For an air traffic controller, bright spots on a radar screen often indicate the need for decisive action. It is the controller’s job to closely monitor everything within his scope to ensure successful outcomes. Using a radar diagram as a method for discovery in design can work in much the same way. This method provides a template where people can organize items within a given scope based on how important or relevant they consider them to be. So, whether you are dealing with concrete items or abstract concepts, the diagram is a useful way for people to assign rank.
Reading the diagram is straightforward: the things people assign to the center circle (which is deliberately small) are most significant, while those in successive circles are less so, and those outside the diagram are not even blips on their radar. The format forces participants to express clear distinctions between what is primary, what is secondary, and what is tertiary.