scholarly journals A computationally efficient depression-filling algorithm for digital elevation models applied to proglacial lake drainage

2016 ◽  
Author(s):  
Constantijn J. Berends ◽  
Roderik S. W. van de Wal
Keyword(s):  
Geographical Area ◽  
Computation Time ◽  
Equation Model ◽  
Limiting Factor ◽  
Computationally Efficient ◽  
Digital Elevation ◽  
Lake Drainage ◽  
Elevation Model ◽  
Flood Fill

Abstract. We present and evaluate several optimizations to a standard flood-fill algorithm in terms of computational efficiency. As an example, we determine the land/ocean-mask for a 1 km resolution digital elevation model (DEM) of North America and Greenland, a geographical area of roughly 7000 by 5000 km (roughly 35 million elements), about half of which is covered by ocean. Determining the land/ocean-mask with our improved flood-fill algorithm reduces computation time by 90 % relative to using a standard stack-based flood-fill algorithm. In another experiment, we use the bedrock elevation, ice thickness and geoid perturbation fields from the output of a coupled ice-sheet–sea-level equation model at 30,000 years before present and determine the extent of Lake Agassiz, using both the standard and improved versions of the flood-fill algorithm. We show that several optimizations to the flood-fill algorithm used for filling a depression up to a water level, that is not defined at forehand, decrease the computation time by up to 99 %. The resulting reduction in computation time allows determination of the extent and volume of depressions in a DEM over large geographical grids or repeatedly over long periods of time, where computation time might otherwise be a limiting factor.

scholarly journals A computationally efficient depression-filling algorithm for digital elevation models, applied to proglacial lake drainage

2016 ◽  
Vol 9 (12) ◽  
pp. 4451-4460 ◽  
Author(s):  
Constantijn J. Berends ◽  
Roderik S. W. van de Wal
Keyword(s):  
Geographical Area ◽  
Ice Sheet ◽  
Computation Time ◽  
Equation Model ◽  
Limiting Factor ◽  
Dynamical Process ◽  
Computationally Efficient ◽  
Digital Elevation ◽  
Lake Drainage ◽  
Flood Fill

Abstract. Many processes govern the deglaciation of ice sheets. One of the processes that is usually ignored is the calving of ice in lakes that temporarily surround the ice sheet. In order to capture this process a “flood-fill algorithm” is needed. Here we present and evaluate several optimizations to a standard flood-fill algorithm in terms of computational efficiency. As an example, we determine the land–ocean mask for a 1 km resolution digital elevation model (DEM) of North America and Greenland, a geographical area of roughly 7000 by 5000 km (roughly 35 million elements), about half of which is covered by ocean. Determining the land–ocean mask with our improved flood-fill algorithm reduces computation time by 90 % relative to using a standard stack-based flood-fill algorithm. This implies that it is now feasible to include the calving of ice in lakes as a dynamical process inside an ice-sheet model. We demonstrate this by using bedrock elevation, ice thickness and geoid perturbation fields from the output of a coupled ice-sheet–sea-level equation model at 30 000 years before present and determine the extent of Lake Agassiz, using both the standard and improved versions of the flood-fill algorithm. We show that several optimizations to the flood-fill algorithm used for filling a depression up to a water level, which is not defined beforehand, decrease the computation time by up to 99 %. The resulting reduction in computation time allows determination of the extent and volume of depressions in a DEM over large geographical grids or repeatedly over long periods of time, where computation time might otherwise be a limiting factor. The algorithm can be used for all glaciological and hydrological models, which need to trace the evolution over time of lakes or drainage basins in general.

scholarly journals Compartimentação dos elementos do relevo da bacia hidrográfica do arroio Pantanoso – Canguçu/RS, através da proposta dos geomorphons

2020 ◽  
Vol 13 (2) ◽  
pp. 713
Author(s):  
Danilo Da Silva Dutra ◽  
André Ricardo Furlan ◽  
Luís Eduardo De Souza Robaina
Keyword(s):  
Digital Elevation Model ◽  
River Basin ◽  
Spatial Resolution ◽  
Advantages And Disadvantages ◽  
Digital Elevation ◽  
Relief Elements ◽  
Gis Environment ◽  
Elevation Model

O relevo é a base onde todas as populações vivem e desenvolvem suas atividades, derivando dessa relação vantagens e desvantagens, daí a importância de conhecê-lo através do estudo de suas diferentes formas e elementos. Nesse contexto insere-se a importância de metodologias para o seu estudo, sendo que atualmente vivencia-se a expressividade de dados disponíveis para aplicação de geoprocessamento. A partir das geotecnologias pode-se empreender diversas análises sobre o relevo, destacando-se nesse contexto, a proposta dos geomorphons a qual foi aplicada na bacia hidrográfica do arroio Pantanoso. O objetivo da pesquisa é a identificação e análise dos elementos do relevo definido por geomorphons, quais sejam: 1) Planos, 2) Picos, 3) Cristas, 4) Ressaltos, 5) Crista secundária, 6) Encostas, 7) Escavado, 8) Base de encosta, 9) Vales e 10) Fosso. A determinação dos geomorphons foi a partir do processamento em ambiente SIG do Modelo Digital de Elevação (MDE) do Shuttle Radar Topograph Mission (SRTM) com resolução espacial 3 arcsec (90 metros), “L” Lookup (distância em metros) definiu-se como de 20 pixels (1800 metros) e o “T” Theresholdt (nivelamento em graus) definiu-se em 2º. Para visualização do comportamento dos elementos do relevo na área de estudo realizaram-se trabalhos de campo, o que contribuiu para evidenciar a padronização desses elementos. Os quatro elementos geomorphons mais representativos são encostas, vales, cristas e planos. Subdivision of relief elements through the proposal of geomorphons: river basin of arroio Pantanoso - Canguçu/RS A B S T R A C TRelief is the basis where all populations live and develop their activities, deriving from this relation advantages and disadvantages, hence the importance of knowing it through the study of its different forms and elements. In this context, the importance of methodologies for its study is inserted and geoprocessing application for data available for is currently experienced. From the geotechnologies one can undertake several analyzes on the relief, highlighting in this context, the proposal of the geomorphons which was applied in Pantanoso stream basin. The objective of the research is to identify and analyze the elements of the relief defined by geomorphons, namely: 1) Flats, 2) Peaks, 3) Ridges, 4) Shoulders, 5) Spurs, 6)Slopes, 7) Hollows, 8) Footslope, 9) Valley and 10) Pits. The determination of the geomorphons was based on the GIS environment of the Shuttle Radar Topograph Mission (SRTM) Digital Elevation Model (DEM) with spatial resolution 3 arcsec (90 meters), "L" Lookup (distance in meters) was defined as of 20 pixels (1800 meters) and the "T" Theresholdt (leveling in degrees) was defined in 2º. In order to visualize the behavior of the relief elements in the study area, fieldwork was carried out, which contributed to the standardization of these elements. The four most representative geomorphons, which are: Slopes, Valleys, Ridges and Flat.Keywords: SIG, Geomorphons; Canguçu/RS; relief

scholarly journals Sensitivity analysis of the DEM resolution and effective parameters of runoff yield in the SWAT model: a case study

2019 ◽  
Vol 69 (1) ◽  
pp. 39-54 ◽  
Author(s):  
Mohammad Nazari-Sharabian ◽  
Masoud Taheriyoun ◽  
Moses Karakouzian
Keyword(s):  
Sensitivity Analysis ◽  
Assessment Tool ◽  
Swat Model ◽  
Computation Time ◽  
Effective Parameters ◽  
Digital Elevation ◽  
Elevation Model ◽  
The Impact ◽  
Reduce Computation Time

Abstract This study investigates the impact of different digital elevation model (DEM) resolutions on the topological attributes and simulated runoff, as well as the sensitivity of runoff parameters in the Mahabad Dam watershed in Iran. The watershed and streamlines were delineated in ArcGIS, and the hydrologic analyses were performed using the Soil and Water Assessment Tool (SWAT). The sensitivity analysis on runoff parameters was performed, using the Sequential Uncertainties FItting Ver. 2 algorithm, in the SWAT Calibration and Uncertainty Procedures (SWAT-CUP) program. The results indicated that the sensitivity of runoff parameters, watershed surface area, and elevations changed under different DEM resolutions. As the distribution of slopes changed using different DEMs, surface parameters were most affected. Furthermore, higher amounts of runoff were generated when DEMs with finer resolutions were implemented. In comparison with the observed value of 8 m3/s at the watershed outlet, the 12.5 m DEM showed more realistic results (6.77 m3/s). Comparatively, the 12.5 m DEM generated 0.74% and 2.73% more runoff compared with the 30 and 90 m DEMs, respectively. The findings of this study indicate that in order to reduce computation time, researchers may use DEMs with coarser resolutions at the expense of minor decreases in accuracy.

Determination of the drainage structure of a watershed using a digital elevation model and a digital river and lake network

2001 ◽  
Vol 240 (3-4) ◽  
pp. 225-242 ◽  
Author(s):  
R Turcotte ◽  
J.-P Fortin ◽  
A.N Rousseau ◽  
S Massicotte ◽  
J.-P Villeneuve
Keyword(s):  
Digital Elevation Model ◽  
Digital Elevation ◽  
Elevation Model

Investigating the Impacts of DEM Type, Resolution, and Noise on Extracted Hydro-Geomorphologic Parameters of Watersheds via GIS

2018 ◽  
pp. 133-175
Author(s):  
Vahid Nourani ◽  
Safa Mokhtarian Asl ◽  
Maryam Khosravi Sorkhkolaee ◽  
Aida Hosseini Baghanam ◽  
Masoud Mehrvand
Keyword(s):  
Water Resources ◽  
Catchment Area ◽  
Hydrological Modeling ◽  
Integrated Management ◽  
Quality Data ◽  
Distributed Modeling ◽  
Digital Elevation ◽  
Topographic Attributes ◽  
Elevation Model

Water resources management is dependent on knowledge and understanding of water quantity and quality information with the latest developments in information technology such as geographic information system (GIS) to develop effective hydrological modeling within the water-based systems. The efficiency of such hydrological modeling relies on the accuracy of applied data. In this way, the application of low-quality data in developing models for integrated management of water resources can impose irreparable financial and human resources and environmental costs in the catchment area. Thus, in regions that shortage of data is the issue, semi-distributed modeling is a useful tool. In this chapter, three aims are followed: (1) effect of digital elevation model (DEM) type and resolution on extracted hydro-geomorphologic parameters, (2) effect of wavelet-based de-noising method on extracted hydro-geomorphologic parameters, (3) determination of the optimal cell size to extract topographic attributes with good agreement to the real features.

scholarly journals Hierarchical Sea-Land Segmentation for Panchromatic Remote Sensing Imagery

2017 ◽  
Vol 2017 ◽  
pp. 1-8 ◽  
Author(s):  
Long Ma ◽  
Nouman Q. Soomro ◽  
Jinjing Shen ◽  
Liang Chen ◽  
Zhihong Mai ◽  
...  
Keyword(s):  
State Of The Art ◽  
Temporal Variations ◽  
Memory Storage ◽  
Computationally Efficient ◽  
High Resolution Data ◽  
Digital Elevation ◽  
Segmentation Approach ◽  
Fully Automatic ◽  
Elevation Model ◽  
Coarse To Fine

Automatic sea-land segmentation is an essential and challenging field for the practical use of panchromatic satellite imagery. Owing to the temporal variations as well as the complex and inconsistent intensity contrast in both land and sea areas, it is difficult to generate an accurate segmentation result by using the conventional thresholding methods. Additionally, the freely available digital elevation model (DEM) also difficultly meets the requirements of high-resolution data for practical usage, because of the low precision and high memory storage costs for the processing systems. In this case, we proposed a fully automatic sea-land segmentation approach for practical use with a hierarchical coarse-to-fine procedure. We compared our method with other state-of-the-art methods with real images under complex backgrounds and conducted quantitative comparisons. The experimental results show that our method outperforms all other methods and proved being computationally efficient.

TGF: A New MATLAB-based Software for Terrain-related Gravity Field Calculations

2020 ◽  
Author(s):  
Meng Yang ◽  
Christian Hirt ◽  
Roland Pail
Keyword(s):  
Gravity Field ◽  
Adaptive Algorithm ◽  
Computation Time ◽  
Spherical Approximation ◽  
Constant Density ◽  
The Earth ◽  
Digital Elevation ◽  
Gravity Effects ◽  
Residual Terrain Modelling

<p>With knowledge of geometry and density-distribution of topography, the residual terrain modelling (RTM) technique has been broadly applied in geodesy and geophysics for the determination of the high-frequency gravity field signals. Depending on the size of investigation areas, challenges in computational efficiency are encountered when using an ultra-high-resolution digital elevation models (DEM) in the evaluation of Newtonian integration. This paper presents a new MATLAB-based program, terrain gravity field (TGF), for the accurate and efficient determination of the terrain-related gravity field based on an adaptive algorithm. Depending on the attenuation character of gravity field with distance, the adaptive algorithm divides the integration masses into four zones, and adaptively combines four types of geometries and DEMs with different spatial resolutions. The most accurate but least efficient polyhedron together with the finest DEM are only considered for the innermost zone, while prism approximation for the second zone, the third zone with the more efficient tesseroid and a coarse DEM, and the most efficient but least accurate point-mass with the coarsest DEM for distant masses. Compared to some publicly available algorithms depending on one type of geometric approximation, the TGF achieves accurate modelling of gravity field and greatly reduces the computation time. Besides, the TGF software allows to calculate ten independent elements of gravity field, supports two types of density inputs (constant density value and digital density map), and considers the sphericity of the Earth by involving spherical approximation and ellipsoidal approximation. Further to this, the TGF software is also capable of delivering the gravity field of full-scale topographic gravity field implied by masses between the Earth’s surface and mean sea level. Results from internal and external numerical validation experiments of TGF confirmed its accuracy of sub-mGal level. Based on TGF, the trade-off between accuracy and efficiency, values for the spatial resolution and extension of topography models are recommended. The TGF software has been extensively tested and recently been applied in the SRTM2gravity project to convert the global 3” SRTM topography to implied gravity effects at 28 billion computation points. This confirms TGF the capability of dealing with large datasets.</p>

Changes in topography of Cracow centre during the last millennium, Poland

2020 ◽  
Author(s):  
Adam Łajczak ◽  
Roksana Zarychta
Keyword(s):  
Laser Scanning ◽  
Spatial Differentiation ◽  
Contour Line ◽  
Last Millennium ◽  
Small Areas ◽  
Modern Development ◽  
Digital Elevation ◽  
Spatial Aspect ◽  
Elevation Model

<p>In the investigations on changes of topography of historical town centres the attention is focused on estimation of the thickness of cultural layers and on determination of changes of land topography in selected small areas or along profiles. Less often the attention is focused on determination of spatial differentiation of these changes within larger parts of centres of historical towns. The aim of presentation is to reconstruct differences between paleotopography and modern topography of historical centre of Cracow, Poland, during the last millennium. The paleotopography studied represents situation before the 10<sup>th</sup> century without any significant human impact. The paleotopography was reconstructed using the published contour-line maps basing on archeological and geoengineering investigations and showing the roof of in situ fossil soil. The preliminary contour-line map represented a Digital Elevation Model (DEM) base map. DEM from aerial laser scanning (ALS DEM) shows the contemporary topography of Cracow centre. The application of selected morphometric indices makes it possible to describe quantitatively changes in spatial aspect in altitude, local relative height, slope, and aspect classes. The analysis of changes of values of the studied elements of topography shows that in the scale of the whole study area, the changes are directed towards the flattening of the area. In more local scale, the areas of flattening trends are adjacent to the areas of undulating trends.</p><p>Only few papers discuss the changes in town topography as the consequence of long lasting increase of anthropogenic deposits resulting in land flattening or undulation increase. These papers, however, do not consider the quantitative evaluation of many-sided character of this process. Similar remarks concern the papers on modern development of towns. Revealed in the newest literature positive vertical changes in the topography of Cracow centre which occurred during the last millennium show large spatial differentiation and range to over 10 m. In the older literature the value 5 m was so far suggested in the area of Old Town in Cracow. Other parameters of changes in Cracow topography studied by the Authors have never been considered in literature.</p>

scholarly journals Validation of High-resolution and Simple River Monitoring Technique using UAV-SFM Method

2020 ◽  
Vol 8 (5) ◽  
pp. 5409-5414
Keyword(s):  
Correction Method ◽  
Coefficient Of Determination ◽  
Error Analyses ◽  
Accuracy And Precision ◽  
Digital Elevation ◽  
Aerial Vehicle ◽  
Elevation Model ◽  
Submerged Area ◽  
First Time

This study tested the accuracy and precision of the UAV-SfM method, an automated photogrammetry technique called SfM (Structure from Motion) using multiple pictures taken by UAV (Unmanned Aerial Vehicle), in a section of Saba river, Yamaguchi, Japan. The method was applied in the submerged area as well as in the exposed area, taking into account the refraction at the water surface, for the first time in domestic rivers. When the resultant DEM (Digital Elevation Model) is considered as the map of riverbed elevation, the RMS (Root Mean Square) error and R2 (coefficient of determination) of UAV-SfM were 0.165 m and 0.93, respectively. In pixels with thick algae cover, large apparent overestimations reaching 0.351 m at maximum were observed because UAV-SfM actually measures the algae surface elevation, not the riverbed elevation. Error analyses also showed that the refraction correction method adopted in this study is working well in spite of its simplicity.

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