A system is disclosed for recognizing typing from typing transducers that
provide the typist with only limited tactile feedback of key position.
The system includes a typing decoder sensitive to the geometric pattern
of a keystroke sequence as well as the distance between individual finger
touches and nearby keys. The typing decoder hypothesizes plausible key
sequences and compares their geometric pattern to the geometric pattern
of corresponding finger touches. It may also hypothesize home row key
locations for touches caused by hands resting on or near home row. The
resulting pattern match metrics may be combined with character sequence
transition probabilities from a spelling model. The typing decoder then
chooses the hypothesis sequence with the best cumulative match metric and
sends it as key codes or commands to a host computing device.