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7.3 Low Level Vision Domain: a Finger Tip Location Finder 105

Figure 7.6: Some examples of hand images with correct (cross-mark) and pre-
dicted (plus-mark) finger tip positions. Upper left image shows average case, the
remaining three pictures show the three worst cases in the test set. The NRMS
positioning error for the marker point was 0.11 for horizontal, 0.23 for vertical
position coordinate.

Even with the very small training set of only 16 images, the resulting
PSOM achieved a NRMS-error of 0.11 for the x-coordinate, and of
for
the y-coordinate of the finger tip position (corresponding to absolute RMS-
errors of about 2.0 and 2.4 pixels in the image, respectively). To give
a visual impression of this accuracy, Fig. 7.6 shows the correct (cross mark)
and the predicted (plus mark) finger tip positions for a typical average
case (upper left image), together with the three worst cases in the test set
(remaining images).