نتایج جستجو برای: مدل جهانی egm2008

تعداد نتایج: 143439  

در این تحقیق از خاصیت تکرار شوندگی زمانی مشاهدات ماهواره ارتفاع‌سنجی توپکس پوزایدون برای ایجاد سری‌های زمانی در پای حرکت ماهواره در دریای عمان و خلیج فارس استفاده شد. برای این منظور بر هر نقطه مکانی یک سری‌ زمانی ایجاد گردید. سپس با استفاده از روش کمترین مربعات قسمت خطی آن به عنوان برآورد سطح متوسط دریا و بخش وابسته به زمان آن به عنوان تغییرات زمانی سطح متوسط دریا آنالیز گردید. نظر به اهمیت تعی...

سیمای جدیدی از مفهوم شهروندی با عنوان شهروند جهانی در حال شکل­گیری و تکامل است. پژوهش حاضر با هدف تهیه و رواسازی مقیاسی برای اندازه‌گیری نگرش دانشجویان به مفهوم شهروند جهانی انجام‌ شد. جامعه آماری دانشجویان دانشگاه سمنان در سال تحصیلی 1394-95 بودند (15214=N). شرکت‌کنندگان 460 دانشجو بودند که با روش نمونه‌گیری تصادفی طبقه­ای از تمام دانشکده­های این دانشگاه انتخاب شدند. ابزار پژوهش پرسشنامه 37 سؤ...

Journal: :Remote Sensing 2023

We introduce an approach for the direct measurement of gravitational potential (GP) along trajectory a satellite, with specific focus on Low-Earth Orbit (LEO) satellites. A LEO satellite communicates several Geosynchronous Equatorial (GEO) satellites via frequency signal links. The GP difference can be measured in real-time using shift by equipping both and GEO precise atomic clocks. Since at h...

2012
C. Hirt

In the numerical evaluation of geodetic convolution integrals, whether by quadrature or discrete/fast Fourier transform (D/FFT) techniques, the integration kernel is sometimes computed at the centre of the discretised grid cells. For singular kernels a common case in physical geodesy this approximation produces significant errors near the computation point, where the kernel changes rapidly acro...

2011
Wouter van der Wal Lin Wang Pieter Visser Nico Sneeuw Bert Vermeersen

GOCE gravity fields are assessed in an area around Reykjanes Ridge. Ship gravity measurements were found to be to inaccurate to determine possible improvement of GOCE gravity field models compared to the best available GRACE gravity field model. Differences between the GOCE gravity field models and EGM2008 does not appear to contain a component of the mid-ocean ridge signal. However the differe...

2011
H. Yildiz R. Forsberg J. Ågren C. C. Tscherning L. E. Sjöberg

The remove-compute-restore (RCR) technique for regional geoid determination implies that both topography and low-degree global geopotential model signals are removed before computation and restored after Stokes' integration or Least Squares Collocation (LSC) solution. The Least Squares Modification of Stokes' Formula (LSMS) technique not requiring gravity reductions is implemented here with a R...

2012
R. Tenzer R. Čunderlík N. Dayoub A. Abdalla

Weapply a novel approach for the gravimetricmarine geoidmodellingwhich utilise the boundary elementmethod (BEM). The direct BEM formulation for the Laplace equation is applied to obtain a numerical solution to the linearised fixed gravimetric boundary-value problem in points at the Earth's surface. The numerical scheme uses the collocation method with linear basis functions. It involves a discr...

Journal: :Computational Geosciences 2023

Abstract The numerical approach for solving the fixed gravimetric boundary value problem (FGBVP) based on finite element method (FEM) with mapped infinite elements is developed and implemented. In this approach, 3D semi-infinite domain outside Earth bounded by triangular discretization of whole Earth’s surface extends to infinity. Then FGBVP consists Laplace equation unknown disturbing potentia...

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