Identifying multiple signal reflections in Sonar systems
Improving Multiple-Beam Echo Sounders: Enhancing Port and Starboard Beam Distinction and the Benefits of Multiple Side-Lobes
In the realm of hydrographic surveys, the use of multiple-beam echo sounders is becoming increasingly popular due to their ability to provide more detailed and comprehensive seafloor mapping. One of the key challenges in using these systems is distinguishing port and starboard beams to accurately identify features on the seabed.
A common approach to achieving this distinction is through the system's directional array configuration and signal processing. Multi-beam echo sounders employ transducer arrays that emit multiple beams side-to-side, covering an arc across the seafloor from the vessel’s port side (left) to starboard side (right). Each beam corresponds to a specific angle relative to the vessel’s centerline, allowing the system to differentiate returns from the port side from those on the starboard side [1][3][4].
When it comes to the benefits of using transducers with multiple side-lobes in seafloor examination, side-lobes are secondary lobes of transmitted or received acoustic energy apart from the main beam. While conventional sonar systems strive to minimize side-lobes (to reduce noise and false echoes), some advanced multi-beam echo sounders intentionally use transducers designed with multiple controlled side-lobes to improve bottom coverage and data density.
The benefits include:
- Enhanced seabed coverage: Multiple side-lobes extend the swath width and help detect features outside the main beam footprint, leading to more comprehensive mapping in a single pass.
- Improved resolution and detail: Side-lobes can illuminate areas at different angles, allowing the system to pick up finer variations in seafloor texture and topography.
- Reduced data gaps: The overlapping coverage from multiple lobes fills in potential gaps that single beams might miss.
- Better feature discrimination: Multi-lobed signals can help distinguish between seabed types and objects by analyzing echoes arriving from slightly different angles.
By employing transducers with multiple side-lobes, hydrographic surveys can become more efficient and effective, providing denser, more detailed, and more reliable bottom imaging [3][4].
In practice, multi-beam systems such as the SIMRAD EM300 series used on research vessels like RV Tangaroa deploy multi-element arrays for detailed seafloor mapping [3], and in commercial/fishing sonars, the port-to-starboard (lateral) beam width is controlled for situational navigation and seabed feature visualization [1][4].
For instance, the record shown in Fig. 3, taken approximately 30 miles ESE of Cape St. Vincent on a course of 290°, shows a submarine canyon. This application uses a transducer arranged to have a series of beams pointing sideways from the ship as well as vertically. Using a transducer with a stronger axial beam and tilting it to one side can help distinguish port and starboard beams by their different intensities.
The paper "Beam identification in multiple-beam echo sounders" by M. J. Tucker discusses these topics in more detail and can be found at this link: https://journals.lib.unb.ca/index.php/ihr/article/view/26493. Relevant research on the subject includes works by Chesterman, Clynick, and Stride (1958), Tucker (1960), Tucker and Stubbs (in press), and Howson and Dunn (in press).
In summary:
| Aspect | Description | |-------------------------------------|--------------------------------------------------------------------------------------------------| | Distinguishing port/starboard beams | Achieved by directional vertical arrays that steer and separate beams side-to-side across vessel. | | Benefits of multiple side-lobes | Wider seabed coverage, higher resolution, reduced data gaps, and better discrimination of seafloor features. |
- The benefits of using advanced multi-beam echo sounders, such as intentional use of transducers with multiple controlled side-lobes, can significantly contribute to the field of science by providing enhanced seabed coverage, improved resolution, reduced data gaps, and better feature discrimination in technology-driven hydrographic surveys.
- In the realm of technology, hydrographic surveys have been revolutionized by the employment of transducers with multiple side-lobes, which not only improves the resolution and detail of seafloor mapping but also makes the surveys more efficient and effective in providing denser, more reliable bottom imaging, contributing to the advancements in the field of science.
