نتایج جستجو برای: geoid

تعداد نتایج: 931  

2004
B. Erol

According to wide spread use of satellite based positioning techniques, especially GPS (Global Positioning System), a greater attention has started to be paid to precise determination of geoid models with an aim to replace the geometric levelling measurements with GPS measurements during geodetic and surveying works. In this paper, geoid modelling is evaluated as a surface fitting problem accor...

2012
L. E. Sjöberg

Li andWang recently comparedgeoiddeterminationbyvariousgravimetricmethods formodifyingStokes' formula vs. usingGPS/levelling geoid heights as a reference model. Possible large systematic errors in the differences of gravimetric and GPS/levelling geoid models deteriorate the results and conclusions. Moreover, spectral combination, the only stochastic method in the study, was applied in an unreal...

Journal: :فیزیک زمین و فضا 0
مهدی گلی استادیار، دانشکده مهندسی عمران، دانشگاه شاهرود، ایران مهدی نجفی علمداری دانشیار، گروه هیدروگرافی، دانشگاه آزاد اسلامی واحد تهران شمال، ایران پتر ونیچک استاد، دانشکده ژئودزی و ژئوماتیک، دانشگاه نیوبرانزویک، کانادا

the use of stokes boundary values problems for the determination of the geoid requires that gravity anomalies (as boundary values) are known on geoid (as boundary). while, the gravity observations are measured on the earth's surface, to obtain boundary data, the surface gravity anomalies does are downward from the terrain onto geoid. for downward continuation (dwc) of surface gravity anoma...

2008
Kai-Chien Cheng Chung-Yen Kuo C. K. Shum Xutong Niu Rongxing Li Keith W. Bedford

There is a need to accurately link the water level to the shoreline vertical datum for various applications including coastal management, lake/river/estuary/wetland hydrological or storm surge modeling/forecasting. Coastal topography is historically surveyed and referenced to the predetermined vertical datum in terms of orthometric heights, or the heights above the geoid, which is poorly known ...

Ali Reza Azmoudeh Ardalan Hassan Hashemi Farahani

Using satellite altimetry derived mean sea level (MSL), geopotential coefficients in terms of ellipsoidal harmonics from recent satellite gravimetry missions, gravity potential values over a grid consisting of 33,486 points at global sea areas are computed and the mean value of the gravity potential at MSL is calculated as a new geoid’s potential value. In this way we have exactly followed the ...

2015
Matthew R. Mazloff Sarah T. Gille Bruce Cornuelle

Satellite gravity mapping missions, altimeters, and other platforms have allowed the Earth’s geoid to be mapped over the ocean to a horizontal resolution of approximately 100 km with an uncertainty of less than 10 cm. At finer resolution this uncertainty increases to greater than 10 cm. Achieving greater accuracy requires accurate estimates of the dynamic ocean topography (DOT). In this study t...

Journal: :International Association of Geodesy symposia 2023

Abstract This article is a short introduction to the debate on choosing geoid and orthometric heights or quasi-geoid normal as vertical coordinate system. It mainly compiles some more less already known facts for comparing two systems.

2011

AGlobal Vertical Datum (GVD) is naturally defined by the geoid, and there is a well-established consensus to adopt Gauss-Bessel-Listing's definition of the geoid (i.e. as being the level surface of the Earth's gravity field that best fits the undisturbed sea level). Themain problem in defining the geoid is therefore to fix its constant geopotential (W0). Nevertheless, this definition can be int...

Journal: :E3S web of conferences 2022

The relevance of geoid research involves examining a number problems, the consideration which reveals evolution geoid. Measurements help to understand internal structure our planet.

2007
R. Tenzer

The differences between gravity anomalies and gravity disturbances are numerically investigated in this study. In particular, we demonstrate how the topography, atmosphere and mass irregularities enclosed within the geoid contribute to these differences. The numerical analysis is conducted at the area of study in the Canadian Rocky Mountains. Results reveal that the dominant contributions due t...

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