3oulder detection |

A

sS55

VBES BS

MBES Slope

bh

As
a

BES Depth

B SsQ

ABES Depnth

BES combined

APES BS

ABES combined

= m A-A
E vs
— -18.0 50 5
& S
Ö -18.5 m
— 0
0 1 2 3
Distance [m]
— MN B-B'
E -17.75 40 5
— GI
& 18,00 205
En A
—18.25 > +

3

2
Distance [m]

MBES Slopr

E -19.50 I AN C-C'F 75 _
zZ 1: Y
E Fr 5.0 5
& 19,55 ; 2
X . 2.5
—
1 2
Distance [m]
Pe D-D' | —
45
2

E -19.550
S _19,575
WU
o
—19.600

ü

Z

Distance [m]

OWw RS hi. *-iR

 ar.

m“

F

012m
3

Fig. 3: The appearance of boulders in the different data sets. A) At a distance of 45 m to the nadir individual boulders are recognised in S5S backscatter.
The same boulders (27 m to the nadir) are more difficult to recognise in MBES backscatter. The boulders are visible in bathymetry, slope, and combined
data sets. B) Small boulders as imaged in the outer part (75 m to nadir) of a side-scan sonar swath. The characteristic boulder pattern is hard to recognise
and appears smeared in the along-track direction, due to yaw movements or decreasing along-track resolution. The appearance of boulders is difficult to
nterpret in MBES (20 m to nadir) backscatter, but the objects are recognised in slope, bathymetry and combined data sets. The position of SSS images was
shifted bv several metres to account for positional differences to the MBFS. The green arrow points to the nadir. SSS data was recorded with a (MSS-annr

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