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Advances in Human-Computer Interaction
Volume 2014 (2014), Article ID 908690, 13 pages
Research Article

PaperCAD: A System for Interrogating CAD Drawings Using Small Mobile Computing Devices Combined with Interactive Paper

1Department of Computer Science & Engineering, University of California, Riverside, CA 92521, USA
2Department of Mechanical Engineering, University of California, Riverside, CA 92521, USA

Received 31 July 2014; Revised 19 October 2014; Accepted 20 October 2014; Published 13 November 2014

Academic Editor: Kerstin S. Eklundh

Copyright © 2014 WeeSan Lee and Thomas F. Stahovich. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Smartphones have become indispensable computational tools. However, some tasks can be difficult to perform on a smartphone because these devices have small displays. Here, we explore methods for augmenting the display of a smartphone, or other PDA, using interactive paper. Specifically, we present a prototype interface that enables a user to interactively interrogate technical drawings using an Anoto-based smartpen and a PDA. Our software system, called PaperCAD, enables users to query geometric information from CAD drawings printed on Anoto dot-patterned paper. For example, the user can measure a distance by drawing a dimension arrow. The system provides output to the user via a smartpen’s audio speaker and the dynamic video display of a PDA. The user can select either verbose or concise audio feedback, and the PDA displays a video image of the portion of the drawing near the pen tip. The project entails advances in the interpretation of pen input, such as a method that uses contextual information to interpret ambiguous dimensions and a technique that uses a hidden Markov model to correct interpretation errors in handwritten equations. Results of a user study suggest that our user interface design and interpretation techniques are effective and that users are highly satisfied with the system.