Finer Timing Information

A small investigation was made to see if the delay between strokes of separate symbols was longer than that of the delay between strokes in the same symbol. This investigation was not in depth, and only provides an indication of the possible success of such an approach. The idea was that strokes within symbols would be drawn with less delay than strokes of separate symbols.

  

Figure 4.3: Delays between strokes for writing the alphabet.

(a) Sorted by delay.

(b) In order of entry.

The two graphs in Figure 4.3 show the delays between strokes as the letters of the alphabet were swiftly written out from a to z. The labels on the x-axis show which strokes the delay was between. The label ``a-b'' means that this is the delay between the letters a and b. Labels such as ``x2'' indicate the second stroke for the symbol ``x''. The lighter shaded bars indicate the eight strokes which are second strokes for single symbols.

If the assumption that shorter delays imply that two strokes belong to the same symbol is correct, then this should be evident in Figure 4.3(a) that shows the sorted delay data. The assumption holds true apart from the o-p, n-o, and i2-jdelays. If a threshold is to be determined, there is a small difference in the duration of the delay between the last of the gray bars, and the beginning of the solid bars: the difference between the k-k2 and d2-e delays is only seven milliseconds.

Looking at Figure 4.3(b), where the data is in its original entry order, suggests that it may also be possible to determine which strokes belong to the same character by noticing that they fall in troughs. Still, this is not reliable as the o-p and q-r delays also come into this category, and the p-p2 delay which should, does not.

Timing information on its own does not appear to be sufficient for segmenting strokes into symbols. It is not possible to consistantly determine where strokes should be grouped together or separated. For such a scheme to work, variations due to the user pausing or slowing down as they write would also have to be compensated for, and thresholds would have to be automatically determined as the strokes are progressively entered by the user.