Measuring the linear and rotational user precision in touch pointing

This paper addresses the limit of user precision in pointing to a target when the finger is already in contact with a touch surface. User precision was measured for linear and rotational pointing. We developed a novel experimental protocol that improves the estimation of user's precision as compare to previous protocols. Our protocol depends on high-resolution measurements of finger motions. This was achieved by the means of two optical finger trackers specially developed for this study. The trackers provide stable and precise measurements of finger translations and rotations. We used them in two user experiments that revealed that (a) user's precision for linear pointing is about 150dpi or 0.17mm, and (b) user can reliably point at sectors as narrow as 2.76 degrees in 2s in rotational pointing. Our results provide new information for the optimization of interactions and sensing devices that involve finger pointing on a surface.

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