Multibeam echo sounder – Full ocean depth, 10-11,000m

The EM 304 MKII is the successor of the highly acclaimed EM 302 and the EM 304 MKI multibeam echo sounder. With its broad frequency span, this system sets a new standard in the market with no compromises between range and resolution, which require minimal post-processing. The EM 304 MKII can map the shallow-to-medium water depths with high resolution and still map the deepest depths with a superior coverage. Compared to the EM 304 MKI, the MKII has an increase of 75% swath performance at 6000m. Image credit:  NOAA Ocean Exploration.

Full ocean depth

The depth capability of the EM 304 MKII extends to full ocean depth, or 11000 meters. The swath width is typically 5.5 times the water depth to almost 2000 m depth. A swath width of more than 12000 m is generally achievable for deep waters (down to 6000 m), depending upon bottom conditions and chosen system beamwidth. A low noise vessel with the right bottom conditions should achieve more than 10000 m swath width even at full ocean depth.

Image: Courtesy of NOAA Ocean Exploration.

Modular and flexible design

The EM 304 MKII uses state-of-the-art electronics and separate transmit and receive transducers in a Mills Cross configuration. It utilizes the same field-proven receive transducer as its predecessors, EM 304 MkI/EM 302, and a new redesigned wide band transmit transducer increasing the depth range and coverage. The design is highly modular and flexible with compact electronics for easier and faster installation. The flexible transducer design makes it possible to tailor the system to almost any required size. Ultimate system performance - resolution and range - is achieved with the largest standard size, 0.3 x 0.5 degrees, whereas the smaller 4 x 4 degrees solution can be installed on any vessel of opportunity.

Acoustic ice protection windows can be offered for vessels going to the ice edge and for ice breakers. Both TX and RX ice windows are made of hyperlast, reinforced with titanium rods, proven to withstand surveys across the North Pole.

Image: Gondola for Ifremer Thalassa before painting. Courtesy of Brieuc Crénan, Ifremer.

Full and clean seabed coverage

The transmit fan can be divided into up to 16 individual sectors in dual swath mode. This allows for unique control of the transmit fan, enabling active stabilization in real time to correct for any yaw and pitch movement of the vessel, while roll stabilization is applied on the receiving beams. The result is a stabilized system for full ensonification of the seabed with equally distributed footprints, even in bad weather conditions, leaving no gaps or holes in the mapped area. All beams are maintained and automatically adjusted according to achievable coverage or operator defined limits. The two individual transmitting fans are generated with a small difference in tilt to provide a constantly sounding separation along track, resulting in a dense sounding pattern on the seafloor. 

The system produces a strong dampening of multi bounce interference from false echo, resulting in significantly cleaner data. Near field beam focus is applied in real lime, both during transmission and reception. Due to sector transmission, the focal point will be individual for each sector, resulting in a much sharper transmit beam over the entire swath. On reception, the focus is done dynamically for each beam. The result is a much higher resolution representation of the seabed.

Image: Courtesy of NOAA Ocean Exploration.

Key features

  • KMall format datagrams
  • Choice of beamwidths
  • Dual swath, up to 1600 beams
  • FM chirp
  • Roll, pitch and yaw stabilisation
  • Transmit and receive nearfield focusing
  • Water column phase logging
  • Seabed image
  • Mammal Protection
  • Ice windows available
  • Extra detections available
  • Choice of beamwidths: 0.3x0.5, 0.5x0.5, 0.5x1, 1x1, 1x2, 2x2, 2x4, 4x4

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