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Comparison of the qualities of recent global and local gravimetric geoid models in Iran
KTH, School of Architecture and the Built Environment (ABE), Transport and Economics.
KTH, School of Architecture and the Built Environment (ABE), Transport and Economics, Geodesy.
2005 (English)In: Studia Geophysica et Geodaetica, ISSN 0039-3169, Vol. 49, no 3, 289–304- p.Article in journal (Refereed) Published
Abstract [en]

A number of regional gravimetric geoid models have recently been determined for the Iran area, and a common problem is to select the best model, e.g. for engineering applications. A related problem is that in order to improve the local geoid models, the selection of the best Global Geopotential Model (GGM) model for the region is essential, to be used in a combined solution from GGM and local gravimetric data. We discuss these problems by taking advantage of 260 GPS/levelling points as an external tool for validation of different global and local geoid models in the absolute and relative senses. By using relative comparisons of the height differences between precise levelling and GPS/geoid models we avoid possible unknown systematic effects between the different types of observables.

The study shows that the combination of the newly released GRACE model (GGM02C) with EGM96 geoid model fits the GPS/levelling data in Iran with the best absolute and relative accuracy among the GGMs. Among the local geoid models, the newly gravimetric geoid model IRG04 agrees considerably better with GPS/levelling than any of the other recent local geoid models. Its rms fit with GPS/levelling is 55 cm. Hence, we strongly recommend the use of this new model in any surveying engineering or GPS/levelling projects in the area.

Place, publisher, year, edition, pages
2005. Vol. 49, no 3, 289–304- p.
Keyword [en]
geoid, GRACE, GGM, accuracy, GPS/levelling
National Category
Earth and Related Environmental Sciences
Identifiers
URN: urn:nbn:se:kth:diva-6191DOI: 10.1007/s11200-005-0011-7ISI: 000230691400003Scopus ID: 2-s2.0-23344440297OAI: oai:DiVA.org:kth-6191DiVA: diva2:10832
Note
Tidigare titel: The qualities of Iranian gravimetric geoid models versus recent gravity field missions QC 20100906 Available 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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Publisher's full textScopushttp://dx.doi.org/10.1007/s11200-005-0011-7

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