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BACKGROUND There is great concern within health surveillance, on how to grapple with environmental degradation, rapid urbanization, population mobility and growth. The Internet has emerged as an efficient way to share health information, enabling users to access and understand data at their fingertips. Increasingly complex problems in the health field(More)
BACKGROUND Disease data sharing is important for the collaborative preparation, response, and recovery stages of disease control. Disease phenomena are strongly associated with spatial and temporal factors. Web-based Geographical Information Systems provide a real-time and dynamic way to represent disease information on maps. However, data heterogeneities,(More)
In this paper, we present a formalism for representing spatio-temporal changes and a method for map updates, based on the topological properties of the line Voronoi diagram. This new approach can overcome some of the problems with existing spatio-temporal models. We preserve the spatio-temporal changes in a data structure that combines events and(More)
In this paper, we explore image reconstruction from irregularly spaced samples using natural neighbour interpolation. We sample the image irregularly using techniques based on the Laplacian or the derivative in the direction of the gradient. Local coordinates based on the Voronoi diagram are used in natural neighbour interpolation to quantify the(More)
Local coordinates based on the Voronoi diagram are used in natural neighbour interpolation to quantify the " neighbourliness " of data sites. In an earlier paper, we have extended the natural neighbour or stolen area interpolation technique from ordinary Voronoi diagrams to Voronoi diagrams for sets of points and line segments, by providing direct vectorial(More)
Areal features are of great importance in applications like shore line mapping, boundary delineation and change detection. This research work is an attempt to automate the process of extracting feature boundaries from satellite imagery. This process is intended to eventually replace manual digitization by computer assisted boundary detection and conversion(More)