Why 3D Sonar: A Basic Sonar Primer from Echo-sounders to Water Depths

There are many different types of marine sonars in use today. Some sonars use one narrow,
downward-looking beam, such as depth-sounders and fish finders. Others only look at a narrow slice of water and are called 2D sonars. Examples are sidescan sonar and small craft navigational sonars. Effective obstacle detection and avoidance, however, requires continuously updated range, bearing, and depth information on all of the underwater hazards in front of the vessel. Unlike 1D and 2D sonar systems, FarSounder’s unique 90 degree forward-looking sonar displays a new 3D underwater map every 2 seconds, and provides mariners with a major advancement in obstacle avoidance and navigation technology.

Examples of Differences Between 1D, 2D, and 3D sonar

Figure 1: 1 dimensional sonar

Figure 2: 2 dimensional sonar

Figure 3: 3 dimensional sonar

First, there is the simple echo-sounder, also known as a depth-sounder. It tells the user how deep the water is directly below the sounder. Basically, it draws a picture of where the user has traveled. However, it does nothing to warn the user of the rock ahead, as illustrated in figure 1. This type of sonar is a 1D system, and it provides the user with only one of the three pieces of information they need: depth.

Moving beyond 1D to 2D - There are sonars currently called forward-looking sonars. These sonars are only 2D. They only provide the user two of the components needed: range and bearing. They do not provide depth, and in shallow water, they do not provide navigationally useful information. By definition, shallow water means that there is a bottom that a mariner needs to know about. With these systems, the user is told that there is bottom everywhere. The key to figure 2 is that today's systems let you know there is something in front of you, but not necessarily that you will hit it. Some products try to solve this problem by simply rotating their system 90 degrees. This creates a single, narrow vertical slice giving range and depth but not bearing. In this orientation, the user is not shown options, and does not know what lies ahead.

FarSounder technology provides a complete 3D picture of what is ahead of the vessel.

FarSounder technology provides a complete 3D picture of what is ahead of the vessel. Unlike other forward-looking sonars, FarSounder provides all three navigationally significant components: range, bearing, and depth. With color mapped to depth, where blue is deep, figure 3 shows a simple representation of how dangerous obstacles can be depicted. With all three components, the user is able to accurately understand the navigational picture ahead of the vessel. The user is able to determine where or where not the vessel is able to pass. Uncharted obstacles such as submerged shipping containers, whales, and rocks are some of the obstacles of which the user now has a complete picture. -- Learn more about 2D versus 3D processing.

Understanding Water Depth Performance

Besides operating as a true 3D sonar, creating a 3D image with a single ping, FarSounder's technology distinguishes itself as a shallow water sonar system with its impressive Water Depth Performance and its ability to detect objects in shallow water even beyond its water depth limit. To best understand how FarSounder's technology is able to operate so well in shallow water it is first necessary to understand the metrics used in shallow water sonars.

There are two metrics used when talking about the maximum range of a forward looking sonar: Maximum Range and Water Depth Performance. Both of these metrics are important, yet most other FLS products don't like to talk about their Water Depth Performance.

The Maximum Range is the farthest distance at which the system can detect targets under ideal conditions.

Water Depth Performance is how far ahead bottom depths can be mapped as a multiple of the depth of water below the transducer. As an example, if a 2 water depth sonar system is operating in 50 feet of water, that system can generate bottom maps only out to 100 feet.

Breaking the Water Depth Barrier

One of the most impressive features of FarSounder's technology is its shallow water operations capability. FarSounder's products are specified as 8 Water Depth systems. However, even beyond their water depth capability they are still able to detect objects out to farther ranges. For instance, in shallow water areas, FarSounder systems can create bottom maps to 8 water depths giving the user depth information over the full field-of-view. In addition, these systems can also detect obstacles at much farther ranges. In these cases, the sonar may not be able to determine the actual depth of the target, but it is able to tell the user that something is there. Please visit our screen shot gallery for examples of shallow water operation at ranges well beyond our water depth capability.

FarSounder technology is capable of detecting obstacles even beyond its water depth capability.

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