Ergonomics for Interaction Designers: Part 2 | | |
Part 1 of E *IxD set up the conceptual background on why ergonomics is a valuable knowledge area for interaction designers and discussed some of the basics of anthropometrics (designing for fit). We were looking at Eye Height as a critical attribute for positioning the height of a kiosk display, so that a broad range of users could comfortably view the screen. But having the display at an appropriate height for visibility is just addressing one aspect of interaction - the user also needs to control the interface - in this case via a touch screen. | | |
Designing for Multiple Anthropometric Dimensions | | |
There are several body measurements that could be relevant for reaching a touch screen, but a practical one would be Forward Grip Reach distance - roughly the distance from the shoulder axis to the palm of the hand. With those two metrics in mind - eye height and forward grip reach - you could picture any user as the function of two perpendicular lines - a vertical line, representing the individual's eye height, and a horizontal line representing arm reach. This is illustrated above for a range of three different users - note that the wheelchair user has a sitting eye height compared with the two standing users. | | |
While it might seem relatively straightforward as to how to situate the kiosk- place the screen at a distance and height that accommodates the greatest range of users - the story gets more complicated, because, well people are complicated. Not just complicated in a psychological sense, but in an anthropometrical sense as well. The factor that adds complexity is the lack of correlation among anthropometric measurements within people. What do I mean by that? Let's take a step back and think in interaction design terms. | | |
In interface design, one is typically working within the constraints of a display. For example, a common resolution for web browsers is 1024 pixels x 768 pixels. Some older displays might be set at 800x600. So while the specific vertical and horizontal dimensions change, the relationship between height and width, or aspect ratio, remains constant at approximate;y 1.3 in both cases. So if you're taking a design originally intended for 1024x768 and then need to scale it down to 800x600, it will need to be reduced proportionally. | | |
