Doc no: 430-041-01
25 of 64
4.2.1. Roll
A section of
flat
seabed should be selected and lines run at the same speed but on reciprocal headings:
Figure 4-3 Roll lines
The roll offset can be approximated, using the following equation (Eq 15):
𝜌 =
tan
−1
(
𝑑
𝑧
𝑑
𝑎
)
2
(Eq 15)
Where
ρ
= Roll offset (deg)
d
z
= depth difference (m)
d
s
= across-track distance (m)
Figure 4-4 [Sketch courtesy of A Godin]
Prior to processing, the pitch correction derived in Section 4.2.2 should be applied.
The inconsistency in observed cross profiles angle is as a result of an error in roll alignment between MRU
and MBES head. During processing, an arbitrary subset of the flat seabed observed in both directions and
perpendicular
to the run-line direction should be extracted and processed using the patch test utility in the
MBES processing package.
The output of this process should be the roll correction, that when applied would bring the seabed cross
profiles to the same angle.
Same line, reciprocal
headings
Summary of Contents for DT101Xi
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