Real-Time Kinematic Precise Point Positioning (PPP–RTK) is inextricably linked to external ionospheric information. The PPP–RTK performances vary much with the accuracy of ionospheric information, ...which is derived from different network scales, given different prior variances, and obtained under different disturbed ionospheric conditions. This study investigates the relationships between the PPP–RTK performances, in terms of precision and convergence time, and the accuracy of external ionospheric information. The statistical results show that The Time to First Fix (TTFF) for the PPP–RTK constrained by Global Ionosphere Map (PPP–RTK-GIM) is about 8–10 min, improved by 20%–50% as compared with that for PPP Ambiguity Resolution (PPP-AR) whose TTFF is about 13–16 min. Additionally, the TTFF of PPP–RTK is 4.4 min, 5.2 min, and 6.8 min, respectively, when constrained by the external ionospheric information derived from different network scales, e.g. small-, medium-, and large-scale networks, respectively. To analyze the influences of the optimal prior variances of external ionospheric delay on the PPP–RTK results, the errors of 0.5 Total Electron Content Unit (TECU), 1 TECU, 3 TECU, and 5 TECU are added to the initial ionospheric delays, respectively. The corresponding convergence time of PPP–RTK is less than 1 min, about 3, 5, and 6 min, respectively. After adding the errors, the ionospheric information with a small variance leads to a long convergence time and that with a larger variance leads to the same convergence time as that of PPP-AR. Only when an optimal prior variance is determined for the ionospheric delay in PPP–RTK model, the convergence time for PPP–RTK can be shorten greatly. The impact of Travelling Ionospheric Disturbance (TID) on the PPP–RTK performances is further studied with simulation. It is found that the TIDs increase the errors of ionospheric corrections, thus affecting the convergence time, positioning accuracy, and reliability of PPP–RTK.
Pathogens exploit multiple cellular and molecular pathways in the host organisms for their entry, survival and dissemination. The cell surface receptors such as G protein-coupled receptors (GPCRs) ...and receptor tyrosine kinases (RTKs) constitute the targets of many pathogens. This is due to the ubiquitous expression of these two receptor families in the organism and their pivotal role in various cellular and physiological processes. At the molecular level, receptor hijacking implies either direct or indirect interactions between pathogens' effectors or toxins with GPCRs and RTKs at the cell surface thereby interfering with their activation and their downstream signaling pathways inside the host cells. As a result, the pathogens manipulate and redirect GPCR/RTK-mediated signaling pathways and different aspects of cell function for their benefit. The review presents a compilation of the major examples of pathogen infections where GPCRs and RTKs and their related intracellular signaling pathways are targeted. This provides a molecular basis for pathogens hijacking cell signaling and their virulence. Our understanding of such complex host-pathogen interactions at the molecular level will open new opportunities to develop new prophylactic and therapeutic approaches against infections. In this context, the pharmacological targeting of GPCRs and RTKs may be a promising approach.
•Pathogens use GPCRs and RTKs to enter the host cells.•Pathogen-receptor interaction leads to the activation of downstream signaling pathways•The blockade of GPCR and RTKs may prevent against bacterial and viral infection.
The 3-D digitalization of contents and their visualization using augmented reality (AR) has gained a significant interest within the scientific community. Researchers from various fields have ...acknowledged the potential of these technologies, actively exploring the ability to provide users with easy access to digitized information, by seamlessly integrating content directly into their field of view. One of the most promising ways to approach the problem in outdoor scenarios consists of the so-called location-based AR, where contents are displayed to the user by integrating satellite positioning as global navigation satellite system (GNSS) and inertial as inertial measurement units (IMUs) sensors. Although the number of application fields is numerous, the accuracy of the over-imposition of contents in the virtual view still hinders the widespread adoption of such technologies. In this article, we propose the combination of a GNSS device equipped with real-time kinematic (RTK) positioning, and a regular smartphone. To this aim, we implement a novel offline calibration process that leverages the potential of a motion capture (MoCap) system. The proposed solution is capable of ensuring temporal consistency and allows for real-time acquisition at centimeter-level accuracy.
Statybos planavimo ir valdymo veikloje taikomos technologijos, susijusios su įvairiomis erdvinių duomenų kombinacijomis, iš kurių gaunami reikšmingi rezultatai apie tiriamą objektą. Geodeziniais ...matavimais nustatomos statinių, kelių ir kitų inžinerinių objektų geografinė padėtis. Analizuojant ir vertinant naujus ir esamus inžinerinius įrenginius, atliekant svarbių linijinių inžinerinių objektų monitoringą ir pan. siekiama užtikrinti maksimalų tikslumą ir kaupti pilnaverčius duomenis. Vienas iš būtiniausių statybos etapų yra statinio (inžinerinių sistemų) geodezinis nužymėjimas. Plečiantis GPNS referencinių stočių tinklui, matavimo sistemų spektrui, GPS palydovų kiekiui ir t.t., gauti optimalų rezultatų tikslumą, ypač sudėtingomis matavimo sąlygomis, galimybės didėja. Praktikoje dažniausiai yra naudojamas RTK (realaus laiko kinematinis) metodas, taikant valstybinio GPNS referencinių stočių tinklo LitPOS RTKNet paslaugą. GPNS RTK matavimai urbanizuotose teritorijose dažniausiai atliekami sudėtingomis sąlygomis. Atliktas taškų koordinavimas skirtingomis geografinėmis ir matavimo sąlygomis ir analizuotos matavimų kokybės galimybės. Atlikti GPNS RTK matavimai geromis (atvirose vietovėse su geru regimuoju horizontu, kai medžiai dar neturi lapų ir yra geros oro sąlygos), realiomis ir sudėtingomis sąlygomis (miško žemėje arba šalia medžių ir po jais; urbanizuotoje teritorijoje, tarp pastatų; kalvotame reljefe, tarp uolų; aukštos elektros įtampos poveikio zonoje ir pan.). Nustatyta kad didžiausi koordinuotų taškų nesutapimai fiksuojami intensyviai užstatytose ir miškingose teritorijose. Rekomenduojama kiekvienoje situacijoje taikyti individualų sprendimą, kuris priklausytų nuo matavimų tipo ir GPNS imtuvo galimybių.
The PPP–RTK method, which combines the concepts of Precise of Point Positioning (PPP) and Real-Time Kinematic (RTK), is proposed to provide a centimeter-accuracy positioning service for an unlimited ...number of users. Recently, the PPP–RTK technique is becoming a promising tool for emerging applications such as autonomous vehicles and unmanned logistics as it has several advantages including high precision, full flexibility, and good privacy. This paper gives a detailed review of PPP–RTK focusing on its implementation methods, recent achievements as well as challenges and opportunities. Firstly, the fundamental approach to implement PPP–RTK is described and an overview of the research on key techniques, such as Uncalibrated Phase Delay (UPD) estimation, precise atmospheric correction retrieval and modeling, and fast PPP ambiguity resolution, is given. Then, the recent efforts and progress are addressed, such as improving the performance of PPP–RTK by combining multi-GNSS and multi-frequency observations, single-frequency PPP–RTK for low-cost devices, and PPP–RTK for vehicle navigation. Also, the system construction and applications based on the PPP–RTK method are summarized. Moreover, the main issues that impact PPP–RTK performance are highlighted, including signal occlusion in complex urban areas and atmosphere modeling in extreme weather events. The new opportunities brought by the rapid development of low-cost markets, multiple sensors, and new-generation Low Earth Orbit (LEO) navigation constellation are also discussed. Finally, the paper concludes with some comments and the prospects for future research.
Triple-frequency signals have thus far been available for all satellites of BeiDou and Galileo systems and for some GPS satellites. The main benefit of triple-frequency signals is their formation of ...extra-wide-lane (EWL) combinations whose ambiguities can be instantaneously fixed for several 10–100 km baselines. Yet, this benefit has not been fully exploited and only used as a constraint for narrow-lane (NL) ambiguity resolution (AR) in most previous studies. In this study, we comprehensively investigate the real-time kinematic (RTK) capabilities of EWL observations, also referred to as EWL RTK (ERTK). We begin by mathematically expressing the ease of EWL AR and the difficulty of NL AR, respectively, using a numerical demonstration. We then present the mathematical models for ERTK including the ionosphere-ignored, ionosphere-float and ionosphere-smoothed types. The experiments are conducted using a four-station network of real triple-frequency BeiDou data with baseline lengths from 33 to 75 km. The results show that the ionosphere-ignored ERTK achieves real-time solutions with a horizontal accuracy of about 10 cm. Although the ionosphere-float ERTK solutions are very noisy, they can be quickly improved at the centimetre level by further applying the ionosphere-smoothed model. Note that such accurate results are very promising and already satisfy many applications without complicated NL AR. To the best of our knowledge, this is the first comprehensive study to make full use of EWL observations of triple-frequency signals on RTK.
The availability of raw Android Global Navigation Satellite System (GNSS) data is driving innovation in high-precision positioning using Android smartphones. However, inconsistent pseudorange and ...phase observations, low dual-frequency data integrity, and unknown receiver-side hardware biases prevent the ambiguity resolution of GNSS precision point positioning (PPP) for smartphones. In this study, we thus provide a comprehensive real-time kinematic precise point positioning (PPP-RTK) strategy. First, carrier phase observations are adjusted to be consistent with the pseudorange observations. Next, rapid single-frequency PPP convergence is achieved by regional atmospheric enhancement. Finally, inter-satellite difference ambiguities are formed to eliminate unknown receiver-side hardware biases and combined with the partial ambiguity resolution strategy to achieve ambiguity-fixed centimeter-level smartphone PPP-RTK positioning. The results show that using the proposed PPP-RTK strategy, the root mean square (RMS) of ambiguity-fixed solution positioning errors is 0.7, 1.3, and 2.5 cm in the east, north, and upper components, respectively, for a representative Huawei P40 smartphone connected to an external survey-type antenna, and 1.2, 1.5, and 5.8 cm for the P40 smartphone using its embedded antenna in an open-sky environment. And their ambiguity fixing rates all reached more than 98%. In 21 sets of experiments, PPP-RTK for smartphones with external and embedded antennas took an average of 1.0 and 63.5 seconds, respectively, to converge to an ambiguity-fixed solution with a horizontal positioning error within 5 cm. This provides a way for rapid and high-precision GNSS positioning in stand-alone mode for smartphones, which may facilitate the development and widespread use of smartphone high-precision GNSS positioning.
Currently, Global Navigation Satellite System (GNSS) Real-Time Kinematic positioning (RTK) and Precise Point Positioning (PPP) techniques are widely employed for real-time monitoring of landslides. ...However, both RTK and PPP monitoring techniques have their limitations, such as limited service coverage or long convergence times. PPP-RTK technique which integrates RTK and PPP is a novel approach for monitoring landslides with the advantages of rapid convergence, high-precision, and a wide service area. This study summarizes the limitations of RTK, PPP, and PPP-RTK monitoring techniques and suggests some improved strategies. Their performances are compared and analyzed using real monitoring data. The experiment results demonstrate that RTK is the best option for small-scale (the baseline distance < 15 km) and real-time landslide monitoring without considering the cost. PPP technique converges to centimeter-level accuracy in tens of minutes, only suitable for the stability analysis of reference stations. Over a large area (the baseline distance < 100 km), PPP-RTK can provide excellent horizontal accuracy and adapt the service range in response to the demand for monitoring accuracy, as the vertical accuracy is significantly impacted by the service range and elevation difference. Finally, the characteristics of three techniques are integrated to form a comprehensive landslide monitoring technique that considers intelligence, robustness, and real-time.
The RAS/MAP kinase and the RAS/PI3K/AKT pathways play a key role in the regulation of proliferation, differentiation and survival. The induction of these pathways depends on Receptor Tyrosine Kinases ...(RTKs) that are activated upon ligand binding. In cancer, constitutive and aberrant activations of components of those pathways result in increased proliferation, survival and metastasis. For instance, mutations affecting RTKs, Ras, B-Raf, PI3K and AKT are common in perpetuating the malignancy of several types of cancers and from different tissue origins. Therefore, these signaling pathways became prime targets for cancer therapy. This review aims to provide an overview about the most frequently encountered mutations, the pathogenesis that results from such mutations and the known therapeutic strategies developed to counteract their aberrant functions.
•Both RTK and RT-PPP provide cm-level positioning accuracy in kinematic survey.•Using RTK methods in rough topography is limited due to the loss of correction.•RTX RT-PPP service compensates for RTK ...methods disadvantages.•RTX RT-PPP provides real-time high accurate seamless positioning.
The main objective of this study is to assess the performance of the relative Real-time Kinematic (RTK) Global Navigation Satellite System (GNSS) Methods; i.e., Single-baseline & Network RTK, and Real-time Precise Point Positioning (RT-PPP); i.e., Trimble CenterPoint Real Time eXtended (RTX) Correction Service in a dynamic environment. For this purpose, a kinematic test was done within a vessel in Obruk Lake Dam in Çorum province, Turkey. The test area was situated in a deep valley and surrounded by high hills covered with dense trees. The real-time coordinates of each measurement epoch were simultaneously determined with Single-baseline RTK, Network RTK, and RTX RT-PPP methods by using three GNSS receivers. The real-time coordinates obtained from both RTK and RT-PPP methods were compared against the post-processed relative solution epoch-by-epoch. The results show that, the 3D position accuracies of real-time methods were found as ±6 cm, ±3 cm and ±7 cm for Single-baseline RTK, Network RTK and RT-PPP methods, respectively. This study demonstrates that although the Network RTK methods provided the best solution among the others, the positioning did not conduct most of the time due to the loss of cellular connection. This was also partially valid for the Single-baseline RTK method because the corrections from the base station via radio-link couldn’t be received due to the rough terrain conditions. However, it was possible to make positioning with RTX Real-time PPP technique using satellite delivery GNSS products (corrections) continuously and in a robust manner within the cm-level accuracy. Our study showed that the use of the global multi-GNSS RTX correction service outcompetes conventional RTK methods with providing consistent, reliable, and seamless cm-level accurate positioning almost without any interruption especially in challenging marine environments with severe terrain obstructions.
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