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What Can Sonar and USBL Do For You?

Rachel Doornekamp   |   January 17, 2020

In an ideal world all water would be crystal clear for miles, making it easy to navigate and see deep underwater. Unfortunately, however that is not always the case. Unless you’re off the coast of Guadalupe Island you may not be lucky enough to work in such clear waters.

Visibility below the surface can sometimes limit underwater operations if teams do not have the right equipment. In many situations though, turbid water can’t limit a mission - the job still has to get done!

In addition to numerous lighting and sensor options, Deep Trekker provides ROV pilots with advanced tools to greatly improve low visibility working conditions. USBL and sonar technologies allow operators to easily determine where they are underwater and what they are looking at, making them an ideal tool for underwater remotely operated vehicles (ROVs).

From search & rescue to salvage operations to defense, sonar and USBL technologies help get the job done in a wide range of industries. Deep Trekker offers a variety of accessories to help with getting imagery through water and locating the position of the ROV. Whether you are completely new to acoustic technology or are curious how Deep Trekker uses the different options, this article is for you.

Sonar

Sound Navigation and Ranging (Sonar) technology is a system for the detection of objects underwater by means of sound waves sent out and reflected by those objects. Especially helpful for low visibility underwater operations when a camera system or diver would be unable to see clearly on their own, sonar is useful in a variety of applications.

Sonar has been used effectively by operators in various industries and working environments. Sonar technology has the ability to help locate underwater objects in deep salvage operations where turbid waters may hinder maximum camera visibility. Sonar can also help locate underwater infrastructure for inspection and repair purposes. In underwater discovery, sonar can locate sunken ships in murky water or help researchers monitor aquatic life and environmental conditions. Perhaps most well known for search & recovery operations, sonar can help police and rescue teams locate evidence or victims underwater.

Generally accepted understanding of sonar delivers 4 points that will provide clarity as we summarize our available sonar options.

  • Lower frequency often delivers across a longer range with lower resolution.
  • Higher frequency has a shorter range but higher resolution.
  • The higher the number of beams, the better the image quality.
  • Smaller windows provide more reflections and more data for better image quality.

Side Scan Sonar

Side scan sonar comes in the form of a towfish or a side mounted sonar on a boat. While this option is not attached directly to an ROV, it is an important option to discuss as it is typically the best option for search and rescue operations. Typically a side scan sonar is used to sweep an area and determine points of interest. From there, an ROV is deployed to closer investigate these points of interest.

Pros

  • Side scan sonar covers large areas.
  • Side scan sonar allows for great detail.

Cons

  • The boat must always be moving in a straight line to create a picture.

Mechanical Scanning Sonars

Mechanical scanning sonars use a single acoustic beam rotating in 360 degree motion. The Tritech Micron Sonar can be integrated into our ROVs for navigation in murky water.

Pros

  • Large areas can be covered.
  • Users can stay still or move with the sonar.

Cons

  • Image clarity can be lower.

Imaging Sonars

Imaging Sonars, such as the Oculus Blueprint Multi Beam Sonar or Tritech Gemini, use hundreds of beams in a 120 degree pattern.

Pros

  • Imaging sonars provide very high resolution images compared to Mechanical Scanning Sonars.
  • Direct integration onto handheld controller to avoid needing a laptop, as well as make recording together easy.

Cons

  • Covers forward facing area only.
  • Smearing of the image can occur while moving.

Blueprint Oculus Multibeam Sonar M370s

The M370s is a very long range sonar (200m) that is best suited for search and rescue operations in a large area. The most affordable of the Blueprint Subsea series, the M370s has lower resolution than the M750d and M1200d with 256 beams and 375kHz.

Pros

  • The M370s has a long range.
  • The M370 is the most affordable of the Blueprint Subsea series.
  • This sonar has a high resolution in comparison to other single beam sonars.

Cons

  • Does not have Dual Frequency Mode, which allows the sonar to switch to a higher frequency concentrated on a smaller window. This mode creates a much higher resolution image at a shorter range.
  • This sonar has a lower resolution when compared to the other imaging sonars mentioned in this blog.

Blueprint Oculus Multibeam Sonar M750d

The M750d is a great general purpose sonar, offering the benefits of longer range with higher quality imagery. With a 120m range and 512 beams this is the most commonly sold sonar by Deep Trekker.

Pros

  • The M750d has a long range at 120m but also has a strong resolution at 750kHz/1.2MHz with the Dual Frequency Mode.
  • Dual Frequency Mode allows the sonar to switch to a higher frequency concentrated on a smaller window, providing much higher resolution at a shorter range.

Cons

  • Slightly lower resolution than the M1200d.

Blueprint Oculus Multibeam Sonar M1200d

The highest resolution imaging sonar available, the M1200d is perfect for shorter range and shallow water inspections. With a range of up to 30m, the M1200d also has 512 beams but a resolution of 1.2MHz/2.1MHz with Dual Frequency Mode engaged.

Pros

  • The M1200d has a very high resolution.
  • Dual Frequency Mode can be engaged on the M1200d.

Cons

  • The M1200d has a limited range at 30m.

TriTech Gemini 720ik Multibeam Imaging Sonar

The 720ik is another great sonar for large, open areas with a range of up to 120m. Much like the M750d, the 720ik has great range but slightly lower resolution with 512 beams and a frequency of 720kHz.

Pros

  • The 720ik is an affordable sonar option.
  • The 720ik has a longer range at 120m.

Cons

  • There is no dual frequency mode available.
  • The resolution of the 720ik is lower in comparison to other units.

USBL Positioning

One option to consider that integrates with sonar is USBL. Ultra-short baseline, or USBL uses triangulation to indicate the position on the ROV. Consisting of a transducer at the surface and a transponder on the ROV, USBL is the closest thing to underwater GPS as possible. A relative position is plotted in a laptop generated software, this position can then be overlaid on maps such as Google Earth. Using a GPS coordinate from your computer or a device at the transducer, you can then estimate the GPS coordinate of the ROV within 20cm of accuracy.

As maps can be overlaid onto the software in real time, positioning and navigation is made even easier. Industries such as search & recovery use USBL systems to navigate large and potentially unfamiliar search areas. USBL is also helpful in maritime applications to help pilots determine where their vehicle is located under the water. Underwater inspection services use USBL positioning systems to determine where they are located in relation to the infrastructure they are inspecting. In short, having a USBL positioning system is extremely helpful for understanding where you are and where you are going under the water.

Oculus SeaTrac USBL

The Oculus SeaTrac USBL is suitable for a wide range of underwater applications. Their multi-purpose acoustic transponder beacons are capable of simultaneously tracking asset position and undertaking bi-directional data exchange.

Pros

  • The SeaTrac has a 1km range.
  • The SeaTrac is more affordable than other USBL options.
  • Direct integration onto handheld controller to avoid needing a laptop, as well as make recording together easy.

Cons

  • The SeaTrac does not work well in smaller, enclosed spaces.

MicronNav USBL

The MicronNav USBL positioning system is specially designed for smaller vehicles like our ROVs. It has been primarily designed to be used in conjunction with Tritech sonars however it is compatible with a wide variety of sonar options.

Pros

  • SeaNet Pro software is an alternative to Bridge by being able to show sonar, video and USBL positioning on one screen and record it together in one file.

Cons

  • The MicronNav has a smaller tracking range than other options at 500m.
  • Most expensive of USBL options from Deep Trekker.

Waterlinked Underwater GPS

The Waterlinked Underwater GPS uses four dunking transducers instead of one, and each one needs to be placed a few metres apart and 1 to 1.5m below the surface.

Pros

  • Waterlinked is best for small areas like hull or reservoir inspections.
  • Direct integration onto handheld controller to avoid needing a laptop, as well as make recording together easy.

Cons

  • The 100m range is relatively short.
  • The Waterlinked requires a more complicated setup than other options.

A big advantage of Deep Trekker and our BRIDGE technology is our ability to integrate imaging sonars and USBL Positioning system data via our handheld controller. Our display shows this data and allows you to record video, sensor data, sonar data and USBL data all as one. The USBL also allows for time stamped position data via a .csv file for easy interpretation after a dive. This eliminates the need for bulky setups with laptops and makes operations easier on the ROV pilot.

Check out our ROV FAQs to learn more about our vehicles. As always, our team of industry experts are here to answer any questions you may have!