento para o futuro.
The paper presents the results of research on improving the accuracy of aircraft positioning using RTK-OTF (Real Time Kinematic-On The Fly) technique in air navigation. The paper shows a new solution ...of aircraft positioning for the application of the differential RTK-OTF technique in air navigation. In particular, a new mathematical model is presented which makes it possible to determine the resultant position of an aircraft based on the solution for the method of least squares in a stochastic process. The developed method combines in the process of alignment of GPS (Global Positioning System) observations, three independent solutions of the aircraft position in OTF mode for geocentric coordinates XYZ of the aircraft. Measurement weights as a function of the vector length and the mean vector length error, respectively, were used in the calculations. The applied calculation method makes it possible to determine the resultant position of the aircraft with high accuracy: better than 0.039 m with using the measurement weight as a function of the vector length and better than 0.009 m with the measurement weight as a function of the mean error of the vector length, respectively. In relation to the classical RTK-OTF solution as a model of the arithmetic mean, the proposed method makes it possible to increase the accuracy of determination of the aircraft position by 45-46% using the measurement weight as a function of the vector length, and 86-88% using the measurement weight as a function of the mean error of the vector length, respectively. The obtained test results show that the developed method improves to significantly improve the accuracy of the RTK-OTF solution as a method for determining the reference position in air navigation.
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