Visualization is, according to McCormick et al (1987)... a method of computing. It transforms the symbolic into the geometric, enabling researchers to observe their simulations and computations. Visualization offers a method for seeing the unseen... Visualization embraces both image understanding and image synthesis. That is, visualization is a tool both for interpreting image data fed into a computer, and for generating images from complex multidimensional data sets. It studies those mechanisms in humans and computers which allow them in concert to perceive, use and communicate visual information.

In addition to a variety of disciplines, visualization has received considerable attention in GIS and cartography. However, visualization is not new to cartographers who have long produced maps, which, according to Jiang (1996:2), are a graphic representation of an abstracted reality. In mapping, visual variables are used to abstract, generalize and represent reality where the final product is then perceived through visual thinking.

Although visualization is not new to cartographers, cartography has been affected by the development of modern computer technology. Maps are no longer just a paper product representing data, but also a digital product within a digital mapping environment that can be used for analysis and communication. Digital developments have brought new cartographic visualization tools and functions such as animation, interactive exploration and hypermedia structure - which go beyond representation to analysis (Jiang 1996:2).

Visualization is a powerful tool and helps us humans to understand and communicate data and results, this is logical as the majority of our brain neurons are connected to vision. Cartographic visualization is therefore, according to Jiang (1996:2), a powerful tool for analysis and communication together with visual variables and exploratory actions. 

To exemplify the power of visualization, which of the images on the left allows you to most easily answer the question: Which city is the largest?

Cartographic visualization is concerned with the visual representation of spatial and geographical data. This includes both cognitive action and the use of concrete visual representations to make spatial contexts and problems visible. Cartographic visualization has both a communicative function - by representing data - and an analytical function - by examining and making visible patterns in data.  The functionality of cartographic visualization is therefore partly communicative and partly analytical. Jiang (1996:3) refers to these two components of cartographic visualization as presentation and exploration, where presentation is about presenting known information and communication is about exploring unknown information. 

This means that cartographic visualization is not only a tool after the analysis phase of research. Rather, cartographic visualization can also be used in the analysis phase as an effective tool in transforming information into knowledge - and it is, according to Jiang (1996:4), thanks to new technologies and research in GIS that visualization plays an important role in understanding large data sets and in analytical processes today.

Scientific research is often divided into four stages which according to Jiang (1996:6) are exploration, confirmation, synthesis and presentation. Within these stages, visualization plays different roles. The first two stages, exploration and confirmation, involve visual thinking. This means that visualization is used to help understand and process information, especially when you are unsure of what you are looking for or need to explore. At this stage, it is all about visualizing to create ideas and formulating questions. After these two stages come synthesis and presentation. Here the role of visualization shifts from visual thinking to visual presentation. These phases involve more public actions, where visualization is used for communication. It can, for example, involve using images and graphics to convey finished results and ideas to others (Jiang 1996:6). Visualization is therefore a communication tool and analysis tool, rather than just one and the other.