Comment on the Mapping of Iron-Manganese Nodule Fields Using Reconnaissance Sonars Such as GLORIA


Neil C. Mitchell

Scanlon and Masson (1992) recently showed that GLORIA is capable of mapping fields of iron-manganese (Fe-Mn) nodules and follow a similar study by Huggett and Somers (1988). These results are important for maritime nations hoping to exploit their Exclusive Economic Zones because mapping with GLORIA is so efficient: the sonar has a swath width of 40 km or more and can be towed at up to 10 knots. I wish to draw attention to some results from the acoustical literature which demonstrate that, because nodules are generally smaller than GLORIA's wavelength, the sonar is potentially unreliable for mapping Fe-Mn nodule fields. However, a combination of GLORIA with sonar imagery collected at a higher frequency, or a multifrequency sonar, could map Fe-Mn nodules less ambiguously.

Mitchell, N. C., "Comment on the mapping of iron-manganese nodule fields using reconnaissance sonars such as GLORIA", Geo-Mar. Letts. 13, 244-247, 1993.


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