A Global Geoid Computation by a Solution of the Bipotential Equation

1991 ◽  
pp. 311-320
Author(s):  
Johannes Engels
Keyword(s):  
Geoid Computation

Evaluation of the latest GOCE GGMs in support of regional geoid modeling over Greece

2021 ◽  
Author(s):  
Georgios S. Vergos ◽  
Ilias N. Tziavos ◽  
Dimitrios A. Natsiopoulos ◽  
Elisavet G. Mamagiannou ◽  
Eleftherios A. Pitenis
Keyword(s):  
Maximum Degree ◽  
Gravity Data ◽  
Ground Truth ◽  
Satellite Gravity ◽  
Disturbing Potential ◽  
Geopotential Models ◽  
Potential Functionals ◽  
Geoid Computation ◽  
Goce Satellite

<p>In the frame of the GeoGravGOCE project, funded by the Hellenic Foundation for Research Innovation, GOCE Satellite Gravity Gradiometry (SGG) data are to be used for regional geoid and gravity field refinement as well as for potential determination in the frame of the International Height Reference Frame (IHRF). An inherent step in the geoid computation with either stochastic or spectral methods is the reduction of the related disturbing potential functionals within the well-known Remove-Compute-Restore (RCR) procedure. In this work we evaluate the latest, Release 6 (R6), satellite only and combined Global Geopotential Models (GGMs) which rely solely on GOCE and on land gravity data. The evaluation is performed over the established network of 1542 GPS/Levelling benchmarks over Greece mainland (BMs), which have been used in the past for the evaluation of GOCE GGMs. We employ the spectral enhancement approach, during which the GOCE-based GGMs are evaluated every one degree to the maximum degree of expansion coupled by EGM2008 and high-frequency RTM effects. This synthesis resolves wavelengths corresponding to maximum degree 216,000, hence the omission error is at the few mm-level. TIM-R6, DIR-R6, GOCO06s and XGM2019e are evaluated using EGM2008 residuals to the GPS/Levelling as the ground truth. From the results achieved, the optimal combination degree of a GOCE-only GGM augmented with EGM2008 is selected to be used in the sequel as reference field for the practical determination of the gravimetric geoid over Greece.</p>

scholarly journals A Numerical Study of the Analytical Downward Continuation Error in Geoid Computation by EGM08

2011 ◽  
Vol 1 (1) ◽  
pp. 2-8 ◽  
Author(s):  
L. Sjöberg ◽  
M. Bagherbandi
Keyword(s):  
Numerical Study ◽  
Analytical Continuation ◽  
Downward Continuation ◽  
The Pacific ◽  
Topographic Bias ◽  
Significant Difference ◽  
Topographic Potential ◽  
Zero Degree ◽  
High Degree ◽  
Geoid Computation

A Numerical Study of the Analytical Downward Continuation Error in Geoid Computation by EGM08Today the geoid can be conveniently determined by a set of high-degree spherical harmonics, such as EGM08 with a resolution of about 5'. However, such a series will be biased when applied to the continental geoid inside the topographic masses. This error we call the analytical downward continuation (DWC) error, which is closely related with the so-called topographic potential bias. However, while the former error is the result of both analytical continuation of the potential inside the topographic masses and truncation of a series, the latter is only the effect of analytical continuation.This study compares the two errors for EGM08, complete to degree 2160. The result shows that the topographic bias ranges from 0 at sea level to 5.15 m in the Himalayas region, while the DWC error ranges from -0.08 m in the Pacific to 5.30 m in the Himalayas. The zero-degree effects of the two are the same (5.3 cm), while the rms of the first degree errors are both 0.3 cm. For higher degrees the power of the topographic bias is slightly larger than that for the DWC error, and the corresponding global rms values reaches 25.6 and 25.3 cm, respectively, at nmax=2160. The largest difference (20.5 cm) was found in the Himalayas. In most cases the DWC error agrees fairly well with the topographic bias, but there is a significant difference in high mountains. The global rms difference of the two errors clearly indicates that the two series diverge, a problem most likely related with the DWC error.

IMPLEMENTING SEISMIC MOHO DEPTHS IN GEOID COMPUTATION

Survey Review ◽  
2003 ◽  
Vol 37 (289) ◽  
pp. 235-245 ◽  
Author(s):  
Hussein Abd-Elmotaal
Keyword(s):  
Moho Depths ◽  
Geoid Computation

Higher-degree reference field in the generalized Stokes-Helmert scheme for geoid computation

1995 ◽  
Vol 70 (3) ◽  
pp. 176-182 ◽  
Author(s):  
Petr Vaníček ◽  
Mehdi Najafi ◽  
Zdeněk Martinec ◽  
Lars Harrie ◽  
Lars E. Sjöberg
Keyword(s):  
Reference Field ◽  
Geoid Computation

scholarly journals Open access to regional geoid models: the International Service for the Geoid

2021 ◽  
Vol 13 (4) ◽  
pp. 1653-1666
Author(s):  
Mirko Reguzzoni ◽  
Daniela Carrion ◽  
Carlo Iapige De Gaetani ◽  
Alberta Albertella ◽  
Lorenzo Rossi ◽  
...  
Keyword(s):  
International Association ◽  
Research Field ◽  
Added Value ◽  
Free Access ◽  
Training Material ◽  
International Service ◽  
Field Service ◽  
Wide Range ◽  
Training Courses ◽  
Geoid Computation

Abstract. The International Service for the Geoid (ISG, https://www.isgeoid.polimi.it/, last access: 31 March 2021) provides free access to a dedicated and comprehensive repository of geoid models through its website. In the archive, both the latest releases of the most important and well-known geoid models, as well as less recent or less known ones, are freely available, giving to the users a wide range of possible applications to perform analyses on the evolution of the geoid computation research field. The ISG is an official service of the International Association of Geodesy (IAG), under the umbrella of the International Gravity Field Service (IGFS). Its main tasks are collecting, analysing, and redistributing local, regional, and continental geoid models and providing technical support to people involved in geoid-related topics for both educational and research purposes. In the framework of its activities, the ISG performs research taking advantage of its archive and organizes seminars and specific training courses on geoid determination, supporting students and researchers in geodesy as well as distributing training material on the use of the most common algorithms for geoid estimation. This paper aims at describing the data and services, including the newly implemented DOI Service for geoid models (https://dataservices.gfz-potsdam.de/portal/?fq=subject:isg, last access: 31 March 2021), and showing the added value of the ISG archive of geoid models for the scientific community and technicians, like engineers and surveyors (https://www.isgeoid.polimi.it/Geoid/reg_list.html, last access: 31 March 2021).

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