This option lets the user manually set the TGC amplification. He can set a constant amplification gain, a slope amplification (which increases exponentially the gain as a function of the depth), or define gains in up 1024 to user-defined zones.

The functioning TGC modes that can be used when this package is installed are the following:

• Automatic: An optimal TGC curve automatically computed in order to avoid strong echoes or low energy gate problem.
• Uniform: The amplification coefficient is the same for all gates.
• Slope: The farther the gates are from the transducer, the more the echo signal is amplified according to an exponential slope (a line on the dB scale). This slope is defined by two values, at the nearest and at farther depths.
• Custom: The user can fine-tune the TGC in any gates or group of gates independently.

Possible problem encountered without this package	Solution to this problem

If a constant amplification factor is applied to the echo signal scattered by a highly attenuation liquid, the echoes from far away will be so weak that the velocimeter won't be able to compute accurately the velocity of these gates. On the other hand, applying a higher amplification factor to the gates far away will provide a more powerful signal to the correlation algorithm, without saturating the echo from the first gates.