Stefan Diewald

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We report on our extended research on GymSkill, a smartphone system for comprehensive physical exercising support, from sensor data logging, activity recognition to on-top skill assessment, using the phone’s built-in sensors. In two iterations, we used principal component breakdown analysis (PCBA) and criteria-based scores for individualized and(More)
Self-reporting techniques, such as data logging or a diary, are frequently used in long-term studies, but prone to subjects' forgetfulness and other sources of inaccuracy. We conducted a six-week self-reporting study on smartphone usage in order to investigate the accuracy of self-reported information, and used logged data as ground truth to compare the(More)
Vision-based approaches for mobile indoor localization do not rely on the infrastructure and are therefore scalable and cheap. The particular requirements to a navigation user interface for a vision-based system, however, have not been investigated so far. Such mobile interfaces should adapt to localization accuracy, which strongly relies on distinctive(More)
In this position paper, we present MoCCha, a mobile campus application used not only as a subject of research, but as a research platform for a number of scientific disciplines. Following the approach of using an app that is available from a mobile application store, we want to study user behavior in the field with the aim for ecological validity that(More)
With physical mobile interaction techniques, digital devices can make use of real-world objects in order to interact with them. In this paper, we evaluate and compare state-of-the-art interaction methods in an extensive survey with 149 participants and in a lab study with 16 participants regarding efficiency, utility and usability. Besides radio(More)
People feel very comfortable when they interact with their mobile devices by using natural user interfaces (NUIs). However, when they enter a vehicle, this feeling degrades rapidly, since many in-vehicle infotainment systems (IVIs) still do not offer natural user interfaces and use different user interface interaction paradigms. For this reason, we show how(More)
MobiDics is a mobile didactic platform for smartphones and tablets, targeted at university teaching staff. It eases structuring courses and the targeted application of didactic techniques to support learning, in order to improve the quality of university education. MobiDics enables peer learning through cooperative experience sharing and academic exchange(More)
We present GymSkill, a personal trainer for ubiquitous monitoring and assessment of physical activity using standard fitness equipment. The system records and analyzes exercises using the sensors of a personal smartphone attached to the gym equipment. Novel fine-grained activity recognition techniques based on pyramidal Principal Component Breakdown(More)
Vision-based approaches are a promising method for indoor navigation, but prototyping and evaluating them poses several challenges. These include the effort of realizing the localization component, difficulties in simulating real-world behavior and the interaction between vision-based localization and the user interface. In this paper, we report on initial(More)