Calibrating current meter

We have a 2004 Nortek VMCP on a survey vessel. We are having trouble with getting a calibration to 'fix'. The stick plots indicate that a calibration is needed. Our vessel is towing 6 x 5km cables so is limited in ability to turn quickly - takes 2 hours to turn round. We are working in an area of 90 metre water depthy and has strong diurnal tidal component rather than local currents. How can we best calibrate the VMCP given our slow turn and the fact that by the time we do turn the tide will have shifted?

thanks,
Sean

Dear Sean

Sorry for the late response - summer is here and our main concern right now is the sea surface water temperature  " />'>

Two hours is a long time but it should still be possible to calibrate the instrument to some reasonable degree of accuracy.  Maybe the best path is to use the  capability in the calibration software to pick out exactly which profile numbers you will use. This means that you can take the data from a single file (I believe).  It then becomes the matter of picking out two time periods before and after a turn that looks the best.  For example, you could pick out a data set where the peak tidal current occurs during the turn - in which case the currents should be about the same before and after the turn.

It may not be perfect but it should at least give you something to work with.

Good luck " />'>

Best regards,

Atle Lohrmann