![]() It’s a great new tool for any angler who fishes in less than 600 feet of water. ![]() With CHIRP or without, side-scanning sonar is here to stay and can help you locate the fish while staying on them. To find out the details on how CHIRP works, see our West Advisor on CHIRP sonar. Because CHIRP sonar transmits more energy directly into the water column, it yields further improvement in range and clarity compared with traditional sonar. Some fishfinders combine high-frequency imaging with CHIRP technology. They will also have traditional 50/200kHz sonar, which is still superior for displaying big fish arches in a way most fishermen find familiar, and down-looking scanning sonar. Many anglers will show their side-scan image full-width across their display. You can easily customize what you see onscreen on your fishfinder with just a few quick drag-and-drop motions on the touchscreen. This screenshot is from a Lowrance SonarHub module, networked with an HDS gen3 display. Side-scanning sonar fills the bottom of this screen. Or you can move in quietly and drop your hook. You can observe from a distance and when you see something interesting, easily create a waypoint on your GPS-interfaced display for later reference. ![]() This technology is great for looking into shallow water and finding structures where fish hide such as brush piles, docks, channels, and other ledges, humps and bumps. This is the typical range for these side-scan units-two football fields on each side of your boat-exponentially multiplying the bottom coverage over conventional sonar. The Lowrance StructureScan HD, for example, has a maximum side-scan range of 600 feet, using 455kHz and trolling slowly through the water at 2 to 8mph. The basic concept here is that higher frequencies generally give you better clarity and resolution, but do not penetrate as deeply as lower frequencies. You can even see a pack of hungry predator fish attacking the school of baitfish. Higher frequency sonar resolves the red blob into a school of small, white dots. Scanning sonar removes much of the guesswork from this situation. Lake Murray bridge using Garmin ClearVü (left) and SideVü (right) scanning sonar at 455kHz, enhanced by CHIRP technology. Some scanning sonar models have had three beams that look down and to both sides of your boat, often with three transducer elements that produce a wide (180 degree side to side) and very thin (1.5 degree to 3 degree fore and aft) beam. ![]() When a school of fish swims below your boat, you’ll see a red blob, and you can interpret that image, based on water temperature and location, and guess that you’re looking at a school of small individual forage fish. If you’re lucky, a fish will swim into the beam, and you’ll see it on your display. The cone-shaped beam of the typical transducer is 20 degrees or less, so if you’re fishing in 10 feet of water, you’ll see an area of with a diameter of about 3 feet. It operates at a lower frequency, usually 50kHz and 200kHz. Traditional SonarĬompare this to a traditional sonar. Views like this can help fishermen and divers find structure, wrecks and other underwater features more precisely than with traditional sonar. Scanning sonar produces near-photographic quality sonar images, like those shown in the screenshot above. Instead of a cone-shaped beam, scanning sonars sweep a narrow beam of very high-frequency energy (often 455 or 800kHz) from side to side, producing “slices” that are combined to create the highly detailed images shown. Mid-angle for medium depths is shown here. The angles of the SideVision™ sonar are adjustable for shallow or deep water. Raymarine’s CP200 Sonar Module with CHIRP SideVision™ scanning sonar, combined with their CP100 DownVision Sonar, gives a 180 degree view.
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