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Ramin Kiamehr

KTH Royal Institute of Technology, Geodesy, Graduate Student

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Ramin Kiamehr, Assistant Professor (1968, Orumieh, Iran, Married, One Daughter)
Supervisors: MSc Thesis: Prof. Petr Vaníček and PhD Thesis: Prof. L.E. Sjöberg
Phone: +98 241 5152407,
Address: Address: Zanjan University, Head of Department of Geography, 45195-313 Zanjan, Iran.

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Books by Ramin Kiamehr

Practical Concepts in Geoid Modelling, With Geophysical and Geodynamical Interpretations

Engineering Surveying in Practice

Dynamics Planet

A New Height Datum for Iran Based on the Combination of the Gravimetric and Geometric Geoid Mode... more A New Height Datum for Iran Based on the Combination of the Gravimetric and Geometric Geoid Models
Book Series International Association of Geodesy Symposia
ISSN 0939-9585
Volume Volume 130
Book Dynamic Planet
Publisher Springer Berlin Heidelberg
DOI 10.1007/978-3-540-49350-1
Copyright 2007
ISBN 978-3-540-49349-5 (Print) 978-3-540-49350-1 (Online)
Part Part IV
DOI 10.1007/978-3-540-49350-1_70
Pages 480-487
Subject Collection Earth and Environmental Science
SpringerLink Date Tuesday, January 15, 2008

Papers by Ramin Kiamehr

The New Gravimetric Quasi-geoid Model KTH08 over Sweden

Ambiguity Resolution Techniques Using Syntactic Data, Case Study: Comparison of the LAMBDA and KTH Methods

Estimating of variance components of ellipsoidal, orthometric and geoidal heights through the GPS/levelling Network in Iran

EGMlab, a scientific software for determining the gravity and gradient components from global geopotential models, J Earth Science Informatics

Nowadays, Global Geopotential Models (GGMs) are used as a routine stage in the procedures to comp... more Nowadays, Global Geopotential Models (GGMs) are used as a routine stage in the procedures to compute a gravimetric geoid. The GGMs based geoidal height also can be used for GPS/levelling and navigation purposes in developing countries which do not have accurate gravimetric geoid models. Also, the GGM based gravity anomaly including the digital elevation model can be used in evaluation and outlier detections schemes of the ground gravity anomaly data. Further, the deflection of vertical and gravity gradients components from the GGMs can be used for different geodetic and geophysical interpretation purposes. However, still a complete and user-friendly software package is not available for universities and geosciences communities. In this article, first we review the procedure for determination of the basic gravity field and gradient components from the GGMs, then general MATLAB based software is presented and applied as a sample case study for determination of gravity components based on the most recent EIGEN-GL04C GRACE model in Sweden.

General geophysical patterns in Iran based on GRACE gradient component analysis

Evaluation of robust techniques in suppressing the impact of outliers in a deformation monitoring network – A case study on the Tehran Milad tower network

Qualification and refinement of the gravity database based on Cross-Validation approach, A case study of Iran

A Strategy for Optimum Designing of the Geodetic Networks from the Cost, Reliability and Precision Views

A new height datum for Iran based on combination of the Gravimetric and GPS/levelling geoid models

The Impact of the lateral density variation model in determination of the precise gravimetric geoid in mountainous areas: A case study of Iran

The existence of topography above the geoid violates the basic assumption of Stokes' formula for ... more 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.

Precise Gravimetric Geoid Model for Iran Based on GRACE and SRTM Data and the Least-Squares Modification of Stokes' Formula: with Some Geodynamic …

Iran is one of the most complicated areas in the world from the view of rough topography, tectoni... more 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.

AN OPTIMUM LOCAL GEOID MODEL FOR IRAN BASED ON THE LEAST-SQUARES MODIFICATION OF STOKES'S FORMULA

ncc.org.ir

The modification of Stokes's formula allows the user to compensate the lack of a global coverage ... more The modification of Stokes's formula allows the user to compensate the lack of a global coverage of gravity data by a combination of terrestrial gravity and a global geopotential model. The minimization of the errors of truncation gravity data and potential coefficients could be treated in a least-squares sense as is the basic ingredient in the Royal Institute of Technology (KTH) approach as proposed by Sjöberg in 1984. This article presents the results from a recent research, whose main purpose is to evaluate the KTH approach numerically and to compute a gravimetric geoid model for Iran. The new geoid model (IRG04) was computed based on the least-squares modification of Stokes's formula, the GRACE global geopotential model, a high-resolution digital terrain model and the NKG gravity anomaly database. The IRG04 was fitted to 247 GPS/levelling points by a 7-parameter transformation, yielding an all-over fit of 43 cm and 3.5 ppm. Also, we found a significant expected difference between the IRG04 and TUG06 models in rough topographic areas (up to ± 4 m). As the major ground data and global geopotential model were almost same in the two models, we believe that there are different reasons that come into play for interpreting the discrepancies between them, as the method for eliminating outliers from the gravity database, the interpolated denser gravity observations using the high-resolution digital elevation model before Stokes's integration, the potential of the LSM kernel, which matches the errors of the terrestrial gravity data, GGM and the truncation error in an optimum way, and the effect of applying more precise correction terms in the KTH approach compared to the remove-computerestore method. It is concluded that the least-squares modification method with additive corrections is a very promising alternative for geoid computation.

Effect of the SRTM global DEM on the determination of a high-resolution geoid model: a case study in Iran

Journal of Geodesy, Jan 1, 2005

Any errors in digital elevation models (DEMs) will introduce errors directly in gravity anomalies... more Any errors in digital elevation models (DEMs) will introduce errors directly in gravity anomalies and geoid models when used in interpolating Bouguer gravity anomalies. Errors are also propagated into the geoid model by the topographic and downward continuation (DWC) corrections in the application of Stokes's formula. The effects of these errors are assessed by the evaluation of the absolute accuracy of nine independent DEMs for the Iran region. It is shown that the improvement in using the high-resolution Shuttle Radar Topography Mission (SRTM) data versus previously available DEMs in gridding of gravity anomalies, terrain corrections and DWC effects for the geoid model are significant. Based on the Iranian GPS/levelling network data, we estimate the absolute vertical accuracy of the SRTM in Iran to be 6.5 m, which is much better than the estimated global accuracy of the SRTM (say 16 m). Hence, this DEM has a comparable accuracy to a current photogrammetric high-resolution DEM of Iran under development. We also found very large differences between the GLOBE and SRTM models on the range of −750 to 550 m. This difference causes an error in the range of −160 to 140 mGal in interpolating surface gravity anomalies and −60 to 60 mGal in simple Bouguer anomaly correction terms. In the view of geoid heights, we found large differences between the use of GLOBE and SRTM DEMs, in the range of −1.1 to 1 m for the study area. The terrain correction of the geoid model at selected GPS/levelling points only differs by 3 cm for these two DEMs.

Progress in the determination of a gravimetric quasigeoid model over Sweden

Potential of the Iranian Geoid For GPS/Leveling

Proc National Cartographic Center of Iran, Geomatics, Jan 1, 2001

We know that leveling survey is a slow, expensive, and labor intensive operation and especially i... more We know that leveling survey is a slow, expensive, and labor intensive operation and especially in Iran until today we try to complete only the first order-leveling network. It is obvious that we need the second and three-order network for civil engineering project but it need several years. In this research in order to getting the absolute and relative accuracy of the Iranian gravimetric geoid in GPS/leveling, I selected 55 points of Global Positioning System (GPS) network with stations of Iranian first order leveling network in different parts of the country. For studying the effect of topography and gravity data coverage in geoid accuracy I also select five separate traverses in different parts of the country from these points. According to the results of this research the absolute accuracy is estimated as 1.56 m; similarly, for the five selected profiles, the results was in the range of 0.90 m to 1.92 m.

A strategy for determining the regional geoid in developing countries by combining limited ground data with satellite-based global geopotential and topographical …

Journal of Geodesy, Jan 1, 2006

The computation of regional gravimetric geoid models with reasonable accuracy, in developing coun... more

Multi Object Optimization Of Geodetic Network

NCC Geomatics 82 conferences, Jan 1, 2003

networks based on well-specified quantitative considerations and techniques, it suggests planning... more networks based on well-specified quantitative considerations and techniques, it suggests planning for the best solution. In particular with respect to terrain difficulties and the choice of methods of measurement, the planning of networks means in practice that one starts with a solution that is feasible under the given circumstances and available material means, and then introduces improvement until the plan in not too expensive and good enough (Alberda-1974). However in the surveying engineering and geodetic science in order to mapping and staking out of civil engineering projects, GIS, earthquake and land slid hazard assessment, monitoring of deformation of civil structure such as dams and towers, aerial photography and in many other applications we need a framework of points that we called geodetic network.

Practical Concepts in Geoid Modelling, With Geophysical and Geodynamical Interpretations

Engineering Surveying in Practice

Dynamics Planet

A New Height Datum for Iran Based on the Combination of the Gravimetric and Geometric Geoid Mode... more A New Height Datum for Iran Based on the Combination of the Gravimetric and Geometric Geoid Models
Book Series International Association of Geodesy Symposia
ISSN 0939-9585
Volume Volume 130
Book Dynamic Planet
Publisher Springer Berlin Heidelberg
DOI 10.1007/978-3-540-49350-1
Copyright 2007
ISBN 978-3-540-49349-5 (Print) 978-3-540-49350-1 (Online)
Part Part IV
DOI 10.1007/978-3-540-49350-1_70
Pages 480-487
Subject Collection Earth and Environmental Science
SpringerLink Date Tuesday, January 15, 2008

The New Gravimetric Quasi-geoid Model KTH08 over Sweden

Ambiguity Resolution Techniques Using Syntactic Data, Case Study: Comparison of the LAMBDA and KTH Methods

Estimating of variance components of ellipsoidal, orthometric and geoidal heights through the GPS/levelling Network in Iran

EGMlab, a scientific software for determining the gravity and gradient components from global geopotential models, J Earth Science Informatics

Nowadays, Global Geopotential Models (GGMs) are used as a routine stage in the procedures to comp... more Nowadays, Global Geopotential Models (GGMs) are used as a routine stage in the procedures to compute a gravimetric geoid. The GGMs based geoidal height also can be used for GPS/levelling and navigation purposes in developing countries which do not have accurate gravimetric geoid models. Also, the GGM based gravity anomaly including the digital elevation model can be used in evaluation and outlier detections schemes of the ground gravity anomaly data. Further, the deflection of vertical and gravity gradients components from the GGMs can be used for different geodetic and geophysical interpretation purposes. However, still a complete and user-friendly software package is not available for universities and geosciences communities. In this article, first we review the procedure for determination of the basic gravity field and gradient components from the GGMs, then general MATLAB based software is presented and applied as a sample case study for determination of gravity components based on the most recent EIGEN-GL04C GRACE model in Sweden.

General geophysical patterns in Iran based on GRACE gradient component analysis

Evaluation of robust techniques in suppressing the impact of outliers in a deformation monitoring network – A case study on the Tehran Milad tower network

Qualification and refinement of the gravity database based on Cross-Validation approach, A case study of Iran

A Strategy for Optimum Designing of the Geodetic Networks from the Cost, Reliability and Precision Views

A new height datum for Iran based on combination of the Gravimetric and GPS/levelling geoid models

The Impact of the lateral density variation model in determination of the precise gravimetric geoid in mountainous areas: A case study of Iran

The existence of topography above the geoid violates the basic assumption of Stokes' formula for ... more 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.

Precise Gravimetric Geoid Model for Iran Based on GRACE and SRTM Data and the Least-Squares Modification of Stokes' Formula: with Some Geodynamic …

Iran is one of the most complicated areas in the world from the view of rough topography, tectoni... more 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.

AN OPTIMUM LOCAL GEOID MODEL FOR IRAN BASED ON THE LEAST-SQUARES MODIFICATION OF STOKES'S FORMULA

ncc.org.ir

The modification of Stokes's formula allows the user to compensate the lack of a global coverage ... more The modification of Stokes's formula allows the user to compensate the lack of a global coverage of gravity data by a combination of terrestrial gravity and a global geopotential model. The minimization of the errors of truncation gravity data and potential coefficients could be treated in a least-squares sense as is the basic ingredient in the Royal Institute of Technology (KTH) approach as proposed by Sjöberg in 1984. This article presents the results from a recent research, whose main purpose is to evaluate the KTH approach numerically and to compute a gravimetric geoid model for Iran. The new geoid model (IRG04) was computed based on the least-squares modification of Stokes's formula, the GRACE global geopotential model, a high-resolution digital terrain model and the NKG gravity anomaly database. The IRG04 was fitted to 247 GPS/levelling points by a 7-parameter transformation, yielding an all-over fit of 43 cm and 3.5 ppm. Also, we found a significant expected difference between the IRG04 and TUG06 models in rough topographic areas (up to ± 4 m). As the major ground data and global geopotential model were almost same in the two models, we believe that there are different reasons that come into play for interpreting the discrepancies between them, as the method for eliminating outliers from the gravity database, the interpolated denser gravity observations using the high-resolution digital elevation model before Stokes's integration, the potential of the LSM kernel, which matches the errors of the terrestrial gravity data, GGM and the truncation error in an optimum way, and the effect of applying more precise correction terms in the KTH approach compared to the remove-computerestore method. It is concluded that the least-squares modification method with additive corrections is a very promising alternative for geoid computation.

Effect of the SRTM global DEM on the determination of a high-resolution geoid model: a case study in Iran

Journal of Geodesy, Jan 1, 2005

Any errors in digital elevation models (DEMs) will introduce errors directly in gravity anomalies... more Any errors in digital elevation models (DEMs) will introduce errors directly in gravity anomalies and geoid models when used in interpolating Bouguer gravity anomalies. Errors are also propagated into the geoid model by the topographic and downward continuation (DWC) corrections in the application of Stokes's formula. The effects of these errors are assessed by the evaluation of the absolute accuracy of nine independent DEMs for the Iran region. It is shown that the improvement in using the high-resolution Shuttle Radar Topography Mission (SRTM) data versus previously available DEMs in gridding of gravity anomalies, terrain corrections and DWC effects for the geoid model are significant. Based on the Iranian GPS/levelling network data, we estimate the absolute vertical accuracy of the SRTM in Iran to be 6.5 m, which is much better than the estimated global accuracy of the SRTM (say 16 m). Hence, this DEM has a comparable accuracy to a current photogrammetric high-resolution DEM of Iran under development. We also found very large differences between the GLOBE and SRTM models on the range of −750 to 550 m. This difference causes an error in the range of −160 to 140 mGal in interpolating surface gravity anomalies and −60 to 60 mGal in simple Bouguer anomaly correction terms. In the view of geoid heights, we found large differences between the use of GLOBE and SRTM DEMs, in the range of −1.1 to 1 m for the study area. The terrain correction of the geoid model at selected GPS/levelling points only differs by 3 cm for these two DEMs.

Progress in the determination of a gravimetric quasigeoid model over Sweden

Potential of the Iranian Geoid For GPS/Leveling

Proc National Cartographic Center of Iran, Geomatics, Jan 1, 2001

We know that leveling survey is a slow, expensive, and labor intensive operation and especially i... more We know that leveling survey is a slow, expensive, and labor intensive operation and especially in Iran until today we try to complete only the first order-leveling network. It is obvious that we need the second and three-order network for civil engineering project but it need several years. In this research in order to getting the absolute and relative accuracy of the Iranian gravimetric geoid in GPS/leveling, I selected 55 points of Global Positioning System (GPS) network with stations of Iranian first order leveling network in different parts of the country. For studying the effect of topography and gravity data coverage in geoid accuracy I also select five separate traverses in different parts of the country from these points. According to the results of this research the absolute accuracy is estimated as 1.56 m; similarly, for the five selected profiles, the results was in the range of 0.90 m to 1.92 m.

A strategy for determining the regional geoid in developing countries by combining limited ground data with satellite-based global geopotential and topographical …

Journal of Geodesy, Jan 1, 2006

The computation of regional gravimetric geoid models with reasonable accuracy, in developing coun... more

Multi Object Optimization Of Geodetic Network

NCC Geomatics 82 conferences, Jan 1, 2003

networks based on well-specified quantitative considerations and techniques, it suggests planning... more networks based on well-specified quantitative considerations and techniques, it suggests planning for the best solution. In particular with respect to terrain difficulties and the choice of methods of measurement, the planning of networks means in practice that one starts with a solution that is feasible under the given circumstances and available material means, and then introduces improvement until the plan in not too expensive and good enough (Alberda-1974). However in the surveying engineering and geodetic science in order to mapping and staking out of civil engineering projects, GIS, earthquake and land slid hazard assessment, monitoring of deformation of civil structure such as dams and towers, aerial photography and in many other applications we need a framework of points that we called geodetic network.

Analysis of surface deformation patterns using 3D finite element method: A case study in the Skåne area, Sweden

Journal of Geodynamics, Jan 1, 2005

A recent study of the active distortion of Sweden based on 200 earthquake solutions in southern S... more A recent study of the active distortion of Sweden based on 200 earthquake solutions in southern Sweden and the offset of contours of postglacial land uplift rate picked out several active faults in the region of our Skåne GPS network. We estimate crustal deformation parameters in Skåne, southern Sweden, using observations of the Global Positioning System (GPS) from 1996 and 1998 using 3D finite element approch. With using of two stations of the Swedish permanent GGPS network (Onsala and Hässleholm), it includes seven GPS sites spaced approximately 80 km apart. The network straddles the Tornquist zone; potentially one of the most active fault zones in Sweden. The precisions of the relative horizontal components for these stations approximately 3 mm in the north-south direction and about 2 mm in the east-west direction in the campaigns in the reference frame ITRF96. About 70% of the GPS integer carrier phase ambiguities were resolved for these campaigns. The Skåne GPS network was chosen to straddle the WNW-ESE trending Tornquist zone, which, as the north boundary to the transition zone between the 42-45 Precambrian (> 1 Ga) gneisses of the Baltic shield to the north from the c. 30 km thick Phanerozoic Europe to the south, might be expected to be one of the most active faults in Sweden. This results of research indicates that

Interpretation of General Geophysical Patterns In Iran Based on GRACE Gradient Component Analysis

Acta Geophysica, Jan 1, 2008

Only with satellites it is possible to cover the entire earth densely with gravity field related ... more Only with satellites it is possible to cover the entire earth densely with gravity field related measurements of uniform quality within a short period of time. However, due to the altitude of the satellite orbits, the signals of the individual local masses are strongly damped. Based on the approach of we determine the gravity gradient tensor directly from the spherical harmonic coefficients of the recent EIGEN-GL04C combined model of the GRACE satellite mission. Satellite gradiometry can be used as a complementary tool to gravity and geoid information in interpreting the general geophysical and geodynamical features of the Earth. Due to the high altitude of the satellite, the effects of the topography and the internal masses of the Earth are strongly damped. However, the gradiometer data, which are nothing else than the second order spatial derivatives of the gravity potential, efficiently counteracts signal attenuation at the low and medium frequencies. In this article we review the procedure for estimating the gravity gradient components directly from spherical harmonics coefficients. Then we apply this method as a case study for the interpretation of possible geophysical or geodynamical patterns in Iran. We found strong correlations between the cross-components of the gravity gradient tensor and the components of the deflection of vertical, and we show that this result agrees with theory. Also, strong correlations of the gravity anomaly, geoid model and a digital elevation model were found with the diagonal elements of the gradient tensor.

Impact of a precise geoid model in studying tectonic structures--A case study in Iran

Journal of Geodynamics, Jan 1, 2006

Iran is one of the most active regions in the world with respect to earthquakes and tectonic moti... more Iran is one of the most active regions in the world with respect to earthquakes and tectonic motions in the lithosphere. In order to study the impact of the geoid model in detecting plate tectonic boundaries and in the establishment of an accurate height datum for future geodynamic observations, a new combined gravimetric geoid model for Iran (IRG04C) was computed by the method of least squares modification of Stokes formula based on the most recent gravity anomaly database, SRTM high resolution Digital Elevation Model (DEM), GRACE GGM02 Global Geopotential Model and GPS/levelling data. The RMS fit of the new geoid model versus GPS/levelling data is 9 cm, which is a 10 times better fit compared to the most recent published gravimetric geoid model in the area. An integrated approach, combining gravity, geoid and seismology data as well as a digital elevation model, was used to find possible correlations between these parameters. Our investigation indicates that all earthquakes with magnitude over 6.0 in the Richter scale are located in areas with a geoid slope exceeding 7.5%. The study shows a significant correlation between the horizontal gradient of the geoid and plate tectonic activities.