Like a Memory Lost in Time

Langran and Chrisman (1988) covered various conceptualizations of temporal GIS, stressing temporal topology and the need to visualize temporal structure, trap errors, and minimize data storage requirements. In a topic based on the conceptualization of abstract and multidimensional notions, it was enormously useful for the authors to include simple visualizations of the conceptualizations of time, especially in terms of temporal topology (i.e. how events are connected and related temporally).

One visualization of time that the authors ultimately reject as flawed in several ways is that of showing separate “scenes” or “states” in chronological order. I completely agree that this is a flawed practice primarily because of the hidden topological structure of the “states” (e.g. proof that one state occurred before or after another scene, and the interval between them). However, it is also the simplest for a layperson to understand. The authors drew the analogy of a motion picture, and that is significant because films function much as our own memories do, one scene at a time. We cannot capture events in time as anything other than isolated from one another. When we remember an event, we imagine a single image, followed by another and another if the memory is strong. Likewise, those images are from only one perspective—our own. I mention this as a slight digression only to draw a parallel to GIS. Even if we were to adopt the overlay or multi-polygon methods that the authors recommended, we would be ignoring the fact that mapping (at least traditional, top-down mapping) is drawn from a single perspective and that change, the manifestation of time, happens differently from any given perspective.

– JMonterey

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