23 research outputs found

    A methodology for transformation between geodetic datums used in Syria

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    The Global Navigation Satellite System (GNSS) provides geodetic coordinates referenced to the world ellipsoid WGS84, whereas positions are computed on the local ellipsoid adopted for geodetic computation in various countries. Thus, to take advantage of GNSS in geodetic applications, the need arises to transform coordinates from the global ellipsoid to the local ellipsoid. This is usually carried out by applying geometric transformation models to convert coordinates from The Global Geodetic System WGS84 into the local systems used in each country of the world and into the grid coordinates of local systems. Over the past years, with the increase in the utilization of GNSS in several geodetic projects, numerous methodologies are available for the solution of transformation issues. These methods can be classified into three categories, the first is based on direct mathematical formulas, the second on iteration approaches, and the last category depends on direct transformation from the global system to the local system based on the calculation of transformation parameters (three, seven, nine …etc.). In this study, a methodology has been proposed for direct transformation from global geodetic coordinates to local geodetic coordinates for a limited area in Syria. It is based on the properties of the ratio and proportion between the geometric elements of points on global and local ellipsoids without the calculation of transformation parameters. The results are compared with some studied methods (Bursa-Wolf, Molodensky Abridge, and Cassini). The resulting accuracy is about ± 3.5 cm. The main conclusion drawn is that the proposed method provides a promising alternative approach in coordinates transformation. Therefore, the capability of the suggested methodology as a powerful method for converting geodetic coordinates from one referenced frame to another has been demonstrated in this present study

    Guidelines for the management of atrial fibrillation: the Task Force for the Management of Atrial Fibrillation of the European Society of Cardiology (ESC).

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    Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia, occurring in 1\u20132% of the general population. Over 6 million Europeans suffer from this arrhythmia, and its prevalence is estimated to at least double in the next 50 years as the population ages. It is now 4 years since the last AF guideline was published, and a new version is now needed. AF confers a 5-fold risk of stroke, and one in five of all strokes is attributed to this arrhythmia. Ischaemic strokes in association with AF are often fatal, and those patients who survive are left more disabled by their stroke and more likely to suffer a recurrence than patients with other causes of stroke. In consequence, the risk of death from AF-related stroke is doubled and the cost of care is increased 1.5-fold. There has been much research into stroke prevention, which has influenced this guideline. In the majority of patients there appears to be an inexorable progression of AF to persistent or permanent forms, associated with further development of the disease that may underlie the arrhythmia. Some advance has been made in the understanding of the dynamic development of AF from its preclinical state as an \u2018arrhythmia-in-waiting\u2019 to its final expression as an irreversible and end-stage cardiac arrhythmia associated with serious adverse cardiovascular events. Much recent therapeutic effort with \u2018upstream therapies\u2019 has been expended to slow or halt the progression of AF due to underlying cardiovascular disease and to AF itself. Limited success has been achieved and is recognized in this guideline
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