Limited sensitivity analysis of ARAIM availability for LPV-200 over Australia using real data

Current availability of Advanced Receiver Autonomous Integrity Monitoring (ARAIM) for LPV-200 in aviation is experimentally investigated using real navigation data and GPS measurements collected at 60 stations across Australia. ARAIM algorithm and fault probabilities were first discussed. Availability sensitivity analysis due to changes in the elevation mask angle and the error model parameters URA, URE, and nominal biases for integrity and accuracy used for computation of the protection level is presented. It is shown that incorporation of other GNSS constellation with GPS in ARAIM is needed to achieve LPV-200 Australia wide. The inclusion of BeiDou with GPS at two tests sites in Western and Eastern Australia demonstrates the promising potential of achieving this goal

Performance evaluation of different troposphere delay models and mapping functions

Tropospheric delay is a major error source in positioning by Global Navigation Satellite Systems (GNSSs). System users often apply one of the available troposphere models without giving sufficient background on their performance. In this study, the performance of different known hydrostatic and wet troposphere delay models and mapping functions are internally and externally compared and analysed at selected sites around the globe. International GNSS Service (IGS) products were used as a reference. The best performing models are presented. Results showed that small discrepancies are present between different models. All models perform significantly better at the mid-latitudes than at the Equator

Maintaining real-time precise point positioning during outages of orbit and clock corrections

The precise point positioning (PPP) is a popular positioning technique that is dependent on the use of precise orbits and clock corrections. One serious problem for real-time PPP applications such as natural hazard early warning systems and hydrographic surveying is when a sudden communication break takes place resulting in a discontinuity in receiving these orbit and clock corrections for a period that may extend from a few minutes to hours. A method is presented to maintain real-time PPP with 3D accuracy less than a decimeter when such a break takes place. We focus on the open-access International GNSS Service (IGS) real-time service (RTS) products and propose predicting the precise orbit and clock corrections as time series. For a short corrections outage of a few minutes, we predict the IGS-RTS orbits using a high-order polynomial, and for longer outages up to 3 h, the most recent IGS ultra-rapid orbits are used. The IGS-RTS clock corrections are predicted using a second-order polynomial and sinusoidal terms. The model parameters are estimated sequentially using a sliding time window such that they are available when needed. The prediction model of the clock correction is built based on the analysis of their properties, including their temporal behavior and stability. Evaluation of the proposed method in static and kinematic testing shows that positioning precision of less than 10 cm can be maintained for up to 2 h after the break. When PPP re-initialization is needed during the break, the solution convergence time increases; however, positioning precision remains less than a decimeter after convergence

Family medicine postgraduate clinical training in two universities in Egypt: Physicians’ perspectives

Background: The Family Medicine Specialty was endorsed to fulfill the needs of qualified Primary Health Care providers. Family Medicine Postgraduate Training in Egypt had started in the universities under the umbrella of Medical Colleges in the form of postgraduate trainings and degrees.Objectives: This paper aimed to identify the strengths and weaknesses of the different clinical rotations in Family Medicine in relation to the learning outcomes and to assess trainees' satisfaction.Methods: A mixed research exploratory study was conducted among 48 postgraduate family physicians’ candidates in their final year of training from two purposively selected universities (Cairo University and El Menoufia University) during 2019.Results: The attitude of the physicians towards their clinical education experience differs significantly between the Internal Medicine & Pediatrics. About 72% of participants were from Cairo University and 28% from Menoufia. Internal Medicine training was the best perceived among trained physicians. More than (71%) of the physicians believed they understood the common clinical cases.Conclusions: These findings can be useful for the policy makers to emphasize the importance of raising awareness among staff member regarding family practice and to implement the suggested recommendations and deal with obstacles to improve the Family Medicine training in order to provide effective and efficient primary care services

Investigating the ability of high-rate GNSS-PPP for determining the vibration modes of engineering structures: small scale model experiment

This study evaluates the performance of the Precise Point Positioning method using Global Navigation Satellite System measurements (GNSS-PPP) for monitoring vibration modes of shear type buildings excited by harmonic ground motions and hammer tests. For experimental testing, the shear type lumped-mass building system is represented by a specially designed metal frame model, resembling a three story building, which was excited on a small scale shaking table. The excitation protocols applied were harmonic motions with different frequencies and amplitudes. The metal model has special deformation plates at the column tips to prevent the nonlinear rotations and out-of-plane motions for the entire system. The fundamental vibration periods of the model structure were computed by a Finite Element Mathematical (FEM) model, which were compared with the position variations determined by GNSS-PPP. Two GNSS receivers were mounted on top of the model structure on the line perpendicular to the motion axis to measure the rotation motion. The GNSS data comprised dual-frequency observations with a 10 Hz sampling rate. GNSS-derived positioning was obtained by processing the data using a post-mission kinematic PPP method with fixed phase ambiguities. Analysis of the characteristics of the vibration frequencies showed that the high-rate GNSS PPP method can capture the frequencies of first motion mode of shear type structural response when compared with the FEM output. Results demonstrate the efficiency of the high-rate GNSS PPP method in monitoring first motion mode of a natural frequency

Crustal deformation across and beyond Central Europe and its impact on the boundaries

Land is a critical and limited natural resource. The Land Administration System (LAS) has been developed to resolve and adjudicate over any disputes that might arise concerning the rights and boundaries of land. Land registration and cadastre are types of land recording that need to be established. To secure the property rights, we must be sure of accuracy of the boundary points determining the size of the property. However, in addition to typical factors considered when determining the boundary point positions, such as accuracy of geodetic networks and measurement errors, the global and local crustal deformation, resulting, e.g., from the movement of tectonic plates, should be considered. In this work, the focus is on the movement of points inside the European plate due to tectonic movement, without taking into account local events caused by erosion, landslides, etc. The study area is Europe, and particular attention was paid to Poland, which is located in the centre of the European continent and does not have significant anomalous sub-areas, making it an authoritative research object. In this study, we analysed the velocity of point displacements and the boundary deformation, using GPS observations. For this reason, we used both global (IGS) and regional (ETRF) reference frames, to show differences in point velocities for the studied areas. Overall, for the needs of the real estate cadastre in Poland, information about parcel boundary points must be obtained with an accuracy better than 0.30 m. Within 25 years, the border mark may be shifted by 0.13 m due to tectonic plate movement, which is within the required accuracy. Pursuant to the current legal regulations, the measurements of the boundary points can be performed with any method, ensuring the required accuracy (0.30 m). The most commonly used are direct measurements (GNSS and tacheometry) and photogrammetric measurements. It is recommended that periodic verifications and update of the cadastre data in Poland be carried out at least once every 15 years. In the case of such relatively frequent verification and possible modernisation of data, the potential impact of tectonic plate movement on the relative boundary point displacement can be ignored, particularly in the short term. However, for a long time period it has an influence. We suggest “relatively frequent” cadastral boundary verification to be able to ignore such influence

Investigating Performance of High-Rate GNSS-PPP and PPP-AR for Structural Health Monitoring: Dynamic Tests on Shake Table

© 2020 American Society of Civil Engineers. This paper investigates the usability of Global Navigation Satellite System (GNSS) Precise Point Positioning (PPP) methods, traditional PPP with a float-ambiguity solution and with ambiguity resolution (PPP-AR), in structural health monitoring applications based on experimental tests using a single-axis shake table. To evaluate the performance of the PPP methodologies, harmonic oscillations of the motion table with amplitudes ranging from 5 to 10 mm and frequency between 0.1 and 3 Hz were generated representing a wide range of possible structural motions. In addition, ground motion similar to those experienced during a real earthquake, the 1995 Kobe earthquake, and step motions were generated on the shake table. GNSS PPP-derived positioning results at 20 Hz were compared, in both of the frequency and time domains, with reference data comprising LVDT data and relative positioning data. Results show that both PPP methods' measurements can be used in the computation of harmonic oscillation frequencies compared to the LVDT and relative positioning values. The observed amplitudes of the harmonic oscillations are slightly different from the LVDT values on the order of millimeters. The results of a step motion experiment demonstrated that PPP-AR is better than traditional PPP in exhibiting quasi-static or static displacement. Moreover, the capabilities of traditional PPP and PPP-AR methods are evaluated with respect to the natural frequency of a small-scale structural model excited on the shake table. The frequency spectrum of this small-scale structural model derived from the PPP methods is consistent with finite-element model (FEM)-predicted values and relative positioning. The research presented here demonstrates the potential of the high-rate GNSS PPP and PPP-AR methods to reliably monitor structural and earthquake-induced vibration frequencies and amplitudes for both structural and seismological applications. Specifically, all results reveal that high-rate PPP-AR is more accurate than traditional PPP for both dynamic and static displacement detection

Dual inoculation of Bradyrhizobium and Enterobacter alleviates the adverse effect of salinity on Glycine max seedling

The aid of beneficial microbes, which is a well-accepted strategy, may improve plant salt tolerance. However, the mechanisms that underpin it are unclear. In this study, seedling experiments were carried out to assess the effect of Bradyrhizobium and Enterobacter on the germination, growth, nonenzymatic and enzymatic content in soybean (Glycine max L.) under salt stress. Water was sprayed on the seeds as a control, and with 75 mM, 150 mM NaCl as salt stress. The findings demonstrate that salt stress (75, 150 mM) caused a significant decrease in germination, morphological criteria, and membrane stability index (MSI) when compared to control seeds but increased lipid peroxidation (MDA), electrolyte leakage (EL), osmotic pressure, proline, citric acid, sugar content, antioxidant enzymes. Furthermore, endophytic Bradyrhizobium and Enterobacter inoculation resulted in a significant rise in all of the above metrics.; however, these treatments resulted in significant reductions in ROS, EL, and MDA in stressed plants. Finally, the findings showed that combining Bradyrhizobium and Enterobacter was the most efficient in reducing the harmful effects of salt on soybean plants by boosting antioxidant up-regulation and lowering membrane leakage and ROS