scholarly journals Topography and structural changes of Anak Krakatau due to the December 2018 catastrophic events

2020 ◽  
Vol 52 (3) ◽  
pp. 402
Author(s):  
Herlan Darmawan ◽  
Bachtiar Wahyu Mutaqin ◽  
Wahyudi Wahyudi ◽  
Agung Harijoko ◽  
Haryo Edi Wibowo ◽  
...  
Keyword(s):  
High Resolution ◽  
Structural Changes ◽  
Structural Investigation ◽  
Satellite Image ◽  
Volcanic Edifice ◽  
Volcanic Cone ◽  
Flank Collapse ◽  
Digital Elevation ◽  
Before And After ◽  
Elevation Model

The flank collapse of Anak Krakatau on 22 December 2018 caused massive topography losses that generated a devastating tsunami in Sunda Strait, which then followed by eruptions that progressively changed the topography and structure of Anak Krakatau. Here, we investigated topography and structural changes due to the December 2018 flank collapse and the following eruptions by using high resolution Digital Elevation Model (DEM) before and after the events and sentinel 1A satellite image post-flank collapsed. Results show that the volumetric losses due to the 22 December 2018 flank collapsed is ~127 x 106 m3, while the following eruptions caused ~0,8 x 106 m3 losses. Structural investigation suggests two structures that may act as failure planes. The first structure is located at the western part of volcanic edifice that associated with hydrothermal alteration and the second failure is an old crater rim which delineated an actively deform volcanic cone.

Line of Sight Analysis 

2021 ◽  
Author(s):  
Emily Law ◽  
Natalie Gallegos ◽  
Shan Malhotra
Keyword(s):  
High Resolution ◽  
Solar System ◽  
High Gain ◽  
Line Of Sight ◽  
Time Intervals ◽  
Ground Station ◽  
Points Of Interest ◽  
Digital Elevation ◽  
Initial Release ◽  
Elevation Model

<p>The Line of Sight (LoS) is one of the latest tools to join the analytics suite of tools for the Solar System Treks (https://trek.nasa.gov) portals.  The LoS tool provides a way to compute visibility between the entities in our solar system. More concretely, this utility searches for windows of communication or a “line of sight” between any two entities. Entities include orbiters, rovers, planetary bodies, ground stations, and other topographical locations. In addition to establishing communications between the two entities, the tool also takes into account local terrains of the entities in question.</p> <p>The software seeks to answer questions about establishing communications between a rover and an orbiter, or an orbiter to a ground station. In mission planning, LoS can be used to determine possible traverses for a rover that must maintain communications with a lander, or find time intervals of communication to an orbiter when a rover or lander are near an obstructing surface feature such as a crater rim or mound. Computations can be even more granular and lines of sight can be computed between mission instruments, thus allowing to ask questions such as “Is the High Gain Antenna on a rover visible from an orbiter?”</p> <p>The initial release of the software focuses on the lunar surface and the LRO spacecraft. Users can ask whether a topographical location on the moon is visible from the orbiter or a discrete set of ground stations on Earth. The tool uses NAIF SPICE and various mission kernels for computing planetary geometries. LoS also uses high resolution Digital Elevation Model (DEM) to model the terrain surrounding the points of interest. In-house software is used to convert high resolution DEMs into a format compatible with the tool. Users can provide their own DEMs to model the terrain on different topographical locations to use for their own computations.</p>

scholarly journals A High-Resolution Gravimetric Geoid Model for Kuwait Using the Least-Squares Collocation

2022 ◽  
Vol 9 ◽  
Author(s):  
Hamad Al-Ajami ◽  
Ahmed Zaki ◽  
Mostafa Rabah ◽  
Mohamed El-Ashquer
Keyword(s):  
High Resolution ◽  
Least Squares ◽  
Geopotential Model ◽  
Gravimetric Geoid ◽  
Least Squares Collocation ◽  
Geoid Model ◽  
Terrestrial Gravity ◽  
Digital Elevation ◽  
Elevation Model ◽  
Gps Leveling

A new gravimetric geoid model, the KW-FLGM2021, is developed for Kuwait in this study. This new geoid model is driven by a combination of the XGM2019e-combined global geopotential model (GGM), terrestrial gravity, and the SRTM 3 global digital elevation model with a spatial resolution of three arc seconds. The KW-FLGM2021 has been computed by using the technique of Least Squares Collocation (LSC) with Remove-Compute-Restore (RCR) procedure. To evaluate the external accuracy of the KW-FLGM2021 gravimetric geoid model, GPS/leveling data were used. As a result of this evaluation, the residual of geoid heights obtained from the KW-FLGM2021 geoid model is 2.2 cm. The KW-FLGM2021 is possible to be recommended as the first accurate geoid model for Kuwait.

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 An Improved Method Constructing 3D River Channel for Flood Modeling

Water ◽  
2019 ◽  
Vol 11 (3) ◽  
pp. 403 ◽  
Author(s):  
Pengbo Hu ◽  
Jingming Hou ◽  
Zaixing Zhi ◽  
Bingyao Li ◽  
Kaihua Guo
Keyword(s):  
High Resolution ◽  
River Channel ◽  
Hydrodynamic Process ◽  
River Channels ◽  
Section Data ◽  
Terrain Model ◽  
Digital Elevation ◽  
Hydrodynamic Processes ◽  
Hermite Spline ◽  
Elevation Model

The high-resolution topography is very crucial to investigate the hydrological and hydrodynamic process. To resolve the deficiency problem of high resolution terrain data in rivers, the Quartic Hermite Spline with Parameter (QHSP) method constructing the river channel terrain based on the limited cross-section data is presented. The proposed method is able to not only improve the reliability of the constructed river terrain, but also avoid the numerical oscillations caused by the existing constructing approach, e.g., the Cubic Hermite Spline (CHS) method. The performance of the proposed QHSP method is validated against two benchmark tests. Comparing the constructed river terrains, the QHSP method can improve the accuracy by at least 15%. For the simulated flood process, the QHSP method could reproduce more acceptable modeling results as well, e.g., in Wangmaogou catchment, the numerical model applying the Digital Elevation Model (DEM) produced by the QHSP method could increase the reliability by 18.5% higher than that of CHS method. It is indicated that the QHSP method is more reliable for river terrain model construction than the CHS and is a more reasonable tool investigating the hydrodynamic processes in river channels lacking of high resolution topography data.

DEM Generation and Accuracy Assessment Using ZY-3 Stereo Image Pairs

2015 ◽  
Vol 738-739 ◽  
pp. 613-617 ◽  
Author(s):  
Guo Yin Cai ◽  
Jie Huan ◽  
Yang Liu ◽  
Ming Yi Du
Keyword(s):  
3D Visualization ◽  
Accuracy Assessment ◽  
Satellite Image ◽  
Stereo Image ◽  
Stereo Pair ◽  
Topographic Analysis ◽  
Digital Elevation ◽  
Data Source ◽  
Image Pairs ◽  
Elevation Model

Digital Elevation Model (DEM) is an important data source for topographic analysis, 3D visualization and satellite image ortho-rectification. This paper focused on the DEM extraction and accuracy assessment from ZY-3 satellite with 3 stereo images. DEM was extracted using three different stereo pair image groups composed of forward and nadir view images, nadir and backward view images as well as forward and backward view images. The accuracy of the DEM was indicated by root-mean-square error (RMSE) values. The results showed that the stereo pair of nadir and forward view images achieved the best accuracy, while the pair of forward and backward view images obtained the worst. This might be useful for the selection of the stereo pair images for extracting DEM using ZY-3 satellite images.

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