Depth 130 meters
The seafloor is at 167 ms and the last strong echo is seen at 203 ms. The peak
penetration observed at this depth was 50 ms, corresponding to about 40 meters of
Depth 4470 meters
These data were recorded while the dynamic positioning system was running. The
main source of noise is (we believe) from the thrusters. The seafloor is at range
5954 ms. The penetration seen in this image is approximately 65 ms corresponding
to more than 50 meters of penetration.
Bottom slope correction
The bottom slope correction is a new feature introduced by the SBP120 sub bottom
profiler. The EM 120 calculates alongtrack and acrosstrack slopes and sends this
information to the SBP 120. The operator can select to adjust the transmit beam
and the receive beam such that normal incidence is obtained. This will give the
best penetration and the best image of the layers parallel to the seafloor.
This image shows a section logged in the “canyon” during the sea trials. While
the EM 120 seemed to give good estimates for the bottom slopes (indicated by a quality
factor displayed in the operators unit), we mainly used bottom slope correction.
In the middle of the image above we see how the image changed when the bottom slope
correction was switched off for eleven pings: The bottom return became much less