ALBERT

Description:    The space–time prism demarcates all locations in space–time that a mobile object or person can occupy during an episode of potential or unobserved movement. The prism is central to time geography as a measure of potential mobility and to mobile object databases as a measure of location possibilities given sampling error. This paper develops an analytical approach to assessing error propagation in space–time prisms and prism–prism intersections. We analyze the geometry of the prisms to derive a core set of geometric problems involving the intersection of circles and ellipses. Analytical error propagation techniques such as the Taylor linearization method based on the first-order partial derivatives are not available since explicit functions describing the intersections and their derivatives are unwieldy. However, since we have implicit functions describing prism geometry, we modify this approach using an implicit function theorem that provides the required first-order partials without the explicit expressions. We describe the general method as well as details for the two spatial dimensions case and provide example calculations. Content Type Journal Article Category Original Article Pages 327-354 DOI 10.1007/s10109-010-0139-z Authors Tetsuo Kobayashi, Department of Geography, University of Utah, 260 S. Central Campus Dr. Room 270, Salt Lake City, UT 84112-9155, USA Harvey J. Miller, Department of Geography, University of Utah, 260 S. Central Campus Dr. Room 270, Salt Lake City, UT 84112-9155, USA Walied Othman, Theoretical Computer Science Group, Department WNI, Hasselt University, Agoralaan, Gebouw D, 3590 Diepenbeek, Belgium Journal Journal of Geographical Systems Online ISSN 1435-5949 Print ISSN 1435-5930 Journal Volume Volume 13 Journal Issue Volume 13, Number 4