On global and regional spectral evaluation of global geopotential models

Ustun, Aydin; Abbak, Ramazan Alpay

doi:10.1088/1742-2132/7/4/003

Cited by 27 publications

(11 citation statements)

References 11 publications

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“…Assessing GGMs may be achieved locally by comparing GPS data and gravity potential and its functionals computed from terrestrial gravity data with GGMs, for example, (quasi-)geoid heights and gravity anomalies, and globally by comparing GGMs based on their degree variances. In terms of a global inter-comparison of GGMs, the error degree variance σ 2 at a certain frequency band is given as [14]:…”

Section: Global Geopotential Models (Ggms) and Errorsmentioning

confidence: 99%

Towards the Selection of an Optimal Global Geopotential Model for the Computation of the Long-Wavelength Contribution: A Case Study of Ghana

2017

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Abstract:The selection of a global geopotential model (GGM) for modeling the long-wavelength for geoid computation is imperative not only because of the plethora of GGMs available but more importantly because it influences the accuracy of a geoid model. In this study, we propose using the Gaussian averaging function for selecting an optimal GGM and degree and order (d/o) for the remove-compute-restore technique as a replacement for the direct comparison of terrestrial gravity anomalies and GGM anomalies, because ground data and GGM have different frequencies. Overall, EGM2008 performed better than all the tested GGMs and at an optimal d/o of 222. We verified the results by computing geoid models using Heck and Grüninger's modification and validated them against GPS/trigonometric data. The results of the validation were consistent with those of the averaging process with EGM2008 giving the smallest standard deviation of 0.457 m at d/o 222, resulting in an 8% improvement over the previous geoid model. In addition, this geoid model, the Ghanaian Gravimetric Geoid 2017 (GGG 2017) may be used to replace second-order class II leveling, with an expected error of 6.8 mm/km for baselines ranging from 20 to 225 km.

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Section: Global Geopotential Models (Ggms) and Errorsmentioning

confidence: 99%

Towards the Selection of an Optimal Global Geopotential Model for the Computation of the Long-Wavelength Contribution: A Case Study of Ghana

2017

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“…Satellite altimeter data and orbit parameters were also used by Klokočník et al (2002) and Förste et al (2009) in comparative assessments of the EGMs. Erol et al (2009), Ustun & Abbak (2010) and Yılmaz & Karaali (2010) provided some specific results on spectral evaluation of global models and on their local validations using terrestrial data in territory of Turkey. Motivated research conducted by Lambeck&Coleman (1983) and , we tested some of the recent global geopotential models having various orders of spherical harmonic expansion for Turkish territory, the results of which have been recorded later in this chapter.…”

Section: Testing Global Geoid Modelsmentioning

confidence: 99%

GNSS in Practical Determination of Regional Heights

Erol¹,

Erol²

2012

Global Navigation Satellite Systems: Signal, Theory and Applications

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“…In this study, in addition to external accuracy assessments of few CHAMP and GRACE only and combined EGMs (Wenzel 1985;Lemoine et al 1998;Reigber et al 2004;Tapley et al 2005;Förste et al 2005;Förste et al 2006) against GNSS/levelling and gravity anomalies similar to Erol et al (2009) and Ustun and Abbak (2010), the EGMs were also compared with the spherical harmonic expansions, which were derived by the improvement of the original geopotential models with terrestrial gravity data in and out of the computation area (Weber and Zomorrodian 1988;Kearsley and Forsberg 1990). For these comparisons, improvement of each EGM using the terrestrial gravity anomalies in the territory was done using the method by Weber and Zomorrodian (1988).…”

Section: Introductionmentioning

confidence: 98%

“…Satellite altimeter data and orbit parameters were also used by Klokočník et al (2002) and Förste et al (2009) in relative assessments of the EGMs. Erol et al (2009) and Ustun and Abbak (2010) gave some results on spectral evaluation of EGMs and their local validations using terrestrial data in the territory of Turkey. In the validation of EGMs with external data, it should be considered that the terrestrial data represent the full spectrum of the gravity signal, whereas the EGM contains only lowfrequencies.…”

Section: Introductionmentioning

confidence: 99%

Spectral evaluation of Earth geopotential models and an experiment on its regional improvement for geoid modelling

Erol

2012

J Earth Syst Sci

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As the number of Earth geopotential models (EGM) grows with the increasing number of data collected by dedicated satellite gravity missions, CHAMP, GRACE and GOCE, measuring the differences among the models and monitoring the improvements in gravity field recovery are required. This study assesses the performance of recent EGMs derived from CHAMP, GRACE, and other data in comparison to the earlier two models in Turkish territory. Also the improvement capacities of these EGMs using local terrestrial data are inspected with two different approaches. In the first approach, the spherical harmonic coefficients of EGMs are modified depending on the local gravity data. In the second part, the original EGMs with their maximum harmonic expansions are employed in Remove Compute Restore algorithm for high resolution local geoid modelling. The assessment results with the local terrestrial data exhibited large disagreements among the models in Turkey. The outputs from regional improvements of EGMs using the gravity observations clarified the important role of the ground truth data contribution in geopotential models. The validations of the computed high resolution geoids rely on the EGMs at the GNSS/levelling networks, having 451 and 309 benchmarks, provided an absolute accuracy by means of standard deviations of the geoid height differences around 20 cm. These results from the final stage of the case study provide a comparison among the EGMs by means of their fit to the local gravity field.

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On global and regional spectral evaluation of global geopotential models

Cited by 27 publications

References 11 publications

Towards the Selection of an Optimal Global Geopotential Model for the Computation of the Long-Wavelength Contribution: A Case Study of Ghana

Towards the Selection of an Optimal Global Geopotential Model for the Computation of the Long-Wavelength Contribution: A Case Study of Ghana

GNSS in Practical Determination of Regional Heights

Spectral evaluation of Earth geopotential models and an experiment on its regional improvement for geoid modelling

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