Calibration of active sonars requires a small sphere(s) to be suspended some distance below the transducers, which are often mounted on the keel, forward of the centre of the vessel. On large vessels this poses challenges, which can be exacerbated by new ship designs which have axe or bulbous bows. Here, I invite contributions on solutions to such problems so that people embarking on new ship designs can consider their options and learn form the experience of others.
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I haven’t dealt with a boat with enclosed foredeck, but for calibrations on large (110 m) trawlers that had a lot of junk on their keels to foul calibration lines, we used divers to position the sphere. Turn sounders off, get them to swim lines under vessel and join under transducer then pay out equidistant on three lines. Expensive, but guaranteed that we had sphere in beam within 30 minutes of starting calibration so cost-effective in terms of saving vessel time
Hi Paul,
For the Ek80 calibration of our three large vessels Atalante (85m), Pourquoi Pas? (107m) and Marion Dufresne (120m) we are now using our Bille automated system with magnetic poles close to the sea surface, a zodiac is needed for fixing the poles on the hull
Enclosed some pictures for Atalante and Marion Dufresne, a full documentation for deployment for each vessel is available in French if needed
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