What Can Sonar and USBL Do For You?
Rachel Doornekamp | October 5, 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.
What is 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.
When is Sonar used?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.
Different Types of Sonar
Imaging Sonars, such as the Oculus Blueprint Multi Beam Sonar or Tritech Gemini, use hundreds of beams in a 120 degree pattern.
- 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
- Covers forward facing area only
- Smearing of the image can occur while moving
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.
- Large areas can be covered
- Users can stay still or move with the sonar
- Image clarity can be lower
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.
- Side scan sonar covers large areas
- Side scan sonar allows for great detail
The boat must always be moving in a straight line to create a picture
What is 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.
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