• Water Engineering Research
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• v.1 no.3
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• pp.187-197
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• 2000

This paper describes an adaptive quadtree-based 2DH wave-current interaction model which is able to predict wave breaking, shoaling, refraction, diffraction, wave-current interaction, set-up and set-down, mixing processes (turbulent diffusion), bottom frictional effects, and movement of the land-water interface at the shoreline. The wave period-and depth-averaged governing equations are discretised explictly by means of an Adams-Bashforth second-order finite difference technaique on adaptive hierarchical staggered quadtree grids. Grid adaptation is achieved through seeding points distributed according to flow criteria(e.g. local current gradients). Results are presented for nearshore circulation at a sinusoidal beach. Enrichment permits refined modelling of important localised flow features.

• Journal of the Korean Society of Hazard Mitigation
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• v.4 no.2 s.13
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• pp.71-76
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• 2004

To investigate the inundation of tsunamis in the vicinity of a circular island, a numerical model has been developed based on quadtree grids. The governing equations of the model are the nonlinear shallow-water equations. The governing equations are discretized explicitly by using a finite difference leap-frog scheme on adaptive hierarchical quadtree grids. The quadtree grids are generated around a circular island where refined with rectangular or circular domain. Obtained numerical results have been verified by comparing to available laboratory measurements of run-up heights. A good agreement has been achieved.

• Journal of Korean Society for Geospatial Information Science
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• v.19 no.3
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• pp.41-47
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• 2011

Processing of the raw LiDAR data requires the high-end processor, because data form is a vector. In contrast, if LiDAR data is converted into a regular grid pattern by filltering, that has advantage of being in a low-cost equipment, because of the simple structure and faster processing speed. Especially, by using grid data classification, such as Quadtree, some of trees and cars are removed, so it has advantage of modeling. Therefore, this study presents the algorithm for automatic extraction of ground points using Quadtree and refion growing method from LiDAR data. In addition, Error analysis was performed based on the 1:5000 digital map of sample area to analyze the classification of ground points. In a result, the ground classification accuracy is over 98%. So it has the advantage of extracting the ground points. In addition, non-ground points, such as cars and tree, are effectively removed as using Quadtree and region growing method.

• Journal of the Korean Society of Hazard Mitigation
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• v.7 no.2 s.25
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• pp.45-52
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• 2007

In this study, the flood inundations of the Nam River catchment running through the Uiryeong and Haman regions have been simulated using the numerical model based on quadtree grids. The nonlinear Saint Venant equation is employed as the governing equation for a numerical model in this study. The governing equations are discretized explicitly with a finite difference leap-frog scheme on adaptive hierarchical quadtree grids. Results from this study are compared with those of established numerical models such as the HEC-RAS and the FLUMEN. A numerical model is also simulated according to the frequency variations of flood event. Obtained numerical results show good agreements with them of commercial models. It is found from this study that the flood inundations in the studied area can be occurred at a 500 year frequency event.

• 한국방재학회:학술대회논문집
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• 2007.02a
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• pp.163-167
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• 2007

For numerical analysis of a tidal flow, a two-dimensional hydrodynamic model is developed by solving the nonlinear shallow-water equations. The governing equations are discretized explicitly with a finite difference leap-frog scheme and a first-order upwind scheme on adaptive hierarchical quadtree grids. The developed model is verified by applying to prediction of tidal behaviors. The calculated tidal levels are compared to available field measurements. A very reasonable agreement is observed.

• Journal of Korea Water Resources Association
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• v.46 no.6
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• pp.655-666
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• 2013

Lately, intensity and frequency of natural disasters such as flood are increasing because of abnormal climate. Casualties and property damages due to large-scale floods such as Typhoon Rusa in 2002 and Typhoon Maemi in 2003 rapidly increased, and these show the limits of the existing disaster prevention measures and flood forecasting systems regarding irregular climate changes. In order to efficiently respond to extraordinary flood, it is important to provide effective countermeasures through an inundation model that can accurately simulate flood inundation patterns. However, the existing flood inundation analysis model has problems such as excessive take of analysis time and accuracy of the analyzed results. Therefore, this study conducted a flood inundation analysis by using the Gerris flow solver that uses quadtree grid, targeting the Baeksan Levee in the Nakdong River Basin that collapsed because of a concentrated torrential rainfall in August, 2002. Through comparisons with the FLUMEN model that uses unstructured grid among the existing flood inundation models and the actual flooded areas, it determined the applicability and efficiency of the quadtree grid-based flood inundation model of the Gerris flow solver.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.49 no.9
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• pp.538-545
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• 2000

In this paper we proposed a new map construction and path planning method for mobile robot. In our proposed method first we introduced triangular representation map that mobile robot can navigate through shorter path and flexible motion instead of grid representation map for mobile robot navigation. method in which robot can navigate complete space through as short path as possible in unknown environment is proposed. Finally we proposed new path planning method in a quadtree representation map. To evaluate the performance of our proposed new path planning method in a quadtree representation map. To evaluate the performance of our proposed triangular representation map it was compared with the existing distance transform path planning method. And we considered complete coverage navigation and new path planning method through several examples.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.13 no.1
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• pp.1-8
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• 2001

Wave-induced currents drive nearshore transport processes, and hence an accurate understanding of wave-current interaction is required for proper management of coastal zone. This paper presents details of an adaptive quadtree grid based numerical model of the coupled wave climate and depth-averaged current field. The model accounts for wave breaking, shoaling, refraction, diffraction, wave-current interaction, set-up and set-down, mixing processes, bottom friction effects, and movement of land-water interface at the shoreline. The wave period- and depth-averaged governing equations arc discrctized explicitly by means of an Adarns¬Bashforth second-order finite difference technique on adaptive hierarchical staggered quadtree grids. Results from the numerical model are in reasonable agreement with the laboratory data of longshore current generated by oblique waves on a plane beach (Visser 1980, 1991).

• Journal of the Korean Society of Hazard Mitigation
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• v.8 no.3
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• pp.129-136
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• 2008

All measures to cope with flooding rely on flood predictions to some extent. To investigate these predictions such as maximum water level or inundation area, a numerical model has been developed. The governing equations of the model are the two-dimensional Saint-Venant equations. The governing equations are discretized explicitly by using the leap-frog scheme and upwind scheme based on quadtree grids. The predicted numerical results have been verified by comparing to those of a Thacker problem. As a result of verifications, the present model is not only nearly four times as efficient as uniform grids but also in close agreement with the previous models. Next, the developed model is applied to several flood events in the Uiryeong basin. A general tendency is found that as a frequency is increasing, overall water levels including peak water level are increasing. At only a 500 year frequency, maximum water level is higher than 18.5 m. Therefore, it can be predictable that inundation will be generated in a 500 year frequency.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.3
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• pp.136-148
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• 2000

In this work, a general method for the mathematical description of three-dimensional trimmed surface is proposed by introducing the base parametric surface and boundary curves. Since mesh density distribution for the analysis may vary by cases, a grid-based mesh generation algorithm using quadtree is proposed in the present work. For the assurance of connectivity of generated meshes among surfaces, a method for the pre-cleaning of boundary curves has been developed to be used in the automatic generation of the finite elements. In addition, mesh-smoothing algorithm is suggested which can be used in the general trimmed surface. In this algorithm nodes are moved on the original surface by the normal projection in each iterative smoothing procedure.