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located at almost every 2-minute interval. Nodule abundance in the area
went up to more than 17 kilograms per square metre.
Much effort and many ships had been employed, using more than
55 cruises and 2200 ship days. The main ships currently in use were the
Sidorenko and the Oceanographic Research Vessel Sagar Kanya. ORV
Sagar Kanya belonged to the Department of Ocean Development (DOD) and
was the department’s pioneering contribution to the EIA studies and the
exploration for polymetallic nodules.
Equipment
Professor Ravindran next discussed the instrumentation used and
the parameters measured, remarking that the choice of data standards
would require a realistic look at the instruments and the variations in
measurements. He began by listing the equipment used for position fixing,
hydrosweep, deep-towed sonar surveys, deep-sea photo and television
cameras, mooring systems with current meters and sediment traps,
conductivity-temperature-depth (CTD) profiling and water sampling.
For position fixing, NIO had used a Magnavox Global Positioning
System (GPS) receiver, with which the depth and reliability of the position
reading averaged plus or minus 40-50 m. The hydrosweep provided
coverage of 200 percent of the depth and gave 59 depth points per ping.
The survey of the pioneer area had been completed in 1992-93.
Deep-towed sonar surveys used frequencies of 150 and 14
kilohertz for position fixing of depth. The photographic and TV cameras
were from the “Neptun” system on the Russian vessel. The focal length
was about 21.6 millimetres, within 5 m of the seabed. The still camera had
a capacity of 3000 frames per sink.
Mooring systems had been positioned all over the area. They bore
current meters with an accuracy of ±0.03 m/second, a transmissometer for
light measurement accurate to ±1% and sediment traps programmed to
open for five days, with measurements in grams. CTD had been measured
using the SeaCat, made by Sea-Bird Electonics (SBE). Box corers and
mulitcorers were used for sediment studies.
Five areas had been selected, each 10 by 10 miles. Later, two of
these areas having identical characteristics had been singled out as test
and reference sites. High-resolution bathymetric maps had been created
174 INTERNATIONAL SEABED AUTHORITY