Figure 22: Typical Sound Velocity Values - Teledyne SeaBat T Series Operator's Manual

ACTIVE SONAR USAGE
6.4.3.2 Recommended Use of SVP Filter
The speed of sound impacts the beam angles. If a sonar ping is processed with a sound velocity
value that is not reflecting the speed of sound right in front of the receiver, the beam angles will
be wrong and hence the targets or bottom detects will have wrong coordinates.
Some software packages allows post-compensation of wrong sound velocity, but it is typically
possible to avoid this extra complication of processing by setting a proper filter on the SVP data
during real-time recording. For instructions on how to adjust this setting, refer to the RESON
Sonar UI User Manual (see Appendix E Reference Documentation).
 No Filtering: Although this setting does not filter data in the classical sense, it still
ignores readings outside the range 1350m/s to 1800m/s.
Use this filter if there is a requirement for immediate response to sound velocity
changes. When using this filter any false reading will cause distinct false output. This
filter may be preferred for certain scientific sonar work.
 SVP Light: Removes occasional false readings.
Use this filter if there is a need for fast filter response, for instance in regions with
mixing waters.
If the SVP update rate is less than 10Hz it may be preferred to use this filter as the
standard filter.
 SVP Normal: Removes single and double false readings and outliers, and smoothens
the SVP value across 10 readings.
The filter is recommended for most sonar work on systems using an SVP (SVP 70)
with no internal filtering and an update rate of 10-20Hz.
The SVP Normal filter is typically the best filter to use.
 SVP 70 Wizard: This filter only works with the SVP 70 if the internal SVP 70 filter is
set to mode 1 (low pass filtering).
Sensors with a low pass filter cause a special artifact in the output in case of outliers
and invalid readings. The SVP 70 Wizard filter removes these artifacts and makes the
system work well despite of the low pass filter.
SeaBat T-Series Subsea Operator's Manual
Version 7
Sound velocity (at surface)
1560
1540
1520
1500
1480
1460
1440
1420
1400
0 5 10
Temperature (degrees C)

Figure 22: Typical Sound Velocity Values

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January 31, 2019