We just started the survey after calibrating our echosounder in de NIOZ harbour on Texel yesterday.
The calibration of the 200 kHz went rather well to the surprise of all involved! Unfortunately we had to fix our towed body (the frame carrying our transducers (the devices that make ‘ping’ at 38 or 200 kHz and sent the information to the transceiver –> the machine that translates the ‘pings’ to our computers) but now everything is settled and we are sailing.
The weather is not the best nor the worst at the moment. According to the radio we have wind force 3-4 –5 –6 –7-8 some rain and the television just informed us that the wind comes from west to east…
Calibrating is of crucial importance for any scientific acoustic research. Without calibration no accurate results can be expected and nor species differentiation nor any quantitative assumptions can be made.Calibrating can be a very time consuming job, whereas the lower frequencies such as the 38 kHz are rather easy the 200 kHz is always a challenge. In practice we hang a copper ball down into the acoustic beam. This ball has known backscattering (echo) properties. Now we “just” have to move the ball accordingly to fill up the entire beam.