What is a visualization? The word is problematic, and there have been very few definitions that try to define this field we are working in. More importantly: what is not a visualization? It is easy to argue that anything visual is a visualization in some way – but does that mean anything? Here is a definition of visualization and a few examples to illustrate the different criteria.

The term visualization is used to mean different things in different contexts, and even visualization that is based on data can be done for different reasons and with different goals. Mixing up these different types of visualization leads to misunderstandings and confusion. Here is an attempt at teasing apart the two major types of data-based visualization, and understanding the differences.

While working on the ZIPScribble map, I started to wonder how to untangle the beautifully scribbly lines, and finding the shortest path through all ZIP codes. In computer science, this is called the Travelling Salesman Problem (TSP), and so I decided to make this the Travelling Presidential Candidate Map.

Visualization people often talk about mapping. Mapping is the process that translates data into a visual representation, and the main challenge in the visualization of abstract data. A good mapping is one that leads to insights into the data, while a bad mapping does not. It is important, however, to keep in mind what the purpose of the depiction is, or one runs the risk of applying the wrong standards.

What would happen if you were to connect all the ZIP codes in the US in ascending order? Is there a system behind the assignment of ZIP codes? Are they organized in a grid? The result is surprising and much more interesting than expected.

Visual representations of time are particularly interesting, because they seem so logical. A point in time is a point in the visualization, an interval is a line. But things are not always that simple: planning and temporal uncertainty require more powerful visual tools. Sets of Possible Occurrences (SOPOs) are an example of a visual representation of time that is very flexible and powerful – and totally unintuitive.

Making visualization more aesthetically pleasing is certainly an important goal. Another one is to make visualization a part of our everyday lives. Ambient information displays are a way of doing both, and they are often inspired by pieces of art. But what if the viewers think they are just looking at a picture, and don't realize that it presents information to them?