| 1. |
- Drouin, Vincent, et al.
(författare)
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Crustal movements at a divergent plate boundary: interplay between volcano deformation, geothermal processes, and plate spreading in the Northern Volcanic Zone, Iceland since 2008.
- 2014
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Ingår i: Geophysical Research Abstracts, EGU General Assembly, 27 April–02 May, 2014, Vienna, Austria. ; 16(EGU2014-10740-3)
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 2. |
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| 3. |
- Islam, Md. Tariqul, 1980
(författare)
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Least Square Approach to Estimate 3D Coordinate Transformation Parameters: A Case of Three Reference Systems in Sweden
- 2014
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Ingår i: International Journal of Remote Sensing and GIS. - 2277-9051. ; 3:3, s. 30-38
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Tidskriftsartikel (refereegranskat)abstract
- Seven parameters of Helmert transformation are estimated using three-dimensional Cartesian coordinates in Sweden. Here, two cases are studied. Cartesian coordinates of RT90 and SWEREFF 93 in mm level accuracy for Case A are generated from secondary source. However for Case B, coordinates have been obtained by a field measurement. Trimble differential GPS has been used to measure coordinate in both SWEREFF 99 TM and RT90 reference systems in Gothenburg region, Sweden. It provides the coordinates in decimeter level accuracy. Helmert transformation parameters are estimated by applying MATLAB code. Seven parameters of Helmert transformation between RT90 and SWEREFF 93, and RT90 and SWEREFF 99 TM, and vice-versa are estimated. The average variance-covariance and, difference between measured and transformed coordinates in Case A is estimated to 3.86e-7 and 0.082 meter, respectively. However in Case B, the estimated transformation parameters is poor due to low level accuracy of measured coordinates and not fit in proper Cartesian system since the height component in 3D coordinate system provides geoid height which does not correspond to Cartesian coordinate. Therefore it gives high average variance-covariance as to 0.2165 and difference between measured and transformed coordinates to 5.498 meter. So estimation of Helmert transformation parameters requires Cartesian coordinates with high accuracy.
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| 4. |
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| 5. |
- Islam, Md. Tariqul, 1980
(författare)
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RIVER CHANNEL MIGRATION: A REMOTE SENSING AND GIS ANALYSIS
- 2010
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Ingår i: Proceedings of ESA Living Planet Symposium. 28 June - 2 July 2010, Bergen, Norway / edited by H. Lacoste-Francis. - 1609-042X. - 9789292212506 ; :SP-686
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Konferensbidrag (refereegranskat)abstract
- Remote sensing and geographic information system provide tools for quantitative and qualitative river morphological analysis. Bangladesh is a riverine, flood prone country and, the Padma and the Jamuna are two of major three rivers in the country. The aim of this research is to monitor the channel migration of the Padma and the Jamuna rivers since 1977 to 2004 using remote sensing and GIS. Four scenes for dry season’s cloud free Landsat images were used in this study. Images were processed using PCI Geomatica and ArcGIS 9.3 was used for GIS analysis. The Landsat images were visualized and identified nine locations to investigate the channel migration. The images were classified into two broad categories, i.e. water and nonwater body. ArcGIS 9.3 was used to transfer these classified images into GIS layers. A standard measurement tool of ArcGIS was applied to measure the movement of river channel based on initial river channel in 1977. General trend of the Padma and the Jamuna river channel migration at locations A, B, C, D, F, G, H and I towards north, northeast and southwest eventually, north, northeast, east, east, west and west, respectively. The confluence point of the Padma and Jamuna (at location E) migrated toward southeast with high rate. During 1977-2004, it migrated about 9000m toward southeast. Trend of migration of the confluence point was faster than any other locations in the channel of the Padma river.
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| 8. |
- Islam, Md. Tariqul, 1980
(författare)
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VEGETATION CHANGES OF SUNDARBANS BASED ON LANDSAT IMAGERY ANALYSIS BETWEEN 1975 AND 2006
- 2014
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Ingår i: Landscape & Environment. - 1789-4921 .- 1789-7556. ; 8:1, s. 1-9
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Tidskriftsartikel (refereegranskat)abstract
- paper is to show changes in vegetation cover of Sundarbans since 1975 using Landsat imagery. Normal - ized Difference Vegetation Index is applied to quantify and qualify density of vegetation on a patch of land. Estimated land area (excluded water body) of this forest is 66% in Bangladesh, and 34% in India, respectively. Net erosion since 1975 to 2006 is ~5.9%. In vicinity of human settlement, areal changes are not observed since 1975. The mangrove forest is decreased by 19.3% due severe tropical cyclone in 1977 and 1988. Moreover, the dense forest is damaged by about 50%. However, more than 25 years is taken by Sundarbans to recover from damage by a severe tropical cyclone. The biodiversity of Sundarbans depends to fresh water flow through it. Therefore, the future of Sundarbans depends to the impact of climate change which has further effect to increasing intensity and frequency of severe tropical cyclone and salinity in water channels in Sundarbans
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| 9. |
- Sturkell, Erik, 1962, et al.
(författare)
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Continuous subsidence in the Thingvellir rift graben, Iceland: Geodetic observations since 1966 compared to rheological models of plate spreading
- 2013
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Ingår i: AGU (American Geophysical Union) Fall Meeting, 9-13 December, 2013, San Francisco, USA.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Plate spreading across the Mid-Atlantic Ridge in south Iceland is partitioned between overlapping rift segments - the Western Volcanic Zone (WVZ) and the Eastern Volcanic Zone. The Thingvellir graben lies along the central axis of the WVZ. A central piece of the graben, between main boundary faults spaced 4.7 km apart, has subsided over 30 m since the postglacial lava last covered it about 9000 years ago. A rifting episode without eruptions occurred in 1789. An ~7 km long leveling profile crosses the graben was initially measured in 1966. It has been remeasured five times, most recently in 1990 and 2007. A subsidence of about 1.5 mm/year is observed along the central part of the profile, compared to its end. GPS measurements since 1994 document a spreading rate of 3.5 mm/yr or less, distributed over the ~50 km width of the WVZ. This is only a fraction of full spreading between the North American and Eurasian plates in South Iceland, which is 18.7 mm/yr in direction N103°E according to the MORVEL plate motion model and mostly accommodated by the EVZ. The GPS vertical velocities, corrected for post-glacial rebound, suggest maximum subsidence of ~4.00 mm/yr in the center of the rift, and a broad (>50 km) zone of subsidence across the WVZ. The length of the leveling profile is short compared to the width of the zone of subsidence, so it only captures a fraction of the overall subsidence. A two-dimensional (length and depth) finite element model (FEM), considering a temperature-dependent non-linear rheology is used to fit the observed surface deformation. The model is stretched to reproduce the observed deformation, with varying rheological parameters and thermal boundary conditions. The model considers, in particular, different depth to 700°C isotherm at the rift axis. The best-fit model, solved by minimizing the residual between the observed and modeled surface displacements, is found for a 700°C isotherm at 5 km depth at the rift axis, with a thermal gradient of 140°C/km above. This depth is consistent with a locking depth inferred from previous elastic dislocation models. The magma inflow in the system is not sufficient to keep up with the subsidence caused by the stretching, causing subsidence. The combined observations and model show that the deformation zone of the WVZ is almost ten times larger than the width of the central segment of the Thingvellir graben.
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