• Spatial Information Research
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• v.10 no.3
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• pp.439-453
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• 2002

Researches using DEM are actively progressed in field of water resource, and especially the extraction of watershed and stream based on topographic and hydrologic analysis, is widely used in GIS analysis recently. However, because it is extracted that watershed which is type of sliver polygon and stream which is type of straight line in low topographic region, they're not efficient for application. This study determined buffer zone from stream and tried smooth elevation change to buffer zone in order to efficiently extract abnormal watershed and stream being occurred in low topographic region. Especially, we applied equal-distance assignment model using Voronoi Diagram to determine smooth elevation change. Also, we extracted watershed and stream using stream recognition DEM and origional DEM, and evaluated the efficiency of research through comparing the shape of watershed and stream in low topographic region.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.32 no.2
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• pp.87-93
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• 2014

Cadastral parcel objects as polygons are fundamental dataset which represent land administration and management of the real world. Thus it is necessary to assure topological seamlessness of cadastral datasets which means no overlaps or gaps between adjacent parcels. However, the problem of overlaps or gaps are frequently found due to non-coinciding edges between adjacent parcels. These erroneous edges are called uncertain edges, and polygons containing at least one uncertain edge are called uncertain polygons. In this paper, we proposed a new algorithm to efficiently search parcels of uncertain polygons between two adjacent cadastral datasets. The algorithm first selects points and polylines around adjacent datasets. Then the Constrained Delaunay Triangulation (CDT) is applied to extract triangles. These triangles are tagged by the number of the original cadastral datasets which intersected with the triangles. If the tagging value is zero, the area of triangles mean gaps, meanwhile, the value is two, the area means overlaps. Merging these triangles with the same tagging values according to adjacency analysis, uncertain edges and uncertain polygons could be found. We have performed experimental application of this automated derivation of partitioned boundary from a real land-cadastral dataset.