Читать книгу Mapping Time - Menno-Jan Kraak - Страница 6

All maps tell time. They portray a particular moment in the past, present, or even the future. For example, a map might show the boundaries of European countries in the early nineteenth century. It might depict a street plan or a future high-speed rail network in the present.

How maps represent time, however, can be ambiguous. The date 2012 on a street map, for example, may refer to the moment when the map’s dataset was collected, the date that the map was drawn, or the date that the final version was published. Provenance matters, too. A map depicting the spread of the Bubonic Plague in fourteenth century Europe might be a new map based on current knowledge or an old map rooted in the past. Maps depicting future railroad plans may have been composed today or at the end of the last century. References to time, like space, are also scale dependent. A map reader must pay attention to the temporal units used, such as weeks, months, or years. Sometimes, one is left to puzzle over which calendar system mapmakers have applied.

People today have high expectations for the maps they use. Whenever they look at maps, they expect real-time content, especially from maps displayed online. Of course, such expectations cannot be met in all circumstances, which vary according to both location and topic. The proliferation of in situ and human sensors promises to fully realize these expectations. For example, current technology allows people to observe in near real-time the water levels in Dutch rivers or the whereabouts of people through social media.

The maps featured here provide snapshots that display moments in time. Often, people look at maps in order to understand change itself, in processes and dynamics. Better-known examples of these kinds of maps come from social geography (such as migration, trade, or traffic) and physical geography (such as landslides, continental drift, or weather). In creating dynamic maps, cartographers ask questions such as the following: How have the borders in Europe changed since the nineteenth century? What is the traffic situation in the city during the day? When will the thunderstorm reach the recreation area?

The predominance of questions with a temporal component has grown, motivated by the increasing availability of information, which has stimulated demand for information still further. How do we best map change? More specifically, how do we design a map so that its temporal component properly narrates the story of change? This question, for me, owes its inspiration to Charles Joseph Minard’s map of the French invasion of Russia (see figure I-1). His map has enjoyed longstanding fame in both statistics (Funkhouser 1937) and cartography (Robinson 1967). Edward Tufte, an expert on information design, has helped to make it more widely known. In his book, The Visual Display of Quantitative Information (Tufte 1983), he analyzes Minard’s map in a section devoted to the “Narrative Graphics of Space and Time,” observing “how multivariate complexity can be subtly integrated into graphical architecture, integrated so gently and unobtrusively that the viewers are hardly aware that they are looking into a world of four or five dimensions” (Tufte 1983).

Tufte’s contention that Minard’s map “may well be the best statistical graphic ever drawn” (Tufte 1983) probably encouraged many readers to use this map to create their own variations of it using modern techniques (see chapter 2, section 2.2). Moreover, the quote implies a challenge: Can Minard’s map be improved?

Minard’s map originated as one of two that he drew in 1869 (see figure 1-1). The now-forgotten second chart depicts Hannibal’s Italian campaign in 218 BC during the Second Punic War. Together, the maps compare the huge losses that Hannibal’s and Napoleon’s armies suffered; Hannibal’s army of 96,000 soldiers shrank to 26,000 but fared better than Napoleon’s, whose 422,000 soldiers were decimated to a mere 10,000. Minard created his maps to protest the senselessness of war, something he personally experienced during the Napoleonic Wars at the siege of Antwerp in 1813 while he was posted there.

Figure I-1. Minard’s map: Top, Hannibal’s Italian campaign in 218 BC during the Second Punic War (“Carte figurative des pertes successives en hommes de l’armé qu’Annibal conduisit d’Espagne en Italie en traversant les Gaules [selon Polybe]”). Bottom, Napoleon’s Russian campaign in 1812 (“Carte Figurative des pertes successives en hommes de l’Armée Française dans la campagne de Russie 1812-1813”), published in 1869.

Minard’s map, by design a simplification and abstraction of reality, combines point, line, area symbols, and text. These symbols represent geographic objects, like houses, rivers, or administrative regions. Three components characterize each object: location, attribute, and time. Figure I-2a provides an example of Minard’s composition. Here, the map represents its object, the bridge at the Berezina River near the town of Studianka, with a symbol, a yellow dot. It defines the bridge’s location in longitude and latitude and lists its attributes, such as the material used to make it. It bears a time stamp, which establishes the point at which the information was considered valid.

Within a map, time can have various aspects, as figure I-2b shows. One aspect reveals the map’s topic. Another reveals the age of the document itself. Still another bears the age of the data used to make up the map’s content. These shifting aspects of time change the questions cartographers must ask in order to build the map. Of its topic, we might ask if this topic refers to past, present, or future phenomena. Turning to its age, we might ask if this a historical map, a recent map, or a current map. Finally, answering when a map’s data was collected changes the way we understand other aspects like where, why, and how. Time refers not only to map elements but to process, too. This suggests questions about the moment of data collection, map design, or display. Some aspects of time may not even occur to most map users who probably are not aware of the time gaps that separate map production phases that affect their “real-time” content. Yet all these factors change the way in which a map represents time.

Figure I-2. Maps and time. Maps represent geographic objects using symbols. Time presents many faces in maps. The moment in time represented could be a historical event, current situation, or future infrastructure plan. A map’s age matters, too, for a chart drawn two centuries ago differs significantly from an online map just recently made. People expect up-to-date, real-time content in their contemporary maps, although even in these they must tolerate some delay between data collecting, design, and display.