On Friday 24th of July our Geo Focus finished successfully her long term project on the Gemini Offshore Windpark.
A multibeam echo sounder is a system, which is used for detailed seafloor mapping and inspection in waterdepths from less than 1 meter up to 200-1000 meters (depending of operating frequency and beamwidth). The system transmits a broad acoustic fan shaped pulse from directly beneath a vessel’s hull. It measures and records the time it takes for the acoustic signal to travel from the transmitter (transducer) to the seafloor (or object) and back to the receiver. In this way, a multibeam echo sounder produces a “swath” of soundings (i.e. depths) for broad coverage of a survey area. The coverage area on the seafloor depends on the depth of the water, typically 3,5 tot 7 times the water depth.
The multibeam transducer(s) can be installed temporarily on a bracket and lowered down in a vessel’s moon pool or permanently in a vessel’s hull. The advantage of the latter installation is that the transducer(s) is/are slightly tilted(approximate 30), which will increase the range and, depending on the incline and the bank, measurements can be taken in very shallow water, covering the largest possible surface. Another advantage is that survey scan be carried out at high speed (between 6 to 9 knots).
Practical examples of usage
The multibeam echo sounder system is one of the most essential devices on board of the Geo Plus survey vessels. On these vessels two different kind of systems are used:
Kongsberg EM2040 multibeam echo sounder
The EM2040 is one of the most modern multibeam echo sounder systems on the market nowadays. The EM2040 is the first system tob ring all the advanced features of deep water multibeams to the shallow bottom sounding environment. The EM2040 is the successor of the EM3002.
Kongsberg EM3002 multibeam echo sounder
The EM3002 is an advanced multibeam echo sounder system with extremely high resoluition and dynamically focused beams. It suits perfectly for detailed seabed mapping in shallow waters until a depth of 150 meters. The performance is stable even in worse weather conditions.
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