Closed kstierhoff closed 2 months ago
Will focus on Transect 118, sampled by SD-1060:
We conducted a pre- and post-survey calibration, which resulted in the following for 38 kHz
Parameter | PRE | POST |
---|---|---|
Gain | 19.04 | 19.10 |
BW_along | 17.8 | 17.9 |
BW_athwt | 17.8 | 17.9 |
Offset_along | 0.2 | 0.2 |
Offset_athwt | -0.6 | -0.9 |
EBA | -12.6 | -12.6 |
Sa_corr | -0.04 | 0.03 |
RMS | 0.16 | 0.13 |
So both were very similar, and we applied the Pre-survey results for the data processing. The template ECS file appears to have the correct environment and calibration parameters entered:
The CTD cast used to process this transect was cast 158 from the Shimada hake survey, which appeared to have a harmonic sound speed of 1495.67 m/s, which matches with what's in the ECS file used to process this transect:
The calibration parameters in the ECS value are from the template file but compensated by change in sound speeds. With a calibration (template) sound speed of 1501.37 and transect sound speed of 1495.67, my calculations are:
Parameter | Template | Transect |
---|---|---|
Gain | 19.04 | 19.073 |
EBA | -12.6 | -12.633 |
BW_along | 17.8 | 17.7324 |
BW_athwt | 17.8 | 17.7324 |
This matches what's in the transect ECS file, so looks like it's being compensated correctly.
So unless both calibrations were way off for this echosounder, I think this checks out just fine. Suppose the question then becomes if the scatterers near the seabed are indeed CPS.
Compelling and thorough analysis. I think we can consider that item completed and debunked.
Final biomass estimates computed for all species/stocks, after accounting for deep backscatter from CSNA in the nearshore region of the SCB. Results incorporated into biomass report.