Georg Röhl

Smartwatches have gotten smaller over the past years, increasing wearing comfort but at the same time posing challenges in terms of human-computer interaction. Direct input via the touchscreen suffers from limited interaction space, content occlusion and the fat finger problem. Physical input modalities on smartwatches such as buttons or rotating crowns provide effortless and intuitive input, but only have limited expressiveness. Buttons only provide binary input and rotating crowns only provide one-dimensional input.

In this thesis, we present a novel input modality that enables two-dimensional con- tinuous input while still providing an unrestricted view of the screen. Our proposed Tilt-Watch measures the distance of the smartwatch towards the wrist at nine points with which an algorithm calculates the inclination in two dimensions.

Previous research on inclination-based input on mobile devices found that users could accurately control the inclination and found it intuitive. To our knowledge, the presented implementation of inclination-based smartwatch input in relation to the forearm has not been explored already. Using a physical prototype that we produced, we were able to evaluate the proposed interaction in a user study. The study found that, on average, participants tilted the smartwatch to a maximum of 25 degrees and preferred tilting over the sides, rather than the corners. Feedback in the user study was generally positive and users quickly understood the interaction. Based on the study, we give design guidelines for future prototypes. Additionally, we implemented two applications to demonstrate the new input capabilities of Tilt-Watch.