| 1. |
- Abdollahzadeh, Makan, 1982-, et al.
(author)
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Application of Molodensky's Method for Precise Determination of Geoid in Iran
- 2011
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In: Journal of Geodetic Science. - Poland : Versita. - 2081-9919 .- 2081-9943. ; 1:3, s. 259-270
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Journal article (peer-reviewed)abstract
- Determination of the geoid with a high accuracy is a challenging task among geodesists. Its precise determination is usually carried out by combining a global geopotential model with terrestrial gravity anomalies measured in the region of interest along with some topographic information. In this paper, Molodensky's approach is used for precise determination of height anomaly. To do this, optimum combination of global geopotential models with the validated terrestrial surface gravity anomalies and some deterministic modification schemes are investigated. Special attention is paid on the strict modelling of the geoidal height and height anomaly difference. The accuracy of the determined geoid is tested on the 513 points of Iranian height network the geoidal height of which are determined by the GPS observations.
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| 2. |
- Eshagh, Mehdi, 1977-, et al.
(author)
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Simplification of geopotential perturbing force acting on a satellite
- 2008
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In: Artificial Satellites. - Warsaw : Versita. - 0208-841X .- 2083-6104. ; 43:2, s. 45-64
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Journal article (peer-reviewed)abstract
- One of the aspects of geopotential models is orbit integration of satellites. The geopotential acceleration has the largest influence on a satellite with respect to the other perturbing forces. The equation of motion of satellites is a second-order vector differential equation. These equations are further simplified and developed in this study based on the geopotential force. This new expression is much simpler than the traditional one as it does not derivatives of the associated Legendre functions and the transformations are included in the equations. The maximum degree and order of the geopotential harmonic expansion must be selected prior to the orbit integration purposes. The values of the maximum degree and order of these coefficients depend directly on the satellite's altitude. In this article, behaviour of orbital elements of recent geopotential satellites, such as CHAMP, GRACE and GOCE is considered with respect to the different degree and order of geopotential coefficients. In this case, the maximum degree 116, 109 and 175 were derived for the Earth gravitational field in short arc orbit integration of the CHAMP, GRACE and GOCE, respectively considering millimeter level in perturbations.
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