MD DSS in depthAs with any survey sonar system, the MD DSS operation is based on transmitting sound waves into the water and receiving their reflections from obstacles such as the sea bottom and underlying material layer interfaces. The portion of energy reflected from an interface is proportional to the angle of incidence and the characteristic acoustic impedance ratio in the layer interface.
In conjunction with MD DSS, we often are asked to provide answers to two questions. First, what is multi-mode operation? Second, how much sediment penetration can we expect to get with MD DSS? Below we will address these two issues.
Not surprisingly, with multi-mode
operation we refer to the system's ability to function in
different modes. MD DSS supports the following operation modes:
Below are examples of data acquired with MD DSS in different
MD DSS multi-mode operation allows multi-faceted, single-pass surveys to be carried out with just one system.
Penetration in sub-bottom profiling
Penetration varies with frequency and material. As a
general rule, the lower the frequency, the better the penetration.
With all other factors constant, a lower frequency travels a
longer distance. Rougher materials are better at absorbing sound
The above two profiles portray the subsea geology along a fairway in the Baltic Sea. At places, penetration differs markedly.
In this pair of profiles, there is an even more noticeable
difference in penetration.
Finally, above is a pair of profiles from quite the opposite ends of MD DSS's operating frequency spectrum. Although the frequencies are several orders of magnitude apart, the difference in penetration is hardly perceptible.
For acquisition of this survey data and for permission to publish views thereof, we would like to thank Tele1Europe in Finland, Geological Survey of Finland, Primatel Ltd, Stockholm university, Department of Geology and Geochemistry, and University of Sao Paulo, Institute of Oceanography.