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A new height datum for Iran based on combination of the Gravimetric and GPS/levelling geoid models
KTH, School of Architecture and the Built Environment (ABE), Transport and Economics.
2007 (English)In: Acta Geodaetica et Geophysica, ISSN 1217-8977, Vol. 42, no 1, 69-81 p.Article in journal (Refereed) Published
Abstract [en]

A new geoid model for Iran (IRG04) was computed based on the least squares modification of the Stokes formula. IRG04 was derived from the most recent gravity anomaly database, SRTM high resolution Digital Elevation Model (DEM) and GRACE GGM02 global geopotential model. In order to define a new height datum for Iran, we attempted to combine this high resolution gravimetric geoid model with GPS/levelling data using the corrective surface approach. The corrective surface was constructed from 224 GPS/levelling points and then evaluated with 35 independent points. Different interpolation techniques were tested for the creation of the corrective surface; among them the Kriging method was selected as it gave the smallest RMS and 'noise level' at the comparisons with GPS/levelling data. The RMS fit of the new combined geoid model versus the independent GPS/levelling data is 0.09 m, it is near four times better compared to the original gravimetric geoid model. The combined model should be more convenient and useful in definition of the new height reference surface, specifically in engineering and GPS/levelling projects.

Place, publisher, year, edition, pages
2007. Vol. 42, no 1, 69-81 p.
Keyword [en]
Corrective surface, Geoid, GPS/levelling, GRACE, Kriging, Least squares modification, SRTM
National Category
Earth and Related Environmental Sciences
Identifiers
URN: urn:nbn:se:kth:diva-6195DOI: 10.1556/AGeod.42.2007.1.4ISI: 000258221700004Scopus ID: 2-s2.0-33847154669OAI: oai:DiVA.org:kth-6195DiVA: diva2:10836
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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