User’s Manual INNOMAR Parametric Sub-Bottom Profilers / SESWIN 145
Innomar Technologie GmbH (2023-01) 145
The gain is set for both data channels (LF and HF) separately. As a rule of thumb, the gain should
be set in a way that the received signals use the whole dynamic range available.
Adjust the gain based on the signal monitoring window and not on the colour of the
seabed and reflectors within the echo plot!
Avoid to use “Auto Gain”, this will level the seabed reflectivity and we are interested to
see those changes due to changing sediment properties.
Do not change the Gain to often – the signal will always fluctuate a bit. Change at
significant increase/decrease of water depth or when other settings are changed, such
as frequency or pulse length.
Do not over-amplify the signal, this will clip raw signals, you lose near-seabed resolution
and you may introduce false reflectors near to the seabed echo.
Gain changes do not change the signal to noise ratio, i.e. noise and signal will both be
amplified.
12.4 Data Acquisition: Example Settings
Some example parameter sets are given below. The parameters may be different from vessel to
vessel due to different background noise level and characteristics. The given settings should be
used as a starting point with different survey conditions and application requirements kept in
mind. Please see also the checklist given in appendix A.20 on page 219.
Survey of upper sediments (about 10 m to 20 m) with highest possible resolution
Frequency: highest frequency of the system with the best signal to noise ratio (15 kHz for the
shallow-water models).
Pulse Length: 2
Gain: depends on water depth and needs to be adjusted by using the signal window
Range Length: as small as possible (e.g. 25 m) in order to maintain a high ping rate, but would
require longer ranges (e.g. 50 m) for areas with changing topography for easier tracking of the
seabed and adjustment of the operating window
Survey to detect bedrock below the sediments as far down as possible
Frequency: 6 kHz or 8 kHz
Pulse Length: longest possible setting (depends on frequency)
Gain: depends on water depth and needs to be adjusted by using the signal window
Range Length: as small as possible (e.g. 40 m) in order to maintain a high ping rate, but would
require longer ranges (e.g. 100 m) for areas with changing topography for easier tracking of the
seabed and adjustment of the operating window
Site Survey in areas with relatively constant water depth (e.g. change of ±20 m only)
Frequency: 8 kHz or 10 kHz (for good resolution)
Pulse Length: 2 (for good resolution)
Gain: depends on water depth and needs to be adjusted by using the signal window
Range Length: could be set very small, because the water depth doesn’t change much, e.g. 20
to 30 m, this will result in very high ping rates for good lateral resolution, especially in shallower
water depths where the foot print is small as well.
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