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?? The abundance data from the photographs were compared with
those from the FFG samplers to derive a correction factor for the
FFG sampling data.
Correction formula used to estimate abundance:
Y = 1.3 ? X
Y: bottom abundance (C. Ab. of FFG sample)
X: sample abundance (Ab. of FFG sample)
The constant was 1.3, the mean of 1.29 and 1.31 in 1994.
4.2. Nodule tonnage
4.2.1. Average nodule abundance at each station
?? Arithmetic means of the nodule abundance at the 4 or 5 sampling
sites were calculated.
?? Abundance figures were corrected for each site.
?? Average abundance includes null abundance and abundance when
no analysis was available.
4.2.2. Total nodule tonnage in each sector
1) To estimate the abundance of manganese nodules in an area, we
delineated a cell at intervals of ten minutes centred on each station,
then multiplied the average density of nodule abundance of stations
in the cell by the cell area, using Universal Transverse Mercator
(UTM) coordinates.
2) Another method, without delineating a cell, is to multiply the total
area of a sector by the nodule abundance or the average of
abundance density at each station.
3) Variogram analysis can be used to estimate abundance. However,
confidence in the results is low, because the spacing is so far apart.
Total amounts of nodules estimated by methods 1 and 2 show few
discrepancies.
4) Metal tonnage:
?? Samples from each station were selected. The coverage, shape
and size distribution of nodules were analysed. A nodule was
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