Functional Cartography

One of the great things about working at a company with both interaction and industrial designers is that when collaboratively designing a device, you have better control over where bits of its functionality are located: in the hardware or the software. At Kicker, we call the activity of figuring out where a feature “lives” Functional Cartography.

As an example, take turning off the ringer on your mobile phone. In many handsets, that functionality lives digitally, onscreen (sometimes via far too many menus). On the iPhone, it’s a physical switch on side of the device. The feature is the same; its controls can live in either place depending on what the designers (and manufacturers) decide.

Functional Cartography at Kicker works like this: Once we have a list of functionality and an understanding of their context of use, we set about determining whether the controls for that functionality should be physical, digital (onscreen controls), or some hybrid of the two (e.g. soft keys). (Personally, I hate soft keys and will always argue against them. With their cost dropping and their availability rising, touchscreens obviate the need to have soft keys in many instances.) The functionality might also be accessed in both ways.

How the functional cartography is decided depends on a number of factors: context, priority, cost, ergonomics, aesthetics, and tangibility:

  • Context. When and where will the functionality be used? Does it need to be accessed rapidly? In the dark or unseen (in a pocket or behind the device)? With the screen idle or off?
  • Priority. How important is this piece of functionality? Does it always need to be available? Is it used very often?
  • Cost. How much does it cost (in terms of money, resources, weight, and power consumption) to have a screen at all? Or an additional physical control?
  • Ergonomics. For the target users, what is the easiest physically to use?
  • Aesthetics. Is another physical control going to ruin the form? Is the screen we need going to be too large?
  • Tangibility. How tactile does the feature need to be? Does it need to have the presence (and resulting affordance) of a physical control, or does a touchscreen (perhaps with haptic feedback) work as well?

The resulting functional cartography can be documented in a variety of ways. Often a simple table will suffice, with columns for Physical and Digital, and the functionality in rows below, showing in which category they will be placed. Another way to document (if you are farther along in the design process) is an illustration or sketch of the physical form, noting the functionality that resides on and off-screen.

Once a functional cartography is done, it becomes easier to sketch, model, and prototype the device, since more focus has been applied. A functional cartography need not be set in stone, however. During prototyping or modeling, it might become clear that a physical control is necessary, or visa versa. But a functional cartography will at least give a starting place to distribute features and discuss the interplay between form and function.