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Register a new userEstimating Offsets the Syrian Height Datum and the EGM2008 Geoid using the Normal Gravity Field
حساب انحرافات الشبكة الارتفاعية السورية عن الجيوئيد العالمي EGM2008 باستخدام حقل الجاذبية الأرضية الناظمي
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إن التطور الحالي في نظام التموضع الجغرافي العالمي و تقنيات رصد الأقمار الصناعية و طرق المعالجة الرياضية الحاصلة خلال الثلاثين عاما الأخيرة أدى إلى ثورة حقيقية في تطوير نماذج حقول الجاذبية الأرضية. بالإضافة إلى ذلك فإن زيادة نسبة المناطق المغطاة بقياسات الجاذبية الأرضية أدى إلى زيادة في تفصيلات و دقة هذه النماذج. هذا بدوره أدى إلى تحسن ملحوظ في حسابات سطوح الجيوئيد الضرورية لتحويل الارتفاع الجيوديزي إلى ارتفاع أورثومتري. يعرض هذا البحث طريقة توظيف حقل الجاذبية الناظمي في حساب انحرافات الشبكة الارتفاعية السورية عن الجيوئيد العالمي EGM2008 المعرف بجهده الأرضي W0=62636856.0 m2s-2. تعتمد هذه الطريقة على حساب متوسط انحرافات قيم الجهد الأرضي عند مجموعة نقاط المعلومة المنسوب و الارتفاع الإهليلجي في بعض المناطق السورية. تم حساب الجهد الأرضي في منطقة البحث باستخدام النموذج العالمي للجاذبية الأرضية EGM2008. لقد تم الحصول على فروقات بين الجهد الأرضي الفعلي و الجهد الأرضي عند السطح المرجعي للشبكة الارتفاعية السورية في المجال من [-10.62 m2s-2 ~ -4.51 m2s-2] بقيمة متوسطة 6.72±0.70 m2s-2 بموثوقية 95% و هذا موافق لـ[-108.4cm ~-46.0cm] و القيمة المتوسطة -69.7±7.1 cm. هذا يعني أن السطح المرجعي الارتفاعي السوري يتوضع أسفل الجيوئيد العالمي.
Within the last thirty years, the recent development in GPS, satellite tracking techniques and processing strategies has revolutionized development of Earth gravity field models. In addition, the increase of gravity data coverage led to an increase in the resolution and accuracy of these models. This in turn led to a noticeable improvement in determination of geoid surfaces which are essential in transformation of the geodetic height to the orthometric height. This study utilizes the normal gravity field for estimating offsets the Syrian leveling network from the EGM2008 geoid defined by its geopotential value W0=62636856.0 m2s-2. This approach uses the average of the gravity potential values at the GPS/levelling points in some areas in Syria. The gravity potential value in the study regionis estimated using the Earth gravity field model EGM2008. The residuals between the actual gravity potentials and the values at the Syrian height reference surface are estimated in the range between [-4.51 m2s-2 ~ 10.62m2s-2] and a mean value of -6.72±0.70 m2s-2 with 95% confidence level. This corresponds to [-46.0 cm ~ 108.4 cm] and a mean value of -63.7±7.1 cm which means that the Syrian height datum is located underneath the global geoid.
References used
Pavlis, N., Kenyon, S., Factor, J. and Holmes, S. (2008) 'Earth gravitational model 2008',in SEG Technical Program Expanded Abstracts. Vol. 27 , 761-763
Burke KF, True SA, Burša M, Raděj K (1996) Accuracy estimates of geopotential models and global geoids. In: Rapp RH, CazenaveAA, Nerem RS (eds) Proceedings of Symposium No 116 held in Boulder, CO, USA, July 12, 1995. Springer Verlag, Berlin- Heidelberg, 51−61
Burša M, Kouba J, Kumar M, Müller A, Radej K, True SA, VatrtV,Vojtíšková M (1222b) Geoidal geopotential and world height system. Studia Geoph Geod 43:327–337
Molodensky MS, Yeremeev VF, Yurkina MI (1960) Methods for study of the external gravitational field and figure of the Earth. TRUDY TsNIIGAiK, 131, Geodezizdat, Moscow. English translatation
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