Browsing by Author "Goyal, Ropesh"

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Citation - WoS: 1
Citation - Scopus: 1
Combined Effects of Terrain Corrections and Deterministic Modifiers on the Stokes-Helmert Geoid Over Sophisticated Topography
(Springer, 2025) Abbak, Ramazan Alpay; Goyal, Ropesh; Ustun, Aydin; Olgun, Sevda
This study focuses on analysing the impact of deterministic modifications of the Stokes kernel and terrain correction methods for precise geoid determination using the Stokes-Helmert method over a sophisticated topography. Three deterministic modification methods of Stokes's kernel (Wong-Gore, Van & iacute;& ccaron;ek-Kleusberg, and Featherstone-Evans-Olliver) are tried to minimize the truncation error emanating from the non-availability of gravity data all over the Earth by utilizing two independent satellite only global geopotential models. In parallel to the modified Stokes kernel functions, two terrain correction techniques, i.e., spatial-spectral combined method with mass-prisms and spatial method with mass-cylinders, have also been examined to assess their combined effects on geoid heights over the Konya Closed Basin in T & uuml;rkiye. The developed geoid models are validated with GNSS-levelling data and inter-compared pixel-wise. The numerical results show that although the overall statistical values depict consistent precision for various combinations of TCs, Stokes kernel modifiers, and GGMs, a holistic validation-comparison analysis reveals significant variations in view of the cm-precise geoid.
Citation - WoS: 7
Citation - Scopus: 5
A User-Friendly Software Package for Modelling Gravimetric Geoid by the Classical Stokes-Helmert Method
(Springer Heidelberg, 2024) Abbak, Ramazan Alpay; Goyal, Ropesh; Üstün, Aydın
With the progress in Global Navigation Satellite Systems (GNSS) technology, accurate geoid modelling has started to play an essential role in geodetic applications such as establishing height datum as a continuous surface model and related vertical control for infrastructure projects. Thus, numerous geoid modelling methods have been offered since 1990's, each of them has its own algorithm and approximation theories. Classical Stokes-Helmert is one of the most well-known methods all over the world by geodetic communities. However, a user-friendly software package of the method is not publicly accessible on the Internet. Therefore, a compact and user-friendly software package CSHSOFT is developed and presented for scholars in this field. A fractionated programming strategy has been treated to build individual components striving high accuracy and computational efficiency for geoid heights. Subsequently, the CSHSOFT is simply tested to construct a geoid model in the mountainous area in Auvergne test-bed where several geoid modelling techniques are implemented. Afterward, the new geoid model of the region is externally evaluated by GNSS-levelling data in terms of rigorous orthometric heights. The fitting statistics of 2.75 cm and 0.36 ppm in absolute and relative height differences fairly indicate that the CSHSOFT is a vigorous tool for gravimetric geoid modelling, and can be comfortably employed for geoscientific and technical studies.