Zimmermann and Rooper: Comparison of echogram measurements for distinguishing seafloor substrates 
297 
FV Gladiator 2003 shallow FV Gladiator 2003 deep 
RV Resolution 2003 
0.90 
Echogram measurement 22 
RV Pallasi 2004 
f.OO 
0.90 
0.80 
0.70 
0.60 
0.50 
0.40 
0.30 
0 20 
0.10 
0.10 0.30 0.50 0.70 0.90 
RV John P. Tully 2002 
Echogram measurement 22 
Figure 1 
Significant linear regressions (P<0.0005) between the unitless Quester Tangent Corpora- 
tion echogram measurements 22 and 23 for the shallow (n = 14,432) and deep (n = 3598) FV 
Gladiator 2003 data sets, the RV Resolution 2003 cruise 02=3680), the C.C.G.S. RV John 
P. Tully 2002 cruise (n= 727), the RV Pallasi 2004 cruise (n = 736), and the RV Rangithi 
1999 cruise (n = 736). Note the different scales on the x axes. 
EMs in each of the third (EMs 40-70) and fourth (EMs 
71-101) groups, there were 16 original EMs grouped 
into 15 succeeding sums, with the final EM (EM 40 in 
the third group and EM 71 in the fourth group) being 
the sum of the whole group (Fig. 2). In the third group, 
EM 40, which was always 1.0, was created by the sum 
of EM 41 and EM 56, which are complements to each 
other and therefore are entirely dependent. 
Variability and covariance of echogram measurements 
There were several unusual observations of variance 
or covariance among the 166 QTC IMPACT-generated 
EMs. Three EMs — 16, 31, and 40 — never varied (were 
always 1.0000000 or 0.9999999) and it is presumed 
these are the same three that Legendre et al. (2002) 
stated never varied from one. Additionally, three EMs 
from the RV Rangithi 1999 cruise data were always 
zero. Although it is difficult to describe all the depen- 
dent relationships (the sums and correlations) between 
the remaining 160 to 163 EMs, it is much simpler to 
note that among the six data sets, a range of 148 to 
155 EMs (Table 1) were fully collinear (causing the 
variance-covariance matrix determinant to be zero; 
Neter et al., 1990). Among the eight to 12 EMs within 
each data set that were not fully collinear, four to 
