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Register a new userStudy of the possibility of getting elevation deviations by GPS and a specimen of the global earth gravity / EGM2008/
دراسة إمكانية الحصول على الفروقات الإرتفاعية باستخدام تقنية GPS و نموذج الجاذبية الأرضية العالمي EGM2008
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منير يحيى( باحث )
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إن استخدام نتائج أرصاد الأقمار الصناعية أدى إلى ثورة حقيقية في العلوم الجيوديزية و تطبيقاتها, و يتم حاليا دراسة إمكانية استبدال الطرق التقليدية في قياس الإرتفاعات باستخدام تقنية الـ GPS و الذي يوفر وسيلة للحصول على الإحداثيات ثلاثية الأبعاد مباشرة,علما أن الـ GPS يقيس الإرتفاعات الاهليلجية, لكن كي نتمكن من قياس ارتفاعات مهمة فيزيائيا كالارتفاع الأورثومتري فلا بد من وجود نموذج دقيق يعطي بعد الجيوئيد عن الإهليلج (الانفصال الجيوئيدي). ففي بعض مناطق العالم (كماهو الحال في بحثنا) لا يتوافر إلا جيوئيدات عالمية. و هذه الجيوئيدات يتم حسابها كسلاسل من التوابع التوافقية إلى درجة و مرتبة معينة. إن الاختلاف بين السطوح الارتفاعية المرجعية و سطح الجيوئيد العالمي يؤثر في الارتفاع المراد إنتاجه من الـ GPS, و لكن بما أننا نتعامل في هذا البحث مع فروق الارتفاعات, فلا تعد هذه مشكلة.من هنا تكمن أهمية البحث في دراسة إمكانية الحصول على فروق الإرتفاعات باستخدام تقنية GPS التي لا يزيد البعد بينها عن /500 م/ و تحسين هذه النتائج باستخدام نموذج الجيوئيد العالمي /EGM2008/ إضافة إلى مقارنة بين نتائج الفروقات الإرتفاعية من قياسات ال GPS و نموذج الجيوئيد العالمي /EGM 2008/ و بين نتائج التسويتين الهندسية المباشرة و المثلثاتية وصولا إلى نتائج و توصيات من شانها زيادة الدقة في العمل و توفير في الجهد و الزمن.
The use of GPS readings has led to a real revolution in Geodesic sciences and their applications. Now, the possibility of replacing the conventional methods used in measuring elevations by using GPS technology which is a good method to get the 3D points providing that the GPS measures the helical elevations. In order to measure the Physically important elevations such as the ortho-metric elevation, there must be an accurate specimen that gives the Geoids of the helix ( Geoids separation ) .In some parts of the world ( as in the case of our study ), there are only universal Ganoids .Those ganoids are calculated as series to reach a certain defined degree. The difference in the elevation ref. surfaces and the surface of the global geoids affects the optimized elevation of the GPS, but if we deal in this paper with the deviations in elevations, there will be no problem . The importance of this paper starts here , as we can get the possibility of taking the deviations in elevations by using The GPS tech that does not exceed /500m/ distance along with improving the results by using EGM2008 model. The results of the deviations in elevation taken by GPS, the Universal Geoids specimen /EGM 2008 / the direct engineering and triangular settlements, will be compared so that we reach some recommendations that increase accuracy in work and save time and efforts.
References used
jekel, C.(2000) heights, the Geopotential, and Vertical Datum's , Geodetic Science and Surveying , Department of Civil Environmental Engineering and Geodetic Science . The Ohaio State University , Columbus, Oh Report
Hofmann – Wellenhof, B. and Mortiz , H(2006) physical geodesy . Vienna > springer verlag
(Lemoine, F.G,Kenyon, S.C,Factor ,J.K, Trimmer , R.G, pavlis, N,K, Chinn , D,S.COX.C,M,Lluthcke, S,B. and torrence ,M,H.(1998)The De-velopment of the joint NASA GSFC and the National Imagery and Mapping Agency (NIMA) Geopotential Model EGM 96, NASA,(19980218814
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