| 1. |
- Kiamehr, R., et al.
(author)
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Combination of satellite altimetry data and EGM2008 model for evaluation of the height datum in Iran
- 2011
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In: Ecology, Environment and Conservation. - 0971-765X. ; 17:4, s. 653-659
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Journal article (peer-reviewed)abstract
- The repetitive periodic coverage from Topex/Poseidon altimetry satellite during 1992-2003 from the Oman Sea and Persian Gulf were used to prepare time series covering the study area. The linear portion of series were analyzed to calculate mean sea level as its temporal changes using the least-squares method. Due to the significance of sea level topography in oceanographic studies a new model proposed using the combined altimetry satellite data and the EGM2008 global geoid model in order to determine and equalize the current height datum for Iran. The maximum and minimum of sea surface topography vary within the range of -0.7 to 1.1m in the study area. Adjustment of the current precise network for Iran established based on the Bandar Abbas tide gauge station, which its corresponding SST estimated up to -0.5 m. Effect of such large systematic error in national height system cannot be ignored in geodynamical and engineering researches.
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| 2. |
- Sadatipour, S. M. T., et al.
(author)
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The Evaluation of Sea Surface Topography Models based on the Combination of the Satellite altimetry and the Global Geoid Models in the Persian Gulf
- 2012
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In: International Journal of Environmental Research. - 1735-6865 .- 2008-2304. ; 6:3, s. 645-652
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Journal article (peer-reviewed)abstract
- One of the difficulties in using absolute altitudes is the separation between the mean open sea level and geoid. Theoretically, geoid is the base level in absolute altitudes, but practically, the mean open sea level is used as a base level for absolute altitudes. The difference between these two levels is called as the sea surface topography. In this research, it is dealt the mean sea level modeling by using the observations of three altimeter satellites (i.e. Topex/Poseidon, Jason-1 and GFO) in Persian Gulf and then it is dealt with the evaluation of existing models of the sea surface topography based on the altimeter satellites data and the global geopotential geoid models (i.e. European Improved Gravity model of the Earth by New techniques, Gravity field and steady-state Ocean Circulation Explorer, Earth Gravitational Model 2008. The results of this research indicate that the sea surface topographical model resulting from the EIGEN06C geoid is the most precise model with changes range between -2.482 m and -1.511 m and mean -0.23 m.
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| 3. |
- Sjöberg, Lars, et al.
(author)
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The observed geoid height versus Airy's and Pratt's isostatic models using matched asymptotic expansions
- 2014
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In: Acta Geodaetica et Geophysica Hungarica. - : Springer Netherlands. - 1217-8977 .- 1587-1037 .- 2213-5812 .- 2213-5820. ; 49:4, s. 473-490
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Journal article (peer-reviewed)abstract
- Isostasy is a key concept in geodesy and geophysics. The classical isostatic models of Airy/Heiskanen and Pratt/Hayford imply that the topographic mass surplus and ocean mass deficit are balanced by mountain roots and anti-roots in the former model and by density variations in the topography and the compensation layer below sea bottom in the latter model. In geophysics gravity inversion is an essential topic where isostasy comes to play. The main objective of this study is to compare the prediction of geoid heights from the above isostatic models based on matched asymptotic expansion with geoid heights observed by the Earth Gravitational Model 2008. Numerical computations were carried out both globally and in several regions, showing poor agreements between the theoretical and observed geoid heights. As an alternative, multiple regression analysis including several non-isostatic terms in addition to the isostatic terms was tested providing only slightly better success rates. Our main conclusion is that the geoid height cannot generally be represented by the simple formulas based on matched asymptotic expansions. This is because (a) both the geoid and isostatic compensation of the topography have regional to global contributions in addition to the pure local signal considered in the classical isostatic models, and (b) geodynamic phenomena are still likely to significantly blur the results despite that all spherical harmonic low-degree (below degree 11) gravity signals were excluded from the study.
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