Side-scanned sonars: a complete guide to selection and operation

Modern boat fishing has changed dramatically with the advent of technology that allows you to look underwater without diving. While classical sonar showed only a narrow strip of the bottom directly under the bottom of the vessel, the new systems give the angler a panoramic view of the underwater world. Side scanning. It was a breakthrough, turning the sonar from a simple depth meter into a powerful intelligence tool.

Imagine you're floating on an unfamiliar body of water, and you see on the screen not just dots, but a clear map of the relief, snags and shoals of fish on either side of the boat tens of meters away. Lowrance, Garmin and Humminbird Understanding the workings of these devices allows you not only to buy expensive equipment, but to effectively use its potential.

In this article, we will discuss in detail the physical basis of the technology, the features of mounting sensors on different types of floating craft and the subtleties of frequency setting. angle of view to 120 degrees It changes the tactics of finding fish and how to interpret the resulting picture in order not to miss the trophy.

Principle of work and differences from traditional sonar

The traditional 2D sonar emits a cone-shaped signal that scans the bottom directly under the boat. It's like a flashlight shining vertically down. In contrast, side-scanning systems use high-frequency beams that are perpendicular to the boat's movement. They form two fan-shaped beams on the sides, creating a detailed image of the bottom.

The key here is signal frequency. Side-by-side viewing typically uses frequencies ranging from 455 kHz to 800 kHz and above. High frequency provides incredible detail, allowing you to distinguish between individual branches of sunken trees or stones the size of a fist. But there is a trade-off: the higher the frequency, the smaller the depth of penetration of the signal.

It is important to understand the difference between technology Side Imaging and SideVüAlthough they have similar working principles, signal processing algorithms and beam shapes may differ from manufacturer to manufacturer. Side Imaging Humminbird is often praised for its contrasting image, while SideVü Garmin is known for its ease of customization and integration with mapping.

⚠️ Attention: High-frequency side scanning is not very effective at great depths (over 30-40 meters) and will be noisy and uninformative at depth, so you need to switch to low frequencies or traditional 2D mode for deep-sea fishing.

Modern sonar processors can process hundreds of thousands of pulses per second, creating a photo-photo effect of the bottom, which allows the angler to see not only the terrain, but also the structure of the bottom cover, which is critical when looking for specific predator sites.

Benefits of using fishing from a boat

The main advantage of side scanning is the speed of the survey of the water area, and when you go in a straight line, you actually scan a strip up to 60-80 meters wide (30-40 meters each way), which allows you to quickly find eyebrows, dumps, pits and sunken objects that you would otherwise have to search for hours, making many passes on a regular sonar.

And it's also a safety technology, because when you're driving in shallow water or in unfamiliar places, the side beams are showing the shoals and the obstacles that are hidden under the water that are still far away, and you can maneuver around the boat in a calm way, seeing the full picture around the boat, not just under the keel.

For spinning and trolling players, seeing fish away from the boat opens up new tactical possibilities: you can swim over the jamb, spot it on the screen, come back and anchor, or throw an anchor stretch upstream to gently catch the spot.

• 🚀 Saving time: Surveying large areas in one pass accelerates the search for active fish at times.
• 🗺️ Detailed navigation: The ability to create your own topography maps with high accuracy for repeat visits.
• 🐟 Parking search: Visualization of the snags and thickets of grass where the predator hides, even if it is not active.

Model selection: frequency, power and screen

When choosing a device, you should pay attention to the supported frequencies first. Budget models can only have 455 kHz, which is not bad for shallow water, but limits the possibilities at depth. Top-end devices offer switchable frequencies of 455/800 kHz or even 1.2 MHz, which gives flexibility in different conditions.

The power of the emitter also plays a role, especially if you plan to fish in the current or deep waters. However, for side scanning, it is not so much the power that matters, but the sensitivity of the receiver and the quality of the noise reduction algorithms. The screen of the device must be high resolution, because the detail of the side scanning image requires a clear matrix.

And it's worth considering the presence of combined sensors. Garmin Echomap or Lowrance EliteThey come with transducers that support 2D, DownVü/SideVü and sometimes even CHIRP technology.

Parameter	Budget segment	Middle class	Top level.
Frequency	455 kHz	455/800 kHz	455/800/1200 kHz + CHIRP
Power	250 W.	500 watts	1000 W and more
Screen resolution	480x272	800x480	1280x720 and higher
Viewing angle	90 degrees.	110 degrees.	Up to 120 degrees.

Keep in mind the screen size. For a complex side-scanning image, the minimum comfortable size is 7 inches. On 5-inch screens, details can merge, and you have to zoom constantly, losing context.

Proper installation of the sensor on the boat

The quality of the side scanning image depends 90% on the correct installation of the sensor. Unlike a conventional sonar, the orientation of the beams is critical here. The sensor must be installed strictly perpendicular to the water surface and parallel to the diametric plane of the vessel.

There are two main ways of installing the sling and the cut-in (or under the bottom). Trans fitting is easier, but at high speeds, the sensor can catch air bubbles, which creates interference. Twisting provides better hydrodynamics and stable picture even when moving fast, but requires drilling of the housing.

If you're using a PVC boat, make sure that the mounting of the sensor doesn't damage the cylinders and can withstand the vibration of the motor. For metal boats, you can't use cut-in sensors without special fairings, because the metal shields the signal. In these cases, you use plastic fairing linings that stick the sensor in.

Pay special attention to the cable. It should not sag or create a loop into which water can be stuffed. All connections should be sealed. Even a microscopic crack in the insulation at the depth will lead to water getting in and expensive equipment will fail.

⚠️ Warning: When installed on a transom of plastic boats or PVC, avoid placing the sensor in the zone of "turbulent flow" from the redan or motor. Air bubbles hitting the emitter completely "muffle" the side scan signal, turning the screen into porridge of noise.

Setting and interpreting the image

Once installed, you need to adjust the device correctly. The basic parameters that you have to rotate constantly are sensitivity and contrast. Too high sensitivity will add noise and graininess to hide real objects. Too low will make the picture pale and uninformative.

Interpreting the image takes habit. The fish on the side-scan screen looks like arcs or dots in the water column. The bottom is displayed as a detailed texture. The rocks and driftwoods give a characteristic shadow behind them (in the direction of the sensor), which helps determine their volume and height.

Use the function Split Screen (split screen) to see the traditional 2D view and side scan at the same time, which helps you map what's right under the boat to what's on the side. Pause (pause), allowing you to stop scrolling and study in detail the interesting area.

The secret of adjusting sensitivity

For the perfect picture, set the sensitivity to maximum until there's a lot of noise, and then reduce the value by 5-10%. That's the middle ground for most bodies of water.

It's important to learn to distinguish between real objects and artifacts. For example, a second bottom signal (double echo) might appear in deep places with a hard bottom, it would look like a copy of the relief, but below the real bottom, and understanding the physics of sound propagation would help to ignore such false signals.

Comparison of technologies of leading brands

The sonar market is shared by several major players, and each has its own strengths. Humminbird He is considered a pioneer of Side Imaging technology, offering perhaps the most detailed image yet for finding the structure of the bottom, and their interface is tailored to fishermen who are used to the classic sonogram.

Garmin They're betting on integration. SideVü It works great with navigation and autopilot, and if you like to build routes and use maps, the Garmin ecosystem will be the most convenient, and they have a slightly smoother picture and less contrast than the Humminbird, but very understandable for beginners.

Lowrance (and its premium brand) Simrad) offers technology StructureScanIt's famous for its stability and excellent performance at high speeds. Many professionals choose Lowrance for its reliability and extensive customization capabilities through third-party plugins and network extensions.

• 🏆 Humminbird: The best detail for finding fine structure and fish.
• 🧭 Garmin: Best navigation and integration with mapping.
• ⚓ Lowrance: Optimal balance of price, quality and network capabilities.

The choice also includes map availability for your region, and some brands have more detailed depth maps (LakeVü, C-MAP) for your favorite water bodies, which, when combined with side scanning, is amazing.

Frequent errors and operating tips

One of the most common mistakes is to expect a sonar to show a fish in real time, with a fraction of a second delay, like in a movie. In fact, the image on the screen is a story. What you see on the right of the center line happened a few seconds ago, when the sensor was passing that point. The center lane is what's under the boat right now.

Another mistake is ignoring the speed of the boat: for a high-quality side scan, the boat speed should not exceed 10-15 km / h (depending on the model); at a higher speed, the rays are smeared, and the picture loses clarity; For a detailed study of the point, it is better to reduce the gas to a minimum.

Remember to maintain. After every fishing trip, especially in salt water, the sensor and cable must be washed with fresh water. Salt deposits on the emitter can impair the signal's permeability. Also check the condition of the fasteners - the vibration of the motor can weaken them in a season.

⚠️ Warning: Never turn on a sonar with a sensor raised from the water at high power and frequency. The emitter, operating "dry" even for a few seconds, can overheat and fail due to lack of water cooling.

Remember, a sonar is a helper, not a guarantee of catch, and it shows the structure and the presence of fish, but it does not replace fishing experience, understanding fish habits, and choosing the right baits, and technology only gives you information, and you decide how to use it.

FAQ: Frequently asked questions

Is the size of the fish visible on the side scan?

It's hard to pinpoint the size, but you can measure the size relative to the structure. A large fish will look like a fatter, brighter arc or dot. But sounders are not measuring length, they show the presence of a reflective object.

Does the side scan work on the ice?

Yes, if you use a special transducer sensor that goes down the hole from the side, you don't use a standard transom sensor on ice, because the rays must pass through water, not through ice (although the signal theoretically passes through the ice, but with great losses and distortion).

Can I use a sounder in winter at low temperatures?

Modern sonars operate at temperatures as low as -10...-15°C, but lithium-ion batteries discharge very quickly in the cold. It is recommended to keep the battery warm (in a heat bag or under clothes), bringing out only the screen and the sensor.

Why is there so much noise and grain on the screen?

This can be caused by high sensitivity, motor operation near the sensor, plankton in the water, or just air bubbles under the sensor. Try to reduce sensitivity or change the speed of the boat.