It has come to our attention that incorrect values of transducer gain could be used in the calculation of wideband TS and Sv variables for Simrad EK80 data.
Simrad data files contain a lookup table of pulse durations, with corresponding tables for gain and Sa correction. When a ping is read from file it lists the pulse duration that was used when the ping was recorded. The corresponding value of gain and Sa correction is read from the lookup table and used accordingly.
EK80 data files can include both PulseDuration and PulseDurationFM attributes. Echoview was incorrectly using the PulseDurationFM lookup table for wideband data when PulseDuration should have been used. Depending on a user’s setup, this could mean that an incorrect value of gain is applied when calculating wideband TS and Sv variables. The attributes can be viewed by opening an EK80 data file with a text editor.
Take the following example:
PulseDuration="0.000128;0.000256;0.000512;0.001024;0.001536"
PulseDurationFM="0.000512;0.001024;0.002048;0.004096;0.008192”
Gain="25.1;25.2;25.3;25.4;25.5"
SaCorrection="0;0;0;0;0”
If a ping was recorded at a pulse duration of 1.024 ms, then Echoview was incorrectly using a gain of 25.2 when it should have been using 25.4. Note that Sa correction is not applied to wideband data in Echoview so SaCorrection values are not relevant, even if non-zero values exist.
This lookup issue has been fixed in Echoview 11.1.49, which is available by opening the Help menu in Echoview and clicking Check for Updates, or by downloading the latest installation package.
We recommend checking data files and recalculating any Sv, TS or single target-based analyses in the latest version of Echoview if you are affected by this problem.
This issue does not affect:
- TS or Sv data if:
- an ECS file was used to override the transducer gain value read from the data file
- a full wideband calibration was performed and frequency-dependent calibration corrections are included in the raw data file
- EK80 files that are FileFormatVersion earlier than 1.2
- Narrowband (CW) EK80 data
- Any other file formats
We apologize for any inconvenience this issue may cause. Please contact support@echoview.com if you have any questions.
