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The Impact of lateral density variation model in the determination of precise gravimetric geoid in mountainous areas: A case study of Iran
KTH, School of Architecture and the Built Environment (ABE), Transport and Economics.
2006 (English)In: Geophysical Journal International., ISSN 0956-540X, Vol. 167, no 2, 521-527 p.Article in journal (Refereed) Published
Abstract [en]

The existence of topography above the geoid violates the basic assumption of Stokes' formula for the determination of the geoid. Usually a constant density of 2.67 g cm(-3) is used in the determination of the geoid. However, we know that the density of the topographical mass departs by about 10-20 per cent from the actual mean value of the crustal density. Iran has one of the largest relief and density variations in the world and the geoid computation in this area is affected the most by topographical density effects. The influence on the geoid height coming from the actual and Pratt-Hayford's isostatic models are studied. Numerical results show that the differences in the geoid height due to actual and isostatic density models can reach up to 0.22 and 0.29 m, respectively, which is not negligible in a precise geoid determination with centimetre accuracy. Our results suggest that the effect of topographical density lateral variations is significant enough and ought to be taken into account specially in mountainous regions in the determination of a precise geoid model.

Place, publisher, year, edition, pages
2006. Vol. 167, no 2, 521-527 p.
Keyword [en]
geoid, GPS, levelling, Iran; isostasy, lateral density variation
National Category
Earth and Related Environmental Sciences
Identifiers
URN: urn:nbn:se:kth:diva-6196DOI: 10.1111/j.1365-246X.2006.03143.xISI: 000241766800004Scopus ID: 2-s2.0-33750682012OAI: oai:DiVA.org:kth-6196DiVA: diva2:10837
Note
QC 20100906Available from: 2006-10-03 Created: 2006-10-03 Last updated: 2010-09-06Bibliographically approved
In thesis
1. Precise Gravimetric Geoid Model for Iran Based on GRACE and SRTM Data and the Least-Squares Modification of Stokes’ Formula: with Some Geodynamic Interpretations
Open this publication in new window or tab >>Precise Gravimetric Geoid Model for Iran Based on GRACE and SRTM Data and the Least-Squares Modification of Stokes’ Formula: with Some Geodynamic Interpretations
2006 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

Iran is one of the most complicated areas in the world from the view of rough topography, tectonic activity, large lateral density and geoidal height variations. The computation of a regional gravimetric geoid model with high accuracy in mountainous regions, especially with sparse data, is a difficult task that needs a special attention to obtain reliable results which can meet the needs of the today geodetic community.

In this research different heterogeneous data has been used, which includes gravity anomalies, the high-resolution SRTM Digital Elevation Model (DEM), recently published GRACE Global Geopotential Models (GGMs), geological maps and GPS/levelling data. The above data has been optimally combined through the least-squares modification of Stokes formula with additive corrections. Regarding the data evaluation and refinement, the cross-validation technique has been used for detection of outliers. Also, several GGMs and DEMs are evaluated with GPS/levelling data. The impact of utilizing a high resolution SRTM DEM to improve the accuracy of the geoid model has been studied. Also, a density variation model has been established, and its effect on the accuracy of the geoid was investigated. Thereafter a new height datum for Iran was established based on the corrective surface idea. Finally, it was found that there is a significant correlation between the lateral geoid slope and the tectonic activities in Iran.

We show that our hybrid gravimetric geoid model IRG04 agrees considerably better with GPS/levelling than any of the other recent local geoid models in the area. Its RMS fit with GPS/levelling is 27 cm and 3.8 ppm in the absolute and relative senses, respectively. Moreover, the relative accuracy of the IRG04 geoid model is at least 4 times better than any of the previously published global and regional geoid models in the area. Also, the RMS fit of the combined surface model (IRG04C) versus independent precise GPS/levelling is almost 4 times better compared to the original gravimetric geoid model (IRG04). These achievements clearly show the effect of the new gravity database and the SRTM data for the regional geoid determination in Iran based on the least-squares modification of Stokes’ formula.

Place, publisher, year, edition, pages
Stockholm: KTH, 2006. viii, 89 p.
Series
TRITA-INFRA, ISSN 1651-0216 ; 06-003
Keyword
Gravity database, least-squares modification of Stokes, geoid determination, SRTM, GRACE, GPS/levelling, density variation model, height datum, geodynamics, Iran
National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:kth:diva-4125 (URN)978-91-85539-06-2 (ISBN)
Public defence
2006-10-27, D1, Lindstedtsvägen 17, 2tr, 13:00
Opponent
Supervisors
Note

QC 20100906

Available from: 2006-10-03 Created: 2006-10-03 Last updated: 2017-02-23Bibliographically approved

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