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Characterizing User Performance with Assisted Direct Off-Screen Pointing

The limited viewport size of mobile devices requires that users continuously acquire information that lies beyond the edge of the screen. Recent hardware solutions are capable of continually tracking a user?s finger around the device. This has created new opportunities for interactive solutions, such as direct off-screen pointing: the ability to directly point at objects that are outside the viewport. We empirically characterize user performance with direct off-screen pointing when assisted by target cues. We predict time and accuracy outcomes for direct off-screen pointing with existing and derived models. We validate the models with good results (R2 ? 0.9) and reveal that direct off-screen pointing takes up to four times longer than pointing at visible targets, depending on the desired accuracy tradeoff. Pointing accuracy degrades logarithmically with target distance. We discuss design implications in the context of several real-world applications.


Barrett Ens, David Ahlström, Andy Cockburn and Pourang Irani. 2011. Characterizing User Performance with Assisted Direct Off-Screen Pointing. In Proceedings of the 13th international conference on Human computer interaction with mobile devices and services (MobileHCI '11). Stockholm, Sweden. ACM, 485-494.

Bibtext Entry

author = {Ens, Barrett and Ahlstr\"{o}m, David and Cockburn, Andy and Irani, Pourang},
title = {Characterizing user performance with assisted direct off-screen pointing},
booktitle = {Proceedings of the 13th International Conference on Human Computer Interaction with Mobile Devices and Services},
series = {MobileHCI '11},
year = {2011},
isbn = {978-1-4503-0541-9},
location = {Stockholm, Sweden},
pages = {485--494},
numpages = {10},
url = {http://doi.acm.org/10.1145/2037373.2037445},
doi = {10.1145/2037373.2037445},
acmid = {2037445},
publisher = {ACM},
address = {New York, NY, USA},
keywords = {Fitts' law, direct off-screen pointing, off-screen target visualizations, performance models, steering law},


Barrett Ens

Barrett Ens

Pourang Irani

Pourang Irani

Canada Research Chair
at University of British Columbia Okanagan Campus

As well as: , David Ahlström and Andy Cockburn