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

Table 2

Interpretation of extension lines.

Event	Correct	Incorrect
Correctly interpreted	375
Ink capture failure (H)		2
Drawn in wrong direction, not parallel/perpendicular to anything (U)		3
Drawn in wrong location (U)		9
Drawn incorrectly, over-stroked (U)		2
Drawn incorrectly, tapped first (U)		3
Drawn on the perimeter of a circle (U)		1
Drawn too far from the drawing (U)		5
No pause before drawing another (U)		5
Not recognized (S)		29
Angle misinterpreted (S)		1
Location misinterpreted (S)		8
Misinterpreted as a single arrow (S)		3
Misinterpreted as a tap (S)		4
Total	375	75

H: hardware error; U: user error; S: system error.