SONAR is a term that refers to a device that uses sound to locate things inside a water column (sound navigation and ranging). Active sonars generate their distinct sound waves and analyze the reflected (echo) waves (echosounder). Active sonars include multibeam and single beam sonars. Multibeam sonar can visualize the soil topography underwater.
How Does A Multibeam Sonar Operate?
Echosounders operate on the following principle: a projector creates sound waves picked up by a receiver or hydrophone. A transmitter is referred to as a transducer if it can both produce and receive sound waves.The multifrequency bathymetry mode was designed to optimize the bottom detect resolution. The outcomes are dependent on the frequencies transmitted. Because low frequencies are less absorbed, they can travel further than high frequencies. This is why low frequencies monitor a large region with a lesser resolution than high frequencies.
Multibeam sonar is capable of emitting several single narrow beams. The transducer is placed in the keel of the vessel and generates a variety of sound waves. Thus, the seabed is scanned using a line of continuous points perpendicular to the vessel’s journey direction. The swath length is the width of every line drawn on the soil.
It can be represented in meters or as the angle (in degrees) at which the line is produced. The transducer determines the timing and energy differential between emitted and reflected sound waves. As a result, the depth and characteristics of the seabed may be calculated. An even hard surface reflects more waves than an uneven substrate.
Apart from the seabed, a vessel mounted with multibeam echosounder equipment can also map the features of the water column. The emitted beams interact with the particles in the water column and create reflections of their own. One may intuitively deduce that the quantity of reflected energy is proportional to the number of particles in the water column.
In practice, the particle size and type, as well as the transmitted frequency, are critical. Nowadays, much study is being conducted on the connection between multibeam data from water columns and turbidity.
Single Beam Vs Multibeam Sonar
A single beam system, which generally has beam widths ranging from 10 to 30 degrees, estimates depth by measuring the distance between the main beam and the seabed along with the shortest slant range. Slant range and elevation angle estimations are provided by multibeam (swath sonar) systems along a set azimuth in a sequence of measurements. This approach is preferred since it measures the entire area of the seabed rather than just a single line of it.
A Multibeam Sonar Can be Used In
- Underwater sonar for marine construction or dredging
- Bathymetric map making
- Water column turbidity mapping
- Underwater habitat mapping
- Underwater marine cultural heritage mapping
The advantages of multibeam echo sounders are that they scan the seabed using a fan of thin acoustic beams, allowing them to cover the whole bottom with complete coverage. Compared to single-beam mapping, the resultant seabed maps are more detailed than those obtained through single-beam mapping. The maps are generated more quickly, which reduces the amount of time required for ship surveying.
For the best results in underwater mapping, getting a multibeam sonar is the best choice you can make.