The map communication model and critical cartography

(Updated)

The theory that prevailed in cartography until the advent of critical cartography was known as the "map communication model" (MCM). Actually it still persists as a kind of naive folk wisdom today. I say naive because it is accepted as an unexamined assumption, particularly among GIS practitioners and some cartographers. Here's the basic outline as it was prevalent in the 1960s and 70s:




This diagram, taken from Alan MacEachren's 1995 book How Maps Work derives from his earlier work in cartography, which endorsed the MCM. MacEachren, known today for his work on geovisualization, admits in the book that he now rejects the MCM, and goes on to explain his about-face (and his embrace of geovisualization).

The MCM is a processual model that characterizes mapping as a process of transmitting information (geographic information) via the map from the cartographer to the end-user. In order to see what's wrong with that, we have to first make a distinction between information and knowledge. Information is data that lets you make a decision, and since Claude Shannon's classic work on information theory in the 1930s we can define the lowest possible unit of information as two binary digits (0, 1) or bits. For example, if you're waiting in the gas chamber to hear from the governor whether to execute the prisoner, the phone can ring with a "yes" or "no" message. That's information.

This insight allows us to measure information and compare how much information was successfully transmitted via the map. So the focus is information and its transmission, and it lead to a whole subdiscipline of studies that investigate how well maps are communicating their information.

This work was doomed to eventual failure however because unlike computers we don't live in a world of information, we live in a world of knowledge. Knowledge here can be defined as information that has been interpreted in a meaningful way, usually using theory-based assumptions (that is, "categories"). And the map communication model cannot provide any account of knowledge.

Update: Why not? Because knowledge is information in a cultural context. What is a meaningful information signal to one person is meaningless to another. The Greeks, for all their knowledge couldn't understand what foreigners were saying--it was all just "bar, bar, bar." So of course they called them "barbarians." The MCM doesn't account for this context-dependent meaning of information, so to ask generations of college students if they received the information transmission of the map was always going to fail. What was needed was an understanding of maps and mapping in a cultural context.

The second issue problem with the MCM is that it posits a clear distinction between the cartographer and the end-user with the cartographer the source of information. Today we understand that mapping is increasingly done by the user (as in map mashups), especially in thematic data or analytical-GIS contexts. Location maps and atlases however may still be somewhat accurately described as being produced by a professional cadre of cartographers. For example, the maps in your GPS are often extensively road tested by the company.

By far the most interesting work done in cartography however, probably since the great age of surveying ended in the late 18th and 19th centuries, has been thematic. Even many locational maps (say an environmental map of Canada) has thematic purposes. Thematic mapping really took off in the 19th century, although you can find some examples prior to that.

Critical cartography is the investigation of map use from the perspective of maps, knowledge and their socio-political contexts. It often invokes "social theory" in order to examine the categories of knowledge (such as race, territory, boundaries, or identity) that are produced or reproduced by maps. This is a much richer and more satisfying account of mapping than the MCM, and it is also in my opinion a much more accurate one.

Today the MCM can only be considered a relic of a previous time, a kind of evolutionary dead-end of knowledge. Either that or the MCM will come to be incorporated into some much richer account. We now know that maps really don't work like this, as MacEachren recognized in 1995. Critical cartography is emerging as the strongest contender but has yet to prove itself a coherent theory (and its proponents often explicitly reject the idea of a coherent theory so it may never have one) or a definitive set of new practices. This is due more to a surfeit of ideas and approaches than a lack of them however. And at the least we can say that all critical cartography shares a broad acceptance of the politics of mapping; that is, that mapping is a political act or has political outcomes.