scholarly journals Contribution of Lake-Dune Patterning to the Dune Height of Mega-Dunes in the Badain Jaran Sand Sea, Northern China

2021 ◽  
Vol 13 (23) ◽  
pp. 4915
Author(s):  
Zhenmin Niu ◽  
Nai’ang Wang ◽  
Nan Meng ◽  
Jiang Liu ◽  
Xueran Liang ◽  
...  
Keyword(s):  
Northern China ◽  
Height Distribution ◽  
Aeolian Sand ◽  
Group Area ◽  
Digital Elevation ◽  
Meteorological Observations ◽  
New Perspective ◽  
Elevation Model ◽  
Dune Height

Mega-dunes in the lake group area of the Badain Jaran Sand Sea, China, are generally taller than dunes in the non-lake group area. This spatial distribution of dune heights may provide a new perspective on the controversy regarding the dunes’ formation mechanism. In this study, we calculated the relative heights and slopes of individual dunes based on a digital elevation model, and we confirmed the height distribution of abnormally tall dunes in the lake group area of the sand sea. It was also found that slopes of more than 10° in the lake group area are more common than those in the non-lake group area. Based on meteorological observations, coupled with the measurement of water content in the sand layers, we propose a conceptual model demonstrating that moisture exchange between the lakes and soil via non-rainfall water will humidify dune slopes and form a more favorable accumulation environment for aeolian sand, thus increasing dune heights. Although long-term observations are yet to be carried out, the present study can be used as evidence for understanding the basis of dune formation in the lake group area and assessing groundwater utilization in deserts.

scholarly journals Geodetic work at the archaeological site Tell el-Retaba

2018 ◽  
Vol 17 (2) ◽  
pp. 65-80
Author(s):  
Eva Stopková
Keyword(s):  
Spatial Data ◽  
Statistical Modelling ◽  
Archaeological Site ◽  
The North ◽  
Digital Elevation ◽  
North Eastern ◽  
Elevation Model ◽  
Modern Technologies

The paper summarizes the geodetic contribution for the Slovak team within the joint Polish-Slovak archaeological mission at Tell el-Retaba in Egypt. Surveying work at archaeological excavations is usually influenced by somewhat specific subject of study and extreme conditions, especially at the missions in the developing countries. The case study describes spatial data development according to the archaeological conventions in order to document spatial relationships between the objects in excavated trenches. The long-term sustainability of surveying work at the site has been ensured by detailed metadata recording. Except the trench mapping, Digital Elevation Model has been calculated for the study area and for the north-eastern part of the site, with promising preliminary results for further detection and modelling of archaeological structures. In general, topographic mapping together with modern technologies like Photogrammetry, Satellite Imagery, and Remote Sensing provide valuable data sources for spatial and statistical modelling of the sites; and the results offer a different perspective for the archaeological research.

scholarly journals The J 2 Relative Perturbation Analysis of Satellite Formation under the Requirement of Relative Position Maintenance with Millimeter-Level Accuracy

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Jingji Wang ◽  
Chunyang Liu
Keyword(s):  
Relative Position ◽  
Periodic Motion ◽  
Circular Orbit ◽  
Level Control ◽  
Zonal Harmonic ◽  
Target Indicator ◽  
Digital Elevation ◽  
Elevation Model ◽  
Control Accuracy

With high-precision DEM (Digital Elevation Model) and GMTI (Ground Moving Target Indicator) as the demand background, the influence of J 2 zonal harmonic term perturbation on the relative motion of the millimeter-level short-range leader-follower satellites in near-circular orbit is studied through the relative perturbation method. An equation of motion that can describe the motion of the leader-follower satellites under the influence of J 2 perturbation in near-circular orbit is derived, and the characteristics of the trajectory of in-plane periodic motion are analyzed. A study shows that under the influence of the relative perturbation of the J 2 term, the in-plane periodic motion of the leader-follower satellites in near-circular orbit is a symmetrical closed “drop-shaped” trajectory with a period of 2 π / n . By comparing with the results of numerical simulations, the correctness of the conclusions obtained in this paper is verified. According to the research results, it can be known that only using a thruster as the actuator to maintain the relative position can no longer meet the requirements of the long-term mm-level relative position maintenance. In the future, a new technical approach needs to be explored to achieve the long-term relative position maintenance with millimeter-level control accuracy.

Magma system pressurisation and long-term surface deformation at Soufrière Hills Volcano, Montserrat

2021 ◽  
Author(s):  
James Hickey ◽  
Karen Pascal ◽  
Matthew Head ◽  
Jo Gottsmann ◽  
Nico Fournier ◽  
...  
Keyword(s):  
Surface Deformation ◽  
Numerical Models ◽  
Three Dimensional ◽  
Magmatic System ◽  
System Pressure ◽  
Digital Elevation ◽  
Elevation Model ◽  
Magma System ◽  
Continuous Gps

<p>Soufrière Hills Volcano (SHV) is an andesitic dome-building volcano on the island of Montserrat (British West Indies). SHV began its current, and anomalously long, eruption in 1995, but eruptive activity has been intermittent with phases of lava extrusion separated by periods of relative quiescence. The current pause in eruption started in February 2010 and is the longest yet recorded, 10 years and 11 months at the time of writing (January 2021). Continuous GPS measurements show island-wide inflation from 2010 onwards, with the rate of inflation slowly decreasing with time. However, the length of the eruptive pause raises questions as to whether there have been significant changes to the magmatic system and/or the eruption at SHV might have ended. To assess the behaviour and evolution of the SHV magmatic system since 2010 and the relation to ongoing hazard assessment, we analyse the continuous GPS temporal deformation trends using a suite of geodetic numerical models. Our models incorporate a temperature-dependent viscoelastic rheology, topography derived from a Digital Elevation Model and three-dimensional variations in mechanical properties derived from seismic tomography. The models are driven using one of four possible time-dependent source functions, to simulate differences in the temporal evolution of the magmatic system. The results show that the observed deformation data requires a temporal source function whereby the magmatic system pressure is increasing with time. A viscoelastic crustal response cannot explain the long-term deformation trends alone. The nature of the source pressurisation is unclear, and could be due, for example, to one or a combination of, magma supply, degassing/volatile influx, or overturning within a transcrustal magmatic system. Continued pressurisation within the magmatic system highlights the need for sustained vigilance in the monitoring and management of the volcano and its surroundings.</p>

scholarly journals A New Long-Term Downward Surface Solar Radiation Dataset over China from 1958 to 2015

Sensors ◽  
2020 ◽  
Vol 20 (21) ◽  
pp. 6167
Author(s):  
Ning Hou ◽  
Xiaotong Zhang ◽  
Weiyu Zhang ◽  
Jiawen Xu ◽  
Chunjie Feng ◽  
...  
Keyword(s):  
Solar Radiation ◽  
Dominant Role ◽  
Northern China ◽  
Climate Data ◽  
Surface Solar Radiation ◽  
Term Variation ◽  
Meteorological Observations ◽  
Increasing Demand ◽  
Variation Trends

Downward surface solar radiation (Rs) plays a dominant role in determining the climate and environment on the Earth. However, the densely distributed ground observations of Rs are usually insufficient to meet the increasing demand of the climate diagnosis and analysis well, so it is essential to build a long-term accurate Rs dataset. The extremely randomized trees (ERT) algorithm was used to generate Rs using routine meteorological observations (2000–2015) from the Climate Data Center of the Chinese Meteorological Administration (CDC/CMA). The estimated Rs values were validated against ground measurements at the national scale with an overall correlation coefficient value of 0.97, a mean bias of 0.04 Wm−2, a root-mean-square-error value of 23.12 Wm−2, and a mean relative error of 9.81%. It indicates that the estimated Rs from the ERT-based model is reasonably accurate. Moreover, the ERT-based model was used to generate a new daily Rs dataset at 756 CDC/CMA stations from 1958 to 2015. The long-term variation trends of Rs at 454 stations covering 46 consecutive years (1970–2015) were also analyzed. The Rs in China showed a significant decline trend (−1.1 Wm−2 per decade) during 1970–2015. A decreasing trend (−2.8 Wm−2 per decade) in Rs during 1970–1992 was observed, followed by a recovery trend (0.23 Wm−2 per decade) during 1992–2015. The recovery trends at individual stations were found at 233 out of 454 stations during 1970–2015, which were mainly located in southern and northern China. The new Rs dataset would substantially provide basic data for the related studies in agriculture, ecology, and meteorology.

scholarly journals IKH TURGEN MOUNTAIN GLACIER CHANGE AND 3D SURFACE EXTENTS PREDICTION USING LONG TERM LANDSAT IMAGE AND CLIMATE DATA

2018 ◽  
Vol IV-3 ◽  
pp. 173-176
Author(s):  
Elbegjargal Nasanbat ◽  
Erdenetogtokh Erdenebat ◽  
Bolorchuluun Chogsom ◽  
Ochirkhuyag Lkhamjav ◽  
Lkhagvadorj Nanzad
Keyword(s):  
Air Temperature ◽  
Three Dimensional ◽  
Climate Data ◽  
Mountain Glacier ◽  
Temperature Regimes ◽  
Digital Elevation ◽  
Normalized Difference Snow Index ◽  
Elevation Model ◽  
Variable Precipitation

The glacier is most important the freshwater resources and indicator of the climate change. The researchers noted that during last decades the glacier is melting due to global warming. The study calculates a spatial distribution of protentional change of glacier coverage in the Ikh Turgen mountain of Western Mongolia, and it integrates long-term climate data and satellite datasets. Therefore, in this experiment has tried to estimation three-dimensional surface area of the glacier. For this purpose, Normalized difference snow index (NDSI) was applied to decision tree approach, using Landsat MSS, TM, ETM+ and LC8 imagery for 1975–2016, a surface and slope for digital elevation model, precipitation and air temperature historical data of meteorological station. The potential volume area significantly changed glacier cover of the Ikh Turgen Mountain, and the area affected by highly variable precipitation and air temperature regimes. Between 1972 and 2016, a potential area of glacier area has been decreased in Ikh Turgen mountain region.

scholarly journals Diachronic UAV Photogrammetry of a Sandy Beach in Brittany (France) for a Long-Term Coastal Observatory

2019 ◽  
Vol 8 (6) ◽  
pp. 267 ◽  
Author(s):  
Marion Jaud ◽  
Christophe Delacourt ◽  
Nicolas Le Dantec ◽  
Pascal Allemand ◽  
Jérôme Ammann ◽  
...  
Keyword(s):  
Sandy Beach ◽  
Current Method ◽  
Coastal Hazard ◽  
Digital Elevation ◽  
Coastal Observatory ◽  
Study Case ◽  
Elevation Model ◽  
Operational Modes ◽  
Term Monitoring

In the dual context of coastal hazard intensification and the growing number of stakes exposed to these hazards, coastal observatories are in demand to provide a structured framework dedicated to long-term monitoring. This article describes the drone-based photogrammetry monitoring performed since 2006 on Porsmilin Beach (Brittany, France) in the framework of the DYNALIT (Littoral and Coastline Dynamics) observatory, focusing on data quality and the consistency of long-term time series under the influence of multiple technological evolutions: Unmanned Aerial Vehicles (UAV) platforms with the arrival of electric multirotor drones, processing tools with the development of structure-from-motion (SfM) photogrammetry, and operational modes of survey. A study case is presented to show the potential of UAV monitoring to study storm impacts and beach resilience. The relevance of high-accuracy monitoring is also highlighted. With the current method, an accuracy of 3 cm can be achieved on the digital elevation model (DEM) and the orthophotograph. The question of the representativity and frequency of DEM time points is raised.

Site regions revisited: a climatic analysis of Hills' site regions for the province of Ontario using a parametric method

1996 ◽  
Vol 26 (3) ◽  
pp. 333-354 ◽  
Author(s):  
Brendan G. MacKey ◽  
Daniel W. McKenney ◽  
Yin-Qian Yang ◽  
June P. McMahon ◽  
Michael F. Hutchinson
Keyword(s):  
Clustering Algorithm ◽  
Parametric Method ◽  
Climate Data ◽  
Distributed Models ◽  
Spline Surfaces ◽  
Digital Elevation ◽  
Spatially Distributed ◽  
Forest Planning And Management ◽  
Elevation Model

A climatic analysis was conducted` of Hills' site regions for Ontario using spatially distributed models of long-term, mean monthly climate data. Gridded estimates of eight climatic variables were generated by coupling thin-plate smoothing spline surfaces (fitted as a trivariate function of longitude, latitude, and elevation) to a 1-km resolution digital elevation model of Ontario. The gridded climate estimates were used to characterize the climate of each site region. New climatic classifications for the province were calculated from these data using a clustering algorithm. They were also compared with the existing site region boundaries. The analyses confirm many of the general climatic gradients established by Hills, but also suggest where major revisions should be made. The climatic models present new analytical opportunities for mapping plant–climate response in the context of forest planning and management.

scholarly journals Simulation and comparison of stream power in-channel and on the floodplain in a German lowland area

2014 ◽  
Vol 62 (2) ◽  
pp. 133-144 ◽  
Author(s):  
Song Song ◽  
Britta Schmalz ◽  
Nicola Fohrer
Keyword(s):  
Swat Model ◽  
Peak Discharge ◽  
Stream Power ◽  
Stream Discharge ◽  
Bankfull Discharge ◽  
Digital Elevation ◽  
Lowland Area ◽  
Set Up ◽  
Elevation Model

Abstract Extensive lowland floodplains cover substantial parts of the glacially formed landscape of Northern Germany. Stream power is recognized as a force of formation and development of the river morphology and an interaction system between channel and floodplain. In order to understand the effects of the river power and flood power, HEC-RAS models were set up for ten river sections in the Upper Stör catchment, based on a 1 m digital elevation model and field data, sampled during a moderate water level period (September, 2011), flood season (January, 2012) and dry season (April, 2012). The models were proven to be highly efficient and accurate through the seasonal roughness modification. The coefficients of determination (R2) of the calibrated models were 0.90, 0.90, 0.93 and 0.95 respectively. Combined with the continuous and long-term data support from SWAT model, the stream power both in-channel and on the floodplain was analysed. Results show that the 10-year-averaged discharge and unit stream power were around 1/3 of bankfull discharge and unit power, and the 10-year-peak discharge and unit stream power were nearly 1.6 times the bankfull conditions. Unit stream power was proportional to the increase of stream discharge, while the increase rate of unit in-channel stream power was 3 times higher than that of unit stream power on the floodplain. Finally, the distribution of the hydraulic parameters under 10-years-peak discharge conditions was shown, indicating that only 1-10% of flow stream was generated by floodplain flow, but 40-75% volume of water was located on the floodplain. The variation of the increasing rate of the stream power was dominated by the local roughness height, while the stream power distributed on the floodplain mainly depended on the local slope of the sub-catchment.

scholarly journals Disastrous ice breaks in Eastern Serbia: GIS analysis of their relationship with orographic characteristics

2018 ◽  
pp. 67-75
Author(s):  
Nenad Marković ◽  
Miroslava Marković
Keyword(s):  
Atmospheric Oxygen ◽  
Gis Mapping ◽  
Mapping Software ◽  
Gis Tools ◽  
Digital Elevation ◽  
Forest Division ◽  
Elevation Model ◽  
The One ◽  
The Relationship

At the end of November/beginning of December 2014, an ice wave hit the whole of Eastern Serbia and caused extensive ice and snow breaks in the forest areas managed by SE `Srbijašume` - Forest Estates of Niš, Boljevac, Kruševac, Despotovac and Kučevo. The areas affected were determined by identifying all the affected units of forest division - with the lowest accuracy at the level of forest stands and, where possible by GPS recording in the field in order to ensure greater accuracy. The identified areas were presented in GIS mapping software. The total area affected by ice breaks amounted to 19,419.78 ha. It included 8,301.01 ha of high forests, 8,997.37 ha of coppice forests and 2,121.40 ha of artificially-established stands. Considering the size of the forest area affected by ice breaks on the one hand, and the huge environmental impact of forests on the other hand, this phenomenon may be considered a natural disaster. Having identified the affected forest areas, an analysis of the relationship between orographic characteristics and ice break occurrence was carried out with the use of GIS tools. The following orographic characteristics were studied: the elevation, the terrain aspect and the slope, all obtained from the digital elevation model (DEM) at a resolution of 1 arc-second. Elevation had the greatest influence on the occurrence of ice breaks. The largest area affected (ca.17,000 ha) was in the range from 600 to 900 m above sea level, i.e. in the belt of low-mountain relief. Regarding the aspect of the investigated terrain, the largest areas affected by ice breaks had northern (ca. 4,000 ha) and northeastern aspects (ca. 3,500 ha), while the remaining areas were equally distributed in all other aspects. The slope was not found to have any significant effects on the occurrence of ice breaks. This disaster brought about most severe and extensive consequences in broad-leaved and coniferous ecosystems and the environment in general, with long-term adverse effects such as changing soil water regimes, erosion, declining atmospheric oxygen levels and reduced carbon accumulated in biomass.

scholarly journals PDERL: an accurate and fast algorithm with a novel perspective on solving the old viewshed analysis problem

2020 ◽  
Author(s):  
Chuanjun Wu ◽  
Lingxiao Guan ◽  
Qing Xia ◽  
Gang Chen ◽  
Baohong Shen
Keyword(s):  
Approximation Algorithms ◽  
Coordinate System ◽  
Reference Plane ◽  
Large Area ◽  
Viewshed Analysis ◽  
Urgent Task ◽  
Digital Elevation ◽  
Basic Functions ◽  
New Perspective ◽  
Elevation Model

Abstract Viewshed analysis based on the regular grid digital elevation model (DEM) is one of the basic functions of geographic information systems. Traditional viewshed analysis algorithms are mainly carried out in a geospatial coordinate system, that create complexities when it is necessary to accurately express a perspective relationship. Moreover, it can only reduce the amount of calculation by using approximation methods, which result in decreased accuracy. We found that the error ratio of approximation algorithms is low but uneven and thereby highly likely to result in continuous area visibility errors. Despite the quality of DEM data having improved significantly in the last decade, traditional approximation algorithms have been unable to take full advantage of the improved data. Finding a fast and accurate algorithm has therefore become an urgent task. This study takes a new perspective to solve this problem by establishing a ‘proximity-direction-elevation’ (PDE) coordinate system and proposing a PDE spatial reference line (PDERL) algorithm within it. Many experiments prove that the accuracy of PDERL is the same as the R3 algorithm and its speed is about half that of the XDraw and reference plane algorithms, but much faster than R3. Due to the speed of PDERL, it is now possible and practical to do an accurate large-area DEM-based viewshed analysis.

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