Publication statistics

Pub. period:2005-2012
Pub. count:10
Number of co-authors:23


Number of publications with 3 favourite co-authors:

Martin Halvey:
Alexandra I. Cristea:
Krishna Chandramouli:



Productive colleagues

Craig Stewart's 3 most productive colleagues in number of publications:

Stephen A. Brewste..:108
Matt Jones:63
Michael Rohs:46

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Craig Stewart


Publications by Craig Stewart (bibliography)

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Stewart, Craig, Hoggan, Eve, Haverinen, Laura, Salamin, Hugues and Jacucci, Giulio (2012): An exploration of inadvertent variations in mobile pressure input. In: Proceedings of the 14th Conference on Human-computer interaction with mobile devices and services 2012. pp. 35-38.

This paper reports the results of an exploratory study into inadvertent grip pressure changes on mobile devices with a focus on the differences between static lab-based and mobile walking environments. The aim of this research is to inform the design of more robust pressure input techniques that can accommodate dynamic mobile usage. The results of the experiment show that there are significant differences in grip pressure in static and walking conditions with high levels of pressure variation in both. By combining the pressure data with accelerometer data, we show that grip pressure is closely related to user movement.

© All rights reserved Stewart et al. and/or ACM Press

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Hoggan, Eve, Stewart, Craig, Haverinen, Laura, Jacucci, Giulio and Lantz, Vuokko (2012): Pressages: augmenting phone calls with non-verbal messages. In: Proceedings of the 2012 ACM Symposium on User Interface Software and Technology 2012. pp. 555-562.

ForcePhone is a mobile synchronous haptic communication system. During phone calls, users can squeeze the side of the device and the pressure level is mapped to vibrations on the recipient's device. The pressure/vibrotactile messages supported by ForcePhone are called pressages. Using a lab-based study and a small field study, this paper addresses the following questions: how can haptic interpersonal communication be integrated into a standard mobile device? What is the most appropriate feedback design for pressages? What types of non-verbal cues can be represented by pressages? Do users make use of pressages during their conversations? The results of this research indicate that such a system has value as a communication channel in real-world settings with users expressing greetings, presence and emotions through pressages.

© All rights reserved Hoggan et al. and/or ACM Press

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Rogers, Simon, Williamson, John, Stewart, Craig and Murray-Smith, Roderick (2011): AnglePose: robust, precise capacitive touch tracking via 3d orientation estimation. In: Proceedings of ACM CHI 2011 Conference on Human Factors in Computing Systems 2011. pp. 2575-2584.

We present a finger-tracking system for touch-based interaction which can track 3D finger angle in addition to position, using low-resolution conventional capacitive sensors, therefore compensating for the inaccuracy due to pose variation in conventional touch systems. Probabilistic inference about the pose of the finger is carried out in real-time using a particle filter; this results in an efficient and robust pose estimator which also gives appropriate uncertainty estimates. We show empirically that tracking the full pose of the finger results in greater accuracy in pointing tasks with small targets than competitive techniques. Our model can detect and cope with different finger sizes and the use of either fingers or thumbs, bringing a significant potential for improvement in one-handed interaction with touch devices. In addition to the gain in accuracy we also give examples of how this technique could open up the space of novel interactions.

© All rights reserved Rogers et al. and/or their publisher

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Wilson, Graham, Brewster, Stephen A., Halvey, Martin, Crossan, Andrew and Stewart, Craig (2011): The effects of walking, feedback and control method on pressure-based interaction. In: Proceedings of 13th Conference on Human-computer interaction with mobile devices and services 2011. pp. 147-156.

This paper presents a study looking into the effects of walking and the use of visual and audio feedback on the application of pressure for linear targeting. Positional and Rate-based control methods are compared in order to determine which allows for more stable and accurate selections, both while sitting and mobile. Results suggest that Rate-based control is superior for both mobile (walking) and static (sitting) linear targeting, and that mobility significantly increases errors, selection time and subjective workload. The use of only audio feedback significantly increased errors and task time for Positional control and static Rate-based control, but not mobile Rate-based control. Despite this, the results still suggest that audio control of pressure interaction while walking is highly accurate and usable.

© All rights reserved Wilson et al. and/or ACM Press

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Wilson, Graham, Stewart, Craig and Brewster, Stephen A. (2010): Pressure-based menu selection for mobile devices. In: Proceedings of 12th Conference on Human-computer interaction with mobile devices and services 2010. pp. 181-190.

Despite many successes in desktop applications, little work has looked at the use of pressure input on mobile devices and the different issues associated with mobile interactions e.g. non-visual feedback. This study examined pressure input on a mobile device using a single Force Sensing Resistor (FSR) with linearised output as a means of target selection within a menu, where target menu items varied in size and location along the z-axis. Comparing visual and audio feedback, results showed that, overall, eyes-free pressure interaction reached a mean level of 74% accuracy. With visual feedback mean accuracy

© All rights reserved Wilson et al. and/or their publisher

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Rogers, Simon, Williamson, John, Stewart, Craig and Murray-Smith, Roderick (2010): FingerCloud: uncertainty and autonomy handover incapacitive sensing. In: Proceedings of ACM CHI 2010 Conference on Human Factors in Computing Systems 2010. pp. 577-580.

We describe a particle filtering approach to inferring finger movements on capacitive sensing arrays. This technique allows the efficient combination of human movement models with accurate sensing models, and gives high-fidelity results with low-resolution sensor grids and tracks finger height. Our model provides uncertainty estimates, which can be linked to the interaction to provide appropriately smoothed responses as sensing performance degrades; system autonomy is increased as estimates of user behaviour become less certain. We demonstrate the particle filter approach with a map browser running with a very small sensor board, where finger position uncertainty is linked to autonomy handover.

© All rights reserved Rogers et al. and/or their publisher

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Stewart, Craig, Rohs, Michael, Kratz, Sven and Essl, Georg (2010): Characteristics of pressure-based input for mobile devices. In: Proceedings of ACM CHI 2010 Conference on Human Factors in Computing Systems 2010. pp. 801-810.

We conducted a series of user studies to understand and clarify the fundamental characteristics of pressure in user interfaces for mobile devices. We seek to provide insight to clarify a longstanding discussion on mapping functions for pressure input. Previous literature is conflicted about the correct transfer function to optimize user performance. Our study results suggest that the discrepancy can be explained by different signal conditioning circuitry and with improved signal conditioning the user-performed precision relationship is linear. We also explore the effects of hand pose when applying pressure to a mobile device from the front, the back, or simultaneously from both sides in a pinching movement. Our results indicate that grasping type input outperforms single-sided input and is competitive with pressure input against solid surfaces. Finally we provide an initial exploration of non-visual multimodal feedback, motivated by the desire for eyes-free use of mobile devices. The findings suggest that non-visual pressure input can be executed without degradation in selection time but suffers from accuracy problems.

© All rights reserved Stewart et al. and/or their publisher

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Williamson, John, Robinson, Simon, Stewart, Craig, Murray-Smith, Roderick, Jones, Matt and Brewster, Stephen A. (2010): Social gravity: a virtual elastic tether for casual, privacy-preserving pedestrian rendezvous. In: Proceedings of ACM CHI 2010 Conference on Human Factors in Computing Systems 2010. pp. 1485-1494.

We describe a virtual "tether" for mobile devices that allows groups to have quick, simple and privacy-preserving meetups. Our design provides cues which allow dynamic coordination of rendezvous without revealing users' positions. Using accelerometers and magnetometers, combined with GPS positioning and non-visual feedback, users can probe and sense a dynamic virtual object representing the nearest meeting point. The Social Gravity system makes social bonds tangible in a virtual world which is geographically grounded, using haptic feedback to help users rendezvous. We show dynamic navigation using this physical model-based system to be efficient and robust in significant field trials, even in the presence of low-quality positioning. The use of simulators to build models of mobile geolocated systems for pre-validation purposes is discussed, and results compared with those from our trials. Our results show interesting behaviours in the social coordination task, which lead to guidelines for geosocial interaction design. The Social Gravity system proved to be very successful in allowing groups to rendezvous efficiently and simply and can be implemented using only commercially available hardware.

© All rights reserved Williamson et al. and/or their publisher

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Stewart, Craig, Brailsford, Tim J., Chandramouli, Krishna and Cristea, Alexandra I. (2010): The CAE-L Cultural Framework: Definition, Instances and Web Service. In: ICALT 2010 - 10th IEEEE International Conference on Advanced Learning Technologies 5-7 July, 2010, Sousse, Tuneisa. pp. 604-606.

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Cristea, Alexandra, Ashman, Helen, Stewart, Craig and Cristea, Paul (2005): Evaluation of adaptive hypermedia systems' conversion. In: Proceedings of the Sixteenth ACM Conference on Hypertext 2005. pp. 129-131.

Conversion between different adaptive hypermedia systems has barely been proposed, yet alone tested in realistic settings. This paper presents the evaluation of the interoperability of two adaptive (educational) hypermedia systems, MOT and WHURLE. The evaluation is performed with the help of a class of thirty-one students enrolled in the fourth year of the "Politehnica" University of Bucharest, who were taking a one-week intensive course on Adaptive Hypermedia. This paper describes and interprets our first experiments of the "write once, deliver many" paradigm of adaptive hypermedia creation.

© All rights reserved Cristea et al. and/or ACM Press

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