On nautical charts bottom type is classified by its composition. For instance, ‘S’ indicates a sandy bottom; ‘R’ is for rock, while ‘Sh’ depicts shells. However, you seldom find simply ‘Sh’ on a chart. The ‘Sh’ is mostly preceded by ‘bkn’ (broken). Well, what else would you expect from bottom samples taken in the "As it Was" days, when a heavy lead with a kick filled with tallow was used to take the sample? Shells will most probably end up crushed or broken when a heavy lead is dropped on them. Was it that the Hydrographers did not realise this effect, or was it that they did not trust the reasoning of the mariner (who might not understand that shells could be broken by dropping a lead on them)? Regardless, ‘bkn Sh’ is still shown prominently on many charts compiled more than twenty years ago.
The reason for charting the nature of the seabed was at least two-fold: to give mariners information for anchoring and to serve as an aid to navigation in the days when dead reckoning was more practised than nowadays. One of the first surveys I participated in resulted in the disappearance of the ‘Black Bank’ and the ‘White Bank’ from the nautical chart of the North Sea. This happened because these ‘banks’ did not have the standard depth contour prescribed for charting. However, the rather black and the whitish sand (which was charted as ‘blk S’ or ‘w S’ (black/white sand) had been used for centuries by the local mariners as an update on their dead reckoning. The ‘Brown Ridge’ is, however, not only still there but remarkably visible on your echosounder (a perfect check on your GPS-based position, and vice versa). In reality, if you take a bottom sample in the traditional way, it is really composed of ‘brown clay’.
Modern navigational charts have less detail than older charts, as new positioning methods reduce the importance of certain bottom type/classification information etc. Today you will find only general, more sparse information on the type of bottom (e.g., ‘Sh’ or ‘S’). Although bottom classification equipment is a lot more sophisticated than were the previous leads, the new equipment does not give you the colour of the clay - yet. The articles in this issue mention just a few methods developed to fulfil the requirements of scientists, military, fisherman, environmentalists, offshore operators, etc.
Lesson from the ‘bkn Sh’ above: we have to pay attention to the correctness of the data displayed to us by instruments. As an example, one of the early acoustic bottom classification methods I worked with needed such frequent ground-truthing due, for example, to varying ambient noise conditions, that in practice we did not use it; a lack of regular ground-truthing could mean the chance of charting (absent) coral in the North Sea.
Today, the rainbow-coloured 3-D images of bottom classification processing systems are beautiful to look at. But are we interpreting the ‘samples’ correctly, both for now and for the future? If not - and we still take the ‘bkn Sh’ at face value - are we prepared to accept the risk that an editor of the sixtieth volume of Hydro international may point this out to his readership?

We have to say farewell to a member of our Editorial Advisory Board: Mr Arne Indrieede from Statoil has asked to be relieved of his function as he was involved in so many projects that he simply could no longer spare the time. Arne, thank you very much for all you did for Hydro international and we hope you will stay in touch with us.
Enjoy reading!