The transducer is normally mounted on a drop keel, which allows it to look horizontally. The Simrad MS70 permits characterization and volume estimation of a school of fish using only one single transmission. Schools of fish can be tracked, followed, and studied using multiple consequitive transmissions.
As a consequence of the horizontal transmission using narrow beams, the MS70 allows you to detect and characterize schools of fish even very close to the sea surface.
The MS70 provides an acoustic matrix of 500 beams (25 horizontal and 20 vertical). This enables the MS70 to provide instantaneous 3D volume data. Where other systems need multiple pings to provide 3D volume data, the MS70 can provide this using a single ping. This allows the MS70 to provide more accurate data. For example, a school of fish can change its structure several times during the time other systems need to cover the school.
Multiple consecutive pings enable the MS70 to provide true 4D data, where time is the fourth dimension. This allows for improved characterization of school structures that are changing over time.
Low sidelobes are important for two reasons. The obvious one is to avoid that strong targets in side lobes are mistaken for weak targets in the main lobe. Secondly, you do not wish to see strong bottom echoes from the sidelobes. Very low vertical two-way sidelobe levels are obtained by using two-way side lobe suppressions. Very low beam interleakage is obtained by using Frequency Rotated Sector Transmission (FRST) where the frequency band is distributed over all the sectors.
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