Tuning the CARIS implementation of CUBE for Patagonian Waters.pdf

3.1.2 Central Patagonian Area.
Here, unlike in the northern Patagonian area, the effects of the last glaciations are
stronger. The piedmont has a very irregular structure. Both extremes (north and south)
have fjords and also correspond to the wider area of the piedmont. With depths over 1000
metres, the north sector has morphology typically associated to fjords with moraines
composed of diamicton.
Fjord basins, unlike the piedmont, have a more regular stratification of sediments
(i.e., horizontally stratified) and associated glaciomarine effects. Their moraines also
consist of diamicton, and have many categories associated with different mechanisms of
formation.
The central area has no fjords and it is the narrowest sector of the intermediate
depression. With depths from 50 to 200 metres, the sediments are trapped between
moraines in layers of 10 to 15 metres thickness, which are acoustically weakly reflecting
[Araya, 1996]. Thus, MBES operating in this region could have sea bottom mistracking
due to the strong variability in backscatter signal between the walls (mostly rock
compound) and the basin of the channel (fine, acoustically weakly reflecting, mud).
Some of the problems found in the data acquired by the FANSWEEP 20 (Figure 3.4),
could be due to this effect. Independently of its cause, this noise-data considerably affects
the depth estimation made by CUBE (or by any other algorithm) Rather than the deeper,
sparser true depth estimations, the dense noise-data is more probable to be selected by the
disambiguation engine as the most likely solution.
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