Drowned Forests in the Gulf of Gdansk (Southern Baltic) as an Indicator of the Holocene Shoreline Changes - The Baltic Sea Basin - page 222

sidescan fish EG&G DF-1000 was used, emitting acoutic pulses with the frequen-
cies 100 and 384 kHz. The slant range was 75 m on both sides. The highest
resolution of sidescan images at the seabed amounts to about 20 30 cm per pixel,

depending on the ship velocity. The ship antenna position was measured with dif-
ferential GPS, but due to the changing length of the cable to the towfish and the
movement of the fish relative to the ship, the accuracy of absolute position was
estimated to be about 20 m. After completing the survey, the recorded data were
processed and inspected visually. A sidescan mosaic of the whole area (Fig. 11.2 )
and detailed sidescan images of selected places (such as in Fig. 11.3 ) were created.
Sites with promising textures of the seabed (Fig. 11.3 ) were then inspected by a
remotely operated vehicle with video camera, and finally, scuba divers investigated
the selected sites on the seabed (Fig. 11.4 ) .

×

Fig. 11.2 Sidescan-sonar mosaic of the area of investigation in the Gulf of Gdansk. White arrows
point to dumped material ( brown patches ). The area with fossil tree trunks extends between the
two green arrows .The white square is shown with higher resolution in Fig. 11.3 . Bluish patches
are coarse sand ripple fields and bright grey patches consist of fine sand. Triangles with numbers
are locations explored by scuba divers