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.