Mapping Time

Abstract

Geographic data include locations of places and events, and spatial changes of phenomena. Time is an essential element in tracking changes and in analyzing them to establish patterns, to predict future events, or to explain occurrences. Time information, however, comes in different forms when geographic data are collected. It may be a simple time stamp: the date when a city was incorporated. It may be an expression of duration: how long the forest fires burned. Geographic data may be collected at regular intervals, e.g., the decennial census in the USA. Or they may be recorded only when a change occurs, e.g. a hillside is cut away for development and the change is recorded on the topographic map. Time may be used as a distance measure, and space may be used as a delineator of time. Because of these variations in the uses of time, various types of time information must be understood and the understanding incorporated into methods of producing maps so as to show the information clearly and efficiently. This research categorizes time as it is used by geographers and as it appears in different forms on maps. The categories are Moments, Duration, Structured Time, Time as Distance, and Space as Clock. Each of these categories defines a particular use of time and provides the basic symbology that is used to represent spatiotemporal information on maps according to the spatial dimensions (point, line, or area) typically available to cartographers. The framework for the symbolization of temporal information on maps presented in this research establishes two things: the various categories of time found in geography; and the spatial dimensions and symbology available to the cartographer for representing spatiotemporal information on maps.