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Fakopp 3D Acoustic Tomograph - User’s Manual -
2D map shows the same map, the only difference is that it is shown in 2D and only
colors represent the velocity differences. A line intersection can also be selected with
the right mouse button.
Graph mode displays not the reconstructed interval velocity distribution, but the
measured velocity values between the sensors. The color of the lines corresponds for
the velocity values. Moving the mouse over the lines display the line velocity.
The velocity map has two imperfections.
The sound velocity in a hole inside the tree is same as in the air, 340 m/s but the
measured velocity will be remarkably higher. This is because the waves by-passes the
hole and therefore there is no method to measure the exact velocity inside a hole.
Generally, if the velocity decreases somewhere under 90-85% of the average velocity,
then there can be a hole or decay.
The other problem is that if there is a long narrow crack in the tree then it shadows the
nearby area and the result will not show a narrow crack but a much smaller and wider
area at the boundary.
The real resolution of the image depends of the number of sensors used. With 8
sensors you can detect any decay greater than 5% of the whole cross-sectional area.
With 32 transducers this ratio is 2%.
Figure 17 Velocity map visualization in 3D mode
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