Page 130 - Classification Parameter Estimation & State Estimation An Engg Approach Using MATLAB

DISCRETE STATE VARIABLES 119

video line:
true license
plate pixels:
high–pass filtered: thresholded:

very high–pass filtered: thresholded:

ultra high–pass filtered: thresholded:

Figure 4.15 Definitions of the measurements associated with a video line

One possibility to decode the succession of transitions is to apply
a filter bank and to threshold the output of each filter, thus yielding a
set of binary signals. In Figure 4.15, three high-pass filters have been
applied with three different cut-off frequencies. Using high-pass filters
has the advantage that the thresholds can be zero. As such, the results
do not depend on the contrast and brightness of the image. The three
binary signals define a measurement signal z(i) consisting of N ¼ 8
symbols. Figure 4.16 shows these symbols for one video line. Here,
the symbols are encoded as integers from 1 up to 8.
Due to the spatial context of the three binary signals we cannot
model the measurements as memoryless symbols. The trick to avoid

true license
plate pixels:

measurements:

true states:

Figure 4.16 States and measurements of a video line