Analysis of Time Complexities and Accuracy of Depression FillingAlgorithms in DEM
Journal Title: IOSR Journals (IOSR Journal of Computer Engineering) - Year 2015, Vol 17, Issue 3
Abstract
Abstract: The recent development of digital representation has stimulated the development of automaticextraction of topographic and hydrologic information from Digital Elevation Model (DEM). A DEM is used tocreate hydrologic models which can be used for various purposes such as predicting stream discharges, rivernetwork definition, estimating flood extent and timing, locating areas contributing pollutants to a stream, andsimulating the effects of landscape alterations on surface water runoff. DEM is processed to produce accuratestream delineation. The process includes filling of sinks and depressions, treating flat areas and determining flow direction at every pixel. Depressions (or pits) and flat surfaces (or flats) are general types of terrain inraster digital elevation models. Depressions are lower areas surrounded by terrain without outlets and flatsurfaces are areas with no local gradient. The problem with these pits and depressions is that they interruptcontinuous flow paths in DEMs. To avoid these problems, all pits have to be rectified and create adepressionless DEM before calculating flow directions or any related topographic parameters. Variousalgorithms like Jenson and Dominigue, Planchon and Darboux, Carving etc. have been developed to treat thesinks, depressions and flat areas. The conventional methods are computationally intensive and time consuming.Moreover they are inadequate for high resolution DEMs. The conventional algorithms for creating adepressionless DEM have time complexity of O(n2) where n is the number of cells.Drainage networks obtained after processing the DEM should be accurate. At the same time it is desirable tosimplify the automatic extracting procedure with minimum modification to retain its originality. Recentimprovements are successful in reducing the complexity to O(nlogn) with accuracy, minimum space and timerequirement and less modifications to pixels. This survey analyses on various conventional approaches to filldepressions, their time complexities, advantages, limitations and evolution of modern methodologies withimproved time requirements and accuracy.
Authors and Affiliations
Kritika Pathak , Praveen Kaushik
Keywords
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