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Side Imaging And Down Imaging

Side Imaging And Down Imaging

Back in 1959, Lowrance's launch of the now-legendary Little Green Box opened an amazing new window to the underwater world. Ever since, that window has widened, thanks to never-ending improvements to fishing electronics.  The latest round of advancements yielded a wave of side- and down-scanning products — some with incredible high-definition imagery — offering great promise for enhanced, picture-perfect views of what lies beneath the surface. Unfortunately, only a fraction of the fishing population has fully reaped the benefits — which is why we're offering a rundown on when side- and down-scanning shines, along with tips and tricks for opening your sonar window to the max.

Perception Vs. Reality

Veteran Kentucky Lake guide and sonar educator Randy Kuhens has logged more than 11,000 hours on the water with Lowrance HDS systems with StructureScan and its formidable DownScan and SideScan Imaging options. The technology offers side-scanning beams able to cut a 500-foot swath across the lake, along with a slick array of depth-piercing, downward-facing transducer crystals capable of depicting the watery realm with an accuracy traditional two-dimensional sonar can't touch.

"I call standard sonar 'perception' and StructureScan 'reality' because sonar gives you an idea of what's down there that's open to interpretation," Kuhens says, "while StructureScan clearly shows what you're looking at." Proprietor of Kick'n Bass Guide Service, Kuhens targets largemouth bass, along with crappies, bluegills, and shellcrackers, often targeting offshore sweet spots such as shellbeds and channel ledges.

"I avoid community holes that get pounded by guides and their past clients," he notes. "I'm constantly on the hunt for unpressured fish." But simply locating likely structure isn't enough. "I no longer fish spots, hoping there are fish on them," he says. "I don't get out of my seat until I see the fish I want to catch, and determine their demeanor by their location in the water column, relation to structure or cover, and the presence of baitfish."

High-definition scanning does this by painting a detailed picture of anything in its beams. "Sonar can tell you a lot, but StructureScan processes information and gives it a three-dimensional image," explains longtime Northwoods guide Capt. Ron Hunter. Also a tournament tech support specialist who travels coast-to-coast attending bass and walleye events, Hunter has seen how better sonar information translates into a better understanding of the habitat below the boat — and bigger catches.

"When you look at vegetation with StructureScan, you're able to see each leaf, tell what kind of vegetation it is, and mark baitfish and predators beneath the canopy," he says. "Being able to search for specific species, such as cabbage or coontail, has been a big factor for both walleye and bass fishermen on a lot of systems.

"You can also accurately measure the size of objects, such as rocks and trees, or the height of vegetation, as well as the depth at which baitfish or larger fish are holding — both off bottom and from the surface," he adds. Such data is a goldmine in a number of situations, such as when smallmouth bass prefer a certain size boulder.

Having detailed info from below is key, but the ability to scan sideways adds another dimension to the hunt for fish. You can mark fish suspended to the side of the boat, scan lakeshores and riverbank structure, even shoot underneath docks, and other manmade cover. Over the past several seasons, Hunter has lost count of how many times data from side-scanning has helped anglers develop winning presentations. "On Lake Erie, for example, guys have marked suspended walleyes and put together trolling passes that ran their boards and baits on the fish, without ever coming near them with the boat," he says.

One such success story belongs to Travor Diegel, a South Dakota guide and decorated touring competitor on the walleye scene. Along with teammate and fellow Dakota guide Paul Steffen, he won back-to-back qualifiers on Minnesota's structure-rich Cass Lake on the Cabela's Masters Walleye Circuit, defeating a legion of top local sticks and traveling pros in the process. "On Cass, DownScan was crucial because there are so many baitfish, regular sonar struggles to separate walleyes from forage," he explains. "We were able to see walleyes other anglers missed. On the last day of the 2012 MWC tournament, we were about to leave a spot when we drifted a little deeper off the break and marked four large fish. We dropped down and caught two of them, which turned out to be our biggest fish of the day — and won the tournament."

One of the biggest benefits of high-definition down-scanning systems is their ability to throw back the curtain on the dreaded "dead zones" of traditional two-dimensional sonar, revealing fish along steep dropoffs, amidst boulder fields, and in flooded timber and other hard-to-read areas. With basic sonar, returns bouncing back off the first points of contact — whether tree limbs, boulders or the uppermost edge of the breakline — miss fish tucked in the sonic shadows.

"DownScan was key on the steep breaks of Cass Lake, but it's also a huge plus in western reservoirs like Lake Oahe, where you can see down into the branches of flooded trees," Diegel says. Knowing the makeup of the timber, as well as the presence and depth of baitfish and predators holding there, helps him zero in on fish-holding depths in the best trees.

Diegel uses side-scanning to find transitions between soft and hard bottom, such as mud to gravel. While Diegel primarily targets walleyes, even subtle changes in bottom content can be a big deal on the bass front, according to Mark Fisher, Field Promotions Director at Rapala and tournament ace. "I've used Humminbird's Side- and Down-Imaging sonar since the day it came out," he says. "It's shown me sweet spots on lakes I've fished for years such Minnetonka and Rainy Lake that I never knew existed." For example, side-scanning revealed fingers of hard bottom extending from bass-holding points to subtle humps he was unaware were connected — until now. To aid his search for firm substrate, Fisher sets his gain, "so I get a snow-white return on the hardest bottom."

Tricks and Tips

As with any new technology, there's no substitute for time on the water and experimentation. But there are shortcuts to success. The first step is setting up your sonar correctly. Both Kuhens and Hunter recall countless occasions when anglers frustrated with their sonar systems were actually suffering from improperly mounted transducers or other basic problems. "I give sonar classes on the water, in the angler's boat," says Kuhens. "But before we leave the dock, we check everything out."

Diegel, Hunter, and Kuhens swear by selecting the right color "palette" for peak visibility given the conditions at hand. "Our eyes are a little different, as are the lakes we fish," Hunter begins. "In weeds, a green-black palette works best for me, while black-and-white is best on rocks." He also recommends tweaking the contrast and sonar frequency for different water depths. "The deeper the water, the higher the contrast," he says. "And I switch from 455 kHz to 800 kHz in deep water." Another trick is using total right or total left when scanning structure or cover on one side of the boat. "The unit produces a finite amount of power, so why not focus it on the area you're interested in?" he asks.

Kuhens reports using DownScan roughly 65 percent of the time, chiefly while dissecting the main lake. "But side-imaging is great for checking creeks and bays. In such situations, I run a split-screen view with SideScan on one side and DownScan on the other," he says.

While the crisp, detailed images are a huge help in finding fish, Kuhens says his favorite feature is Lowrance's Trackback tool, which allows him to scroll back in time on the display and place his cursor on a school of fish he'd like to revisit. "When you hit 'GoToCursor,' the unit saves the location, tells you how far away the school is, and guides you back. You don't have to clutter your chartplotter with waypoints to mark such spots. Each one is automatically saved until you put the cursor on another potential hotspot."

While the advantages of high-tech side- and down-viewing sonar are many, Diegel points out there are still times when traditional sonar shines. "Anytime I'm moving over about 6 mph, such as when searching for fish, I use regular sonar," he says. "Once I mark the fish, I slow down, switch to Structure-Scan, and go back to fish 'em." Just another tip for getting the most from your electronics — and catching more fish fast — on every trip.

*Dan Johnson of Harris, Minnesota, is a frequent contributor to In-Fisherman publications, and director of the Cabela's Masters Walleye Circuit,

Side Imaging And Down Imaging

Contact: Kentucky Lake guide Randy Kuhens, 270/703-6133,; Lake Oahe guide Travor Diegel,; Capt. Ron Hunter, 218/209-1074.

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