Inter-calibration of participating vessels in the ICES coordinated surveys of North Sea herring
Original version
This report is not to be cited without prior reference to the authorsAbstract
Summary: Three pairwise acoustic inter-calibrations of the performance of EK500 scientific echosounders
were carried out in July 1997. The first inter-calibration was carried out at about 57 40'N by OE
by GO Sars and Walther Herwig Ill on the morning of 1 July. Due to severe weather Tridens was
unable to reach this location in time, and could not participate as planned. The inter-calibration
was carried out throughout the entire survey day, during which no fishing took place. The
second calibration carried out between Walther Herwig Ill and Dana after the completion of the
first inter-calibration. During 2 July Walther Herwig Ill sailed eastward and contacted and Dana.
The inter-calibration was carried out in the morning of 3 July at a position 57.45'N and 06 00'E
about 30 Nm south west of the Norwegian coast. The third inter-calibration was carried out
between GO Sars and Scotia on 16 July at about 60 45'N 30'W. The results of the calibrations have been examined, analysis includes careful matching of
threshold values and an examination of the impact of weather dependent losses. The
relationships between sequences of points in space are shown and as an approximate
maximum likelihood regression are presented giving confidence intervals for the three
calibrations. The results show excellent agreement between the four vessels involved.