Bottom Classification - BioSonics, Inc

cluster center weighted by that data point’s membership grade. Figure 12 shows clustering of Fractal Dimension
data.
Figure 12. Fuzzy C-Means Clustering technique for different bottom categories. Fractal Dimensions method B4
for data files from VBT Catalogue: mud120.dt4, sand120.dt4 and rock 120.dt4.
2.8. Sediments Layer
A backtracking bottom tracking method is used in the VBT software. In this method, the software tracks the
bottom from the far end of the received echo and moves towards a shorter range. Then, the bottom tracker locks
to the rising edge of the first bottom echo. The sediment layer is located at the range above the bottom echo
(i.e., it is the layer above the bottom). The sampling gate in VBT labeled “sediment layer” is open for sampling
either sediment or bottom plant echoes. The VBT software estimates the thickness of this layer and the integral
of the echo.
2.9. Survey Maps
Survey maps displaying the location of each VBT report acquired with GPS data can be displayed on the
screen. Different bottom categories are color coded at the same time (see Figure 13). The output report of the
VBT is produced in ASCII format. It provides the following information: date and time, report number, latitude,
longitude, depth to the bottom, bottom category (coded as a number) and the energy estimated by calculating
the integral of different parts of first and second bottom echoes.
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