scholarly journals Assessing the accuracy of SRTM altitude data for the hilly area in northeastern Romania

2018 ◽  
Author(s):  
Mihai Niculita
Keyword(s):  
High Resolution ◽  
Vertical Component ◽  
Hilly Area ◽  
The Earth ◽  
Vertical Datum ◽  
North Eastern ◽  
Elevation Data ◽  
Horizontal Wavelength ◽  
Acquisition Method ◽  
Srtm Data

SRTM data is still one of the most used data in geosciences for various purposes: geomorphometric analysis, environmental covariate modelling or geomorphic change detection. Although high resolution national/regional DEMs exist, very often accessing them is expensive, or their coverage is not complete over specific areas (only floodplains or cities are covered). Because of this SRTM still remains the best choice when elevation data is needed for regional/national or global areas. In order to assess the correctness of SRTM data to depict the real shape of Earth surface we used a regional high resolution DEM which cover a part of the hilly area of north-eastern Romanian. Both DEMs were converted to the same horizontal and vertical datum (Stereo 70 Romanian projection and the EGG97 geoid), interpolated to the same grid size and position and compared using raster algebra. The horizontal x and y components and the vertical component errors were assessed. The results show that the errors of the SRTM model are well consistent with its acquisition method (the presence of the trees and the topographic shadow) and does represent reasonably well the Earth’s surface in the study area. Anyhow, the resolution of the Earth features depicted on the SRTM model is limited by the acquisition method and does not incorporate landforms which have a vertical and horizontal wavelength under 100 m.

scholarly journals Assessing the accuracy of SRTM altitude data for the hilly area in northeastern Romania

2018 ◽  
Author(s):  
Mihai Niculita
Keyword(s):  
High Resolution ◽  
Vertical Component ◽  
Hilly Area ◽  
The Earth ◽  
Vertical Datum ◽  
North Eastern ◽  
Elevation Data ◽  
Horizontal Wavelength ◽  
Acquisition Method ◽  
Srtm Data

SRTM data is still one of the most used data in geosciences for various purposes: geomorphometric analysis, environmental covariate modelling or geomorphic change detection. Although high resolution national/regional DEMs exist, very often accessing them is expensive, or their coverage is not complete over specific areas (only floodplains or cities are covered). Because of this SRTM still remains the best choice when elevation data is needed for regional/national or global areas. In order to assess the correctness of SRTM data to depict the real shape of Earth surface we used a regional high resolution DEM which cover a part of the hilly area of north-eastern Romanian. Both DEMs were converted to the same horizontal and vertical datum (Stereo 70 Romanian projection and the EGG97 geoid), interpolated to the same grid size and position and compared using raster algebra. The horizontal x and y components and the vertical component errors were assessed. The results show that the errors of the SRTM model are well consistent with its acquisition method (the presence of the trees and the topographic shadow) and does represent reasonably well the Earth’s surface in the study area. Anyhow, the resolution of the Earth features depicted on the SRTM model is limited by the acquisition method and does not incorporate landforms which have a vertical and horizontal wavelength under 100 m.

scholarly journals Late Quaternary climate change in the north-eastern highlands of Ethiopia: A high resolution 15,600 year diatom and pigment record from Lake Hayk

2018 ◽  
Vol 202 ◽  
pp. 166-181 ◽  
Author(s):  
Katie L. Loakes ◽  
David B. Ryves ◽  
Henry F. Lamb ◽  
Frank Schäbitz ◽  
Michael Dee ◽  
...  
Keyword(s):  
Climate Change ◽  
High Resolution ◽  
Late Quaternary ◽  
The North ◽  
Quaternary Climate ◽  
North Eastern ◽  
Eastern Highlands

scholarly journals Assessing Optimal Digital Elevation Model Selection for Active River Area Delineation Across Broad Regions

2021 ◽  
Author(s):  
Shizhou Ma ◽  
Karen Beazley ◽  
Patrick Nussey ◽  
Chris Greene
Keyword(s):  
High Resolution ◽  
Digital Elevation Model ◽  
Smoothing Algorithm ◽  
Processing Efficiency ◽  
Spatial Approach ◽  
Digital Elevation ◽  
Elevation Data ◽  
Computer Based ◽  
Lidar Dem ◽  
Elevation Model

Abstract The Active River Area (ARA) is a spatial approach for identifying the extent of functional riparian area. Given known limitations in terms of input elevation data quality and methodology, ARA studies to date have not achieved effective computer-based ARA-component delineation, limiting the efficacy of the ARA framework in terms of informing riparian conservation and management. To achieve framework refinement and determine the optimal input elevation data for future ARA studies, this study tested a novel Digital Elevation Model (DEM) smoothing algorithm and assessed ARA outputs derived from a range of DEMs for accuracy and efficiency. It was found that the tested DEM smoothing algorithm allows the ARA framework to take advantage of high-resolution LiDAR DEM and considerably improves the accuracy of high-resolution LiDAR DEM derived ARA results; smoothed LiDAR DEM in 5-meter spatial resolution best balanced ARA accuracy and data processing efficiency and is ultimately recommended for future ARA delineations across large regions.

scholarly journals HIGH-RESOLUTION TSUNAMI-BEDLOAD COUPLED COMPUTATION IN AMR ENVIRONMENT

2018 ◽  
pp. 21
Author(s):  
Yasunori Watanabe ◽  
Yuta Mitobe ◽  
Hitoshi Tanaka ◽  
Kazuya Watanabe
Keyword(s):  
Boundary Layer ◽  
Land Use ◽  
High Resolution ◽  
Boundary Layer Theory ◽  
Wall Roughness ◽  
Pressure Reduction ◽  
High Resolution Data ◽  
Public Facilities ◽  
Elevation Data ◽  
Resolution Data

Conventional tsunami computations on coarser grids have employed Manning’s friction coefficients of subgrid equivalent roughness for buildings, vegetation and public facilities (roads, dikes and so on), depending on land-use at the grid location. This equivalent roughness macroscopically models to integrate all effects of resistances against the flow within the computational cells; that is, drag force and pressure reduction behind structures in addition to wall roughness defined in turbulent boundary layer theory. Recently high-resolution land elevation data (2-m resolution), measured by an aerial laser profiler, has been used for computing local inundation of tsunami flood. Since the high-resolution data resolves major buildings and facilities, the mechanical contributions of the structures, such as drag and pressure reduction, are included in the computed result. In this case, conventional equivalent friction may be unacceptable to use.

Experimental investigation of the instability of a sedimenting suspension of fibres

2007 ◽  
Vol 575 ◽  
pp. 307-332 ◽  
Author(s):  
BLOEN METZGER ◽  
JASON E. BUTLER ◽  
ÉLISABETH GUAZZELLI
Keyword(s):  
Vertical Component ◽  
Orientation Distribution ◽  
Velocity Fluctuations ◽  
Image Velocimetry ◽  
Wide Range ◽  
Fluid Properties ◽  
The Mean ◽  
Using Data ◽  
Horizontal Wavelength ◽  
Short Times

Observations of the flow structures formed by rigid fibres of high aspect ratio sedimenting within a viscous fluid at a Reynolds number of approximately 10−4 confirm the existence of an instability as reported in previous theories, experiments, and numerical simulations. Using data generated from particle image velocimetry measurements, we quantify the sedimentation structures over a wide range of parameters, which include the height of fluid, cross-section of the sedimentation cell, fibre dimensions, fluid properties, and volume fractions ranging from dilute to semi-dilute. Alternating structures of streamers and backflow regions which span the height of the sedimentation cell form at short times and transition from large wavelengths to smaller wavelength as the sedimentation proceeds. No simple dependence of the horizontal wavelength on the length scales and concentration was observed in the experiments, suggesting the need for additional analysis. We also report the mean velocities and velocity fluctuations; the strength of the velocity fluctuations strongly correlates with the size of the vertical component of the sedimentation structure. Measurements of the orientation distribution, using an efficient and newly employed technique, agree with previously published results. A movie is available with the online version of the paper.

“Virtual” Atmospheric and Oceanic Circulation in the Earth Simulator

2007 ◽  
Vol 88 (6) ◽  
pp. 861-866 ◽  
Author(s):  
Wataru Ohfuchi ◽  
Hideharu Sasaki ◽  
Yukio Masumoto ◽  
Hisashi Nakamura
Keyword(s):  
High Resolution ◽  
The Other ◽  
Educational Community ◽  
Oceanic Circulation ◽  
Close Collaboration ◽  
Simulation Research ◽  
The Earth ◽  
Other Hand ◽  
Early Results

High-resolution simulations of the atmospheric and oceanic general circulations on the Earth Simulator are briefly introduced to a wider research and educational community. Some early results have been published and are reviewed in this article. The high-resolution simulations may have more information in certain aspects than observations while the simulations need to be validated. On the other hand, high-resolution observations in which uncertainties are unavoidable are now available. Possible close collaboration between observational and simulation research is proposed.

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