HP Gesture Keyboard - Manual (Page 5)

3.2 Spatial mapping of gestures
In order to limit the technological complexity of recognition and thereby trying to reduce instances of errors, we
have mapped the gestures on the coordinates of the writing space. This means that the number of elements that
needs to be recognized has been reduced. The same gestures made in different areas of the pad produce different
combinations wherein the consonant is selected using the spatial mapping and the modifiers are assigned after
recognition of the gestures.
3.3 Layout
The Varnmala structure was useful for people to locate keys and to reduce the cognitive load. Even users who had
‘forgotten’ the alphabetical order could remember the local sequence of the letters they were searching for. For
example, if they were looking for the (n) key, they would mutter an entire line of consonants ‘(t) (th) (d) (dh) (n)’
before locating the key. (Chand et al. 2004)
Figure 3: Varnmala layout
We tried to design the gesture keypad as cognitively easy for a novice user as possible, so that with minute training
and instructions they are able to achieve a decent writing speed. We kept the layout very basic, as it appears in the
Devnagari varnmala books in the block.
3.4 Feedback
Performance data with keyboards, where the auditory feedback can be switched on and off suggest that typing is
significantly faster and more accurate with auditory feedback on than with off. (Birdwell, Monty & Snyder, 1983;
Blake, Muto & Roe, 1984)
Based on these prior studies we added a click sound on every pen down. This can be
again toggled on and off based on user’s preference. The timings of the feedback and the frequency of sound are still
to be investigated.
In addition visual feedback has been provided so that the user can see his handwritten input on the tablet real-time.
We believe that expert users of the system will not use this functionality much but it should be provided to help the
novice users. With some errors always built in with this keyboard due to handwriting recognition and pen tilt errors
users may be able to catch and correct their errors when they see their handwriting on the computer screen.